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Tim JA
Tim JA, HVAC Technician
Category: HVAC
Satisfied Customers: 2616
Experience:  Owner at Self-employed
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I seem to have lost power to my thermostat all of a sudden,

Customer Question

Hi I seem to have lost power to my thermostat all of a sudden
JA: What's the brand and model of your thermostat? How old is it?
Customer: it is a horstmann h37xl And is about 3 years old I’m sure it’s mains voltage powered but there seems to be cabling running from the thermostat and a connecting Honeywell box next to it
JA: How long has this been going on with your thermostat? What have you tried so far?
Customer: it was working only 3 hours ago as normal and had no prior issues ive tried resetting the thermostat but not bring power back there are electric on/off switches next to the Honeywell box - they have fuses in them too so I’m considering changing the fuses if safe to do so
JA: Anything else we should know to help you best?
Customer: The honeywell box says 42002116-002 on it
Submitted: 7 days ago.
Category: HVAC
Customer: replied 7 days ago.
I’ve also noticed there the power to the solfex thermostat on the wall upstairs (same level as boiler and horstmann) is not powered either. There are some solfex thermostats downstairs which are still powered as normal
Expert:  Tim JA replied 7 days ago.

Good evening, and welcome to the Technical section in JustAnswer, an independent paid question and answer platform that matches customers' questions to experts in various skills. My name is ***** ***** I'll be happy to help you today.

Don't change the fuses without testing the ones in there, or you won't know if you've actually altered the circumstances.

The Honeywell box is a wiring centre.

Please can you tell me the make and model of your thermostat?

Customer: replied 7 days ago.
Hi Tim, it is Horstm***** *****nelplus H37XL
Expert:  Tim JA replied 7 days ago.

The H37XL is a three-channel programmer, not a thermostat.

Customer: replied 7 days ago.
Expert:  Tim JA replied 7 days ago.

Is it a wired thermostat, or wireless?

Customer: replied 7 days ago.
Sorry I’m not sure. There are solfex digital devices that I’m guessing are thermostats then. These can be adjusted digitally to change the temperature. The upstairs one isn’t working (no power to it). It was a few hours ago. The downstairs ones are still working as normal.
Expert:  Tim JA replied 7 days ago.

I don't mind asking questions and hearing about your system little by little, but it would work out faster for you if you just tell me all of the devices that your heating system comprises. Also, whether you have underfloor heating, or radiators, or both.

Customer: replied 7 days ago.
Seems like whatever has killed the power to the solfex has done the same to the horstmann device too. There is a valiant boiler downstairs which also seems to have no power - there is no lighting up of the digital screen
Customer: replied 7 days ago.
There is underfloor heating downstairs and radiators upstairs
Expert:  Tim JA replied 7 days ago.

So do you have three things that appears to have no power?

Are these the boiler, the programmer, and one (of the many) thermostats?

Customer: replied 7 days ago.
I think those 3 devices you have listed are correct
Expert:  Tim JA replied 7 days ago.

Have you checked the consumer unit to see if any circuit breakers have tripped?

Customer: replied 7 days ago.
I checked that and seems all fine, none of the switches are down
Expert:  Tim JA replied 7 days ago.

It would be interesting to know if any of the fuses, for the switches powering the heating system, has blown, but the best thing to do is remove each fuse and put in a plug for an appliance that you know is working, like a table lamp.

If you find one that has blown, then proceed with caution. The reason you shouldn't immediately put a new fuse in its place is because is there's a fault then it's likely to blow again, and you'll be none the wiser. There are potentially many things that could be damaged by a surge or current when the fuse blows.

I still don't know the set of the equipment that you have. For example, are there any underfloor heating controllers? I would expect there to be at least one. Some UFH controllers provide power to wired thermostats.

Customer: replied 7 days ago.
Sorry to waste your time. I’ve realised the problem. There was a wall switch to the boiler which must have been accidentally pressed by my son that turned everything off. Now all the 3 devices are back up and running
Expert:  Tim JA replied 7 days ago.

Well I'm glad that it turned out to be that simple :-)

Customer: replied 7 days ago.
Me too. Thanks for your help
Expert:  Tim JA replied 7 days ago.

I'm sure I caused my parents no end of problems like this when my enquiring mind led me to experiment with various switches ;-)