[GMCnet] Auto transfer switch

[tonka6cuda6--- via Gmclist]

So im getting ready to install a new converter and fuse block to replace the old buzz box thats croaking.....should i put in an auto transfer switch
at the same time?

Ive also noticed that if you have dual a/c things are wired different ....i do not have dual a/c yet but i think thats going to be done as i have a
line on 2 units for the price pf one....so what do i need to do or do i need to do when it comes to the transfer switch and the dual a/c install.
--
Rich Mondor,

Brockville, ON

77 Hughes 2600

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[Richard Denney via Gmclist]

I didn’t install a transfer switch until many years after major wiring
updates. It’s not necessary by any means, and moving the plug is solidly
reliable.

But now that I have it, I love it. The main advantage is that it does not
switch the circuits until the generator has produced stable power for 30
seconds or so. My cheap Generac generator is MUCH happier with that
feature.

Rick “leaving the dual AC question for others” Denney

--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com

[John R. Lebetski via Gmclist]

Bob Stone has a full parts list to convert a TT30 or 14-50 to "either or" breaker type. Manual flip rather than Auto which I would prefer.
--
John Lebetski
Woodstock, IL
77 Eleganza II

[Mike Hamm via Gmclist]

I didn't use a transfer switch.
Easy to just use the plug.

My converter/inverter is on one breaker and most outlets run off the inverter.
The roof AC's and water heater each have there own breaker. The refer and outdoor plug are on one also.
--
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts

[tonka6cuda6--- via Gmclist]

Im just thinking if i want to start the generator while driving....

--
Rich Mondor,

Brockville, ON

77 Hughes 2600

[Charles Boyd via Gmclist]

P&S 1228 dp dt center off 30 amp.

http://www.gmcmhphotos.com/photos/crestmont/p35377-new-transfer-switch.html

[/url]

--
C. Boyd
76 Crestmont
East Tennessee

[Mike Hamm via Gmclist]

I plug the gen in when i disconnect the shore power,

--
1977 Kingsley 455 as stock as it gets except lots of Ragusa parts

[tonka6cuda6--- via Gmclist]

mghamms wrote on Sun, 15 September 2019 16:21

> I plug the gen in when i disconnect the shore power,

Manual transfer switch....guesd that works too....lol.

--
Rich Mondor,

Brockville, ON

77 Hughes 2600

[P. O. Schmidt via Gmclist]

That's why the cable is always connected to the generator when not connected to shore power

--
Regards

P O Schmidt

[James Hupy via Gmclist]

When I converted my Royale from twin bunks and hanging bunks above them to
a full size bed that goes from side to side, I covered up the access to the
toggle breakers as well as the 12 volt fuse board and the old BUZZ BOX
battery destroyer.
So, I pulled out the buzz box and replaced it with a Progressive
Dynamics smart converter. That only left me with the problem of switching
the toggle breakers when going from the shore power cord to the 6000 watt
Onan. So, I installed an automatic transfer switch. It is wired so it
defaults to the generator whether the shore cord is plugged in or not.
Works great, it also has a timed delay to allow for the generator power to
stabilize. Sure beats crawling under the bed and switching breakers.
Jim Hupy
Salem, Oregon

On Sun, Sep 15, 2019, 1:22 PM Mike Hamm via Gmclist <gmc...@list.gmcnet.org>
wrote:

[Johnny Bridges via Gmclist]

I've had both an auto switch and a socket in the electric bay. I will not put in another transfer switch. The socket is passive, gives little or no
trouble, and it's (very infrequent) failure mode I've probably worked with and on a hudred or more (fairly high power) transfer switches. A
reliable one with useful control is expensive. A relay based one which transfers under load will eventually fail. If it fails with a contact fused
you're headed for trouble.
All it gains you is the ability to not walk outside and move the power cord from the pedistal to the plughole. Since you usually know the power
situation where you're stopping, you can set it before leaving or on the way.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[James Hupy via Gmclist]

The Royale power cord does not go into a compartment where you can manually
unplug it and plug in the Generator.
I agree that the manual method of plugging and unplugging is ALMOST
idiot proof. Just remember, we always seem to come up with a different
variety of idiot. (grin)
Jim Hupy
Salem, Oregon

[Mark Sawyer via Gmclist]

I like the convenience of the automatic switch... If you get one and it is mounted in the cabinet inside the coach, you may want to look into one
that uses DC powered relays... From what I'd read, the AC powered ones can hum, which would be annoying if you have it in the living area (vs in the
"basement" like they are on a lot of SOBs....)

