Google Groups no longer supports new Usenet posts or subscriptions. Historical content remains viewable.
Dismiss
arc suppressor for relays
52 views
Skip to first unread message
Jon Elson
Oct 3, 2012, 3:32:02āÆPM10/3/12
to
We have one of those $1K high efficiency washing machines. It does work, and
clearly reduced our water and gas bill, so I'm not complaining.
Lately, it has been getting "slow fill" errors, and I tried a bunch
of typical stuff before finding the REAL problem. They have a bank
of electromechanical relays to operate a bank of solenoid water valves.
There is no arc suppression on these relays, and the cold water valve
relay is totally shot. I have replacement relays on order, but want to
add arc suppression to prolong the life of the relays.
The coils are 120 V AC, the relays are TINY things. I ordered some
Zener-type transient suppressors which indicate a 193 V trip voltage,
bipolar.
I'm not clear about whether this is the level at which all units will
start to conduct or the level at which none will conduct.
Also, would it be better to put the suppressor across the relay contacts
or across the valve solenoid? If the device fails to short when across the
contacts, it will just turn the valve on all the time, causing a flood.
If across the valve coil, it will blow something, hopefully not circuit
traces off the board.
So, I'm looking for practical suggestions on how to choose the supressor
type (Zener or MOV) style, trigger voltage and where to put it in the
circuit.
Thanks,
Jon
clearly reduced our water and gas bill, so I'm not complaining.
Lately, it has been getting "slow fill" errors, and I tried a bunch
of typical stuff before finding the REAL problem. They have a bank
of electromechanical relays to operate a bank of solenoid water valves.
There is no arc suppression on these relays, and the cold water valve
relay is totally shot. I have replacement relays on order, but want to
add arc suppression to prolong the life of the relays.
The coils are 120 V AC, the relays are TINY things. I ordered some
Zener-type transient suppressors which indicate a 193 V trip voltage,
bipolar.
I'm not clear about whether this is the level at which all units will
start to conduct or the level at which none will conduct.
Also, would it be better to put the suppressor across the relay contacts
or across the valve solenoid? If the device fails to short when across the
contacts, it will just turn the valve on all the time, causing a flood.
If across the valve coil, it will blow something, hopefully not circuit
traces off the board.
So, I'm looking for practical suggestions on how to choose the supressor
type (Zener or MOV) style, trigger voltage and where to put it in the
circuit.
Thanks,
Jon
Spehro Pefhany
Oct 3, 2012, 4:05:28āÆPM10/3/12
to
On Wed, 03 Oct 2012 14:32:02 -0500, Jon Elson <jme...@wustl.edu>
wrote:
>We have one of those $1K high efficiency washing machines. It does work, and
>clearly reduced our water and gas bill, so I'm not complaining.
>
>Lately, it has been getting "slow fill" errors, and I tried a bunch
>of typical stuff before finding the REAL problem. They have a bank
>of electromechanical relays to operate a bank of solenoid water valves.
>There is no arc suppression on these relays, and the cold water valve
>relay is totally shot. I have replacement relays on order, but want to
>add arc suppression to prolong the life of the relays.
>
>The coils are 120 V AC, the relays are TINY things. I ordered some
>Zener-type transient suppressors which indicate a 193 V trip voltage,
>bipolar.
>I'm not clear about whether this is the level at which all units will
>start to conduct or the level at which none will conduct.
You ordered parts without looking at the data sheets? Or do you need
help in interpreting the data?
Here's a typical TVS data sheet:
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000720.pdf
Take, for example, the P6KE220CA.
No more than 500nA at 188V
At 1mA nominally 220V, but no less than 209V or more than 231V
At 1.85A (surely beyond your required clamping current) no more than
328V. At 10.3A, no more than 388V.
It's a bipolar device, so the ratings apply for either polarity of
applied voltage.
You could also try one of these, which you may have parts for in your
junk box:
http://www.digikey.ca/product-detail/en/104M06QC100/338-2581-ND/2503688
Those built-up ones are stupid expensive, you can just try a 630V
0.1uF film cap series with a 1/2W 100R resistor for < 1/10 the cost.
wrote:
>We have one of those $1K high efficiency washing machines. It does work, and
>clearly reduced our water and gas bill, so I'm not complaining.
>
>Lately, it has been getting "slow fill" errors, and I tried a bunch
>of typical stuff before finding the REAL problem. They have a bank
>of electromechanical relays to operate a bank of solenoid water valves.
>There is no arc suppression on these relays, and the cold water valve
>relay is totally shot. I have replacement relays on order, but want to
>add arc suppression to prolong the life of the relays.
>
>The coils are 120 V AC, the relays are TINY things. I ordered some
>Zener-type transient suppressors which indicate a 193 V trip voltage,
>bipolar.
>I'm not clear about whether this is the level at which all units will
>start to conduct or the level at which none will conduct.
help in interpreting the data?
Here's a typical TVS data sheet:
http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000720.pdf
Take, for example, the P6KE220CA.
No more than 500nA at 188V
At 1mA nominally 220V, but no less than 209V or more than 231V
At 1.85A (surely beyond your required clamping current) no more than
328V. At 10.3A, no more than 388V.
It's a bipolar device, so the ratings apply for either polarity of
applied voltage.
>
>Also, would it be better to put the suppressor across the relay contacts
>or across the valve solenoid?
I'd put it across the solenoid coil.
