Center programmable Room thermostat

[paulcleaner]

Good evening all.
i was hoping to get to the bottom of my boiler cycling woes.
i have read a few post on here regarding the Center programmable themostat but was looking for any help before i start replacing things or adjusting offsets.

Story so far..

New boiler fitted 18 months ago, Ideal Logic Max Combi.
Boiler is running fine on hot water but my issue is wiith the central heating.
Boiler comes on and runs up to thermostat temperature then swithches off as per normal.
(center programmable wireless thermostat)
Then i get some weird cycling session of boiler on for 10 mins off for 10 mins then again and again.
Sometimes the receiver light is off so its just the pump running, its as if the thermostat is telling the boiler its not hot enough.
Thermostat is out of the box settings so i havent played with anything.
I have seen a post that this is normal but surely at some point the the bolier should stop running?

Any Help or advice welcome

 

[ericmark]

There are a number of ways for a wall thermostat to control a boiler, with my old oil boiler the thermostat needs to use what is called mark/space, that is as it approaches the set temperature it starts to cycle the boiler off/on so it does not over shoot, or it can be "Smart" and it works out how much the heating over shoots, and turns boiler off at the point it has worked out the heat retained in radiators will take the room the last degree or so.

However with modulating boilers the second option could still work, but would be better to use OpenTherm and gradually reduce the boiler output, not use on/off system.

The other option is use thermostatic radiator valves (TRV) which as they close lift the by-pass valve so hot water returns to boiler which in turn tells the boiler to turn down. However there is a problem, it can't tell the boiler when to start as no water flowing, so also can't tell boiler when to stop, so once boiler at minimum output it cycles off/on, and anti cycle software can reduce how often it switches on, but left it would continue to switch on/off all summer, so a on/off thermostat is placed in a cool room on ground floor, with no door to outside and no alternative heating to turn boiler completely off on warm days.

There are also systems where there are wifi links between TRV and wall thermostat/hub but keeping to basic systems.

So with the thermostat designed for the non modulating boiler using mark/space, if fitted to a modulating boiler it completely messes it up. Each time it switches boiler off, any heat in boiler goes out of the flue, and when it turns back on again it turns on flat out, and does not extract the latent heat.

I think the Ideal Logic Max Combi is an OpenTherm enabled boiler, so should be using an OpenTherm thermostat, it will work with on/off thermostats to stop it cycling, but the whole idea of wall thermostat is to stop cycling not to cause cycling, I don't think there is anything wrong with the thermostat or boiler, it is just not the right thermostat for that boiler.

 

[muggles]

As Ericmark says, you've got a cheap nasty thermostat connected to a boiler which is capable of accepting a high quality OpenTherm one. Get an OT stat and you should see a big improvement

 

[paulcleaner]

Cheers for that, any suggestions on open therm stats. I have absolutely no idea where to begin or what I'm looking for.

 

[ericmark]

It depends on your set up, but some pointers.
For zoned central heating EPH that is about the only one which does master/slave.
For no zone valves or thermostatic radiator valves Nest, also if using a combi boiler Nest e is the only 2 wire.
For all singing dancing with TRV heads interconnected there is EvoHome, Tado and Drayton Wiser the latter claims to have smart TRV which over time work out when they need to turn off to stop over shooting.

The problem is cost, the wifi TRV is not cheap when you consider in this house I have 14 TRV's. So we tend to select key rooms for fitting TRV heads with wifi and the rest use cheaper stand alone or bluetooth, the eQ-3 TRV head has worked well for me.

So you likely need a plan, in 5 years time you will have xyz and your going to start with x, so if you plan to only use eQ-3 TRV heads then Nest is great, but if you want every room independently controlled will ability to cause the boiler to fire up then one of the others likely better.

I don't have OpenTherm and I have Nest Gen 3 with 9 non linked programmable TRV heads and 5 non programmable and two zones, but that is unlikely to suit your needs, as said in other posts my rooms have swapped what they are used for throughout my life, so kids bedroom becomes and office or craft room, and dinning room becomes a bedroom as some one can't climb the stairs, heat raises so ground floors need more careful consideration than upper floors. As said I am unusual in having two ground floors as living in a hill.

If not sure, buy a really cheap thermostat, cheaper the better, while you consider how to proceed. With a really cheap thermostat the TRV's are doing the work, you should only see it switch off in good weather.