For what it's worth, my coach came with the Parallax switch.. It did not hum and seemed well made, but the switching was always somewhat noisy, and
in the end, one of the relays froze up and I had to replace it as Parallax said they would not do repairs on out of warranty switches. I ended up
going with the below switch... While the cabinet on it is plastic instead of metal like the Parallax, the switches are dead quiet even when they are
switching over from one source to another... And the plastic cabinet is adequate on my installation as again, it is inside the coach in a cabinet...

http://www.bestconverter.com/Boondocker-50-Amp-Transfer-Switch-BD-ATS50-The-quiet-one_p_437.html#.XYDxKjZKiBY

I'd originally planned to replace my Parallax with a more expensive switch, but the seller ended up being out of the model I'd chosen, and he called
me up and pitched me on the Boondocker and I took a chance... Seller said he'd stand behind it if I was not happy... So far it's been great. No
regrets and the money saved is always a good thing...


--
Mark S. '73 Painted Desert,
Manny 1 Ton Front End,
Howell Injection,
Leigh Harrison 4bag and Rear Brakes,
Fort Worth, TX

[Johnny Bridges via Gmclist]

I'd have to have a look at the contactor(s) and interlock(s) before I'd use it. Harris used to use a large and unreliable contactor in their
transmitters to reduce the start surge current. It was a common failure item and failure led to grief and a couple of fairly expensive resistors when
it stuck.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Johnny Bridges via Gmclist]

If the coach didn't come with a socket for the genset, use a three way 'air gap' disconnect.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Larry via Gmclist]

Fourteen years ago when I rewired my coach, I also put in a 50 Amp Transfer Switch BD ATS50. I didn't have enough room below the closet for both
entrance panel and the ATS, so I took the electronics out of the ATS panel, moved things around in the entrance panel and put the ATS electronics in
the entrance panel with the breakers. The transfer has a 30 second delay that you have to get use to, but has worked flawlessly for 14yrs. That being
said, it will probably give me trouble on this weekend outing :roll: JFWIW
--
Larry
78 Royale w/500 Caddy
Menomonie, WI.

[Mark via Gmclist]

My Royale has a new genset (Onan Emerald Plus 6500) in the bay, which runs to a female 50A plug that the "shore power" cord plugs into. That was fine
and (to me) preferable to complicating the system.

That was fine until I installed an inverter, and really wanted to make sure that it didn't get into a fight with my generator or shore power (it would
lose either way). ;) So I put in a 50A 3-pole contactor. I wired it to energize with shore power, but think I might swap that out since it's on
shore power 99.99% of the time (no need to have a hot contactor under the rear bed). Simple enough, cheap enough, and WAY easier than a 3-way
autoswitch.
--
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen

[Larry Davick via Gmclist]

It looks as if my beloved PO installed a Trans-Tech 30 amp Gen Switch. When I plug in to shore power I hear a beep from inside the coach. Might be
the switch, it might be a shocked mouse. I've never seen the manual plug-here-not-there setup. Thank you, PO. Of course he also installed their
"Power Guard" that I think is some kind of delay. It's decommissioned as the delay seems to be set to "later."
--
Larry Davick
A Mystery Machine
1976(ish) Palm Beach
Fremont, Ca
Howell EFI + EBL + Electronic Dizzy

[Russell Keith via Gmclist]

Rich,
Go for it with the automatic transfer switch. You'll be glad you did.

I don't know about your 2 A/C question.

Safe Travels,
Russell
--
Russell Keith,
1978 E2 "Harry" 403 (still carbureted), Danny Dunn Tranny, Thorley, Stock Brakes w/Remote Vacuum Brake Booster, Quad Bags, Dakota Digital Dash, 6.5 kW
Onan, Dunedin, Florida

[Tyler via Gmclist]

Your signature says "Hughes" which means I have no direct experience. However, just as a point of reference the GMC upfit coach runs both ACs anytime
- on generator or shore power with a OEM 50 amp cord. My Royale runs only the center AC on a 30 amp shore power cord, but will run both on the
generator (with an additional from Coachmen fuse box). So would recommend you keep discovering your existing situation or have an expert decipher it.
If you look on BDUBs gmc site for manuals, you can get the Coachmen electric wiring diagrams and see if they tell you anything helpful.