>Also, would it be better to put the suppressor across the relay contacts
>or across the valve solenoid?
You could also try one of these, which you may have parts for in your
junk box:
http://www.digikey.ca/product-detail/en/104M06QC100/338-2581-ND/2503688
Those built-up ones are stupid expensive, you can just try a 630V
0.1uF film cap series with a 1/2W 100R resistor for < 1/10 the cost.
Jon Elson
Oct 3, 2012, 4:33:12āÆPM10/3/12
to
Spehro Pefhany wrote:
>
> You ordered parts without looking at the data sheets? Or do you need
> help in interpreting the data?
>
I did look at the data sheets, they cover a wide range of devices, and have
>
> You ordered parts without looking at the data sheets? Or do you need
> help in interpreting the data?
>
very little descriptive info on what the columns of numbers actually mean.
I think I could have ordered a slightly higher voltage part and been sure it
would be fine. I ordered the P4KE200CA. But, looking a bit closer, they
show a range of min and max clamping voltage that look like they will
be OK, but right on the edge. For peace of mind, I may just install
one and then order some 220 or 240 V ones later to retrofit the rest of the
unit.
>>Also, would it be better to put the suppressor across the relay contacts
>>or across the valve solenoid?
>
> I'd put it across the solenoid coil.
>
> You could also try one of these, which you may have parts for in your
> junk box:
> http://www.digikey.ca/product-detail/en/104M06QC100/338-2581-ND/2503688
>
> Those built-up ones are stupid expensive, you can just try a 630V
> 0.1uF film cap series with a 1/2W 100R resistor for < 1/10 the cost.
of the board and can put it between the pins of the relay. I don't think
the caps would fit, but the 400W TVS should.
Thanks much,
Jon
Adrian Tuddenham
Oct 3, 2012, 4:28:42āÆPM10/3/12
to
Jon Elson <jme...@wustl.edu> wrote:
> We have one of those $1K high efficiency washing machines. It does work, and
> clearly reduced our water and gas bill, so I'm not complaining.
>
> Lately, it has been getting "slow fill" errors, and I tried a bunch
> of typical stuff before finding the REAL problem. They have a bank
> of electromechanical relays to operate a bank of solenoid water valves.
> There is no arc suppression on these relays, and the cold water valve
> relay is totally shot.
As an aside (which doesn't actually answer your original question), were
> We have one of those $1K high efficiency washing machines. It does work, and
> clearly reduced our water and gas bill, so I'm not complaining.
>
> Lately, it has been getting "slow fill" errors, and I tried a bunch
> of typical stuff before finding the REAL problem. They have a bank
> of electromechanical relays to operate a bank of solenoid water valves.
> There is no arc suppression on these relays, and the cold water valve
> relay is totally shot.
you aware that relays need to be mounted so that the gap between the
contacts is vertical if you want the longest life? This is one of these
useful facts that was known by designers in the 1920s (or even earlier)
and appeared in various textbooks on telephony, but now seems to have
been forgotten.
The reason is that it reduces the chance of dirt falling on the contact
surfaces and helps to dislodge any loose debris resulting from contact
wear.
I have come across an industrial diswasher that was forever burning out
small power relays simply because they were wrongly mounted.
--
~ Adrian Tuddenham ~
(Remove the ".invalid"s and add ".co.uk" to reply)
www.poppyrecords.co.uk
Jon Elson
Oct 3, 2012, 4:45:56āÆPM10/3/12
to
Adrian Tuddenham wrote:
>
> As an aside (which doesn't actually answer your original question), were
> you aware that relays need to be mounted so that the gap between the
> contacts is vertical if you want the longest life? This is one of these
> useful facts that was known by designers in the 1920s (or even earlier)
> and appeared in various textbooks on telephony, but now seems to have
> been forgotten.
>
> The reason is that it reduces the chance of dirt falling on the contact
> surfaces and helps to dislodge any loose debris resulting from contact
> wear.
>
> I have come across an industrial diswasher that was forever burning out
> small power relays simply because they were wrongly mounted.
These relays are semi-sealed (totally enclosed by plastic, but probably
>
> As an aside (which doesn't actually answer your original question), were
> you aware that relays need to be mounted so that the gap between the
> contacts is vertical if you want the longest life? This is one of these
> useful facts that was known by designers in the 1920s (or even earlier)
> and appeared in various textbooks on telephony, but now seems to have
> been forgotten.
>
> The reason is that it reduces the chance of dirt falling on the contact
> surfaces and helps to dislodge any loose debris resulting from contact
> wear.
>
> I have come across an industrial diswasher that was forever burning out
> small power relays simply because they were wrongly mounted.
not hermetic (although the boards are probably washed after assembly,
so they may be darn close to hermetic) so there is no external dirt to
get in them. It is now burning the contacts severely, and you can hear the
solenoid valves rattling and buzzing as the contacts arc. So, this is
not a little speck of dust, but massively burned-away contacts. I
expect on post-mortem, the contacts will be totally vaporized.
Jon
tm
Oct 3, 2012, 5:10:28āÆPM10/3/12
to
"Jon Elson" <jme...@wustl.edu> wrote in message
news:LrOdnT0aBNYvDfHN...@giganews.com...
Another "designed by monkeys" consumer product.
Jamie
Oct 3, 2012, 6:30:34āÆPM10/3/12
to
from 120 DC Or AC, diode them from the coils supply, place a cap on the
control terminal of the SSR. The M1, M2 terminals will go across the
contacts.
