Plumbing problem.Fully pumped system. I have removed and then refitted
a radiator.Refilled system, bled all valves on radiators, pump and
pipe work. Boiler fires, heats up to temperature and then cuts out.
Press reset button when cool and it will fire again. Radiators do not
get warm. Pump is working and hot, as are pipes on both sides of
it.Presume I have an air lock somewhere, but cannot shift it. Have
repeated all the above several times.
Need help please.

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Clarification of Question by raefa-ga on 10 Jan 2005 17:16 PST

Thanks to answerfinder, not either of those suggestions.
Thanks guzzi, pipework system is about 20 years old with all
copper.All radiators & boiler have been replaced within last 6
years.System has been drained completely; drained with radiator valves
shut;drained with header tank not shut off until clean water flowing
and then drain plug closed.All combinations you suggest about bleading
radiators I have done.I have as from today one radiator, third on
system getting warm, first and second not quite cold, all others
cold.I havent tried forcing water in from the drain end as yet. If I
do that it will be me in the roof with the cloths, as the friend(my
wife)will be with the hose. I do not want to think about it the other
way around.It will be Wednesday before I can try it.
Thanks again, I'll report back.

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Clarification of Question by raefa-ga on 14 Jan 2005 08:57 PST

Hi Guzzi, Tried the backfill, but no joy. Seemed to fill very quickly,
which surprised me, so I am wondering if everything had drained
completely. I did open vent in roof to allow air in to avoid a vacuum
and left it a couple of hours to dribble.WIl try it again, tomorrow
Saturday.Eased nuts at joints in roof and all spurtedwater.I was
hoping one would be dry.

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Clarification of Question by raefa-ga on 20 Jan 2005 06:47 PST

Hi Guzzi, Still draining and bleeding and swearing and still no hot
rad's. Since I last reported, I have had floorboards up and drained
system from there, as there was still water in, even after drain plug
had stopped running.I have fitted an extra bleed valve in main pipe in
roof(now has one in flow and one in return), which definitely had air
in as I cut through before draining, very clear gasp heard and some
seconds before water leaked. Followed by very quick descent to outside
drain plug!! Removed paddle from isolator in roof as pipe on each side
was not same temp', so wondered if it was not fully opening and
restricting flow. Pipe both sides now equal temp'. Boiler fires for
about 4 minutes and then cuts out and it is about 30 minutes before it
fires again.
Everytime I bleed in roof, valves and pump, I get air. No air coming
from any radiators now.If I bleed one radiator into a bucket it will
eventually get hot, but starts to cool as soon as I close bleed valve.
Have done this on several different radiators with same result. Flow
and return pipes in roof get hot.
Dont know whether it has any bearing but this is a bungalow. I havent
used compressed air suggestion as I do not have it, but all  radiators
bleed quite freely, but some better than others.

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Clarification of Question by raefa-ga on 21 Jan 2005 03:15 PST

Hi Guzzi, I have had the pump off to clean ports and even reversed it
to see if it would shift whatever it is, but I wont do that again as I
thought the place was going up any minute, all pipes rattling, boiler
making strange noises, I got the impression that you dont do that!!
Pipes are 22mm up and down to ground floor and then 15mm to each radiator.
Have tried boiler on max' but it just shuts down the same.
I feel that the pump is OK as the return from ground floor back into
roof gets hot, so assume water must be circulating.
Just awaiting draining and then going to do yet another back fill.
Have installed a on/off valve in expansion pipe as last time water
eventually ran up it and into header tank. First I knew was when
overflow started running.
Watch this space for the next episode.

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Clarification of Question by raefa-ga on 21 Jan 2005 08:40 PST

Hi Guzzi, Back filled, bled etc, no change. Drained again,incuding
boiler, closed all valves, refilled, bled as per your sequence, then
spent 1 1/2 hours sitting in roof just bleeding 5 valves and the pump
in turn. Loads of air out of each and then eventually it got quieter
and all the pipes were hot and for once I could still hear the boiler
firing.Went down with everything crossed and radiators were hot!!!!!!!
Its been a long week and a lot of wasted time, but many thanks for
your advice and support. Have a good nights sleep and a drink on me.
Kind regards, Raefa.(childhood nickname)

I'm no plumber and not sure wether this is appropriate to your system,
but is the expansion tank full, or is the ballcock stuck?

