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ROBERT JOHNSON · Joined: 22 Jul 2004 Posts: 1 Location: PETERBOROUGH

Hi, i have an old corvec 45 boiler which has been operating fine until recenlty. Not in a position at present to replace it i want to keep it running for a bit longer if possible.
Symtoms: Heating is fine but hot water does not get that hot. The boiler gas valve was relaced about 3 years ago, the thermocouple is new as is the cylinder stat. Its on a Honeywell Y plan i believe and has a three port motorised valve which (appears) to be working. The boiler comes on and starts to heat the water but then goes off too quickly to have any real effect (about 3 - 4 mins). The pump continues to run long after the boiler has switch off and gets very hot. If you adjust the cyclnder stat the boiler does not kick in straight away and can take up to 5 - 10 mins to switch on, but does not stay on very long.

Any help or suggestions on this matter would be greatly recieved.
Many thanks
Robert

vince knight · Posted: Thu Jul 22, 2004 4:19 pm Post subject:

Sounds like the 3 port valve is not operating properly, thus there is no flow from the boiler and it goes out on overheat, which is why the pump overun is running for so long to clear the heat. If possable remove the actuator head from your valve and adjust it manually, then call for hot water. If the valve wont move manually then have it replaced.

Vince

thescruff · Moderator Joined: 03 May 2003 Posts: 4751 Location: Bath

Technically and assuming the thing is wired correctly then the valve will be opening and the pump-boiler will run.

Therefore I would suspect a circulation problem, this could be air in the hot water primary's, the pump not working and should be checked first, or scale in the cylinder coil.

Try running the heating and hot water for an hour.

Check the header tank for water if you have one.

scruff