What this does is the SSR first comes on before the contacts close,
there by removing the load. when the contacts close, the SSR will not
conduct and thus it won't be doing any work.
The cap on the control terminal allows for a slight time off delay,
this allows for the relay to open and the SSR will be conducting for a
very short time afterwards..
Actually, I think there are add on products that already do this.. Not
sure.
Jamie.
Jon Elson
Oct 3, 2012, 6:45:39āÆPM10/3/12
to
tm wrote:
> Can you use a solid state relay? Maybe off the board?
There are 8 of these. If I can find a drop-in SSR that matches the
> Can you use a solid state relay? Maybe off the board?
pinout, I sure will do this the next time it needs to be opened up.
Off the board won't work, there really is limited space in the "console"
that sits above the the washer top/rear. If it was only one relay,
it would have already gotten hacked as you suggest.
> Another "designed by monkeys" consumer product.
Yeah, they must sell a LOT of these $275 controller boards.
Jon
Jon Elson
Oct 3, 2012, 6:49:53āÆPM10/3/12
to
fix the problem, anyway, it occurs on shut-off! The SSR would shut off
first, then the mechanical relay would drop out later, and still arc
(although the off SSR might have an internal snubber or avalanche mode
that would reduce the arc.) First, there are EIGHT of these in a tiny
space, so adding 8 more relays will never work. But, why use TWO
relays when one good one will do it?
A cap big enough to delay the turnoff of the SSR could damage the relay
driver chip, and would also keep the magnetic relay on.
Jon
tm
Oct 3, 2012, 7:40:55āÆPM10/3/12
to
news:a_OdnUzCt-COI_HN...@giganews.com...
I guess the relay switches 120 volts AC, right? What drives the relay? Is it
5 volts, other?
Is there an optoisolated triac arrangement available that could mount to the
solenoids and wire to the board directly?
Can you observe the relay contacts to see if your snubber idea is effective?
You might try something like an X rated 0.068 uF and 10 ohms in series
across the contacts. You want to suppress the high voltage from the solenoid
coil. Almost any amount will help.
What is the make of the washer? I would want to avoid it for sure.
5 volts, other?
Is there an optoisolated triac arrangement available that could mount to the
solenoids and wire to the board directly?
Can you observe the relay contacts to see if your snubber idea is effective?
You might try something like an X rated 0.068 uF and 10 ohms in series
across the contacts. You want to suppress the high voltage from the solenoid
coil. Almost any amount will help.
What is the make of the washer? I would want to avoid it for sure.
tm
Oct 3, 2012, 8:22:13āÆPM10/3/12
to
"tm" <No_on...@white-house.gov> wrote in message
news:k4ii5p$5hf$1...@dont-email.me...
continuos. Google the datasheet from TI for some additional ideas to
increase the current if needed.
http://www.ebay.com/itm/20PCSMOC3023-RANDOM-PHASE-OPTO-TRIAC-DRIVER-OUTPUT-6PIN-/260793421140?pt=LH_DefaultDomain_0&hash=item3cb87fcd54
tm
Phil Allison
Oct 3, 2012, 8:47:21āÆPM10/3/12
to
"Jon Elson"
> We have one of those $1K high efficiency washing machines. It does work,
> and
> clearly reduced our water and gas bill, so I'm not complaining.
>
> Lately, it has been getting "slow fill" errors, and I tried a bunch
> of typical stuff before finding the REAL problem. They have a bank
> of electromechanical relays to operate a bank of solenoid water valves.
> There is no arc suppression on these relays, and the cold water valve
> relay is totally shot. I have replacement relays on order, but want to
> add arc suppression to prolong the life of the relays.
>
> The coils are 120 V AC, the relays are TINY things. I ordered some
> Zener-type transient suppressors which indicate a 193 V trip voltage,
> bipolar.
the instant of opening.
The time honoured fix is a "snubber " across the relay contacts.
100nF ( class X2) and 100 ohms in series is a good start.
... Phil
Spehro Pefhany
Oct 3, 2012, 9:33:23āÆPM10/3/12
to
relays generally fail off (though I've seen them stick on very, very
rare occasion and a very badly made relay).
Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp...@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Tim Williams
Oct 3, 2012, 9:45:31āÆPM10/3/12
to
"tm" <No_on...@white-house.gov> wrote in message
news:k4ikis$h50$1...@dont-email.me...
> Here is an AC opto coup[led triac that can switch 0.1 A/ 400 volts
> continuos. Google the datasheet from TI for some additional ideas to
> increase the current if needed.
>
> http://www.ebay.com/itm/20PCSMOC3023-RANDOM-PHASE-OPTO-TRIAC-DRIVER-OUTPUT-6PIN-/260793421140?pt=LH_DefaultDomain_0&hash=item3cb87fcd54
Not sure about MOC3023 specifically but as I recall the MOCs are made
> continuos. Google the datasheet from TI for some additional ideas to
> increase the current if needed.
>
> http://www.ebay.com/itm/20PCSMOC3023-RANDOM-PHASE-OPTO-TRIAC-DRIVER-OUTPUT-6PIN-/260793421140?pt=LH_DefaultDomain_0&hash=item3cb87fcd54
specifically for driving real TRIACs, and are rated for that service ONLY.
