I have a faulty Honeywell 921 thermostat..

qwertyui1 · 27 Aug 2015

The screen keeps going blank. I have looked on martinsmoneymatters site and seen this is a known fault.

Honeywell are of no help as I do not have a receipt for it. I need to get a replacement, should I get the same (knowing there's a fault) as they may be easier? Do I just buy the thermostat part, will it automatically connect to the receiver wired to the boiler?
Can I buy another type of thermostat if so do I need a new receiver as well?
Any advise would be grateful.

P.s I have a worcester bosh junior boiler

Many thanks

Dan Robinson · 27 Aug 2015

qwertyui1 said:
I have a worcester bosh junior boiler

Then the stat is the least of your worries

A base unit will need binding, unless it comes with a receiver, in which case just swap the heads.

qwertyui1 · 27 Aug 2015

ok so could you traslate for me please into woman-speak

Base unit = thermostatic control unit?
Binding = twinning via wireless?
Heads = haven't a clue on this??

mogget · 27 Aug 2015

I'm not that familiar with Honeywell, Dan is, and he knows far more about it than I do. But I'll have a go.

The thermostat and receiver (relay box) need to be bound (paired), this is so that the receiver only recognises your thermostat and not next door's. Instructions will be in the installation manual.

When you buy the thermostat and receiver (relay box) together they should be pre-bound so you don't need to re-bind as you would when changing just the thermostat on its own.

The receiver mounts to a backplate which is screwed to the wall. This doesn't need changing only the box with the electronics in (the head, ie the receiver itself).

qwertyui1 · 27 Aug 2015

Thank you Mogget that makes sense to me but......Can a new thermostat be bound to the old receiver? And what's the best thermostat to go for if I was going to replace both parts....Would it be be possible to replace any make of thermostat to work with my old head? And is it something I could do or is ithere electric to be considered in the relay box?........Soooh many questions!!!

mogget · 27 Aug 2015

Yes there is mains electric in the relay box although the actual wiring is quite standard.

You need a compatible thermostat and receiver, which in practice means same make.

Yes if you were going to buy a new 921 then you could bind it with the existing receiver.

Honeywell are generally reckoned to be the most reliable in the industry, other makes have their own problems eg displays going upside down on Drayton mistats.

It sounds like you just got a bad one. Tbh I'd replace it with another 921 (I assume the 927 is compatible with the same relay box) and re-bind to save altering the mains wiring if you're not confident with 240v.

Cue discussion about whether the mains is really 240v or not, this being DIYnot

qwertyui1 · 27 Aug 2015

Thank you so much Mogget....you have explained this really well for me. Looks like I'm shopping for just a new 921 then

Dan Robinson · 28 Aug 2015

If you by the thermostat on its own it will need binding (30 second job and in the instructions). If you by a complete set you can unclip the business side of the receiver from the back plate and out the prebound receiver on with no wiring or binding.

Agile · 28 Aug 2015

This may help others.

How do you manage to get a thermostat reasonably recently without a receipt for it to operate the warranty?

Tony

Dan Robinson · 28 Aug 2015

The cm9 range had been around a fair while Tony.... They can tell from the date code on the back whether it was from the known batch of dodgy screens rather than a more vanilla failure.

OP, have you tried removing the battery and forcing the retaining spring out some more so the batteries are held a bit more firmly?

Agile · 28 Aug 2015

Yes, Dan but the lady was talking as if she thought that it was still covered by a warranty and that Honeywell were refusing because of no receipt.

Even so, the initial claim should legally by against the last retail seller.

Tony

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I have a faulty Honeywell 921 thermostat..

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