Fitting a room thermostat

[don72]

I am intending to fit a room stat to a Heatline Compact S30 combi-boiler. Currently the boiler is not working and Heatline are refusing to honour the guarantee unless certain installation faults are made good.

Due to the mains wiring needed to install the reciever unit for a wireless reciever and the cost I'm starting to favour the idea of drilling and chasing out the wall. I'm fairly sure that the heatline wiring for a stat is two wires, currently these are one long very thin white wire in a loop. I believe that you cut this wire and connect it to the room-stat to over-ride the current programmer on the boiler.

I was told by their engineer that the programmable timer was not enough, and that the pump would still be cycling constantly. Is this correct? It's a 24hr dial with lots of little switches. I would have thought that when set to off for a period it would stop the boiler.

I could be wrong, but due to the thinness of the wire I suspect that it's a two-wire milivolt system so wont be compatible with a lot of thermostats. Am I right in thinking that a battery powered thermostat model would be what I am looking for? Models I've looked at so far seem to be designed to connect to 24V AC control lines, but do they have to be?

If I did go the wireless route, I would need to get 230V mains power to the reciever unit, but would I then be able to attatch the boilers thermostat wires, regardless if they are a milivolt style?

Is the current wire loop, once cut, sufficient to connect to the thermostat or do I have to solder on new two-conductor thermostat wire? Can I splice extra wire onto the existing lengths if they are too short?

Basicaly any help or advice would be brilliant. I'd consider getting a sparky in to do the wiring, but if I can DIY it all the better. I've fitted new lights and stuff before and it seems I could do this job without having to touch mains electricity.

Any thoughts or advice on types/models of thermostat or best installation practice?

 

[Paul Barker]

I don't know your boiler.

You need your manufacturers service and installation instructions (MI's). Not User guide that is a pile of useless sh1te which doesn't help anyone and nobody reads.

Normally there is a jumper or link in the wiring centre of the boiler which you cut and replace with a thermostat.

On some boilers one terminal of the link is 230v when the internal time clock is on, this 230v is sent to the thermostat and if there is a call for heat returned to the other terminal.

On some boilers the same link needs cutting but only a no volts contact is made across your thermostat.

Yet others there is a 24 volt signal.

A Honeywell roomstat can handle all three systems and will work without a neutral connection. No need for a cpc.

I expect your manual has the answers to all your questions if you want to scan the relevant page and email it to me I'll report back.

Pump overrun should not be affected by the replacement of the correct link with a roomstat, if you are using the boiler's integral time clock, but I'd rather see MI's.

 

[ArtfulBodger]

I've fitted three of the Heatline condsensing combis and they require the normal volt free relay to replace the bridge on the wiring block.

Any battery powered or RF stat will be fine except those that switch 230V.

 

[don72]

I really appreciate the help guys. So, I do need to get a specific no voltage thermostat? It's not possible to hook up the connections to a 230V powered stat? Trying to narrow down my options.
The honeywell DT200 is volt free, but I'd rather have a programmable stat if possible. Any suggestions for an alternative stat that handles volt-free connections?
When I wire it up will I be able to use the original wire that I cut? It's pretty long, so I got the idea that it was to be used for that purpose. If so will I be able to splice more wire on if I need it longer, which I probably will?

Pump overrun should not be affected by the replacement of the correct link with a roomstat, if you are using the boiler's integral time clock, but I'd rather see MI's.

Do you mean by this that the programmer on the boiler should still work? I'm also still interested to know if the programmable timer on the boiler lets the pump keep running all the time; that's what the engineer that came out implied. I can't get hold of the MI's till monday, when I will be reading up on them thoroughly.

I've fitted three of the Heatline condsensing combis and they require the normal volt free relay to replace the bridge on the wiring block.

Any battery powered or RF stat will be fine except those that switch 230V.

Certain battery-powered ones I found specificaly said they were not suitable for millivolt systems. Could you recommend a specific (cheapish) stat you have used successfully (preferably programmable), and detail how to fit it to the heatline PCB please? Which terminal is which as you are facing the boiler for example or can it be wired either way? Do you need to change the wire?