The heavily inductive load (if this is indeed the failure mode --
remember, _it's EDMing right through entire blob-O'-metal contacts_) might
not even allow the TRIAC to turn off, ever. The solution in either case
(thrysitor SSD or mechanical) is an arc suppressor or snubber, as
mentioned elsewhere.
The reason MOS SSDs were suggested is because they turn off so slowly,
absorbing switching energy and damping transients. They have to be rated
for enough peak thermal dissipation, which unfortunately isn't normally
part of the datasheet. One would suppose the manufacturer rates them
appropriately for the load current, both continuous, turning on, and
turning off.
RC snubbers may work better than TVSs or MOVs because the latter allow any
voltage up to breakdown. A spark will start on the (mechanical) contacts
as soon as they open, growing in voltage roughly proportional to gap
length. If the arc voltage never hits TVS/MOV breakdown, it simply won't
do anything. MOVs may have some advantage because they have fairly high
capacitance.
Now, a capacitor helps greatly because it limits turn-off slew rate;
unfortunately, a cap across the contacts is a similarly bad idea at
turn-on. A series resistor yields an acceptable compromise between
turn-off peak voltage and turn-on peak current. For the solenoids in a
washer I'd be very surprised if 0.1uF / 100 ohm didn't fix things
completely. (A sudden transient would have to carry 2A to reach the same
peak voltage of 200V that a TVS might begin conducting at -- more than
enough, since solenoids can't carry more peak current than the steady
state peak current, which is fractional ampere.)
Tim
--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms
Tim Williams
Oct 3, 2012, 9:47:28āÆPM10/3/12
to
"Spehro Pefhany" <spef...@interlogDOTyou.knowwhat> wrote in message
news:fopp6856rs18f4nua...@4ax.com...
fault current on a residential 50A, 240V circuit (probably ~2kA peak).
;o)
news:fopp6856rs18f4nua...@4ax.com...
> Keep in mind that SSRs virtually always fail 'on' = flood. Mechanical
> relays generally fail off (though I've seen them stick on very, very
> rare occasion and a very badly made relay).
I once welded a 60A contactor. I guess they don't like switching into
> relays generally fail off (though I've seen them stick on very, very
> rare occasion and a very badly made relay).
fault current on a residential 50A, 240V circuit (probably ~2kA peak).
;o)
Jamie
Oct 3, 2012, 10:18:12āÆPM10/3/12
to
back draining. SSR have very little current at the control terminals,
they are so low infact, that we have to put burden resistors on them in
many cases to prevent cross talk from other control lines in the race
way from triggering them on.
THe scheme does work because we do it.. It has increased the life
contacts driving heavy loads greatly.
We use lots of 24 volt logic and in area's where we have a potential
of this happening, we place a small SSR across the contacts with a diode
and cap on the control brick, sometimes we need to have a drain R there
because it stays on too long. Which you do not want to happen, i'll burn
out the SSR if it can't handle the full load for prolong periods.
btw, they make softstart contactors with this topology in them.
Jamie
tm
Oct 3, 2012, 11:13:53āÆPM10/3/12
to
"Tim Williams" <tmor...@charter.net> wrote in message
news:k4ipko$8ef$1...@dont-email.me...
that originally. We do not know any details about the solenoid current, etc.
so yes, reviewing the datasheet for the MOC is in order. It does have
example designs for controlling a secondary triac. For fail safe, maybe put
two in series, who knows? It appears space limitations are forcing the use
of too small a relay. Using a 0.1uf with a fuseable resistor would be my
first choice plus an annual relay inspection :).
Tim Williams
Oct 3, 2012, 11:33:43āÆPM10/3/12
to
"tm" <No_on...@white-house.gov> wrote in message
news:k4iuld$ush$1...@dont-email.me...
> It appears space limitations are forcing the use of too small a relay.
> Using a 0.1uf with a fuseable resistor would be my first choice plus an
> annual relay inspection :).
The real crime is they didn't even reserve the space for basic protection
> Using a 0.1uf with a fuseable resistor would be my first choice plus an
> annual relay inspection :).
like this. I put at least some effort into ESD / overvoltage /
overcurrent protections on all connections entering and leaving my PCBs.
If nothing else, one could hack into the solenoid wires and place the
snubber there. It's low frequency energy, so it's not as big a deal if
it's *at* the switch or not.
Jon Elson
Oct 4, 2012, 1:14:04āÆAM10/4/12
to
tm wrote:
> What is the make of the washer? I would want to avoid it for sure.
Sears kenmore Oasis or Whirlpool Cabrio or Calypso. Probably a
> What is the make of the washer? I would want to avoid it for sure.
dozen more brands using the same control. All of these have a big
knob in the center of the panel to select the cycle. The later ones
have LEDs around the knob to verify the cycle selection, I think the old
ones just had a pointer on the knob.
Jon
Jon Elson
Oct 4, 2012, 1:22:19āÆAM10/4/12
to
snubber. The R is small, but the cap will be fairly big. A
TVS device will fit for sure. I think I'm going to have to retrofit
one SSR for the failed relay just to keep washing clothes until
the replacement relays come in. That will give me some time to
research the situation, and do some experiments with some
spare solenoid valves to determine the best snubber R/C if
I can find components that fit, or work with the TVS devices
to be sure they will work reliably.
