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Tim Cooke
Tim Cooke,
Category: HVAC
Satisfied Customers: 1870
Experience:  Owner at Self-employed
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I have a myson underfloor heating which is connected to

Customer Question

JA: Hi. How can I help?
Customer: I have a myson underfloor heating which is connected to wireless room thermostat. The problem is that it keeps popping on when i have lowered the temperature on the thermostat during the night
JA: What's the brand and model of your thermostat? How old is it?
Customer: Myson FH - RT 088H0121
JA: How long has this been going on with your thermostat? What have you tried so far?
Customer: For at least a year now and I have changed the batteries
JA: Anything else we should know to help you best?
Customer: when it comes on during the night the main controller green light number 3 which I believe to be the thermostat number flashes
Submitted: 9 days ago.
Category: HVAC
Expert:  Tim Cooke replied 9 days ago.

Good morning, and welcome to the Technical section in JustAnswer. My name is ***** ***** I will help you today.

I will just review your question and hopefully will be able to reply with the information you need. Please bear with me as it's quite busy here this morning.


There's no time pressure on this topic - it will stay open to you for many days, and you can reply at any time. I will be away from my desk sometimes, but will respond as soon as I can.

You might see automated adverts for phone support. I'm not available for a phone call today, but we can continue via this Q&A topic.

Customer: replied 9 days ago.
That’s great thanks
Expert:  Tim Cooke replied 9 days ago.

Please tell me more about your system...

What is the make and model of your controller?
How many underfloor zones do you have?
Do you also have radiators?
What is the heat source?

Customer: replied 9 days ago.
4 zones , yes we do have radiators and they are powered by the boiler
The underfloor heating is water
Expert:  Tim Cooke replied 9 days ago.

Have you programmed a night-time set-back temperature on this particular thermostat?

Customer: replied 9 days ago.
It’s set at the sun symbol and I have checked the other 3 and they are also positioned at the sun symbol
Expert:  Tim Cooke replied 9 days ago.

Hm. That should indeed mean no set-back. Unless of course it's faulty.

I can't see from the manual how this thermostat shows that it's calling for heat - is it the LED on the left? Are you able to catch it when it's calling for heat at an unprogrammed moment? Is that LED lit up?

Customer: replied 9 days ago.
The led is that lights up is from the main control box and the led on the left flashes when it’s sending a signal
This all happens during the early hours 3am 5am etc
Customer: replied 9 days ago.
No program settings are set we just turn the dail as and when we need heat to start
Customer: replied 9 days ago.
Can I check with you what batteries are needed , just in case I have the wrong ones in
Expert:  Tim Cooke replied 9 days ago.

The manufacturer says that the battery type should be "3.6 V lithium battery, 2100 mAh, size AA".

What have you fitted?

Customer: replied 9 days ago.
It seems they are the batteries however there is a date on the bottom June 19
Expert:  Tim Cooke replied 9 days ago.

Hm. Might just be worth fitting brand new batteries before deeming it faulty.

Expert:  Tim Cooke replied 9 days ago.

Are you certain that it's not a 1.5V alkaline AA?

Customer: replied 9 days ago.
Expert:  Tim Cooke replied 9 days ago.

Cool. I don't mean to imply any incompetence on your part - it's just worth being extra sure :-)

Customer: replied 9 days ago.
No worries at all
Customer: replied 9 days ago.
Are you able to email me how I can disconnect the thermostat from the main box until I get some new batteries also how to re connect it too please
Expert:  Tim Cooke replied 9 days ago.

Since it's wireless, you can just remove its battery :-)

Customer: replied 9 days ago.
Customer: replied 9 days ago.
I’ll order some new batteries today and get back to you when I’ve done that
Customer: replied 9 days ago.
Thankyou and speak very soon
Expert:  Tim Cooke replied 9 days ago.

Yes indeed. I'll await your news. This topic will stay open for many days, so there's no rush.