Central heating - radiators emptying - help!

[AnonymousImport]

Hi.

Three days ago a gas engineer replaced the pump on my central heating system. Since then the upstairs radiators have needed bleeding frequently (more than once a day), and are often almost empty (I'm pretty sure there's no leak in the pipes!). Various gurgling noises are heard from the radiators and the boiler unit itself (it's an Ideal Elan).

One other clue(?) is that when I came home last night (the heating was on), there had obviously been a fair amount of water coming out of the overflow from the tank in the roof space.

What's happening?????? Will it eventually stop with periodic bleeding? I really couldn't afford the first call-out, so I'm reluctant to book another.

Many thanks,

Andy

 

[masona]

Did the engineer put the pump in the right way round ? ( should be a little arrow on the pump for flow rate ) Get the engineer back in as the problem only happens afterward.

 

[AnonymousImport]

No idea - can't see an arrow, but then I can't see much of the pump without removing it completely. It's oriented so that the writing on the face of the pump is upside-down, and it's located below the boiler (i.e. the boiler connection at the bottom with respect to the writing [geographically the higher connection] feeds into the boiler).

I'll try ringing, but I'm worried sick I'll be landed with another call-out charge - can anyone else help in the meantime?

 

[masona]

Have you got water in the F&E tank ? have you tried bleeding the pump ?and did the engineer drain the system completely or just turn the valves off at the pump ?

 

[AnonymousImport]

No idea what an F&E tank is, but the small tank in the loft is full, and is currently overflowing (about three drips per second) and the main water tank (for the bath?) is full too.

I don't know how to bleed the pump - there's one control which seems to regulate the speed and a slotted round thing (of the type which is turned by using a coin) which is in the centre of the front face, but again doesn't seem like a bleed thing, but then I have no idea.

As far as I know, the engineer would not have drained the whole system.

 

[AnonymousImport]

Thanks for your help, by the way!

 

[AnonymousImport]

Masona - you're a genius!

I've found the pump instructions an spotted the arrow. It's pumping downwards. I followed the pipe up to the F&E tank (feed & expansion!), and it's the one hanging over the rim of the tank - clearly designed for filling, not emptying. The pump is pumping air into the radiators!

Being British Gas, I can't get through to get an engineer out, but I can confidently tell them they've stuffed it up!

Many thanks again,

Andy

 

[masona]

I'm not quite sure yet but if you hang on a bit longer we've got some good plumber guru on this forum and see if they agreed.

But it does seem coincident after the pump was fitted.

 

[MANDATE]

The slotted round thing in the centre of the pump face is where you bleed it.
The pipe going up and hanging over the top edge of the tank allows the water to expand with any excess going into the tank.
Although you have found the arrow on the pump pointing downwards have you established it is pointing in the correct direction.
Hot water rises and leaves the boiler from the top, the return flow enters the boiler at the bottom. Pumps are normally located in the 'supply flow' pipe so the arrow should point away from the boiler, but they can be on the 'return flow' pipe in which case it would be pushing water into the boiler and the arrow would point towards the boiler.
The pump cannot pump air, it can only pump water and it can't do that if there too much air causing an air lock. It can pump water containing air, but this air will not circulate through the system. It will gather in the radiators, which means you may have bleed them more than once
Hope this helps

 

[aci20a]

Er.... no, it's actually frightened me, Mandate!

I can't establish which is the supply line and which is the return line without taking the boiler apart - this is probably beyond me! Externally, the two lines are symmetric, both going up before entering via the top of the boiler. Both lines also go via T-joints to the loft. In the loft, the line which the pump is on goes to the open-ended pipe hanging over the F&E tank (as I said before). The other, as far as I can tell, enters the tank below the water line (near the bottom). In the tank, there's a ballcock, which I imagine replenishes the circulating water when necessary, and an overflow.

More to the point, being unable to get through to British Gas, I went ahead and switched the pump round myself. The system now seems to be working perfectly. None of the radiators is losing water and it's heating nicely. And what's more, the pump's not leaking!

The engineer didn't dismantle the unit, but he did ask to get access to the loft, so his only means of identifying the lines was from seeing the pipes in the loft (though he could obviously just have looked at the old pump and made a direct swap).

Should I panic?

By the way - where has this thread gone to? I can only find it from the e-mail I got sent notifying me of a response!

 

[aci20a]

Ah! I've spotted where the thread went. One less question!

 

[masona]

More to the point, being unable to get through to British Gas, I went ahead and switched the pump round myself. The system now seems to be working perfectly. None of the radiators is losing water and it's heating nicely. And what's more, the pump's not leaking!

Well done mate,a happy ending

 

[aci20a]

Or maybe not.

I've dug up the installation instructions (by some miracle) and they say that the pump must be on the flow side (not the return side). However, it seems that BOTH of the F&E tank lines should be on the flow side too, in the sequence boiler - expansion line (the open ended one) - cold feed - pump.

It's plainly not plumbed that way, what with the cold feed being on the return line. What's happening? Was it bodged, with the pump needing to be reversed to make it work (i.e. turning the flow line into the return line and vice versa)? Or should I go back to the way the engineer put it in (and as shown in the installation guide) and try to work out what the problem is with the draining radiators?

This is starting to annoy me.

 

[ChrisR]

Don't panic!. Pumps and pipes are often put in other than ideal positions and everything works fine.

If you start with a cold boiler you'll be able to work out which is the "flow" pipe out of the boiler. It should be the one which goes to that vent pipe which goes over the small tank. It should also be the higher pipe coming out of the boiler.

Sometimes water can get "pumped over" so it comes out of that vent pipe. if it's doing that try the pump on a lower speed. It's also important that the vent pipe isn't "sucking" air. to check for that you can use your hand, a bit of tissue paper as a flag, or hold a glasss of water up to the pipe.

If you do all that and noting looks wrong I reckon you're OK!

 

[masona]

If you do all that and noting looks wrong I reckon you're OK!

Sod the instructions !, I did it my way