Thanks,
Jon
Jon Elson
Oct 4, 2012, 1:24:39āÆAM10/4/12
to
Jamie wrote:
>
> THe scheme does work because we do it.. It has increased the life
> contacts driving heavy loads greatly.
>
Sure, for heavier loads this makes sense. But, this is probably
>
> THe scheme does work because we do it.. It has increased the life
> contacts driving heavy loads greatly.
>
a 100 mA or less solenoid, but massively inductive. A small
SSR can handle this load and produce minimal heating.
I'm also trying to do this with minimal hacking of the PCB, and
I don't have space to add extra relays.
Jon
Jasen Betts
Oct 4, 2012, 5:49:31āÆAM10/4/12
to
On 2012-10-04, Jamie <jamie_ka1lpa_not_v...@charter.net> wrote:
> You didn't absorb the post.. The diode prevents the other side from
> back draining. SSR have very little current at the control terminals,
> they are so low infact, that we have to put burden resistors on them in
> many cases to prevent cross talk from other control lines in the race
> way from triggering them on.
>
> THe scheme does work because we do it.. It has increased the life
> contacts driving heavy loads greatly.
>
> We use lots of 24 volt logic and in area's where we have a potential
> of this happening, we place a small SSR across the contacts with a diode
> and cap on the control brick, sometimes we need to have a drain R there
> because it stays on too long. Which you do not want to happen, i'll burn
> out the SSR if it can't handle the full load for prolong periods.
>
> btw, they make softstart contactors with this topology in them.
>
> Jamie
do you do this with inductive loads?
> You didn't absorb the post.. The diode prevents the other side from
> back draining. SSR have very little current at the control terminals,
> they are so low infact, that we have to put burden resistors on them in
> many cases to prevent cross talk from other control lines in the race
> way from triggering them on.
>
> THe scheme does work because we do it.. It has increased the life
> contacts driving heavy loads greatly.
>
> We use lots of 24 volt logic and in area's where we have a potential
> of this happening, we place a small SSR across the contacts with a diode
> and cap on the control brick, sometimes we need to have a drain R there
> because it stays on too long. Which you do not want to happen, i'll burn
> out the SSR if it can't handle the full load for prolong periods.
>
> btw, they make softstart contactors with this topology in them.
>
> Jamie
--
āā 100% natural
--- news://freenews.netfront.net/ - complaints: ne...@netfront.net ---
Phil Allison
Oct 4, 2012, 8:11:38āÆAM10/4/12
to
"Jon Elson"
> Phil Allison wrote:
>
>>
>> "Jon Elson"
>>
>>> We have one of those $1K high efficiency washing machines. It does work,
>>> and
>>> clearly reduced our water and gas bill, so I'm not complaining.
>>>
>>> Lately, it has been getting "slow fill" errors, and I tried a bunch
>>> of typical stuff before finding the REAL problem. They have a bank
>>> of electromechanical relays to operate a bank of solenoid water valves.
>>> There is no arc suppression on these relays, and the cold water valve
>>> relay is totally shot. I have replacement relays on order, but want to
>>> add arc suppression to prolong the life of the relays.
>>>
>>> The coils are 120 V AC, the relays are TINY things. I ordered some
>>> Zener-type transient suppressors which indicate a 193 V trip voltage,
>>> bipolar.
>>
>>
>> ** The relays are arcing because of the back emf from the solenoid coils
>> at the instant of opening.
>>
>> The time honoured fix is a "snubber " across the relay contacts.
>>
>> 100nF ( class X2) and 100 ohms in series is a good start.
>
> The problem here is I have practically no space to put a classic
> snubber.
** That is the ** LAMEST ** excuse I ever heard of !!!
>
>>
>> "Jon Elson"
>>
>>> We have one of those $1K high efficiency washing machines. It does work,
>>> and
>>> clearly reduced our water and gas bill, so I'm not complaining.
>>>
>>> Lately, it has been getting "slow fill" errors, and I tried a bunch
>>> of typical stuff before finding the REAL problem. They have a bank
>>> of electromechanical relays to operate a bank of solenoid water valves.
>>> There is no arc suppression on these relays, and the cold water valve
>>> relay is totally shot. I have replacement relays on order, but want to
>>> add arc suppression to prolong the life of the relays.
>>>
>>> The coils are 120 V AC, the relays are TINY things. I ordered some
>>> Zener-type transient suppressors which indicate a 193 V trip voltage,
>>> bipolar.
>>
>>
>> ** The relays are arcing because of the back emf from the solenoid coils
>> at the instant of opening.
>>
>> The time honoured fix is a "snubber " across the relay contacts.
>>
>> 100nF ( class X2) and 100 ohms in series is a good start.
>
> The problem here is I have practically no space to put a classic
> snubber.
YOU have a whole FUCKING washing machine available !!!!
The leads do not have to be very short - use your brain fool.
.... Phil
Jon Elson
Oct 4, 2012, 12:54:43āÆPM10/4/12
to
Phil Allison wrote:
of wire in there already, some low-level for sensors, some
400 V for VFDs to the motors. I don't want to cause an EMC
problem while fixing this. There are 12 relays on two boards
all packed in a nice plastic ventilated housing with a dozen
connectors to the rest of the machine. There are a few reasons
it would be very good to keep all the mods inside this housing.
All the electronics, valves, etc. fit in a little "console"
above and behind the top-loading lid to the washer basket.
This console also has the operators panel, with a big encoder
knob, buttons, and dozens of LEDs.
