Why won't my potterton 80 work?

[Jimpuma80]

Have now spent a few days trying to get my potterton80 to work on CH.
DHW seems to work ok, but can be a little slow.

Had a problem with boiler locking out after using DHW but cleaned the flow switch assembaly and now the boiler recognises when HW is not being demanded.

When the boiler fires up in CH mode on constant the burner goes for a bit then cuts out. It doesn't go into lockout mode. The boiler will then relight after 2/3 mins. It repeats this but the burner never really goes for more than a minute.

The pump appears to be spinning (by checking Hex nut in middle).
I have already replaced the complete diverter valve assembely.
I have removed and checked over the heat exchange and water seems to flow freely through it.
I have also isolated the boiler from the pipework around the house and checked this seperately using a hose. Water flows freely all round the radiator loops and any water coming out is generaly clean looking.

Does anyone know of any other checks I should make or what this problem could possibly be????

Getting v cold.....

 

[Dan Robinson]

What temperature is the boiler at when it cuts out?

 

[Jimpuma80]

Havn't checked it with a thermometer, but generally the pipes from the heat exchange feel hot. checked the resistance of central heating sensor and dhw sensor and are within range specified.

Boiler will fire up again quickly if I de-pressurise the system and then re-pressurise. I assume this is because it is getting a blast of cold water. I feel the problem is related to circulation not happening properly and temperature rising quickly.

Thanks for your interest.

 

[Dan Robinson]

Could be a duff pump.

 

[Jimpuma80]

Took pump out with manifold attached. wired a plug to the side of it and then held manifold in a bucket of water. Pump managed to move water reasonably well. Don't know if there are any other tests I can carry out on pump, it is currently out of the system.

Pump is also fairly new as the boiler was covered by british gas homecare. They installed the pump 6 months ago.

 

[Dan Robinson]

Well it is either a duff diverter (I know you changed it recently) or a problem in the heat exchanger.

 

[Jimpuma80]

Cheers for rapid responses.

Starting to think Diverter valve is faulty as well.

Would be annoying as I fitted it on thursday from new. When I had it next the old valve I put the ends of both of them in hot water and watched the movement. The new one definitely seemed to move differently from the old one. I hoped this was a good thing.

Do you have any experience of these valves being faulty from new?

Don't know if my test on the heat exchange were thorough enough when I had it out. I found I could pour water in all pipes and the water would flow freely through it at the same rate I was pouring it in. Also soaked it in descaling solution overnight.

 

[steve32]

the diverter opens when the temperature reaches 80 degs
when heating is on pump will run boiler will fire when wax stat in diverter gets to 80 it opens valve, if flow pipe from combi is cold diverter is faulty.

 

[Jimpuma80]

Just put back pump and manifold and started up.

Fired up boiler.
1min 15 sec - boiler cuts off (not lockout) pipe for CH initially feels cold as boiler cuts out. then quickly becomes too hot to touch, is this just conduction of heat from hot boiler rather than water flow or is it diverter valve deciding to open at last?

3min 25 sec - Boiler fires up again everything is hot

4min 23 sec - Boiler cuts out


Does this sound like diverter valve? Want to be sure as I just fitted one and am not very experienced with these things so it took a while! Also if it is the valve I would like to be sure of that before I start complaining to the local spares supplier.

Appreciate all input.

 

[steve32]

it seems that diverter is opening
is there any heat at first radiator or any radiators, how far is flow getting hot, leave boiler on for next half hour and see if boiler fires and how often
which pump have bg fitted it should be a 6M high head
is this the 80 or 80e
is the air vent cap top left loose
has boiler worked ok since you changed diverter
when it fires does it sound like a hollow noise or rattling if it does then its air trapped in heat exchanger stopping flow if it is then increase pressure to 2bar cold 2.5 bar hot with pump running this some times clears air locks and if it clears reduce pressure back to 1.25 cold 1.5-1.75 hot

Hope this helps

steve

 

[Jimpuma80]

The sticker on front says potterton combi 80, behind this sticker is another saying puma80/80e. It doesn't have a temperature control on the front and the manual refers to it as a combi 80. I think it is an 80?

The pump bg have finally fitted (after fitting a random one without a gasket that leaked everywhere) is a CP61. Am i right in thinking the 6 part refers to a 6m head?

First rad is feeling warm but I have drawn some h/w which I believe can cause first rad to warm if diverter is faulty. Will try again in the morning ensuring no h/w is drawn.

The screw on the air vent is loose and I have also loosened the whole air vent to see if water comes out. It does so I assume heat exchange is full of water. I have also heard it vent air in the last few days when necessary i.e. system has just been re-filled.

Have put pressure to 2.5 heard slight venting of air but is still cutting out. will leave running for a bit and see if it gets better.

cheers for input

 

[steve32]

the pump on this combi should be a CP63, CP61 is the smaller pump
your combi is a combi 80 newer version of the puma parts are the same
when you turn on a hot tap the diverter valve shuts to allow all heat to go to heat HW when hot tap is turned off pump carries on running if hot water is over 80 diverter will open to dump surplus heat.
The way we test diverter is turn heating off, turn on hot tap run approx 2 galls hot water, tap on slow so boiler fires and gets to max heat, turn off tap pump on combi runs, when wax head on diverter reaches approx 80deg approx 1 min hot flow to heating should get hot (if you hold pipe be careful it will get very hot very quick) if pipe gets hot diverter is working if not then combi will overheat and go to lock out.
if diverter is ok i would then suspect pump

 

[Jimpuma80]

Cheers for the description on how to test the diverter. Just done it and the diverter is functioning as it should.

Since putting the pump and manifold back on the boiler now fires and stays going so its looking like a dodgy pump. Been running for 20 mins, problem sorted by the looks of it. If it stops again I can only suspect the pump now.

Thanks for your help, warm house for the first time in weeks!!!

 

[twgas]

try turning your cold water stop cock off, these boilers wont supply heating if there is the slightest hot water demand (even a hot tap dripping)

 

[Jimpuma80]

Boiler cut out again, found why the pump was being so tempramental.

The bolt form the center of the propellor on the pump had fallen out. This was not obvious to me when i took the pump out to look at. I only noticed it when i sat it next to a new pump (cp63).

Then started hunting for the bolt, found it by removing pressure gauge and return feed for CH. Poked a small screwdriver through the gauge hole and the bolt fell out of the other side! I can only assume that when I removed pump and manifold together the bolt went down the CH pipe and didn't come back until the system was pressurised and trying to run. May not become a professional plumber, took me 4 days to work this one out!

CH going good for the last 8 hours, HW running a little cool though......