CH... not HOT

[NiG_21]

Hi,

I have a Puma80 boiler servicing 7 radiators (3up-4down) and have just replaced some strange microbore plastic pipe which was throughout the CH system (from a bar we think 10mm Od - 6.5mm Id) with good old 15mm copper piping .

System holds pressure fine, rads are bled, but the rads do not get HOT only warm (and cool at the bottom) but even this takes ages.

The boiler fires for about 25 seconds before shutting off and the water circulates (slowly) through the system. Then about 2 minutes later the boiler will fire again. The pumps seems to be spinning and is set to 3 (centre screw check) and I can hear the water circulating in the boiler. The hot pipes from the boiler are very hot but the heat doesn't seem to be getting to the rads.

With all the valves open (not thermostatic) only one radiator gets hot, with them all partially closed this is when I get the warm only thing going on.

Is the boiler simply overloaded or should it be able to cope? Do you think the pump is not working at full flow? What's your thoughts fellas... I would like a nice warm house this winter...

 

[kevplumb]

udersized pipework

 

[brumylad]

presumably the flow and return pipes are run in 22mm for some distance from the puma 80. In an averaged sized semi, I would run two 15mm loops (one for upstairs, one for down) off 22mm flow/return.

Incidentally I thought the original pumps on puma 80's did not have speed settings ?

 

[bathjobby]

When the boiler cycles like this and there is restricted flow through the system, its odds on you have an air lock preventing sufficient flow = boiler trips out on excess heat.
n.b. speedfit type 'upvc' pipe is now fitted in new builds as standard and will outlast copper.

 

[ChrisR]

It could be your pump iompeller is blocked so it isn't pumping anything much. Isolate and drain as you need, then undo the 4 allen screws, pull the body off and have a butchers.

 

[NiG_21]

Thanks for the thoughts guys...

Yes there are 22mm pipes running from and to the boiler iteslf and there are two loops in the house (both 15mm) one upsatirs and one downstairs.

The problem was with the pump, it had a airlock in it and the impeller was cavitating. If I unscrew the centre screw of the pump (and the pump stops) I can hear the air escaping. Then I can just tighten it again and get a nice hot house for the next three our four days.

Then a nother airlock forms and I need to do it again. But at least I'm warm now

 

[kevplumb]

is the aav open ?