There really is NOT a lot of room left in there to add additional
parts.
I did add one Opto-22 style SSR with R/C snubber to replace the
failed relay, as it was getting worse each washer load, and
either sizzling, not making contact or working correctly at
about even chances. This works, but isn't really a permanent
solution. I found a Sharp SSR that looks like it might be able
fit the existing space, but it will be tight. So, I might
be able to fit SSRs and snubbers in fairly cleanly. Or, I
might just use the electromechanical relays with TVS
devices and be done with it for the next 15 years. Without
the snubber, the relays last about 4 years.
I opened up the bad relay and was surprised at how little
damage was visible. The contact plating was gone, exposing
blitzed base metal and some dust all over, but it really wasn't
as bad as I thought it would be.
Jon
> Jon Elson wrote:
> The problem here is I have practically no space to put a classic
> snubber.
>
> ** That is the ** LAMEST ** excuse I ever heard of !!!
>
> YOU have a whole FUCKING washing machine available !!!!
>
> The leads do not have to be very short - use your brain fool.
Thanks, as usual, flying off the handle. There is a HELL of a lot
> The problem here is I have practically no space to put a classic
> snubber.
>
> ** That is the ** LAMEST ** excuse I ever heard of !!!
>
> YOU have a whole FUCKING washing machine available !!!!
>
> The leads do not have to be very short - use your brain fool.
of wire in there already, some low-level for sensors, some
400 V for VFDs to the motors. I don't want to cause an EMC
problem while fixing this. There are 12 relays on two boards
all packed in a nice plastic ventilated housing with a dozen
connectors to the rest of the machine. There are a few reasons
it would be very good to keep all the mods inside this housing.
All the electronics, valves, etc. fit in a little "console"
above and behind the top-loading lid to the washer basket.
This console also has the operators panel, with a big encoder
knob, buttons, and dozens of LEDs.
There really is NOT a lot of room left in there to add additional
parts.
I did add one Opto-22 style SSR with R/C snubber to replace the
failed relay, as it was getting worse each washer load, and
either sizzling, not making contact or working correctly at
about even chances. This works, but isn't really a permanent
solution. I found a Sharp SSR that looks like it might be able
fit the existing space, but it will be tight. So, I might
be able to fit SSRs and snubbers in fairly cleanly. Or, I
might just use the electromechanical relays with TVS
devices and be done with it for the next 15 years. Without
the snubber, the relays last about 4 years.
I opened up the bad relay and was surprised at how little
damage was visible. The contact plating was gone, exposing
blitzed base metal and some dust all over, but it really wasn't
as bad as I thought it would be.
Jon
whit3rd
Oct 4, 2012, 5:14:52āÆPM10/4/12
to
On Wednesday, October 3, 2012 12:23:31 PM UTC-7, Jon Elson wrote:
> We have one of those $1K high efficiency washing machines.
> Lately, it has been getting "slow fill" errors.... They have a bank
> We have one of those $1K high efficiency washing machines.
> of electromechanical relays to operate a bank of solenoid water valves.
> There is no arc suppression on these relays, and the cold water valve
> relay is totally shot.
I'd try the manufacturer's replacement part first; it could just have been
> There is no arc suppression on these relays, and the cold water valve
> relay is totally shot.
a weak spring or some stuck-half-on that caused arcing.
If the relay ratings can be read, you might consider the gas-filled
sealed relays (like, around here, used to be surplused from the aircraft
manufactory...). They're very reliable, and it's hard to find one that
isn't an improvement to the civilian washing machine parts I've autopsied.
Pressurized gas suppresses arcs quite effectively.
Jamie
Oct 4, 2012, 5:53:56āÆPM10/4/12
to
At one time you used to be able to get add on soft start SSR's where you
connect the relay coil to a terminal dedicated for it. This was to
insure the SSR was on (zero crossing) before the coil itself got
energized. The turn off did the opposite.. The control off voltage would
turn off the relay coil and wait for the contacts to open before it was
turned off.
We used to burn up relays every 6 months on a pick of equipment due
to the large inductive response the contacts were wire too. This got cycled
a lot and a modification was done to stop the arcing. Due to the amp
load that is there, the relay still needs to be replaced but it now last
at least 5 years or so.
Jamie
Jon Elson
Oct 4, 2012, 11:16:19āÆPM10/4/12
to
whit3rd wrote:
> I'd try the manufacturer's replacement part first; it could just have been
> a weak spring or some stuck-half-on that caused arcing.
>
> If the relay ratings can be read, you might consider the gas-filled
> sealed relays (like, around here, used to be surplused from the aircraft
> manufactory...). They're very reliable, and it's hard to find one that
> isn't an improvement to the civilian washing machine parts I've autopsied.
Very unlikely to find a 12 V 16 mA coil aircraft relay that will
> I'd try the manufacturer's replacement part first; it could just have been
> a weak spring or some stuck-half-on that caused arcing.
>
> If the relay ratings can be read, you might consider the gas-filled
> sealed relays (like, around here, used to be surplused from the aircraft
> manufactory...). They're very reliable, and it's hard to find one that
> isn't an improvement to the civilian washing machine parts I've autopsied.
also fit the spot available. I may have found a really small SSR
that will fit, but require some fooling around with the leads to
fit the board.