Yet another solution I have seen is leave the main AC wired in a typical fashion, and the second (usually rear) air hard wired to a 20 amp plug that
is plugged into a shore power connection when both a 30 amp and a 20 amp are available on the same pole. Someone else can comment if that actually
provides two sources of power, but I'm just saying it has been done that way.


--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC

[tonka6cuda6--- via Gmclist]

Tilerpep wrote on Tue, 17 September 2019 20:27

> Your signature says "Hughes" which means I have no direct experience. However, just as a point of reference the GMC upfit coach runs both ACs
> anytime - on generator or shore power with a OEM 50 amp cord. My Royale runs only the center AC on a 30 amp shore power cord, but will run both on
> the generator (with an additional from Coachmen fuse box). So would recommend you keep discovering your existing situation or have an expert
> decipher it. If you look on BDUBs gmc site for manuals, you can get the Coachmen electric wiring diagrams and see if they tell you anything
> helpful.
>
> Yet another solution I have seen is leave the main AC wired in a typical fashion, and the second (usually rear) air hard wired to a 20 amp plug
> that is plugged into a shore power connection when both a 30 amp and a 20 amp are available on the same pole. Someone else can comment if that
> actually provides two sources of power, but I'm just saying it has been done that way.

Yah i have Coachmen and Avion schematics which help but not the Hughes..... so i just try to piece it all together. I think both a/c units will work
off the 30amp source (if i go that route) though npt that i think id run them both at the same time....lol.

--
Rich Mondor,

Brockville, ON

77 Hughes 2600

[Johnny Bridges via Gmclist]

The 30 second (overkill) delay in some of the auto transfer switches is a low cost way to keep from having the AC essentially look at itself until the
magnetic field in transformers and/or motors dies down. If the peak waveform of one source sees the peak of the other it may cause enough current to
drop a breaker or open a fuse. (In high power setups it certainly will). It probably isn't necessary in the GMC unless the A/C is running and
doesn't reset the compressor timer. Half a second is plenty. If you have a simple relay and the A/C breaker pops when you swap, that's why. Ask me
how I know thism :)

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[John Wright via Gmclist]

I don’t agree your comments on Transfer switches and RV AC units.

I have had transfer switches on all three of the coaches that I own or have owned. I installed 2 myself and one was already installed on the stretch coach. The transfer switches only have the time delay when they go from shore power to generator power. The 30 second delay is to allow the generator to come up to speed. There is no delay when switching from back to shore power. When I shut my generator off the switch to shore power is almost instantaneous, the power will have a small blip. If your generator is running and your shore power comes back the generator still powers the coach, it doesn’t switch back to shore power.

Now lets discuss AC units. All RV AC units have a time delay relay, typically a 2 minute delay. This is to allow the pressures to equalize in the freon side of the system so the compressor does not start under load and possibly cause the AC breaker to open. It has nothing to do with the transfer switch. If by chance you have a power blip at your campsite and the power just goes off and then back on then the AC unit will not start cooling until the time delay relay times out, only the fan runs. Now if you turn on the AC unit the compressor will start or if you have the AC in Heat ( if it has a heat strip ) or just in FAN mode, it will start with no time delay.

In a sense the transfer switch and AC time delay relay work together to help both the generator and AC unit.

As alway comments are welcome.

J.R. Wright
GMC Great Laker MHC
GMCGL Tech Editor
GMC Eastern States Charter Member
GMCMI
78 GMC Buskirk 29.5’ Stretch
75 GMC Avion (Under Reconstruction)
Michigan

> On Sep 18, 2019, at 9:03 AM, Johnny Bridges via Gmclist <gmc...@list.gmcnet.org> wrote:
>
> The 30 second (overkill) delay in some of the auto transfer switches is a low cost way to keep from having the AC essentially look at itself until the
> magnetic field in transformers and/or motors dies down. If the peak waveform of one source sees the peak of the other it may cause enough current to
> drop a breaker or open a fuse. (In high power setups it certainly will). It probably isn't necessary in the GMC unless the A/C is running and
> doesn't reset the compressor timer. Half a second is plenty. If you have a simple relay and the A/C breaker pops when you swap, that's why. Ask me
> how I know thism :)
>
> --johnny

[Johnny Bridges via Gmclist]

We differ on a couple of points. What's the minimum disruption your A/C will recognize as a power drop? What's the minimum time for your source
relay to pull in? If the second is lower than the first and if the two sources are out of phase, you'll take a breaker or fuse down. Realize, transfer
is not a problem, in that you're leaving a dead source. Retransfer however can bite you since you're switching between two live sources and don't
know the phase relationship between them.
Back in The Day the gensets had 'parallelling' lights, simply lights connected across the A phase of both sources. Throw the switch when the lights
go out. To automate this we hung a relay across the lights and let it inhibit the transfer switch motor when it was energized. This got the transfer
to within 30 degrees or so of equal which didn't hurt anything. The option was/is a trip to the plant, usually in a storm.

