Hi!
Main Combi 24 HE
I had one of these fitted around five years ago, and it's been fine until recently when the DHW became erratic; CH is still fine. Initial symptoms were that hot water was only available when the CH was actually firing. I opened the case and saw that the pushrod on the DHW Pressure Differential Valve was not engaging the microswitch on full extension (i.e. tap on). I did the obvious thing and bent the tang on the switch so that it would engage on extension and all was well for a day. However, now we have not DHW at all as the pushrod does not extend at all.
Two questions:
1) Am I correct to conclude that either the diaphragm in the valve is torn or the pushrod is jammed? (see p.s.)
2) What does it mean to drain the primary circuit, can I isolate the boiler and simply drain that or must I drain the whole heating system?
TIA for your advice
p.s. Quick test this morning (like you do) and the pushrod extended fine under DHW demand. However, a later trial failed, with the pushrod again not moving. I guess that means the diaphragm's probably OK. So, jamming pushrod or something further upstream (i.e. blockage in the pipes to the diff)?
Main Combi 24 HE
I had one of these fitted around five years ago, and it's been fine until recently when the DHW became erratic; CH is still fine. Initial symptoms were that hot water was only available when the CH was actually firing. I opened the case and saw that the pushrod on the DHW Pressure Differential Valve was not engaging the microswitch on full extension (i.e. tap on). I did the obvious thing and bent the tang on the switch so that it would engage on extension and all was well for a day. However, now we have not DHW at all as the pushrod does not extend at all.
Two questions:
1) Am I correct to conclude that either the diaphragm in the valve is torn or the pushrod is jammed? (see p.s.)
2) What does it mean to drain the primary circuit, can I isolate the boiler and simply drain that or must I drain the whole heating system?
TIA for your advice
p.s. Quick test this morning (like you do) and the pushrod extended fine under DHW demand. However, a later trial failed, with the pushrod again not moving. I guess that means the diaphragm's probably OK. So, jamming pushrod or something further upstream (i.e. blockage in the pipes to the diff)?