Thanks again for your help so far guys! If anyone else has further advice, please chime in.

 

[ChrisR]

Who makes Heatline boilers?? Spose I'll have to take my own advice and do a search!

ALL battery operated stats use relays to provide the "Volt free" contacts for the boiler, so I expect some are just being more cautious than others in their application advice re the millivolts, which only a daft boiler maker would use.

Go for one you find easy to program, and put it in your white wire.
You can either leave the boiler's naff timer on constant, or get it out. Often they make an annoying noise!

 

[don72]

Who makes Heatline boilers?? Spose I'll have to take my own advice and do a search!

ALL battery operated stats use relays to provide the "Volt free" contacts for the boiler, so I expect some are just being more cautious than others in their application advice re the millivolts, which only a daft boiler maker would use.

Go for one you find easy to program, and put it in your white wire.
You can either leave the boiler's naff timer on constant, or get it out. Often they make an annoying noise!

http://www.heatline.co.uk/home/welcome.php

They're relatively new, and very cheap. It was not my choice of boiler but was here when I moved in as a new boiler. I've had a constant problem with it that became more and more frequent.

It would switch itself off and display the warning "Check thermal isolation probe or gas-flow". First it lasted three months, then two a couple of times, then it went monthly then fortnightly then daily, then it would fire for minutes at a time. Now it wont fire at all, or rather if you persevere for an hour of resetting it might start to fire now and again for say 30secs then it will fail the last test again and shut-off! It's actual working life has been around 9months I guess, and it's obvious that something has deteriorated.

Heatline are saying because the wrong TVR's were fitted it has caused undue stress on the boiler. Admittedly when it works one or other rad starts banging like crazy every 5mins-1hr till you fiddle with the valves.

The guy they sent out from Lowmack swapped out the pcb and cleaned the probe, tested everything else and left. Three days later it was the same problem and again wouldn't fire even after a dozen reset attempts.

If I fit a programmable stat it should over-ride the boilers inbuilt timer, no? If I just fit a basic stat will the boilers timer still work?

Can someone tell me why the pump would be working if the timer was set to be off for a period of time anyway? That's what the guy from Lowmack seemed to say, and it confuses me...

 

[ArtfulBodger]

Heatline are based in Bedford and are not stocked by many merchants that I use. I think they are better known for their column radiators than boilers & I heard somewhere that the boilers are manufactured in Turkey.

The best programmable stat, IMHO, is the Honeywell CM67. The RF version is just as good - just a bit more expensive.

You will need the MI's to fit the stat, but it is perfectly obvious where it goes. From memory the case needs to come off and the control panel swings down to expose the terminal block.

 

[ricarbo]

You seem to have several problems.
A programmable stat is what we should use now, because it allows you to set different temeratures at different times, therefore more fuel efficient. Whether or not it supplies mains voltage or merely closes a switch (so called 'volt free') depends on the 'stat you choose to buy. I like the Danfoss range, but that's me.
I don't understand you when you say millivolt, that refers to something that is measured in thousands of a volt. Whats that about?
Your problem with the cycling is a different issue. You need to stop the boiler firing to satisfy its internal controls if there is no demand from the house - e.g. it doesn't need to keep itself up to temperature if the dwelling is warm enough. Do you need further explanation of this rather complicated issue?
Your comments about the manufacturer's agent saying there is a problem with the TRV's makes me think you may not have a bypass valve, or if you do have, it's wrongly set. Do you have one? Is it set right?
Most boilers have an 'over run' device which may work on time or temperature, to run the pump so that it shifts the heat out of the boiler into the rads, to prevent the boiler getting too hot when it stops on it's own thermostat or the timer.
There should be one room with no TRV's which should be the room with the programmable 'stat. Do you have this?
'Thermal isolation or gas flow' is beyond me, sounds like an inadequate gas supply, which is likely to be untrue.
All in all, need a bit more information, but should be ok with a bit of attention.