--johnny
--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Richard Denney via Gmclist]

But that isn’t the reason for the 30-second delay. The transfer switch
doesn’t turn shore power off, delay for 30 seconds, and then connect to the
genset. It waits 30 seconds, and then switches the relays/contactors
directly from shore power to genset, just as it switches the reverse
directly when the genset is turned off.

If the relay switching time isn’t enough to handle the phase relationship,
oh well. It’s wise to shut off the air conditioner before switching between
two live loads.

The delay is there to let the engine on the genset stabilize before
imposing a load.

Rick “fulfilling a different requirement” Denney

On Wed, Sep 18, 2019 at 2:04 PM Johnny Bridges via Gmclist <
gmc...@list.gmcnet.org> wrote:

> We differ on a couple of points. What's the minimum disruption your A/C
> will recognize as a power drop? What's the minimum time for your source
> relay to pull in? If the second is lower than the first and if the two
> sources are out of phase, you'll take a breaker or fuse down. Realize,
> transfer
> is not a problem, in that you're leaving a dead source. Retransfer
> however can bite you since you're switching between two live sources and
> don't
> know the phase relationship between them.
> Back in The Day the gensets had 'parallelling' lights, simply lights
> connected across the A phase of both sources. Throw the switch when the
> lights
> go out. To automate this we hung a relay across the lights and let it
> inhibit the transfer switch motor when it was energized. This got the
> transfer
> to within 30 degrees or so of equal which didn't hurt anything. The
> option was/is a trip to the plant, usually in a storm.
>

--
'73 X-Glacier 230 "Jaws"
Northern Virginia
Offlist email: rick at rickdenney dot com

[Johnny Bridges via Gmclist]

I understand the delay for the set to spool up.. we got hospital spec because most transmitters will restart in ten seconds without going through the
start sequence again. If it misses, you might take half a minute to get it cooking again. 30 seconds of dead air in a top ten market was death,
research showed the average listener would tolerate ten to twenty five seconds of silence maximum.
Any more, with transistor radios, the start sequence is much shorter so it isn't the problem it could be. All you want is to have the sources in
phase when you swap back from hot to hot. Given the modern switches we had towards the last, it wasn't a problem and alls you got was a hell of a
BANG and the lights blinked slightly. Hook it out of phase and the breaker on the transmitter and probably the AC point at the floor instantly.
That being said, the dynamics of the profession have changed along with the changes in the Industry. It's the same on a smaller scale here. If you
turn the coach A/C off, as someone noted, you pretty much preclude the problem. I could take the time to turn it off, or I can take the same time to
swap an air gap switch. Cheapskate that I am, I'd do the latter.
My perspective is admittedly somewhat different.

--johnny

--
Foolish Carriage, 76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
I forgive them all, save those who hurt the dogs. They must answer to me in hell

[Ken Henderson via Gmclist]

I'm slightly baffled by this thread's discussion. I've had the transfer
relay in my X-Birchaven since at least 1999. I doubt that it's switched
between two live sources 3 times during those 20+ years.
Ken H.
Americus, GA
'76 X-Birchaven w/Cad500/Howell EFI & EBL,
Manny Brakes & 1-Ton, Troy-Bilt APU, etc., etc., etc.
www.gmcwipersetc.com

[Mark via Gmclist]

Ken Henderson wrote on Wed, 18 September 2019 15:45

> I'm slightly baffled by this thread's discussion. I've had the transfer
> relay in my X-Birchaven since at least 1999. I doubt that it's switched
> between two live sources 3 times during those 20+ years.
> Ken H.
> Americus, GA

That's my thinking as well. I really can't imagine a scenario where it's really important to do an instantaneous switchover. Yes, you might have to
wait for the A/C units to spool back up, but in the five or so years I've been using my coach, it's never, ever been an issue to disconnect
momentarily when changing from shore to generator (or back).

--
Mark Hickey
Mesa, AZ
1978 Royale Center Kitchen