Central Heating packed up over Xmas

[JohnD]

If you have sludge it is common that a blockage prevents the system filling properly. You can test this by opening the bleed valve on the highest radiator and seeing if water squirts out well (this must be a rad higher than the boiler, the pump and the electric valve to give a confident answer).

If is is not filling you can fill with a hose on a drain-off point.

p.s. if you have a blockage, the cleaning chemicals will not circulate past that point so they will not clear it.

Do you have an Aquavac or other wet/dry vacuum cleaner?

 

[McFly]

Thanks for the fast reply I was not expecting anyone to be logged in but worth a try. Just tried you suggestion and the bathroom rad 1st floor (boiler is ground floor) gave a good jet of water no sign of air. New pump is selected to 3 and seems to be pumping as the pipes from the pump(airing cupboard) to the mid position are roasting. They are also roasting coming out of the mid position valve each side depending on selection. I am baffled.. Have noticed that the boiler gurgles when it shuts down. So air in there I expect.but have not the first clue how to do anything about that. Don't even have a user manual. I just dont understand where the flow is going. Have checked tank in loft again and it does not seem to be going there

 

[McFly]

sorry just noticed sorry but I don't have a aqua vax

 

[JohnD]

Are any of the Return pipes hot?

 

[McFly]

I don't know which are the return pipes. Would these be in the airing cupboard?

 

[JohnD]

You recently fitted a new pump. It could be worth chacking that the pump valves are fully open (sometimes they break) and not clogged, and the the pump is not choked with sediment which has been washing round the system.

Also try manually operating the electric valve in case it is not opening fully or has been incorrectly fitted.

You say the supply to and from the pump is hot, and to and from the 3-way valve, so there must be some movement. Check all your valves are open and there is nothing you closed and forgot to open.

Edit: Return pipes: From the Hot Water cylinder, there will be a supply of hot going in to the coil, and a return coming out. There is also a return pipe from each radiator that feeds into the CH return. The returns will probably end up at the boiler, and may be combined into a single 28mm copper pipe.


Edit 2: As bab mentioned earlier, there might be a balance pipe that allows flow to go straight from the Supply to the Return, in case all rads are closed, to prevent pressure having nowhere to go. If there is one, it may be visible or may be hidden under the floor. It will usually have a valve on it to allow you to increase or reduce the flow. Sometimes the bathroom radiator is set up to do that.

 

[McFly]

I have just closed and opened the pump valves again to be sure.. Can't really check the pump again without removing it but from the sound and vibration it looks like a very good flow. By opening the electric valve manually do you mean the mid position? It is indicating selected position and motors when another selection is made. Can not move it manually any farther. I cannot think of any other valves to check. I did notice a hand wheel valve at the bottom of Hot water cylinder. Is that the return from the hot water heating coil in the tank? If so I suppose it should be open? Does it operate like a lockshield valve on the Rads? I don't remember closing off anything else and cannot think of an other valve in the system! Thanks for your patience. I am just a willing amateur.

 

[JohnD]

About the cylinder, yes. It may be worth closing that down. When calling for both DHW and CH the cylinder may be stealing most of the flow (it is a short run in wide pipes) if it is not throttled down.

I suppose it is possible that your desludging work has changed the flow pattern and you need to re-balance when clean.

There should be a cylinder stat that operates the electric valve (you should hear it clicking) though this is sometimes faulty or not present on old systems.

 

[McFly]

Re your edits:

Have shut down all the upstairs rads and have got the downstairs Hall rad to heat up. The return pipe from it by the lockshield is warm while the input flow is now hot. ish

Checked the 2 large pipes from top of boiler output (I assume) is roasting other (return) is luke warm.

Reference the balance pipe. I have shut off the bathroom rad and so it should be out of the equation. If there is one under the floor I certainly have not disturbed it. Although if it exists in this system it would explain a lot eh!

 

[JohnD]

...Checked the 2 large pipes from top of boiler output (I assume) is roasting other (return) is luke warm....

Well, that suggests that your system is using the heat somewhere. Apart from a lag while it heats up the circulating water, this can only be heat going into the hot water cylinder or emitted from the radiators.

If the return pipe was very hot this would indicate that the water is not passing much heat to cylinder or rads... which is certainly wrong!

Try turning the cylinder control down too (but not fully off).

 

[McFly]

Sorry I had cut and pasted your last reply in to ensure I answered all your questions then forgot to delete before submitting

I have closed the cylinder hand wheel fully but did not feel like any flow through it anyway. Would not expect there to be as heating only now selected
Appreciate the thoughts on rebalancing but surely this is impossible until I can get flow to all rads. Currently all upstairs manually closed heat to downstairs hall only.

I am still conviced that the boiler is not staying on long enough to heat enough water to circulate round the system. Is that possible or even make sense? Currently fires up and stays on for about 4/5 mins then off for about 7/8 mins. Don't quopte me on times as I am running round the house checking various things and trying to keep warm...

There is a cylinder stat trried turning it but do not hear any clicks. Is this because hot water not selected?

 

[JohnD]

The cylinder stat should click even without power to it.

The boiler should not turn itself off until the Return pipe is hot (unless the water is not circulating properly).

I think you have a circulation problem. Pump clogged; blockage; valve not operating correctly?

My knowledge is limited and I've run out of ideas

With luck some of the pro's will be along in a minute.

 

[McFly]

Thanks for your time JohnD. If you have run out of ideas guess what I feel like. Been at this for long time now. Thanks again good to bounce ideas off a pro.
Steve

 

[McFly]

Afternoon all,
just a quick post to let you know problem now sorted and thank you all for your help. As you all expected it was a blockage. Had a plumber in for 4 hours this morning ooch! Finally found that an Aerjec 11 in the system was blocking the flow. Not immediately apparent as when draining the system the F&E was draining through the return. Confusing thing was some flow getting through to the pump. So all our time was not wasted as the fault diagnosis was much quicker due to the previous actiones taken. Still need a good de-sludge of the whole system which I will do when the chemicals arrive. I could not have removed the Aerjec to check as it was all soldered joints to the 4 pipes.

Anyway thanks again to everyone involved it has been interesting and a superb site to browse.

All the best