 

[don72]

You seem to have several problems.
A programmable stat is what we should use now, because it allows you to set different temeratures at different times, therefore more fuel efficient. Whether or not it supplies mains voltage or merely closes a switch (so called 'volt free') depends on the 'stat you choose to buy. I like the Danfoss range, but that's me.
I don't understand you when you say millivolt, that refers to something that is measured in thousands of a volt. Whats that about?
Your problem with the cycling is a different issue. You need to stop the boiler firing to satisfy its internal controls if there is no demand from the house - e.g. it doesn't need to keep itself up to temperature if the dwelling is warm enough. Do you need further explanation of this rather complicated issue?
Your comments about the manufacturer's agent saying there is a problem with the TRV's makes me think you may not have a bypass valve, or if you do have, it's wrongly set. Do you have one? Is it set right?
Most boilers have an 'over run' device which may work on time or temperature, to run the pump so that it shifts the heat out of the boiler into the rads, to prevent the boiler getting too hot when it stops on it's own thermostat or the timer.
There should be one room with no TRV's which should be the room with the programmable 'stat. Do you have this?
'Thermal isolation or gas flow' is beyond me, sounds like an inadequate gas supply, which is likely to be untrue.
All in all, need a bit more information, but should be ok with a bit of attention.

I understood that the room-stat would act as a boiler interlock, which would stop it cycling when there was no demand. Is this not correct? I would like further explanation if you could please. Thanks.

A millivolt system is often referred to as an ELV (extremely low voltage) system, I think it's measured in 1/1000th of a volt. It's an alternative to standard 24V-230V connectors. I'm still not sure, but I believe they can be fitted to the plates on most battery or mains powered thermostats though I'm going to go with a stat specificaly confirmed to work with millivolts.

I do not believe there is a bypass valve fitted, just the bathroom rad set fully open as an over-run. The TVR's were incorrectly installed the wrong way round on the system, that was the main issue that the call-out engineer had, so he said they should idealy be replaced with bi-directional valves. How would I go about fitting a bypass valve? Where would it be located in the system, and with a roomstat and balanced system would it be necessary?

Since I'm locating the room-stat in the main living area, I'm removing the heads of the existing trv's in that room. Should I then fit a TRV in the bathroom? The living-room rads should then act as the over-run, no? If it has to be the rad nearest the boiler I'll have to leave a manual head on the bathroom rad.

Thermal isolation probe fault or gas flow is the fault that has been coming up with the boiler since day one. To be honest, I don't expect my new installation measures to fix the boiler at all. It's just the only way to get heatline to honour their guarantee.

The installation was done poorly in the first place. I don't believe the system was really flushed with Ferox, because when I removed a rad it was pretty bad with sludge. The plumber put the valves on the wrong way. He ignored or crossed out parts or the Benchmark log-book. To top it off, I checked his Corgi reg number and it's registered to someone in Nottingham. I've tried to contact him, but he's not responded to my messages. Corgi want to send out an inspector to check his work, but I suspect they will find the gas side of it in order. It just ****es me off that he ignored the 2002 building regs with regards to fitting a room-stat in the first place, and his other cock-ups.

Am I right in thinking since the 2002 reg's a room-stat is mandatory? Fitting TRV's (wrongly) to all the rads but one, and calling that a job done surely isn't even compliant with the necessary values of energy efficiency.

I could really use some further advice on this. Thanks everyone who has chipped in so far.

 

[Paul Barker]

"I understood that the room-stat would act as a boiler interlock, which would stop it cycling when there was no demand. Is this not correct?"

YES

"A millivolt system is often referred to as an ELV (extremely low voltage) system, I think it's measured in 1/1000th of a volt. It's an alternative to standard 24V-230V connectors. I'm still not sure, but I believe they can be fitted to the plates on most battery or mains powered thermostats though I'm going to go with a stat specificaly confirmed to work with millivolts."

You are right, I refer to this control as a no volts control, some boilers can take instructions from all three voltages, no volts, 24 volts and 230 volts. I have found that the basic honeywell stats work on all three without a problem.

"I do not believe there is a bypass valve fitted, just the bathroom rad set fully open as an over-run. The TVR's were incorrectly installed the wrong way round on the system,"

drain down and turn them over, so if the plastic control is presently vertical make it horizontal, flow of water should be in direction of arrow if there is one.

