No central heating

[Freezing2]

Hi I wonder if you can help me

All rads are cold, the Grunfos alpha 2 pump is running and all pipes around it are hot, there is a pipe behind it with a bleed vavle on the end, If I release the air from this pipe and mess around with the speed of the pump, start it and stop it I can get the rads to go hot for 10 to 12 hours but then they go cold so I go back to bleed air mess with pump speed until it goes again.

Any ideas what's causing this problem?

Any help appreciated

Thanks

 

[Chalked]

Your system is pulling air in.
Either plumbed in wrong or pump fitted in a bad location.

As you do with turning the speed on the pump down/on,off. And the bleed the air vent. Also turn the heating off to let it settle and bleed all rads too.
Then try the pump on the lowest setting. If it manages to circulate, leave it at that setting.with your system, to high pump speed will make it suck air back in down the vent pipe that terminates over the header tank in your loft.

As a permenamt fix, get a decent plumber to alter the pump position amd feed/vent location.

 

[chris watkins]

Then try the pump on the lowest setting. If it manages to circulate, leave it at that setting.

Only thing to add to post above is - if it doesn't circulate on speed 1 turn it up to 2 if the circulation is not throughout get the plumber / heating engineer in, system are never designed to run on 3.

Out of interest when did this start ?

 

[Freezing2]

Thanks for the reply's

The pump has always been in the same location for over 20 years and not had any trouble until recently, it's been running on speed 2, bled all rads but with pump going so should I turn pump off and do them again?

 

[Freezing2]

Sorry Chris

I think it started March April time just before we turned the central heatin off for summer, thought it was pump so had new self bleed pump fitted seemed to have sorted it for a while but now this problem

Thanks

 

[chris watkins]

Yes, once air is in a running system it gets knocked about until there are loads of very small (micro) bubbles they are whisked around with the water.
They do not have enough buoyancy to escape the water & come out of the vents unless you stop the water moving & they can join back together into bigger one.

Sounds like you may have got a bit of sludge in the pipes. Have you checked to see that the open vent is not, either pumping over or sucking in air at the small F&E tank ?

By self bleed pump do you mean one with an auto air vent install into it?

 

[Chalked]

Just because it's always been ok, may not mean it's not a problem with pipework. Wrongly connected feed and vent pipes cause most air problems.
Over time air being introduced will cause sludge to form quicker. This can block the cold feed connection, thus causing an imbalance. This then causes the pump to suck in, or pump over. An oxygenated system will rot radiators and block pump impellers. This was proble the cause of your recent pump change.
It's not a big job to alter the pipework. But it also looks like a powerflush is required.

 

[Freezing2]

It pumps over if I put the pump on full speed but not on speed 2, how do I check if it's sucking air?

Thanks

 

[Freezing2]

System was flushed early 2015
If I put hose pipe on down stairs drain point it's pumping it out fast but no air seems to come out and tank upstairs runs to replace what I've drained

 

[Chalked]

It pumps over if I put the pump on full speed but not on speed 2, how do I check if it's sucking air?

Thanks

To check for sucking in, get a clear jar or water and put it under the vent pipe, do the pipe is in the water in the jar.
Get someone to turn the pump off, leave it to settle for a min, then turn it back on. You will see the wayer being drawn out of the jar if it is sucking in.

 

[Freezing2]

Thanks for that, what if I find it is?

 

[Freezing2]

Yes Auto air vent Chris

 

[Chalked]

Thanks for that, what if I find it is?

It will need the system updating. Otherwise will only shorten the life of the new pump.

 

[chris watkins]

Phil I read back over the posts in March.

The chances are it is the combined cold feed / Open vent which is highly restricted. despite what you would have been told the flushing will not have the hard oxides in & around the connection to the system of this pipe.

Are you a good DIY'er, it sounds like it you can do a fair bit so if you are up for it tomorrow here is what I would do. (Tomorrow if you can get the fitting)

Drain the system down just as far as the pump (if this is lower than the Tee connection below).

Cut out the Tee piece where the pipe from the F&E tank join the system, the one behind the pump, you will need 3 x 22mm push fit coupling & 1x 22mm Equal Tee & 2 - 3 Metres of 22mm copper tube.

You will also need a set of 22mm tube cutters (pipe slices would be best)

Cut all the heating pipe about 150/200mm (6-8") away from the tee but not to close as you will need to get the bigger push fittings in.

Once out check the pipe I bet the cold feed open vent is very restricted.

If not, put it back with couplings & take Tee & copper back, if not use to replace the tee.

 

[Freezing2]

Ok Thanks

Here's what I have done this evening

turned everything off, left it half hour, got loads of air out the bleed valve at back of pump, put pump on speed 1 and restarted, sounds like air whizzing in the pump? shall I repeat the process

Thanks again for all your help I am learning

 

[Freezing2]

I'm not bad at DIY and certainly not afraid to have a go

What do I need to do lol?

ps looking at the plumbing I don't think I could do any worse, don't who did it but it looks a balls and I'm not a plumber

 

[Best]

Try a strong magnet on the vent/feed pipe and particularly where it tees into system pipes.
Your system could be running out of water.
Also be aware that any auto vents fitted on certain pipes can cause air to suck into system when heating is on

 

[Best]

I should have added that if the magnet does strongly stick to some parts of the feed, then the pipe might be blocked by magnetite.

 

[chris watkins]

I'm not bad at DIY and certainly not afraid to have a go

What do I need to do lol?

ps looking at the plumbing I don't think I could do any worse, don't who did it but it looks a balls and I'm not a plumber

As per Best above & I have edited my post 14 above.

I feel a little job for tomorrow coming on!

PS if you can get them buy JG Speedfit Twistlock or similar.

Have fun

 

[Freezing2]

Thanks for that Chris I will have a look and see if it all adds up with what I can see, so will I just be basically replacing the cold feed Tee and the vent Tee?

 

[Freezing2]

Just had a look and the feed/vent is same pipe, do I need to replace where it Tee's into the system with a new Tee is that what you are saying?

 

[chris watkins]

Just had a look and the feed/vent is same pipe, do I need to replace where it Tee's into the system with a new Tee is that what you are saying?

Yes, as little water movement along this combined cold feed / open vent pipe (thats what we call it) the magnetite tends to build up over the years.

If you want to do a proper job you could split them up so you a 15mm (or 22mm) cold feed from the F&E tank & a separate 22mm open vent pipe which just goes over the tank. Keep the cold feed tee closes to the inlet of the pump.

 

[Freezing2]

I understand there doesn't look much room for cutting the Tee out between pump and floorboards, they are the soldered fittings that have been used