Combi Central Heating Pump issue ?

[Steve Jones]

I have added a rad to my sealed system and since then half the rads in my h ouse are not getting hot, basically those downstairs are cold. The pipe fro m the boiler goes to the upstairs rads first then down to the ground floor ones. I have tried shutting off all the rads upstairs, and then the downsta irs ones do get a little warm. I wondered if its the pump. I opened the ble ed screw on it and on speed positions 2 and 3 it spins, but on position 1 i t does not, would having the bleed screw removed stop it spinning on posit ion 1? Boiler is a Heatline S30 compact about 10 years old. When draining the rads all seemed pretty clean. (If I have to take the pump out to look at might as well change it) Thanks steve

[Capitol]

I'd say it's an air lock problem.

[Steve Jones]

my house are not getting hot, basically those downstairs are cold. The pipe from the boiler goes to the upstairs rads first then down to the ground fl oor ones. I have tried shutting off all the rads upstairs, and then the dow nstairs ones do get a little warm. I wondered if its the pump. I opened the bleed screw on it and on speed positions 2 and 3 it spins, but on position 1 it does not, would having the bleed screw removed stop it spinning on p osition 1?

rads all seemed pretty clean.

How do I get rid of the airlock? I have tried turning of all the upstairs rads anything else I could do?

[Dan S. MacAbre]

I've managed to keep the same pump going for something like 25 years, and it'll probably go for another 25. The insides will, naturally, get coated in haematite, which will sometimes flake off, and sieze it. Sometimes, it clears itself, but once I did need to dismantle it and scrape it all out. If yours isn't turning on position 1, I'd assume it was filling up with the nasty black stuff. The bleed screw shouldn't actually be touching the shaft, I don't think. Mine doesn't.

When you shut off all the upstairs rads, did you leave all the downstairs ones on at the same time? Until I put a drain c*ck on each one (well worth doing), I found that when refilling, I had to turn on each downstairs rad by itself in turn with the pump on 3. That was the only way I could get it to blow the air down the pipes.

If you're going to take the pump off, have two new rubber washers ready.

[Tricky Dicky]

When we first moved in our last house the heating system had the main pipes running of into the ceiling space with drop feeds to all the radiators on the ground floor and only one had a drain c*ck. Every time the system was d rained down there was always some water in the downstairs pipes and radiato rs and always resulted in air locks on refill. The only solution is to put a drain c*ck on each radiator.

Richard

[Dave Plowman (News)]

Water flow always takes the easiest route. If you are certain there are no air locks, you need to partially close down the lockshields on the rad which are getting hot to add resistance to that path. Note that lock shields ain't linear - you'll probably end up with some only just cracking open. Once you've got them all working, use an infra red thermometer to get the correct flow on each and every one.

Most pumps have more than enough head for any domestic system. Unless faulty, of course.

[Andrew Gabriel]

Did you bleed all the radiators? Did you check the tempertures only at the radiator top? Might be mostly air.

If there's an air-lock in the pump, usually there's no flow and the water boils in the boiler pretty quickly, and/or the boiler will overheat and lockout. (Needless to say, this isn't good for the boiler.)

No. There's usually a screwdriver slot on the shaft-end. With the pump off, does the shaft turn very freely with a screwdriver? It could be that the speed selector switch is faulty and not powering the pump in position 1. What position was it originally in? It shouldn't need changing.

If they worked correctly before, start by assuming they were correctly set. It's probably just the new radiator which is not set correctly. Start by turning that off (so system is just like it was before). Does that make all the previously existing radiators work as they did before? If not, you have some other problem which has to be fixed before adjusting any of the lock-shield valves.

[Steve Jones]

house are not getting hot, basically those downstairs are cold. The pipe f rom the boiler goes to the upstairs rads first then down to the ground floo r ones. I have tried shutting off all the rads upstairs, and then the downs tairs ones do get a little warm. I wondered if its the pump. I opened the b leed screw on it and on speed positions 2 and 3 it spins, but on position 1 it does not, would having the bleed screw removed stop it spinning on pos ition 1?

ds all seemed pretty clean.

Turned all rads of again except the faulty ones and eventually all started working, so it was trapped air!!!