"he said they should idealy be replaced with bi-directional valves."

that is a compromise orientate them correctly is actually better practice, and you have not to shell out on new valves after 9 months. It's all excusology anyway since you have a permanently open bathroom rad.

" How would I go about fitting a bypass valve? Where would it be located in the system"

Buy an automatic bipass and put it between the flow and return pipes a certain distance from boiler according to manufacturers instructions, on the pipes under the floor beside a convenient rad would do.

", and with a roomstat and balanced system would it be necessary?"

Not necessary if the rad where the rstat is, is kept permanently open. Swap the lockshield on the bathroom rad for one living room trv and take the head off the other living room trv.

Yes the person who comissioned the work was had, seemingly by a combi swap profiteer. No it didn't meet regs at the time, you should go and buy some sentinel x400 or a cleanser of your choice leave it in maximum period keep reseting boiler so it functions if at all possible, follow Chris's sticky advice on powerflushing using the mains, get that system clean. Actually take every rad out intot he garden beg steal or borrow a preasure washer and blast the internals, send mains pressure water flying around the flow and return pipes of the boiler also.

Put it all back together but with trv's correct way round or if on same side other way up, change the bathroom rad controls and living room, put in a simple roomstat you problems are so great forget the best practice go for acceptable practice, put in an auto bipass not because it's necessary but because the importer is importing substandard boilers and will look for every excuse to get out of warranty claims before he goes bust.

I can see a new boiler coming, start saving.

 

[don72]

*Advice above and beyond what could be expected on a message board*

Thanks for clearing those nagging questions up Paul, you're a superstar mate. I'll be following what you said to the letter. I'm hoping the rest of what I need to know, I'll find out in the MI's when I get them in front of me tomorrow. Basicly I'm talking about what kind of insulation to put on the wires from the combi to the room-stat, and how to extend this wiring a few meters.
I'll probably engage the services of a plumber to fit the automatic bypass, but I think I feel reasonably confident about handling the rest myself. I have no experience with copper fittings to pipes, so if it is something really simple that I could handle myself, please alert me.
Chances are I'll be back with a question or two that I don't anticipate! Great to know that you guys are there. I truly appreciate your time and efforts to educate people to help themselves.

 

[Paul Barker]

If I were chasing the walls and coming in the roomstat from behind, I would use 1mm twin and earth myself but it's no problem for me to just buy a roll of anything at all, only about 10 quid for 50 meters I think? I don't count the cost of those sort of things. Whatever you use make sure it is double insulated, not just bell wire. Don't bundle it with any cable of different voltages, keep it away from pipes, if it has to cross pipes wrap insulating tape round the pipe.

Probably a good idea to get plumber for bipass because cost of tools would be same.

 

[don72]

If I were chasing the walls and coming in the roomstat from behind, I would use 1mm twin and earth myself but it's no problem for me to just buy a roll of anything at all, only about 10 quid for 50 meters I think? I don't count the cost of those sort of things. Whatever you use make sure it is double insulated, not just bell wire. Don't bundle it with any cable of different voltages, keep it away from pipes, if it has to cross pipes wrap insulating tape round the pipe.

Probably a good idea to get plumber for bipass because cost of tools would be same.

Theres only two wires to be connected to the block, would I just cut back the earth cable?

 

[Paul Barker]

Yes, although the best practice is to sleeve it and terminate it in a crimp or a connecting strip or a terminal placed in the plastic part which doesn't need it, should anyone in future replace that with metal parts that do need it.

Even though I can't picture any metal room thermostats if I don't give you the full jobsworth story another jobsworth will.

Just cut it back in short!

 

[don72]

Yes, although the best practice is to sleeve it and terminate it in a crimp or a connecting strip or a terminal placed in the plastic part which doesn't need it, should anyone in future replace that with metal parts that do need it.

Even though I can't picture any metal room thermostats if I don't give you the full jobsworth story another jobsworth will.

Just cut it back in short!

Thanks Paul, your advice has been invaluable.