Boiler firing up unexpectedly - anomalous behaviour??

[jtboldon]

I have recently installed a Evohome system to control my existing S Plan. I have two BDR91s for CH and HW, and HR92 radiator controllers in four zones. All seems to working perfectly ..... up to a point.
What I now find is that the CH BDR91 is switching on when there is no demand causing the boiler to fire up and the pump to run. Although it appears to happen randomly I do suspect it is doing it in "sessions". An example was last night. My final switching time is 11.00pm when all zones revert to 15deg C for the night. All zones are satisfied since they were previously at 20degC. So why does the boiler fire up at 11.05pm? It does it for about 30 seconds then off again. 11.10 back on again for 30 secs. It did this three or four times at 5 minute intervals before it too went to bed.
It does it again during the day when the heating is supposed to be "off" (set point of 15degC).
I am convinced it is not random. It seems to be always 5 minutes or 10 minute intervals between switching on and it is always for 30 seconds.
So what is happening?
Do I have a fault, or is there a setting I need to fiddle with, or is this intended behaviour by the Evohome system.
In any case it is not acceptable to be woken in the night by a heating system firing up that is supposed to be off.
Any help or hints much appreciated.
GeoffP

[nashdm2]

Interesting as I am sure mine does this also. I was in the kitchen the other day where the boiler is, no room was calling for heat as they were all set really low. The boiler fired up, stayed up for a very short time, then shut down again. Nobody had turned a tap on either.
I have heard it do it on another day with the same conditions.
I wonder if it is a setting in the controller that fires the boiler up at regular intervals just to preheat something so that when the heat is actually called for the boiler is not starting from a cold state (some eco efficiency setting)?

[pompy]

My Evohome also does this, everything shuts down at 11pm but requests for heat are still sent to the boiler for up to 40 mins. Honeywell tech support just tell me that this is normal.......
Apparently it is designed to waste your fuel even though it is sold as energy saving.
I have resorted to getting a sparky to put a switched spur inline with the BDR91 so I can just power it off. not ideal but saves gas.

Im convinced that it is bad programming from Honeywell.

[Richard]

Well, mine doesn't do this and nether do any of the installations I have done.

Can you put some pictures up of the installation of your devices and location of the evohome Controller so I can comment...

[DrKW59]

Well, mine doesn't do this and nether do any of the installations I have done.

Can you put some pictures up of the installation of your devices and location of the evohome Controller so I can comment...

My installation does this randomly also, I have been looking online and I suspect it may be because my BDR91s are too close together! since I installed them I have found instructions that say they should be 30cm away from the boiler and 30cm away from metal objects (which they are) but in the instructions I originally had it didn't say they needed to be 30cm away from each other.
So is this the problem?
BTW i have the older system with HR80s

[Richard]

The instructions actually state a 'minimum' of 30cm... I have always separated mine by 100cm or as far as possible and this will reduce signal saturation.

[davidj]

Mine appears to stay on beyond the Off time. Cant think its a wireless problem as I have had no errors and it generally is okish. Its also next to the Hot Water module which works flawlessly.
More importantly my likely savings in Gas have actually turned into nearly double the equivalent period cost. House generally too hot, often overshoots limits. I have a call into the engineer, who was very competent.
If only we could see when it called for heat and when it shut off would make fault finding much easier.
I'll update accordingly.

[Richard]

Just to note, the CS92A and BDR91's need to be separated also by minimum of 30cm.

[davidj]

Mine are 45cms apart.

[Richard]

Any pics? (wide angle shots to include location to other devices)