Hi,
I have had EvoHome for a little over a year now with no real issues, utilising a BRD91 relay.
I have been reading this forum with interest around Opentherm and have had the BDR91 replaced with the R8810 Opentherm Bridge yesterday.
This was straightforward....however, where I had very few overshoots that I can remember on the old (reliable) BDR91 relay, I'm seeing very large overshoots on multiple rooms even after 24hours of temp set point changes.
One thing that struck me straight away when the Gas Safe engineer first installed and binded the R8810 Opentherm Bridge was that when calling for heat, and where all zones calling for heat were only 1.5 degrees C below set point, it fires the boiler up to full throttle and reaches 81/82 degrees C flow temp according to the Viessmann 111-W Combi boiler (35KW) digital display.
The other problem, and a contributing factor to the overshoots no doubt, are that the radiators get far too hot at this temperature - and there doesn't appear to be a way on this boiler (that I know of) to reduce the max CH flow temp (to say 65 degrees c).
Whilst the burner eventually cuts out, and then let's the flow temp fall down, this happens about 5 minutes or so *after* the EvoHome display shows all zones have reached or even passed beyond the set point in other words, extremely laggy.
Once rooms have fallen back down to set point, it does seem to modulate the flow temp down as expected - but the issues reaching set point as described just don't seem right to me.
Hopefully the attached screenshots of the datalogging shows what I mean here.
Is there any way of reducing the flow temp on a Viessmann 1xx boiler? I think I'll have to go back to the BDR91 relay if not due to the risk of scalding (and excessive gas use whilst no where near condensing temps!!)
I have 11 zones with 1 HR92 in each zone for further context, this has been working really well to date.
I only have a large towel rail (no TRV) and 2 fairly small rads (with TRVs) that are not dynamically controlled.
I have had EvoHome for a little over a year now with no real issues, utilising a BRD91 relay.
I have been reading this forum with interest around Opentherm and have had the BDR91 replaced with the R8810 Opentherm Bridge yesterday.
This was straightforward....however, where I had very few overshoots that I can remember on the old (reliable) BDR91 relay, I'm seeing very large overshoots on multiple rooms even after 24hours of temp set point changes.
One thing that struck me straight away when the Gas Safe engineer first installed and binded the R8810 Opentherm Bridge was that when calling for heat, and where all zones calling for heat were only 1.5 degrees C below set point, it fires the boiler up to full throttle and reaches 81/82 degrees C flow temp according to the Viessmann 111-W Combi boiler (35KW) digital display.
The other problem, and a contributing factor to the overshoots no doubt, are that the radiators get far too hot at this temperature - and there doesn't appear to be a way on this boiler (that I know of) to reduce the max CH flow temp (to say 65 degrees c).
Whilst the burner eventually cuts out, and then let's the flow temp fall down, this happens about 5 minutes or so *after* the EvoHome display shows all zones have reached or even passed beyond the set point in other words, extremely laggy.
Once rooms have fallen back down to set point, it does seem to modulate the flow temp down as expected - but the issues reaching set point as described just don't seem right to me.
Hopefully the attached screenshots of the datalogging shows what I mean here.
Is there any way of reducing the flow temp on a Viessmann 1xx boiler? I think I'll have to go back to the BDR91 relay if not due to the risk of scalding (and excessive gas use whilst no where near condensing temps!!)
I have 11 zones with 1 HR92 in each zone for further context, this has been working really well to date.
I only have a large towel rail (no TRV) and 2 fairly small rads (with TRVs) that are not dynamically controlled.
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