Just wondering what others have configured when OpenTherm demand is very low? The Xclusive has a parameter (P057) "Response for OpenTherm room thermostat" with the following options:
0 = do not respond to heat demand if requested temperature is lower than 30°C
1 = respond to heat demand with minimum flow temperature limited at 30°C
2 = respond to heat demand with maximum set flow temperature (on/off function)
I'm clear that option 2 is not what I want. I'm currently using the default value but I think this is resulting in a lot of cycling of the boiler as it cannot actually modulate low enough to maintain this temperature, given the very minimal heat differential on the return side when there is only one radiator running with minimal demand. Water is then mostly circulating via the Automatic Bypass Valve (ABV). (I appreciate TPI is the only way to reduce heat output when demand is below the lowest that can be achieved by modulation.)
Option 0 might be the way to go but I'm not sure what else should be considered...
P031 ("Maximum capacity of modulating central heating pump") is set to default of 65
P032 ("Minimum capacity of modulating central heating pump") is set to default of 35
P033 ("Central heating pump overrun after central heating demand") is set to default of 1 minute
P034 ("Central heating pump overrun after boiler operation") is set to default of 1 minute
(I am also confused by the description of P032: "Set 15% of parameter P031", as this does not seem to match up with the default set value in any way I can fathom?)
In the evening, my current "living" room is the only zone with a demand and it can be as low as 10%. The radiator makes noise every time the boiler fires up (as a consequence of the pump ramping up) and whilst this can probably be improved by tweaking the ABV, it is highly undesirable as the "living" room is actually a bedroom.
My current feeling is that reducing the minimum flow rate (by altering P032) at low demand might be sensible along with increasing the overrun after boiler operation and/or central heating demand. Hopefully others will be able to steer my thinking more wisely.
0 = do not respond to heat demand if requested temperature is lower than 30°C
1 = respond to heat demand with minimum flow temperature limited at 30°C
2 = respond to heat demand with maximum set flow temperature (on/off function)
I'm clear that option 2 is not what I want. I'm currently using the default value but I think this is resulting in a lot of cycling of the boiler as it cannot actually modulate low enough to maintain this temperature, given the very minimal heat differential on the return side when there is only one radiator running with minimal demand. Water is then mostly circulating via the Automatic Bypass Valve (ABV). (I appreciate TPI is the only way to reduce heat output when demand is below the lowest that can be achieved by modulation.)
Option 0 might be the way to go but I'm not sure what else should be considered...
P031 ("Maximum capacity of modulating central heating pump") is set to default of 65
P032 ("Minimum capacity of modulating central heating pump") is set to default of 35
P033 ("Central heating pump overrun after central heating demand") is set to default of 1 minute
P034 ("Central heating pump overrun after boiler operation") is set to default of 1 minute
(I am also confused by the description of P032: "Set 15% of parameter P031", as this does not seem to match up with the default set value in any way I can fathom?)
In the evening, my current "living" room is the only zone with a demand and it can be as low as 10%. The radiator makes noise every time the boiler fires up (as a consequence of the pump ramping up) and whilst this can probably be improved by tweaking the ABV, it is highly undesirable as the "living" room is actually a bedroom.
My current feeling is that reducing the minimum flow rate (by altering P032) at low demand might be sensible along with increasing the overrun after boiler operation and/or central heating demand. Hopefully others will be able to steer my thinking more wisely.
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