I recently fitted Evohome to an S plan system – Worcester Bosch 30CDi conventional boiler, Grundfos Alpha2L pump, Honeywell 2 port zone valves and Honeywell ABV – all about 2 years old. HR92s on all rads. BRD91 as heating valve controller and second BDR91 as hot water valve controller. 12 out of 15 rads have Danfoss RA/VL TRVs with the HR92 adapters. Boiler temp is set to 60 degrees.
On the one hand, things are mostly ok – hot water and internet control are perfect and the setpoints are largely maintained in each zone. Sometimes the temp in a zone falls well below setpoint and I have to reset the corresponding HR92 – I suspect this is a symptom of my Danfoss RA/VL valve bodies being old. I have managed to resolve quite a few niggles along the way (and many thanks to Richard from Evohome Shop who has been extremely helpful), but I have a further niggle and I thought I would reach out to the experts on this forum for advice.
If I reduce the temp in all zones, the TRVs turn off, but the heating BDR91 remains on for some time before turning off. The BDR91 then comes on from time to time, presumably to keep the temp ‘topped up’ in the zones (or perhaps for some other reason). However, I've noticed in some cases that my heating return pipe remains cool and instead the hot water just circulates round the bypass loop. I don’t know if this is because the HR92s think that they are opening but the underlying RA/VL(s) are not actually opening, or if the HR92s are opening partially such that the flow in the heating circuit is very low and the bypass kicks in to maintain minimum flow rate, or if the BDR91 is firing incorrectly when there is no demand (or some combination of these). When the system is in this state, the boiler gets into a constant cycle of firing up, heating to 60 degrees, going off, water then rises to around 67 degrees as heat is only being dissipated via the bypass loop, cools down below 60 then the boiler fires up again then repeat.
What’s troubling me is that when the system gets into this state, all that appears to be happening is that the bypass loop is being heated all night, which seems to be a waste of energy to me and also unnecessary repeated firing of the boiler.
I’d welcome any advice on how to definitively troubleshoot this issue. I’m concerned that I’ll have to replace all of my RA/VLs (which is a complete pain as I’ll have to extend the pipework at each rad) or continually waste energy or return to a single zone configuration using a room stat and no TRVs in that room (which would be a waste of Evohome’s capabilities).
Thanks,
Graham
On the one hand, things are mostly ok – hot water and internet control are perfect and the setpoints are largely maintained in each zone. Sometimes the temp in a zone falls well below setpoint and I have to reset the corresponding HR92 – I suspect this is a symptom of my Danfoss RA/VL valve bodies being old. I have managed to resolve quite a few niggles along the way (and many thanks to Richard from Evohome Shop who has been extremely helpful), but I have a further niggle and I thought I would reach out to the experts on this forum for advice.
If I reduce the temp in all zones, the TRVs turn off, but the heating BDR91 remains on for some time before turning off. The BDR91 then comes on from time to time, presumably to keep the temp ‘topped up’ in the zones (or perhaps for some other reason). However, I've noticed in some cases that my heating return pipe remains cool and instead the hot water just circulates round the bypass loop. I don’t know if this is because the HR92s think that they are opening but the underlying RA/VL(s) are not actually opening, or if the HR92s are opening partially such that the flow in the heating circuit is very low and the bypass kicks in to maintain minimum flow rate, or if the BDR91 is firing incorrectly when there is no demand (or some combination of these). When the system is in this state, the boiler gets into a constant cycle of firing up, heating to 60 degrees, going off, water then rises to around 67 degrees as heat is only being dissipated via the bypass loop, cools down below 60 then the boiler fires up again then repeat.
What’s troubling me is that when the system gets into this state, all that appears to be happening is that the bypass loop is being heated all night, which seems to be a waste of energy to me and also unnecessary repeated firing of the boiler.
I’d welcome any advice on how to definitively troubleshoot this issue. I’m concerned that I’ll have to replace all of my RA/VLs (which is a complete pain as I’ll have to extend the pipework at each rad) or continually waste energy or return to a single zone configuration using a room stat and no TRVs in that room (which would be a waste of Evohome’s capabilities).
Thanks,
Graham
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