Greetings all,
Just curious really.... While reading through my 20/80 service manual (excellent bedtime reading), I noticed that as part of the commissioning it states that the boiler should have its maximum rate set, so that when it fires for CH it gives the burner the required flow for the required heating output in KW or BTU/h.
The CH range rating potentiometer adjustment only limits the boiler whilst it's on high flame. When it modulates down to low flame, it uses the low burner pressure.
I can't understand why one would need to limit the upper burner pressure for CH. My understanding is that when the CH is switched on, the boiler fires on high and heats up the water in the circuit as quickly as possible. Once it's done this, the thermostat tells the boiler to switch to low flame and continue. Once the low flame has continued to heat the water past the stat's cut off point, the system shuts off until the water temp drops below the thermostat's setting, at which point the boiler fires up again on a low flame and the cycle repeats, going from low flame to off, low flame to off.
From what I can work out, adjusting the maximum burner rate for CH simply means that the boiler will heat up the CH water slowly or quickly before switching to low fire.
Am I completely misunderstanding it? I gather I am, as if it truly worked in the way I have described I doubt it would be adjustable!
Cheers
Stu
Just curious really.... While reading through my 20/80 service manual (excellent bedtime reading), I noticed that as part of the commissioning it states that the boiler should have its maximum rate set, so that when it fires for CH it gives the burner the required flow for the required heating output in KW or BTU/h.
The CH range rating potentiometer adjustment only limits the boiler whilst it's on high flame. When it modulates down to low flame, it uses the low burner pressure.
I can't understand why one would need to limit the upper burner pressure for CH. My understanding is that when the CH is switched on, the boiler fires on high and heats up the water in the circuit as quickly as possible. Once it's done this, the thermostat tells the boiler to switch to low flame and continue. Once the low flame has continued to heat the water past the stat's cut off point, the system shuts off until the water temp drops below the thermostat's setting, at which point the boiler fires up again on a low flame and the cycle repeats, going from low flame to off, low flame to off.
From what I can work out, adjusting the maximum burner rate for CH simply means that the boiler will heat up the CH water slowly or quickly before switching to low fire.
Am I completely misunderstanding it? I gather I am, as if it truly worked in the way I have described I doubt it would be adjustable!
Cheers
Stu