Jon
Phil Allison
Oct 4, 2012, 11:29:59āÆPM10/4/12
to
"Jon Elson"
> Phil Allison wrote:
>> Jon Elson wrote:
>> The problem here is I have practically no space to put a classic
>> snubber.
>
>>
>> ** That is the ** LAMEST ** excuse I ever heard of !!!
>>
>> YOU have a whole FUCKING washing machine available !!!!
>>
>> The leads do not have to be very short - use your brain fool.
>
> Thanks, as usual, flying off the handle.
** As usual, when confronted by a obvious nut case & damn LIAR.
>> Jon Elson wrote:
>> The problem here is I have practically no space to put a classic
>> snubber.
>
>>
>> ** That is the ** LAMEST ** excuse I ever heard of !!!
>>
>> YOU have a whole FUCKING washing machine available !!!!
>>
>> The leads do not have to be very short - use your brain fool.
>
> Thanks, as usual, flying off the handle.
> There is a HELL of a lot
> of wire in there already, some low-level for sensors, some
> 400 V for VFDs to the motors. I don't want to cause an EMC
> problem while fixing this.
You re so full of BULLSHIT.
PISS OFF !!!
josephkk
Oct 6, 2012, 3:11:33āÆAM10/6/12
to
On Wed, 03 Oct 2012 16:05:28 -0400, Spehro Pefhany
<spef...@interlogDOTyou.knowwhat> wrote:
>On Wed, 03 Oct 2012 14:32:02 -0500, Jon Elson <jme...@wustl.edu>
>wrote:
>
>help in interpreting the data?
>
>Here's a typical TVS data sheet:
>
>http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000720.pdf
>
>
>Take, for example, the P6KE220CA.
>
>No more than 500nA at 188V
>At 1mA nominally 220V, but no less than 209V or more than 231V
>
>At 1.85A (surely beyond your required clamping current) no more than
>328V. At 10.3A, no more than 388V.
>
>It's a bipolar device, so the ratings apply for either polarity of
>applied voltage.
>
>You could also try one of these, which you may have parts for in your
>junk box:
>http://www.digikey.ca/product-detail/en/104M06QC100/338-2581-ND/2503688
>
>Those built-up ones are stupid expensive, you can just try a 630V
>0.1uF film cap series with a 1/2W 100R resistor for < 1/10 the cost.
>
Oh yeah. Proper snubbers work great.
<spef...@interlogDOTyou.knowwhat> wrote:
>On Wed, 03 Oct 2012 14:32:02 -0500, Jon Elson <jme...@wustl.edu>
>wrote:
>
>>We have one of those $1K high efficiency washing machines. It does work, and
>>clearly reduced our water and gas bill, so I'm not complaining.
>>
>>Lately, it has been getting "slow fill" errors, and I tried a bunch
>>of typical stuff before finding the REAL problem. They have a bank
>>clearly reduced our water and gas bill, so I'm not complaining.
>>
>>Lately, it has been getting "slow fill" errors, and I tried a bunch
>>of electromechanical relays to operate a bank of solenoid water valves.
>>There is no arc suppression on these relays, and the cold water valve
>>There is no arc suppression on these relays, and the cold water valve
>>relay is totally shot. I have replacement relays on order, but want to
>>add arc suppression to prolong the life of the relays.
>>
>>The coils are 120 V AC, the relays are TINY things. I ordered some
>>Zener-type transient suppressors which indicate a 193 V trip voltage,
>>bipolar.
>>add arc suppression to prolong the life of the relays.
>>
>>The coils are 120 V AC, the relays are TINY things. I ordered some
>>Zener-type transient suppressors which indicate a 193 V trip voltage,
>>bipolar.
>>I'm not clear about whether this is the level at which all units will
>>start to conduct or the level at which none will conduct.
>
>You ordered parts without looking at the data sheets? Or do you need
>>start to conduct or the level at which none will conduct.
>
>help in interpreting the data?
>
>Here's a typical TVS data sheet:
>
>http://www.st.com/internet/com/TECHNICAL_RESOURCES/TECHNICAL_LITERATURE/DATASHEET/CD00000720.pdf
>
>
>Take, for example, the P6KE220CA.
>
>No more than 500nA at 188V
>At 1mA nominally 220V, but no less than 209V or more than 231V
>
>At 1.85A (surely beyond your required clamping current) no more than
>328V. At 10.3A, no more than 388V.
>
>It's a bipolar device, so the ratings apply for either polarity of
>applied voltage.
>>
>>Also, would it be better to put the suppressor across the relay contacts
>>or across the valve solenoid?
>
>I'd put it across the solenoid coil.
>>Also, would it be better to put the suppressor across the relay contacts
>>or across the valve solenoid?
>
>
>You could also try one of these, which you may have parts for in your
>junk box:
>http://www.digikey.ca/product-detail/en/104M06QC100/338-2581-ND/2503688
>
>Those built-up ones are stupid expensive, you can just try a 630V
>0.1uF film cap series with a 1/2W 100R resistor for < 1/10 the cost.
>
Oh yeah. Proper snubbers work great.
bloggs.fred...@gmail.com
Oct 6, 2012, 8:02:29āÆAM10/6/12
to
On Wednesday, October 3, 2012 3:23:31 PM UTC-4, Jon Elson wrote:
> We have one of those $1K high efficiency washing machines. It does work, and
>
> clearly reduced our water and gas bill, so I'm not complaining.