I am a plumber -- or at least a small part of me is. This can be a pig
of a problem. How old is the system? Does it have ancient iron pipes?
Pressurised? etc?

You say the problem only started after you changed a radiator. I take
it the system was drained when you did this? One can actually usually
get away with bunging up the feed in the header tank and relying on
?vacuum? to retain water in the system. Can result in sudden gurgle
discharges though.

Anyway, there is no one solution but several things you can try.
First, lock off the ball cock, close off all the radiator valves then
open the drain. Open the furthest distant radiator valve and its
bleed. After this has flowed through, repeat systematically with all
others. Sometimes it works better if you open the isolation valves as
well, sometimes not. Close everything off again and ?liberate? the
ball cock. Then starting with the radiator nearest the header tank,
open the valve (valves) and the bleed. When water gushes, close it off
(valves too) and work your way down the system. Usually this works but
you may have to experiment with the sequence. Sometimes sucking on the
bleed hole gets things moving too.

In cases of extreme obstinacy, you can fill it up from the bottom with
a (mains pressure) hose. best to have someone in the attic to shout
when the tank is filling. Select one radiator at a time -- open valve
and bleed. To increase the blasting action, you can bung up  the
header feed too.

Guess its a bit superfluous to suggest you have a good mate and lots of towels.

Post if you want more info, but let us know if you succeed.

Best

Oh dear. You must be tearing your hair out at the roots. Didn?t look
last night as 100mph winds took out our power. Typical Scottish
weather!

I think (as I?m sure you do too) that there are lengths of pipe which
are not emptying when you drain the system. I?d hoped you wouldn?t
have to resort to the backward filling as I have on occasion. Perhaps
the slightly less messy route, not involving your wife :-), of purging
with air might work. Assuming there is no blockage -- a rare event and
no reason to suspect. Open the drain, close off all radiators then
open one valve. If you have a compressor, pump air into the bleed -- I
don?t think I have to say anything to you about excess pressure
damaging the system. After that, close the valve and open the isolator
and blow again. Repeat with all radiators. Sometimes one can isolate
which arms are air-locked if you can get your mouth round the bleed.
If there is resistance to blowing....... Suck / blow can sometimes
shift the water. If you are really keen, you can drill a hole in a
bolt of the same thread and fix a tube to it for blowing. I have a
vague recollection of actually seeing such an adapter in use.

Incidentally, as I guess you know, there will be a bleed on the pump,
and perhaps others too.


Hope to hear of progress.

Best

This *really* is one obstinate system raefa (stating the bleeding
obvious -- ha ha ha).

Since you?ve managed to rig up a back-fill -- bung up the top feed /
one radiator at a time / valve open / isolator closed / bleed open /
force water into drain until it flows freely. Then valve closed /
isolator open / bleed open / force water into drain until it flows
freely. A bucket at the bleed might be desirable unless your animals
can go two by two.

This is probably what you were going to do but it?s always worth
mulling things over with another, even if only for sympathy.

Hope to see a post after an enjoyable Saturday, reporting success.

Best

I feel for you raefa, if that is any consolation. A header tank system
in a bungalow will of course not supply very high pressure so could be
instrumental. But it did work previously so something has changed.

Maybe we have to go back to basics. Are the pipes microbore -- ie 8 or
10mm? Could there possibly be a blockage? Unlikely of course but
microbore is more prone to it. Wad of steel wool of something dragged
in from the supply finally packed up solid?

How about the pump? ?Hot on both sides? but that could just be a bit
of natural convection. Being an impeller, water can flow through with
little restriction even if it?s not turning. If you can run the pump
without the burner you should feel slight vibration on it but that
doesn?t guarantee it?s running. Might hear a gurgle from it though.
Removing is a bit of a pig especially if there are no isolators but
we?ve got to tick that one off.

If the pump is OK you could try cranking the boiler thermostat up to
full and brute forcing the water to shift. Might have to crank up room
thermostats too, depending on the arrangement.

This is beginning to keep me awake at night too :-) It?s personal, so
keep in touch.

Best