Gravity Hot Water Help and information on all topics relating to your central heating, air conditioning and ventilation issues.

[AJLPlUMB]

Hello all, a new person in need! I am a Plumber (relitivly young in experience 5yrs)in Kent and have had a nightmare with one job which still i cant seem to resolve. I have replaced a 1050 x 450 indirect hot water cylinder, pumped central heating, gravity hot water piped in 28 mm . The top of the coil connection(flow) to the cylinder had to be lowered to connect to the new cylinder. This was lowered and piped so that there was a raise to the cylinder. The problem is that the flow to the cylinder gets hot at the boiler but no heat at the cylinder, i have tested the coil by blowing through it, i have cracked the flow union of at the cylinder and drained a bucket full but still it comes through cold. Any ideas as its getting fustrating now!! Thanks in advance Andrew[/b]

[marrtin]

Assuming the flow is always rising, and the return always falling, my guess is there is still an airlock somewhere, hidden under the floorboards possibly. Maye someone's had this problem before, and put a bleed nipple in. Otherwise you need to let some serious water out to clear the air.

Try using a hosepipe in the header tank and force water down the feed and then the expansion

[htg engineer]

Sounds like it's just airlocked, check the pipes definately rise from the boiler, and there's no dips.

Try re-filling, venting and cracking cylinder connections. You could tee a manual vent into into the top of primary flow, at cylinder.

If all this fails, pull thermostat from boiler and boil until air clears, you'll hear it. You need to be careful though - don't over do it as you could burst the heating coil.

[AJLPlUMB]

Thanks for the comments, ive drained 2 or 3 buckets out of the flow at the cylinder whilst the boiler is on but it just comes out cold.Last night i tried turning the feed to the f and e off then drained, all it done was emptied the f and e tank and return pipework. Its as if there is a blockage between the flow from the boiler to the cylinder,but dont know what would cause it or how to check it/clear it?!

[marrtin]

Sound advice from htg engineer.

Frightens the life out of the customer tho.........

Lol :wink:

[AJLPlUMB]

Problem resolved! Thanks for your help, found the return pipe to be 1 inch lower than the flow,under the floor run, so not getting all volume of header!