What could be stopping heating working

[KarlAtkins]

So I drained my Central heating system today just to remove 1 radiator in a room I'm decorating. When I refilled the system the central heating nor the hot water will work. I thought it was the motorised valve so I replaced that but to no avail, so the valve came with a new 3 way port so I changed that too, still no joy. No other changes have been made to the system for over a year and no problems at all. The pump runs when the system is powered up and continues to run when hot water is called for but the boiler seems to go in to stand by after a minute or so when powered up. I've even removed the valve again and set the port to the mid position by hand. Nothing send to work, in completely stumped. Any suggestion please. TIA.

 

[Ben-gee]

Why on earth did you change the three port valve on a whim?

Assuming everything was working properly before you drained down, the first thing to do is bleed all of the air out of the system.

 

[SimonG]

Aye airlock. Should be no need to drain down to take a rad off for decorating.

 

[KarlAtkins]

Why on earth did you change the three port valve on a whim?

Assuming everything was working properly before you drained down, the first thing to do is bleed all of the air out of the system.

I wouldn't call it a whim, but why, why is this such a big deal? The system has been bled prior to re energising.

 

[Stu-B]

Difficult to diagnose without being there in person, but as others here have said it’s more than likely an air lock. If you’ve bled the rads try bleeding the pump

 

[KarlAtkins]

Aye airlock. Should be no need to drain down to take a rad off for decorating.

So how do you locate and relieve an airlock?
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Difficult to diagnose without being there in person, but as others here have said it’s more than likely an air lock. If you’ve bled the rads try bleeding the pump

How do you need a pump?
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So how do you locate and relieve an airlock?
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How do you need a pump?

Bleed

 

[John.g]

If you have a open vented system with a feed and expansion tank you could consider draining down the system again and then refill the system very slowly by tying up the ball cock to just allow a trickle of water.

 

[KarlAtkins]

If you have a open vented system with a feed and expansion tank you could consider draining down the system again and then refill the system very slowly by tying up the ball cock to just allow a trickle of water.

I don't, it's a sealed system

 

[John.g]

OK, cant, think of much else if system and pump have been vented except maybe to check for any blockage between the E.vessel and system.

 

[KarlAtkins]

OK, cant, think of much else if system and pump have been vented except maybe to check for any blockage between the E.vessel and system.

I haven't vented the pump, I'm not sure how to do that, can you help with how to vent the pump please

 

[Gasmk1]

have you turned all valves back on after you filled

 

[John.g]

You should see a brass screw in the centre of the pump, just slacken this until air/water comes out, re tighten, if you have a gas fired boiler then you won't be able to access this if inside the boiler casing, some modern pumps don't have any bleed screw on the front and just suggest running the pump on full speed (3) for 30 minutes, others, like mine, have a mode which alters the pump speed up and down for 10 minutes to expel any air,

 

[KarlAtkins]

have you turned all valves back on after you filled

Which valves? If you mean radiator valves I never turned each one off.
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You should see a brass screw in the centre of the pump, just slacken this until air/water comes out, re tighten, if you have a gas fired boiler then you won't be able to access this if inside the boiler casing, some modern pumps don't have any bleed screw on the front and just suggest running the pump on full speed (3) for 30 minutes, others, like mine, have a mode which alters the pump speed up and down for 10 minutes to expel any air,

Ok thanks, yes pump is accessible and separate from the boiler. It is noisy in a gurgling sort of way. I'll see if I can get any air out of it now
[automerge]1599899912[/automerge]

You should see a brass screw in the centre of the pump, just slacken this until air/water comes out, re tighten, if you have a gas fired boiler then you won't be able to access this if inside the boiler casing, some modern pumps don't have any bleed screw on the front and just suggest running the pump on full speed (3) for 30 minutes, others, like mine, have a mode which alters the pump speed up and down for 10 minutes to expel any air,

So i realised the screw and a tiny amount of air cam out but nothing much to speak of

 

[SimonG]

So how do you locate and relieve an airlock?

Numerous ways. Depends on the type of system.

That's the beauty of plumbing, all looks a piece of cake till something goes wrong.

 

[KarlAtkins]

You should see a brass screw in the centre of the pump, just slacken this until air/water comes out, re tighten, if you have a gas fired boiler then you won't be able to access this if inside the boiler casing, some modern pumps don't have any bleed screw on the front and just suggest running the pump on full speed (3) for 30 minutes, others, like mine, have a mode which alters the pump speed up and down for 10 minutes to expel any air,

After releasing the small amount of air in the pump and turning the system back on it is doing the same thing, boiler turns off after about 60 seconds.
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Numerous ways. Depends on the type of system.

That's the beauty of plumbing, all looks a piece of cake till something goes wrong.

I wouldn't dream of touching any of the main components tbf, all I have done is removed a radiator to allow plastering access. The real bummer of it is I've just paid a deposit for all the old stuff in the airing cupboard to be replaced and moved to the loft in 3 weeks time and now I'm spending money on this old one. So the system is a sealed system with the sealed expansion tank. The water which also isn't working is a cylinder fed from tank in loft.

 

[John.g]

Can you now see where the Expansion vessel is located in relation to the pump, ideally it should be teed into the system just before the pump inlet, also what is the pressure, this might be displayed on the boiler front or close to the filling valve for your system, it should be ~ 1.3/1.5 bar when cold, if you bleed some water off the system, say from a rad vent, does the pressure fall.?.

 

[KarlAtkins]

Can you now see where the Expansion vessel is located in relation to the pump, ideally it should be teed into the system just before the pump inlet, also what is the pressure, this might be displayed on the boiler front or close to the filling valve for your system, it should be ~ 1.3/1.5 bar when cold, if you bleed some water off the system, say from a rad vent, does the pressure fall.?.

The expansion vessel is in the loft, the pump is in an airing cupboard in the room below. Yeah pressure when filled is 1.5bar. yes pressure drops when air is bled from radiator valves after refilling system and has to be topped up a couple of times during the process.

 

[John.g]

Is it a gas or oil fired boiler?. An airlock (if) in a oil boiler is easy to get rid of, the way I do it is turn the PRV red knob anti clockwise which lifts the valve off its seat and releases any air, some don't like doing this as the PRV can sometimes leak afterwards but mine never has in 15 years but with very clean system water, not easy to do in a gas fired boiler as you are not allowed to remove the boiler casing.
Is there any manual or automatic air vent fitted where the coil enters the hot water cylinder?, if not you could carefully break the compression fitting at the cylinder and see can you release any air there.

As a last resort you could again drain down the system with the diverter valve manually in mid position (boiler off) and then refill it but much more slowly than before and see what happens.

 

[KarlAtkins]

Is it a gas or oil fired boiler?. An airlock (if) in a oil boiler is easy to get rid of, the way I do it is turn the PRV red knob anti clockwise which lifts the valve off its seat and releases any air, some don't like doing this as the PRV can sometimes leak afterwards but mine never has in 15 years but with very clean system water, not easy to do in a gas fired boiler as you are not allowed to remove the boiler casing.
Is there any manual or automatic air vent fitted where the coil enters the hot water cylinder?, if not you could carefully break the compression fitting at the cylinder and see can you release any air there.

As a last resort you could again drain down the system with the diverter valve manually in mid position (boiler off) and then refill it but much more slowly than before and see what happens.

It's a gas system. I have the casing off the boiler as wanted to check it was ignighted. I've re drained and I'm currently very slowly filling. Fingers crossed that it works but I'm not hopeful.