Puma 80e Hissing? Bubbling? Boiling?

[Joe_MCSE]

Hi All,
After changing the bypass valve due to leaking, the boiler is having weird noises and activities. Here are the circle of events:
Problem
1. CH kicks in, pumps comes on, burner fires up.
2. After about 1min hissing/small bubbling noises come from the heat exchanger then approx 10secs later the burners turn off.
3. After about 10mins have passed the circle of events repeats itself, eventualy the radiators get hot.

It sounds like the boiler is over heating, air in the boiler or both. The bypass vale is half open (22mm Pipe).

How do I bleed the boiler (thats if I can)?

Please advise.
Joe

 

[ChrisR]

Automatic Air Vent, top left.

Make sure the cap is loose a couple of turns

 

[Joe_MCSE]

Hi Chris,
Thanks for that.

This was replaced last year with a 'not a potterton part, but does the same job' (plumbers words) air vent. It is totaly enclosed with a black plastic screw. This has been loose all the time. I loosened its compression nut and hot water flowed out.

Should this happen?

 

[Joe_MCSE]

Hi Chris,

Also looking at the PCB I noticed the R1 resister is scorching the board. Can I just resolder?

 

[kevplumb]

howay dell boy ???????

 

[Joe_MCSE]

Sorry Kev, you have me at a loss!!

 

[kevplumb]

private joke

 

[Bahco]

If water has come out of your vent then there is no air present in your boiler.
You can balance your system with the gate valve on your bypass. Turn all your rads off and with your gate valve fully open, run your boiler. Adjust the gate valve until your system is no longer kettling. Turn all your rads back on. Do not however screw the gate valve completely shut as this is a safety feature

 

[PEDANTICVINDICTIVEMAN]

Not aware that a byepass was a safety feature.

 

[Bahco]

As I understand it the bypass allows for the dissapation of heat from the heat exchanger should all the trvs shut off the rads. Would it not do damage to the boiler if the gate valve was shut by overheating. I am aware that the overheat stat would cut in but this is another method of protection

 

[kevplumb]

so there

 

[PEDANTICVINDICTIVEMAN]

Shouldn't be TRVs on all the rads, the rad in the room with the room stat should have locksheilds on to prevent it being turned off, you can fit TRVs to all the rads if an auto byepass is fitted, some boilers come with one built in.

 

[Joe_MCSE]

Hi All,

Thanks guys for getting back, if i can add this one for all.
I do have drayton TRV's on all but two rads (furthest away, foye) for safety.
I will try the shut all down method to get the balance right.
Just to add also on my symptoms, after the boiler doing the off/on cycle for about 30mins the boiler stays on (thermostat permitting) and works normaly.
So it seems this querk only happens when starting form cold???

 

[Joe_MCSE]

Hi Guys,

Many thanks for all your help. I did try to resolder the R1 and R2 resisters but the erratic cycling of the boiler continued. As a couple of the relays were slightly burt I bit the bullet and purchased a new PCB.

Installed without difficulty and has been great since.

Once again many thanks.

Joe

 

[ChrisR]

Thanks for the feedback, glad its working.