Wiring a room thermostat into my boiler....anyone want to help?

Marcel

Marcel

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We have a Ferroli Modena 80E boiler, 13 years old so getting on a bit.
I have the original installation manual with wiring diagrams etc. We've never had a room thermostat...just TRV's on the radiators and a digital timer panel on the boiler.
I've now got a wireless room thermostat I want to connect up. It's Honeywell made (but unbranded).

I have the installation instructions for it too, but I'm a little confused about it all.

Anyone care to give me pointers if I post the diagrams up here?
 
I think if you look at the back of the timeclock you will see a link on a block between three and four which you remove and fit the two wires from a voltfree room stat... Have a look at page 40 of the manual. Just make sure you use a voltfree stat, something like a Drayton RST4
 
Hi Gerry

Thanks for the reply. I've not opened the boiler yet to look at the board, but I have already looked at page 40 of the manual.
The pins I was looking at were pins 1 and 2, which branch off to Number 72 on the Key, the Room Thermostat.

The voltfree stat was what was I was unsure about. The one I have has three different connection modes and from what I can gather, one of the methods of connection is voltfree (well, not voltfree for the stat, but it doesn't pass voltage through to the boiler).
As it does say in the boiler manual

IMPORTANT : USE A ROOM THERMOSTAT (24V) WITHOUT VOLTAGE TO THE CONTACTS. CONNECTING @£)V TO THE ROOM THERMOSTAT TERMINALS WILL IRREPERABLY DAMAGE THE ELECTRONIC BOARD.

I'll upload the wiring diagrams from both in a sec.
 
This is the wiring diagram for the boiler (Like I say we've never had a room thermostat...well, there wasn't one when we moved in anyway), so I'm not sure if there's anything located in pins one and two on the top right block
View attachment 28119

This is the installation manual for the thermostat
View attachment 28120
 
Marcel said:
The pins I was looking at were pins 1 and 2, which branch off to Number 72 on the Key, the Room Thermostat.
Click to expand...

You would be spot on m8.

Terminal block (72 ) should have a link across it, remove this link and connect A and B from thermostat to terminals 3 and 4.

Just make sure there is NO link on your thermostat between L and A.
 
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Isn't that a mains voltage wireless reciever though?
It'll still need a live and neutral to left hand side just not linked of the right.
 
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Yeah from the video it seems it will still need 230v which you can take from the boiler itself / piggyback the boiler's 230v feed.
I'm assuming that taking the live from there, and only having two connections from the receiver to the boiler (via A/B and 3/4 like Zimmer says), then it keeps the 230v clear from the PCB, which is the warning in the manual.
Like he says, making sure there is no connection between L and A
 
Marcel said:
Yeah from the video it seems it will still need 230v which you can take from the boiler itself / piggyback the boiler's 230v feed.
I'm assuming that taking the live from there, and only having two connections from the receiver to the boiler (via A/B and 3/4 like Zimmer says), then it keeps the 230v clear from the PCB, which is the warning in the manual.
Like he says, making sure there is no connection between L and A
Click to expand...
That's right 230v from the boiler main supply to live and neutral then the two 24v switch wires between the pcb and A and B
 
Absolutely the wireless thermostat relay still needs a 230 V supply at all times or it won't work at all.
The important part in your case is that the thermostat relay does not "send" the 230 V to your boiler thermostat terminals.
 
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I saw this thread and remembered this video I watched a couple of weeks back, not sure if it will help or not but worth a shot

 
Thanks Keith. I'd actually seen that video (and posted it on Facebook), forgot to post it here.

Very similar thermostat and very similar boiler.

Ben/Tom, thanks for the replies. That was my worry, but after checking etc, I ended up wiring it in OK.
Very similar, infact pretty much the same as the above video posted by Keith.

However, I need to do more testing. I'm assuming I leave the boiler set to 'On'? (As opposed to auto or off (auto is the setting which used to use the inbuilt timer / programmer).
The radiators seem to be hot all the time and even when the thermostat says, eg 23.0, and the target temp is 21.0 I can check the boiler and it is sometimes on...feel the radiators and they're hot. It *could* be that the boiler has just not long ago turned off, but it's roasting in this house and roasting means money! :D
 
Marcel said:
The radiators seem to be hot all the time and even when the thermostat says, eg 23.0, and the target temp is 21.0 I can check the boiler and it is sometimes on...feel the radiators and they're hot. It *could* be that the boiler has just not long ago turned off, but it's roasting in this house and roasting means money!
Click to expand...

I think the technical terms for whats happened is, you've ballsed up the install! ;)

Maybe worth signing up to a plumbers forum and asking.
 
Is it programmable room thermostat? If so then yes leave your boiler set to on and then control with the stat.

The boiler quite possibly has pump overrun (I don't know with that boiler off the top of my head but can soon look it up when home.) which means it will continue to circulate heating water for around 3 mins after the heating goes off.

Does the stat most resemble a DT90E or a ST9400c? You'll need to google those for pics :D
 
Marcel said:
However, I need to do more testing. I'm assuming I leave the boiler set to 'On'? (As opposed to auto or off (auto is the setting which used to use the inbuilt timer / programmer).
Click to expand...
Leave it on Auto, the wireless programmer will 'call' on the heating when required.
 
With a room stat you can still use the boiler programmer if you don't want it to control how hot everywhere is all the time.

If there is a demand light on the boiler then that should go off when the thermostat says the room has reached the pre-set temperature.
 
call me mr picky but i would have thought a device that combines mains voltages with highly flamable gas is an area best left to the proffesionals.... any one reporting a large explosion in the manchester area should be assured its not terrorist related, its just marcel getting the spanners out again... :lol:
 
It does have a pump overrun... its 6 minutes. Turn the programmer to demand and the roomstat down.... if it fires up then obviously check the wiring. Live and neutral should be ok as its working and you havent blown the pcb so it would probably be the switch wires (volt free) Unless of course you didnt take out the link (but Im sure you havent done that(wouldnt you???))
 
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The boiler should be set to off, not on

That is what the thermostat is for/meant to do - turn on the boiler when programmed to do so either via time setting or temperature setting
 
If the central heating is set to off then it doesn't matter what the thermostat does. There is no heating on for it to control. The boiler has to be on either via a timed programme or on constant. It's only the frost thermostat that can bypass that and make the boiler come on regardless I thought? That's the case for mine anyway and most of the ones I've had previously.
 
The little box of tricks that is being fitted controls when the heating comes on or not - all that is needed is power to the boiler/PCB to be on for it to work
 
Keith W said:
The boiler should be set to off, not on

That is what the thermostat is for/meant to do - turn on the boiler when programmed to do so either via time setting or temperature setting
Click to expand...
Erm no (in my experience).

Off as in powered down, no. Powered on in 'auto' or idle is waiting for a signal to call upon the heating or DHW, so a room stat (or in this case wireless signal) or the running of a hot tap for DHW.

@Marcel you need to leave the boiler in the same state you had it with the room stat e.g. auto (your description :)).
 
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