Receiver/relay box for central heating dead?

[JoeJoe]

I have had a Honeywell CM927 Wireless Thermostat operating the heating
boiler without a problem for the last ~8 years.

This morning, after trying to turn the heating on - it is quite cold
outside, so I thought it a good time to see that everything works - the
heating would not start...

I set the target temperature on the thermostat to very high (25c, room
temp is <20c). The green light on the relay box comes on as it should,
but then turns itself off within a few seconds/minutes for no apparent
reason. Pressing the Manual Override button on the relay box causes it
to turn on, but again, it turn itself off almost immediately.

On closer inspection it appears that:

- The boiler is in order
- The thermostat itself work as it should: communicates with the relay
box, sends a signal to turn the heating on, etc

I therefore suspect the BDR91 relay box is the culprit.

Am I on the right track?

[Muddymike]

If its the same as my sons remove the receiver from the back plate then link
terminals A and B together on the back plate. If the boiler lights, the
problem is in the receiver.

Mike

[JoeJoe]

> If its the same as my sons remove the receiver from the back plate then link
> terminals A and B together on the back plate. If the boiler lights, the
> problem is in the receiver.
>
> Mike

Thanks a lot!

Done that and the boiler lights, so a new receive is on order.

[John Rumm]

I recall seeing similar problems with a programmer that could only keep
its relay energised for a few seconds.

On that one it had a very crude PSUs - basically the circuit hanging off
the mains via a dropper circuit and a bit rectification and smoothing.
The small(ish) smoothing cap was to blame. Swapping it for a new
electrolytic fixed it.

--
Cheers,

John.

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[Graham.]

On Fri, 28 Aug 2015 16:41:21 +0100, John Rumm
<see.my.s...@nowhere.null> wrote:

>On 28/08/2015 12:09, JoeJoe wrote:
>>
>>> If its the same as my sons remove the receiver from the back plate then link
>>> terminals A and B together on the back plate. If the boiler lights, the
>>> problem is in the receiver.
>>>
>>> Mike
>>
>> Thanks a lot!
>>
>> Done that and the boiler lights, so a new receive is on order.
>
>I recall seeing similar problems with a programmer that could only keep
>its relay energised for a few seconds.
>
>On that one it had a very crude PSUs - basically the circuit hanging off
>the mains via a dropper circuit and a bit rectification and smoothing.
>The small(ish) smoothing cap was to blame. Swapping it for a new
>electrolytic fixed it.

I was going to suggest a visual check for bulging caps.

On a different point I wonder if many wireless thermostats send the
current status to the receiver at intervals?
My "Celect" does not, so when it is no longer calling for heat, if,
due to interference etc, the receiver does not decode the "OFF"
command the heating could be on all night.

Worse still, on a couple of occasions it has spontaneously been
commanded "ON" when the room stat has been in frost protection mode,
this is in the middle of summer. I must change the dip switch settings
when I get round tuit.

--

Graham.

%Profound_observation%

[David]

I might have a receiver coming free shortly.

The display on my CM927 has partially died, so (as advised from this NG) I
am about to replace it with a Plumb{something} own badged older version.

If it all goes well then you are welcome to the receiver for the cost of
postage (can nominate a charity if you are feeling a few pounds more
generous).

Depends, of course, on getting the other thermostat working.

I suspect you may have to struggle to get just the receiver - I only found
complete systems when looking for the thermostat part.

Cheers

Dave R


--
Windows 8.1 on PCSpecialist box

[JoeJoe]

Ordered the receiver unit online at 11:30 yesterday, arrived at 8:30
this morning (seller in London, I'm in Scotland). all was working again
by 8:45 ;-)

Thanks again for the advice.

PS: tried some local plumbing/heating large suppliers earlier yesterday
- prices ranged from £85 to £105 (PlumbCentre), but none had it in
stock. I paid £40 (inc delivery), and was happy to be reminded why I try
to avoid those places at all cost - quote 3x the price, and then start
with the "lets see what I can do just for you, just today, etc...

[JoeJoe]

Thanks a lot for the kind offer, but just bought and installed a new one.

I found that the key to finding the receiver on offer is to know the
part number, and then Google is really your friend.

Thanks again anyway.