no hot water or central heating - vented system

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Hi, I've got a Potterton Flamingo 20-30 boiler and water cylinder (see photos) fed from 2 large tanks feed & expansion tank.

Getting cooler now, so decided to put on the heating for 1st time since April and the boiler keeps cutting out after approx 5 minutes and there's no heating. The hot water is coming from the immersion as the leccy meter flashes fast when I run a hot tap.

I've bled the radiators with the heating off, valve near cylinder was half open and has no effect when fully opened so don't think I can bleed anywhere else.

Thought the problem might be a stuck valve in the pump as not been used since April but I can't see a pump anywhere, even checked under floorboards beside cylinder and cupboard below the water tanks only to find a 30 foot drop :0

No pump under the boiler as integrated washing machine there or in the under sink unit or any units on way to the cylinder.

This makes me think it might be an old gravity system but I'm not sure if the two larger pipes are the ones needed to make a gravity system viable or not?

I noticed that the water tank on the left appears to be considerably more empty than the idenatical one to its right, going by the sound they made when I hit them - not sure if that's significant?
 
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There is a thing at the top of the pipes off the cylinder on which I could use a flat head scredriver which was already half open but had no effect on fully opening - see pic opposit.

Oddly there's no thermostat on the cylinder either.
 
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The thing you are reffering to is an air vent for releasing air out of the system.
I would do some more investigating there should be a pump somewhere.
How many pipes come out the boiler?
You may have what is referred to as a summer valve in the form of a gate valve which is an old style of isolating the central heating circuit when not needed.
 
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Hi, anybody any more ideas they can offer as I can't afford to call anyone out just now?
 
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Have you checked there is sufficient water in the system? Opening the air bleed at the cylinder and getting nothing would indicate there is insufficient water in the system, you should expect reasonable jet of water (after any air is expelled) when opening one of these.

If one of the cisterns (tanks) is empty it could indicate a stuck/faulty ballvalve, and if this is the F&E cistern (to top up the CH system) then that may explain lack of water in the system!
 
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Thanks Huge

I'm not sure if it's an air bleed on the cylinder or a valve to release excess pressure as it has always been half open and nothing comes out if I turn it fully open using a flat head screwdriver?

The F&E tank had some water in it and I added more by holding the ball valve down to try and put more water into the system as the F&E tank only had a couple of inches water in it.

I'm not sure if the empty tank on the left of the photo is an overflow for the one on the right or if it's the 1st one to be fed from the mains - I'll check when I get home tonight.
 
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Pressure relief valves should be connected with an external discharge so any boiling water or steam is directed safely outside the building. Suspect valve in question is some type of air vent, possible an automatic version. If still in doubt about water levels in the system, drain a few bucketfuls off from a suitable point and check to see if the system refills as it should. If it doesn't (and ballvalve appears ok) then look at a possible blockage in the cold feed.

Running a magnet along the pipework may pinpoint a problem. Magnet wont stick to copper, but if there is any build up of sludge inside the pipe the magnet will attract to it.
 
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Pressure relief valves should be connected with an external discharge so any boiling water or steam is directed safely outside the building. Suspect valve in question is some type of air vent, possible an automatic version. If still in doubt about water levels in the system, drain a few bucketfuls off from a suitable point and check to see if the system refills as it should. If it doesn't (and ballvalve appears ok) then look at a possible blockage in the cold feed.

Running a magnet along the pipework may pinpoint a problem. Magnet wont stick to copper, but if there is any build up of sludge inside the pipe the magnet will attract to it.

I've drained off a fair bit of water and the F&E tank is refilling automatically.
I've ran magnets along all accessible pipes and no sludge evident.

2 things I was wondering:

1. Could it be an air lock, which could be fixed by draining the system via hosepipe to garden - only thing is I can't find a drain valve anywhere?

2. Could it simply be the thermostat on the boiler having gone? Is there a way I can test if that's the case before buying a new thermostat?
 

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