How to verify a room stat is functional?

[DoNotUseFullName]

I have this thing on the wall and I have no idea if it's doing anything, how can I verify it is working?

With the heating/boiler on, if I turn this down to zero then presumably the boiler should go off immediately? (Spoiler: it does not)

 

[Jurassicspark]

When you say the boiler doesn't turn off, it could be the overrun so check after a couple of mins.

Is there any other thermostats controlling the boiler?
Remove the thermostat cover and send a picture of the wires leaving it.

 

[Madrab]

Only way really it to run a test on it with the cover off. What boiler is it?

 

[DoNotUseFullName]

When you say the boiler doesn't turn off, it could be the overrun so check after a couple of mins.

Is there any other thermostats controlling the boiler?
Remove the thermostat cover and send a picture of the wires leaving it.

Hmm, I waited a few minutes and it did turn off, likewise I turned it back up, and it turned back on after a few minutes. I just would have thought it would be instant.

No other stat in the house.

Only way really it to run a test on it with the cover off. What boiler is it?

It is a Grant Euroflame 50/90.

 

[Deleted member 267285]

Hmm, I waited a few minutes and it did turn off, likewise I turned it back up, and it turned back on after a few minutes. I just would have thought it would be instant.

Not if part of a motorised valve setup (which sounds likely).

 

[ericmark]

Yes I had the same, lovely box on the wall did not matter what I did, heating did not seem to work, and after investigating and curing one wonders what the previous owners did? Likely just used the open fire.

I hope your house is better than mine was. Looking at the Instructions it seems like my oil boiler you simply power the boiler when required, there is no run on I found a local boiler engineer who found the jets had worn so they needed swapping for it to run in an efficient way, and he advised against using the S plan shown, as it does not let boiler cool, but continue with the C Plan I already had.

So you really do want to get it serviced, and the guy who does it may help. If there are motorised valves you need to see if two or three port, and how many pumps etc. I have two x two port valves and two pumps, it would be easy to assume S plan, when it is a C plan. However the valves have micro switches inside, which do seem prown to failure, so that would be first place to look.

There is often a wiring centre or connection box, and the motorised valves, come pre-wired, so they can help work out what terminal does what.

 

[gas112]

boiler burner will prob have went off straight away but pump and fan over run can take several minutes to go off as they get rid of heat

 

[DoNotUseFullName]

If I set the stat to zero and turn the heating on from cold, the boiler still comes on and stays on. I assume that should not happen?

 

[Justin Passing]

Does the boiler heat your tapwater? Immersion cylinder? Timer/programmer?

If the stat clicks at about the room temperature it's probably switching OK.

Gawd knows how the installer wired it though - or thought he'd wired it.

See #2 above, then you're going to need a voltmeter. (Not a dodgy screwdriver which glows when it feels like it)

 

[ericmark]

My boiler is designed to heat domestic hot water (DHW) and only control is time the boiler runs for. It should have been controlled by the programmer, already posted picture, which is basic a time clock. I have a C Plan, which means no pump or valve for DHW, and it relies on the DHW to allow the boiler to cool.

There is also a Y and M plan, similar to each other, both use three port valves, the Y has a centre position, the M does not, but like the C Plan, the water can cool by heating the DHW.

Then there is the S Plan, this uses two x two port valves, and with no power there is no flow, not even with therm-syphon, so it needs to integrate with the boiler to allow cool down, and normally there is a by-pass valve, so if the motorised valves don't open, there can still be flow if the pump is running.

Modern boilers have this all built into the boiler, but older systems it is exterior, and oil boilers can even have a DHW tank inside the boiler, they are called combi boilers, but unlike gas, many oil boilers are digital i.e. either on or off, where most gas boilers are analogue and can adjust output.

From what little I have said, you should realise there are many different systems, so step one is to work out what your system is, with the Y Plan a proper meter as @Justin Passing says is essential as there are back feeds, so a non-contact voltage (NCV) tester or neon are useless as tracing faults. With the C or S Plan, one may be able to work out what is going on with a neon screwdriver or similar.

If it has not been used for some time, it is common for the micro switches in the motorised valves to stick. But before we can really help, we need to know what you have. Pictures are always good.

 

[DoNotUseFullName]

The boiler does indeed heat the rads and hot water all in one, there is no separate zones in the house. There is the one room stat as I posted above which is in the kitchen, and there is a programmer in the living room.

I am aware there are different types, but I'm not 100% certain on which I have. For one, there are no motorised valves that I can see.

 

[ericmark]

From your answer, I would say you have a C plan, there are two variants, without a cylinder thermostat and with a cylinder thermostat mine is the former, so the programmer runs the boiler only for DHW and boiler and pump for central heating, however even without the pump, upper rooms can heat anyway with therm-syphon. So the wall thermostat should turn the pump on/off, but may not turn the boiler off.

If you select CH only with the programmer, then the thermostat should turn boiler on/off. The programmer I showed, had a minium time, and was to put it blunt a bit useless, I also have a core open circuit, so wanted to control DHW and CH with two wires to the main house, since one wire open circuit, and the core colours changed, I wanted to only use extra low voltage, so I used Nest Gen 3, not the best, but it would work with two wires only to the interface in the main house. There is no wiring diagram for Nest Gen 3 with C Plan so I had to design it myself, so this works. However, likely better off using Hive, as this uses one contact for pump and other for boiler, and it is configured for C Plan, not seen any other combined thermostat/programmers designed to work with C Plan, but not really looked.

I can only talk about Nest Gen 3 as that is all I have used with C Plan, but it allows a slot of ½ hour, and 7 day plan, so I before I got solar panels, set it for ½ hour 4 times a week, which was enough hot water for handwashing. In fact, it only ran for 20 minutes in the summer, by which time the return water would turn off the boiler.

Now I have solar, in the summer I use an immersion heater, but no way to turn DHW off, so still use oil in the winter. I am an electrical engineer, not a heating and ventilation engineer, so just speaking from my own experience. My only wiring is far more complex compared to the version shown, as the one boiler heats both main house and flat under main house, so I have two room thermostats, and two pumps, and two motorised valves. However, if you quote someone on this forum, then it raises an alert, so if you want more info from anyone then quote or at least put the @ sign in front of their username, so they get an alert.