Can't figure out how my thermostats work

robbie1876

This has been driving me nuts! Moved into an 8-year-old house with gas heating and hot water and to date I can't figure out how on earth to keep the house at a reasonable temperature. It's always either too hot (heating on full blast it seems) or too cold.

The setup is:

- Gas boiler in the kitchen which heats rads and hot water
- Flash Immermat timer which seems straightforward enough
- 2 wall thermostats - one in hall, one in master bedroom
- No radiator thermostats anywhere I can see

My questions are:

- I would imagine that setting the temperature on the thermostats should switch on boiler when it gets too cold, but it doesn't seem to do that. The settings on the timer are 'Constant On', 'Constant Off' and 'Timed On'. When on constant on, the thermostats seem to have no effect, so I'm presuming it must be left to timed on. Can anyone clarify?

- Because there is an upstairs and a downstairs thermostat, does this mean the hot water can be split? Where would the valves be for this and are they controlled by the 'stats?

- Last night, as an experiment, I set downstairs thermostat to coldest setting, upstairs to hottest setting and timer on 'timed on' for a few hours. The result was the downstairs rads were on hot and the upstairs ones were off!! This has completely flumuxed me, is my wiring backwards?

- Where are the thermostats wired back to? From looking up the Flash Immermat specs it doesn't look like they would go to there. Any insights?

Thanks, and sorry for all the questions. I have no clue about heating systems and really need to figure out how to keep a more pleasant heat in the house.

Robbie

robbie1876

robbie1876 wrote: »

I would imagine that setting the temperature on the thermostats should switch on boiler when it gets too cold, but it doesn't seem to do that. The settings on the timer are 'Constant On', 'Constant Off' and 'Timed On'. When on constant on, the thermostats seem to have no effect, so I'm presuming it must be left to timed on. Can anyone clarify?

The timer is just a switch, it shouldn't matter if it's on timed or constant, if you find there is no call for heat when on constant have it looked at.

robbie1876 wrote: »

Because there is an upstairs and a downstairs thermostat, does this mean the hot water can be split? Where would the valves be for this and are they controlled by the 'stats?

If wired correctly then with a call for heat from your timer/programmer will go to your room stat(this is just a switch that makes at a given temperature) if your room stat is calling for heat then it will send a signal to a zone valve which will motor open making a switch inside the zone valve when it's fully open, this will bring on your boiler, your zone valves are normally in the hot press but i find plumbers are like artists and they can fit zone valves where ever the mood takes them. If you want better control of your heating i would thing about programmable room stats if you don't have a separate time clock for each zone.

robbie1876 wrote: »

Last night, as an experiment, I set downstairs thermostat to coldest setting, upstairs to hottest setting and timer on 'timed on' for a few hours. The result was the downstairs rads were on hot and the upstairs ones were off!! This has completely flumuxed me, is my wiring backwards?

Sounds like it. I would certainly get in a heating engineer to help you identify what the funk is going on with your heating controls

robbie1876 wrote: »

Where are the thermostats wired back to? From looking up the Flash Immermat specs it doesn't look like they would go to there. Any insights?

Have a look at the link for wiring ideas http://www.gascentralheatinguk.com/, but just to confirm it should go isolation switch to timer/programmer to room stats to motorized/zone valve to boiler, Gary.

crosstownk

Good advice above from Gary.

I'd try it by a process of elimination.

First I'd let the whole system go cold and turn both stats to cold. Switch on the programmer/timer to 'ON'. Turn up one of the stats slowly until you hear click from inside the stat. The boiler should fire up soon afterwards. Wait and see which radiator zone heats up. Once you've determined which zone heats, allow the system to cool again and repeat the process again with the other stat. Be sure to check your hot water cylinder as it may have a stat strapped to it. You may need to repeat the process a third time with the cylinder stat. Alternatively, if you have a hot water setting, be sure that it switched off while you check the operation of the room stats.

If the wiring is backwards, it won't take a whole lot rectify if your motorised valves are located close to one another.

robbie1876

Thanks guys for the replies.

Over the last few nights I've been trying different settings and have come to the conclusion that the wiring between the two thermostats is indeed backwards. I still haven't found out where the valves are. No sign of anything like that in the hot press but then I'm not really sure what I'm looking for.

While I'm on - do you have any recommendations for a good digital wall thermostat to replace the old dial ones already there? I do like the idea of being able to set different times for heat upstairs and downstairs independently. May as well get it done while the heating guy is out.

Many thanks,

Robbie

crosstownk

A motorised valve looks like the pic in the link.

http://www.toolstation.com/images/library/stock/webbig/85125.jpg

Don't go replacing stats until you have the system figured out and operating correctly.

Basically the programmer sends a live feed to the stat. If the ambient temperature is below the stat setting, the stat relays the live feed to the motor. This causes the motor to turn which opens the valve (allowing water from the boiler to flow). At the same time the motor operates another internal switch which sends a live feed to the boiler that switches the boiler on.

If you are familiar with electrics you should be able to proceed using a multimeter and/or a continuity tester.

mightymouse311

guys dont get to hung up over the moto valve thing it could be 2 r 3 pumps doing the job either it depends on plumbers ive used both so have a look and see