Potterton Puma 80 - hot water issues

[mike.talbot]

Hi Guys,

Am hoping someone out there will be able to point me in the right direction!

I have a potterton puma 80 combi which, to all intents and purposes in running absolutely fine and dandy (touch wood) however, I am finding that during "peak water usage" times, i.e. 7-9am when i want a nice hot shower I am struggling to get hot water. The mains pressure is still adequate at these times, but my boiler doesn't seem to think so..... it will fire up on and off as and when the pressure rises/drops, it really is only a minute change in pressure from working to not working, and certainly still enough for the boiler to function correctly without damaging it due to low pressure (which is why i assume the boiler stops heating my water as it foolishly thinks there is no water passing thru it..?) Anyone got any ideas? is there something that can be adjusted to rectify this? I am pretty novice, but after some problems last xmas with the CH know my way around the boiler quite well.

ps - this does only ever happen when the mains pressure is a little low, nothing else is causing me any problems, and it doesnt happen at any other time....

looking forward to your responses.

Cheers

Mike

 

[Agile]

I hope your filling loop has not been left open !!!!!!!!!

Remove the flexible tube and see if you get wet!

Otherwise the boiler should turn on at 2.5 litres per minute. If higher then the DHW diaphragm unit is failing.

Tony

 

[mike.talbot]

Thanks for the tip Tony,

I will have a nosey when i get home, I know the filling loop is attached, but the tap to "top up the boiler is definitely closed, however the tap from the mains may be open............

I suppose next time i get a cold shower I'll have to get the measuring jug and a stopwatch out......... Although I think the pressure will still be well above 2.5 litre per min!

I'll keep you posted!

Thanks

Mike

 

[mike.talbot]

Hiya Tony,

Filling loop was closed both ends - about a millilitre of residual water in there - and I thought I was gonna drown!

Now - whats all this about a diaphragm? When I mentioned the pressure dropped minutely, this is only me making an assumption, maybe it hasnt dropped at all, but normally u do see a slight change, i.e. the water seems to jolt out of the shower head momentarily when the pressure goes back up, then vola hot water again... could this not just be the auto-flow restrictor switching off once temp has been attained? (sorry if i sound arrogant or stupid - just realise that without actually seeing the problem it can be hard to diagnose sometimes....) either way - after some "rough" measurements I dont think I have seen the pressure drop below about 3 litres per min, and still running cold then. its like it will cycle on and off, every couple of mins ill get 60 secs of hot water then nothing again for a couple of mins.....

Like i said, only happens in a morning usually when im late for work - sods law!)

so if u dont think it may be anything else, where is this diaphragm located and how much are they to replace? would i need to get a corgi in, or is it something if i am electrically competent, and generally ok with plumbing i could do myself?

any help/advice would be appreciated....

Cheers

Mike