New CH system -- sometimes house does not get up to temperature

[Mark]

Hi All,

We've recently had a new central heating system fitted (a WB greenstar combi boiler 440). Before the thermostat was fitted the house (obviously) gets very hot! However after the thermostat was fitted the house sometimes does not heat up at all or sometimes the boiler stops firing when the room temperature is 2-3 degrees below that set on the 'stat.

We also sometimes find the boiler only coming on half an hour after the timer should switch the boiler on. I have confirmed this by sitting by the boiler and watching/listening to what it is doing. It does nothing for about 20-30 mins then appears to fire on minimum for

10 minutes and then goes to max (I think).

I have another thermometer next to the thermostat to confirm the room temperature.

The thermostat is a WB TR2 electronic 'stat so it doesn't click.

The hot water seems to work correctly.

Can anyone give me some advise on how to diagnose this problem? I've checked the obvious things like air in the rads and system pressure.

Thanks in advance, Mark

[Ed Sirett]

Turn the thermostat up a little as needed. The absolute numbers are not important, and even if they are correct only relate to the exact location of the thermostat not the house in general.

[Dave Plowman (News)]

Interesting. My programmable Horsmann is battery operated and makes a louder click than the old 'mechanical' one. Some form of stepping relay, I assume. It's actually quite annoying.

[Mark]

I hadn't expected the thermostat to be that inaccurate. Remember I have checked the temperature with a themometer close to the 'stat. I did move the thermometer around to make sure there is not a hot spot near the 'stat.

The boiler does have a night set back unit which is supposed to maintain the temperature at a lower level during the night. This works as expected. i.e. the themometer shows the temperature selected on the night set back unit when the CH timer is selected to off. This suggests that the stat is accurate in this case - so why should it be inaccurate during the day?

For example I set the room stat to 21 and the night set back unit to

1. During the evening (when the CH timer is on) the room temperature goes up to a maximum of 17 degrees. During the day (when the CH timer is off) the room temperature is maintained at 15 degrees. The boiler does fire up on low during the day.

Regards, Mark

[Jeff]

is the time set correctly on the boiler ?

Regards Jeff

[Mark]

Yes. I think I've checked all the obvious things :-) The timer CH light comes on on the boiler at the correct time but the boiler does not fire up for the heating when expected.

I've made sure that no hot water is being used.

Regards, Mark

[Mark]

I wish this device would click or have a light to indicate what it thinks is going on.

Anyone know if there is a test mode?

Mark.

[Jeff]

Mark wrote :-

I believe that these have an optimising controller - but exactly what that means I don't know - something like if the differance between required temp and actual temp is big it switches on early and vice versa

Regards Jeff

[Mark]

There's a vague mention of this on their web pages but I can't find anything in the manuals about it. However I'm not sure why the controller would make it start up _late_ when the temperature is below that required.

Maybe it's just too damn complicated and is making some (incorrect) guesses about our heating requirements.

Mark.