strange problem with heating?!...

[skuba]

we've got quite an old central heating system (regular boiler) with a tank in the loft. i could have sworn the water in this tank used to be hot, but i assume i'm mistaken and that it's a cold water tank? anyway, recently the heating has been making lots of creaking noises and the pump it's moaning and groaning! none of the radiators are getting hot (a couple of them seem to have almost started to get warm but then packed in) and the towel rails in our bathrooms won't bleed at all - there's no water pressure or air coming from them

the boiler is kicking in fine, and the programmer seems to be working okay. i'm pretty sure it's something to do with the water supplier or pump (or air in the system?)

any ideas? any help appreciated!

thanks

 

[oldbuffer]

1. Have you got a large cold water storage cistern (CWSC) (50 gallon / 240 litre) and a small (4 gallon / 18 litre) cold water feed and expansion tank (F&E) in the loft? If so:
1a. Check there is water in the F&E. The level should only be about 4 inches above the outlet pipe at the bottom. If not, make sure the float valve to allow water in is working, and replace if necessary.
1b. If the water level in the F&E is OK, and water comes in if you depress the float valve arm, I'd suspect a blockage in the pipework between the F&E outlet and where the pipe joins the central heating circuit. The only real cure is to cut out and replace the blocked pipework.
1c. There is a blockage of some sort in the central heating circuit.
2. If you have a sealed boiler system (no F&E tank, but an expansion vessel either in the boiler or external to it) then:
2a. The pump is worn out and can't circulate a sufficient volume of water.
2b. There is a blockage of some sort in the central heating circuit.

Not an exhaustive list, but perhaps a good starting point.

 

[skuba]

thanks oldbuffer! i've just taken a few photos. there are 2 tanks in the loft (a large one and a small one). both seem to be working ok in that they're full of water and if i move the ball cock water comes into both tanks...

Tanks_loft

• skuba
• 8 Nov 2019

20191108_154919

• skuba
• 8 Nov 2019

20191108_155144

• skuba
• 8 Nov 2019

 

[oldbuffer]

The F&E tank should NOT be full of water. With the system off and cold(ish) it should have about 4 inches in the bottom. As the name suggests, it is there to feed water into the heating circuit, and handle the expansion when the water heats up. If its full with the system cold, any expansion that goes into it will disappear down the overflow.

The pump looks quite new, so probably not the issue.

Sounds very much as if the feed pipework is blocked. This also ties in with the fact that there's no air or water coming out of some radiators when you bleed them.

The blockage is usually at an elbow and / or in a horizontal section. You could try running a magnet over the copper pipes. If its attracted to the pipe, there is likely to be some haematite in the pipe (from the inside of your radiators) and could well indicate a blockage. Central heating cleaning chemicals won't touch a complete blockage (no circulation), so cutting out and replacement is the only realistic cure.

 

[skuba]

i've put the pump on full power, and it's started to heat the house. i appreciate this probably isn't doing the pump any good as i assume it's desperately trying to push/pull water through the pipes?

 

[ianmcd]

not the answer, I too think you have a blocked cold feed, only way to sort it is to cut it out , as already suggested see if a magnet attracts to it

 

[CBW]

Would I be wrong in thinking there could be a 3 port valve fault?

 

[ianmcd]

Would I be wrong in thinking there could be a 3 port valve fault?

There may very well be , but that wouldnt stop the rads from bleeding, only a blocked cold feed will do that if the F&E tank has water in it