Boiler fine but cold cylinder

[aroundM21]

My boilder seems fine - two piping hot (geddit pipes coming out to supply the central heating and the hot water tank - up they go from the ground floor.

But by the time the pipe gets to the cylinder, it's stone cold.

Is this most likely trapped air ?? If so, is the only solution a full drainage of everything ??

Thanks in advance !!

Mike / Manchester

 

[gas4you]

Are the radiators getting hot ok

 

[gas4you]

I go hot and cold when I have trapped air

 

[Bambergaspipe]

Most likely valve which changes from Heating to Hot water. Probably knackered

 

[aroundM21]

I can get my Rads scorching hot - no issue there.

I don't believe I have a valve that alternates HW/CH/both (every April/May I wish I did have ...).
Also have just found out that it's a Primatic cylinder because the input midway does not go to a vent, it is sealed closed.
I do believe the system was put in around 1975-1980 ish, so this tallies.
Above my cynlinder I have a COLD water tank and also a small feeder tank - but I'd understood the feeder was for the heating only (despite this also having a pump), indeed the heating water was previously drained and had the anti-blocking chemical added a few years ago with no issue.

So if I've understood correctly it's a Primatic, and trapped air is the most likely cause. As I've read that Primatics tune themselves in this respect, I've no idea how to fix this (please don't tell me I need a new tank ...) so very interested in any thoughts.

Thanks in advance.

Mike

 

[werewolf]

Some primatic cylinders have a little air vent fitted on the side about 1/2 way up.

 

[Rotunda82]

Above my cynlinder I have a COLD water tank and also a small feeder tank - but I'd understood the feeder was for the heating only Mike

You dont normally have two tanks in the loft with a Primatic cylinder - are you sure its primatic ?

Sounds like an airlock if there are no motorised valves ?

 

[aroundM21]

ok, mistake in my understanding : it's not Primatic, it's fully pumped and I think sealed (I say "I think" because there is a small - ie feeder - tank in the loft. Is this to help maintain the pressure of such a system ? I thought there was no feeding tank ...)

This explains more easily, and we believe the motor/pump is gone.
I'm now paying royal fees to have this fixed. Here's hoping ....

 

[Rotunda82]

Ok - its not a seled system because you have a F&E tank in the loft which means its open vented ( A sealed system usually consists of a pressure guage and some means of manually filling the system ie. a filling loop )

If it is fully pumped it is more than likely a zone valve or mid position valve failure which shouldn't be too expensive to rectify