No Hot Water circulation

[markatrwe]

Hi Guys,
I replaced my leaking indirect hot water cylinder last week. Cos I'm an amateur it took me a few evenings (with the water off and CH system drained). Now it's all back together, but problem with hot water.

The boiler comes on, but goes off after a few minutes. Once its gone off it wont come on again for a few hours (something cooling down ?) Theres hot water in the boiler out pipe but it doesnt get to the tank.

I have 2 pumps, both seem to be on the CH circuit (no not water booster). Only one seems to work, i.e. it makes a humming noise and gets pretty hot. The other is silent, cant feel any movement in it and its cold. Do boilers have a cut out if the water isnt circulating ? What should I try to identify / fix problem ? Why 2 pumps ?

 

[weareleeds]

First thing to do is remove all air from system especially the dhw flow pipe (there should be a bleed cap to loosen)

 

[twgas]

do the pipes in and out of the hot pump get hot - if not its either air or pump nakkered

boiler may have an overheat but if it comes back on by itself that probably isnt your problem

 

[markatrwe]

having spent the evening in a cramped airing cupboard ...

hot water supply piping all OK. All hot taps run with no air and no hot water.

I seem to have 2 pumps: one for feed to heating coil in cylinder (plus rad in bathroom, plus god knows what else) and one in feed to radiator circuit.


first pump spins I think, but ... water above pump, but no water below pump. It comes on whether CH is selected OR HW is selected. Its mounted vertically just before the feed to the tank heater coil. The bleed valve for the cylinder heater coil feed dribbles water, but I can disconnect the heating coil outlet from tank and nothing happens - no air rushing out, no water rushing out.

second pump definitely spins. Also definitely mostly air in pipe. This one is on a pipe coming out of the boiler. It only comes on if CH is selected AND the air temp thermostat demands it. The fact that it is dry cant help.

P.S. I bled the system via a downstairs radiator near patio door with bleed valve. This drained heater coil in tank as well. Doesnt seem to be refilling though, so I am thinking MASSIVE air lock or HW pump not passing water ? CH feed tank in roof is full and ballcock works fine.

This seems to be a heath robinson affair. No valve to switch hot water supply, just 2 independent pumps. The boiler is an Ideal W2000.

Aaaarrrgggghhhh !!!

 

[Rico99]

Sounds like a blocked cold feed to me.

Bail out the F&E in the loft, then back fill the system with mains cold thru a rad drain cock downstairs. Have someone in the loft to let you know when water starts to fill the F&E from the bottom.

Rico