Are my Boiler and Thermostat Working as They Should?

[gaswizzard]

So the boiler is in the loft with no ladder for access? a royal PITA for the next guy looking at it.

Maybe the stat was second hand? or simply the installer changed the parameters?

 

[Tarandy]

Hi

Sorry for the big time lapse on this post,did you manage to solve the problem?
I have a similar problem where the flame is showing and the boiler does fire up. But it will if I select manual mode at a higher temp.
Reading through the post if I set a target temp of 19deg , if the temp off-set is set to +/- 1.5, am I right in thinking the boiler won't kick in until the temp falls below 17.5 and then won't shut off until the temp reaches 20.5?

 

[D_Hailsham]

I have a similar problem where the flame is showing and the boiler does fire up. But it will if I select manual mode at a higher temp.

That doesn't make sense. Do you mean 'the boiler does not fire up?

If so, there's nothing wrong. The thermostat regularly sends Actual and Target temperature info to the BDR91 receiver. The flame indicates this is happening. The BDR91 determines when, and for how long, the boiler needs to run.

if I set a target temp of 19deg , if the temp off-set is set to +/- 1.5, am I right in thinking the boiler won't kick in until the temp falls below 17.5 and then won't shut off until the temp reaches 20.5?

I think you are confusing 'Temperature Offset' with 'Proportional Bandwidth'.

Temperature Offset is used to correct for temperature 'errors' caused by the location of the thermostat. For example, the stat may be in a location which is warmer than the rest of the house, so it turns the boiler off too early. You use the Temperature Offset to make the stat think the temperature is lower than it really is, so the boiler keeps running for longer.

The CM9XX series of stats control temperature within ±0.5C.

 

[Tarandy]

Noticed the mistake as soon as I posted it, should have read it fully first.

Thanks for the reply, helps me understand a bit more of what is going on.
Moved into the house over summer and first time we've had to use the central heating, no experience of this setup.

We have a CM727 which I assume controls the temp to same range as the CM9**.

 

[D_Hailsham]

We have a CM727 which I assume controls the temp to same range as the CM9**.

Yes.

The CM7XX series is intended for Social Housing and Landlords; it has a Service Interval feature, so the tenant will phone up when the boiler is due for a service & Gas Safety check. It is also missing a few features of the CM9XX version.

PS It's not a good idea to tack questions on to the end of a topic which has been dead for two years.