I want to fit a room thermostat to a CH boiler that currently has a remote (wired) programmer.
It seems to use a 2-wire control to signal to the boiler to turn on (I believe just connects the wires together via some relay presumably).
Can I just use a 2-wire thermostat wired in series with one of those two signal wires?
I don't want to replace the programmer with one with a built-in thermostat (I happen to like the current programmer, and besides they would be more expensive).
Thanks,
That is how they are usually wired.
OK. It's just that all the schematics I've seen only ever show a programmer
*or* thermostat as the sole device wired to the boiler. (And the thermostats I've had before were all complicated multi-wire ones.)
What model of programmer and boiler do you have? Just so I can do a double check for you.
(That is, for different installations.)
The boiler is a Ferroli/Optima 701, with a 2-wire connection ('24V') for an external programmer/thermostat. I think fitted with a shorting loop when using the internal programmer, according to the manual.
And the programmer is a Sunvic Select 107 (mains powered from the boiler). (This has quick and easy buttons for instant overrides, which I haven't seen on the replacement programmer/thermostats I've looked at, so I'd rather keep it.)
That's if you want the new stat to be able to stop the boiler working even if the programmable one is on.
If you want the new stat to be able to turn the boiler on when the programmable one is off you wire them in parallel (eg a frost stat).
So yes, you just need to wire your thermostat in series in the 24V loop just as you first suggested.
Cheers
Well that is how a room stat works (by stopping the boiler working I assume you mean "turns off the call for heat"). Of course the OP does not have or nor does he want a programmable room stat so why you are mentioning one is beyond me.
Well the OP does not want that. He asked a question about adding a room stat to an existing programmer. He never mentioned frost stats or anything else.
Have you been on the piss this dinnertime or do you always talk bollocks?
I recommend you get a Honeywell CM927
Holiday mode, so you tell it how long you are away for, and when you return, the heating has automatically come on before you get home, so the house isn't freezing.
Party mode, to set a particular temperature for up to 23 hours, over-riding the normal programming.
Day off mode, so it will run the weekend program for the number of days you tell it you are going to be at home.
It's wireless, so you can take it into the room you are in too.
Manual here
Well a programable room thermostat doesn't really have the same requirement for "boost" or "advance" that a pure timer has, so you won't find those buttons.
Features vary but the one I have (Danfoss TP75) allows you to adjust the set temperature up or down from the programmed set temp and it will stay there until the next set point (sort of "advance"). It also has +1hr +2hr and +3hr button to extend the current temp for those periods ("boost").
I would recomend that you do get a programmable room stat, they are so much more flexable and provide better comfort automatically than the simple, single temperature, manual, room stat. Take a look at the Danfoss TP7000, I think this is the succesor to the TP75, it has the features as above.
Though the one you posted a link for does actually have manual overrides=20
- page 11 of the user manual.
I love our programmable thermostat. All through the coldest bit of the=20 freeze we could set it to maintain a minimum temperature all night -=20 usually 7=B0C and it just gets on with it. IIRC it only came on once, but= =20 it was nice knowing it was quietly managing stuff.=20
Different temperatures in the morning compared to the evening is good,=20 too.
We've had it about nine years, and it's only on its second set of=20 batteries.
--=20 Skipweasel - never knowingly understood.
Though the one you posted a link for does actually have manual overrides
- page 11 of the user manual.
I love our programmable thermostat. All through the coldest bit of the freeze we could set it to maintain a minimum temperature all night - usually 7°C and it just gets on with it. IIRC it only came on once, but it was nice knowing it was quietly managing stuff.
Different temperatures in the morning compared to the evening is good, too.
We've had it about nine years, and it's only on its second set of batteries.
Ours has been on continuous for years, governed only by the progstat. Unlike neighbours, who seem to leave their heating on continuous full stop. Look out on a not particularly cool night and you can see several houses with plumes from their heating - there can't be that many people taking a bath at 3am.
Maybe they are taking a bath after spending the small hours spying on their neighbours boiler flues?
It's a filthy job, but someone has to do it.
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