>
>
>
> Lately, it has been getting "slow fill" errors, and I tried a bunch
>
> of typical stuff before finding the REAL problem. They have a bank
>
> of electromechanical relays to operate a bank of solenoid water valves.
>
> There is no arc suppression on these relays, and the cold water valve
>
> relay is totally shot. I have replacement relays on order, but want to
>
> add arc suppression to prolong the life of the relays.
>
A "bank" of valves and relays? Usually there are just two, one for cold water and one for hot water, not anything complex. You may actually reduce contact life with the addition of arc suppression. The relay contact materials and operating characteristics such as contact pressure, overtravel, and release geometry have been optimized for the weakly inductive solenoid valve type of loading and any modification will most likely reduce contact life. The solenoid loading should only be a few milliamps.
> We have one of those $1K high efficiency washing machines. It does work, and
>
> clearly reduced our water and gas bill, so I'm not complaining.
>
>
>
> Lately, it has been getting "slow fill" errors, and I tried a bunch
>
> of typical stuff before finding the REAL problem. They have a bank
>
> of electromechanical relays to operate a bank of solenoid water valves.
>
> There is no arc suppression on these relays, and the cold water valve
>
> relay is totally shot. I have replacement relays on order, but want to
>
> add arc suppression to prolong the life of the relays.
>
Mike Perkins
Oct 6, 2012, 8:05:41āÆAM10/6/12
to
contact life not reduce it?
--
Mike Perkins
Video Solutions Ltd
www.videosolutions.ltd.uk
Phil Allison
Oct 6, 2012, 8:16:02āÆAM10/6/12
to
"Mike Perkins"
You may actually reduce contact life with the addition of arc suppression.
The relay contact materials and operating characteristics such as contact
pressure, overtravel, and release geometry have been optimized for the
weakly inductive solenoid valve type of loading and any modification will
most likely reduce contact life.
" There is no arc suppression on these relays, and the cold water valve
relay is totally shot."
** Time for a reality check - sunshine.
relay is totally shot."
And your mindless hypothesising is UTTER CRAP.
Fuck off.
.... Phil
bloggs.fred...@gmail.com
Oct 6, 2012, 9:06:14āÆAM10/6/12
to
Jon Elson
Oct 8, 2012, 4:37:21āÆPM10/8/12
to
bloggs.fred...@gmail.com wrote:
> A "bank" of valves and relays? Usually there are just two, one for cold
> water and one for hot water, not anything complex. You may actually reduce
> contact life with the addition of arc suppression. The relay contact
> materials and operating characteristics such as contact pressure,
> overtravel, and release geometry have been optimized for the weakly
> inductive solenoid valve type of loading and any modification will most
> likely reduce contact life. The solenoid loading should only be a few
> milliamps.
Nope, it has 2 valves for cold and hot water, feeding into a manifold.
> A "bank" of valves and relays? Usually there are just two, one for cold
> water and one for hot water, not anything complex. You may actually reduce
> contact life with the addition of arc suppression. The relay contact
> materials and operating characteristics such as contact pressure,
> overtravel, and release geometry have been optimized for the weakly
> inductive solenoid valve type of loading and any modification will most
> likely reduce contact life. The solenoid loading should only be a few
> milliamps.
Then, there are 4 more, that send the water straight to the basket,
or to the detergent tank, the bleach tank or the softener tank, so these
solutions are added at the right time in the cycle. Yeah, way too
complicated for sure. I think there may be a couple more valves
down in the bowels of the machine to switch the pump lines around
(maybe not). Also, there's a door lock solenoid.
There are also relays for the water heater and the circulate and drain
pumps. So, a hell of a lot of relays in there. Also an IRAMS
module for the direct drive basket motor.
I can't imagine a properly designed arc suppressor making things
worse, this machine is only FOUR years old. If I didn't know how to
fix this, it would be $275 for the entire module plus a service call
every 4 years, that would be about $500 I guess. Quite a racket
Whirlpool has here!
Jon
Jon Elson
Oct 8, 2012, 4:46:20āÆPM10/8/12
to
bloggs.fred...@gmail.com wrote:
> Yes, I am sure. If you have ever read some of the research on relay design
> for the various applications, you would know it is quite sophisticated and
> empirical. You get different patterns of contact mass transfer dependent
> upon the type of load characteristics such as inductive versus resistive
> and inrush. There are design configurations where an unsuppressed
> inductive load results in longer relay life.
OK, I looked up the specific relay by part number, and the data sheet
> Yes, I am sure. If you have ever read some of the research on relay design
> for the various applications, you would know it is quite sophisticated and
> empirical. You get different patterns of contact mass transfer dependent
> upon the type of load characteristics such as inductive versus resistive
> and inrush. There are design configurations where an unsuppressed
> inductive load results in longer relay life.
does not even GIVE a rating for inductive load, they only give a resistive
load rating! Amazing! Who designs this crap? I'll bet they torture
tested it and knew it would last past the warranty, and who cares beyond
that? Looking on fixya and similar web sites, it seems this failure is a
VERY common problem on the washers using this control module. One user
reported it started this failure mode withing a couple weeks of purchase.
Jon
bloggs.fred...@gmail.com
Oct 9, 2012, 10:22:38āÆAM10/9/12
to jme...@wustl.edu
bloggs.fred...@gmail.com
Oct 9, 2012, 10:28:32āÆAM10/9/12
to jme...@wustl.edu
0 new messages