Luke warm/cold radiators no pressure increase when boiler on

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Hi everyone
I wonder if any off you can help me. I have an Ideal Europa 24 combi boiler. A standard pressurised system.
The faults are that the radiators will only get luke warm. Some will stay cold some will heat up and it can be quite random as to which does what.

I have read many forums on here and followed procedures that have been recommended. Very useful but alas not solving the problem.
This is what I have done to date.

New expansion vessel
New pump
New automatic air vent
All radiators removed and flushed
currently circulating a cleaning agent through the system.
Fitted a drain/flush valve at the lowest point (wasn't one)
Have bled all radiators (with TVR's off and on )
checked all TVR's are working correctly.

One thing I am noticing is that the pressure gauge which is set at approx 1 bar is not increasing as the boiler heats up when the CH is on. I'd expect it to rise by half a bar as the water expands in the system.

Boiler fires up ok has about a 30 secs fire up 2 mins rest cycle. I assume this is normal !

Hot water is spot on. And if all but one radiator is closed down they will all get hot individually.

Any advice greatly received.
 
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Since last winter really. Like I said hot water is fine and I can isolate certain radiators as required and draw heat from them all be it not blisteringly hot.
I have been replacing parts as finances dictate. I thought that the pump was faulty but not so sure now.
A lot of sludge came out of the rads and I flushed them yesterday and put the cleanser in. I guess I could take time to work the system.

My concern is the lack of pressure increase on the gauge when the heating is on. Shows lack of expansion !
 
Don't forget some of the expansion will be taken up by your expansion vessel.
If there was a lot of sludge and oxidised partials in the system, you could have pipe blockages. What sized pipe work to the rads?
Might be worth doing a little more investigation, with regards to whether both flow and return pipes are free of obstructions.
 
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15mm pipes. I am currently running each rad in turn for a few hours each. Starting from the furthest from the boiler. They seem to be getting red hot individually. So hoping that with the cleaning solution and forcing all the energy down one radiator at a time will solve the problem. We shall see.
Thanks so far for the advice. I'm sure that it is a case of a build up of grunge etc that will hopefully be working it's way through. Once I can get the rads all working to a reasonable temp then I shall do another flush.
 
fires for 30 secs then switches off for 2 mins, no this isn't normal at all
 
flow problem but then as you are cleaning at the mo then this may sort the problem
 
Ah all leading to a grungy system then. I have heated all rads individually for at least an hour + all rads getting pipping hot. However again all rads have become either luke warm or cold when all are operating.
Seems like the return flow pipes on each rad are getting quite cold even though the feed pipes are staying reasonably hot.
So I guess it could be a blockage somewhere.
A power flush me thinks.
 
The reason the expansion is minimal is that hardly any of the system volume of water is hot. The boiler heats the water, the water expands, the pressure rises. Not much hot water in the radiators = no expansion.

So this is a red herring.

You have poor flow due to an almost complete blockage. Try disconnecting the heating pipes from the boiler and trying to run mains water through. Look for a caked non return or anti gravity valve left in the CH pipework from an earlier boiler.
 
Just a quick check to do, with all radiators on does the return pipe at boiler get hot even though rads are cold??
 
The reason the expansion is minimal is that hardly any of the system volume of water is hot. The boiler heats the water, the water expands, the pressure rises. Not much hot water in the radiators = no expansion.

So this is a red herring.

You have poor flow due to an almost complete blockage. Try disconnecting the heating pipes from the boiler and trying to run mains water through. Look for a caked non return or anti gravity valve left in the CH pipework from an earlier boiler.

Thanks Simon.
I don't have a anti gravity valve due to not having central heating in the house when I bought it 10 years ago. It was the first thing that I put in.

Al
 
ok, def a restriction in flow somewhere, trouble is finding it!!
How long has the cleanser been in, what have you used and is the concentration right?
 
cleanser has been in 48 hours. The bottle could cope with 10 rads I have 5 I stuck the lot in. I'm trying a re flush now just to see if I can blast the blockage.
 

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