Potterton Netheat switching off after 5 mins

[tifano]

I have a Potterton Netaheat boiler which keeps switching off after a while.

I recently drained the CH as one radiator value was leaking. Took me 2 days to get all the radiators working but it's difficult to get the entire CH hot as the boiler keeps switching off. Hot water is fine. Problem is worse in the mornings, radiators are luke warm, but in evening after leaving system on for 5 hours all is well. The water pump is running fine, the pipes out of this are HOT, the honeywell valve doesn't seem to spring back after being left in 'open' position. One vent on the side of the hot water cylinder needs frequent venting though (about 5 seconds worth of air is expelled).

The boiler was serviced last year. Could it be a fan problem (which seems to be running fine when boiler is on).

 

[tifano]

its a 16-22 model

 

[Agile]

It sounds as if you still have some air in the system.

It will probably work itself out after a few days.

Have you vented the pump? See FAQ

Tony

 

[tifano]

does the water pump have a vent ?

 

[gas4you]

Undo the large silver screw in the middle. Air then water should come out.

If you bleed the upstairs rads do you get water out? Is the F&E tank full of water?

 

[JohnD]

didi you clean the system when you drained it? Did you add inhibitor when refilling? If not it will be generating corrosion gas.

 

[tifano]

I bled the upstairs radiator and I get water coming out (initially had some air). Will try undoing the middle screw and see what happens. But the pipe before and after the pump are hot (assume already filled with hot water). Thanks for the inhibitor reminder - have to add that in !

 

[tifano]

opened silver screw on water pump - water immediately came out - still having to vent the vent beside the water cylinder. Any other thoughts ?

 

[bengasman]

Turn timer completely off. Check if any easy movement in the lever on the m/v. if there is, your valve is not working.
Also sounds like you have a bypass hanging open.
If you had a radiator leaking, you have a high chance of sludge blocking the flow somewhere.
Do you have one or 2 valves?
What happens when you run heating only?

 

[tifano]

Ok - I switched off the timer, the Synch Motor gave very little resistance. I've replaced it and the new one gives very little resistance too ! One thing I noticed is that when i switced off the electrical supply before replacing it, the old m/s gave resistance as i moved the lever. Right now the radiators are warmish, and sometimes they are hot.

I have only seen one valve in the system, at the output of the hot water tank. This pipe leadd to the m/s and then the pump.

Turning heating only, get the same problem, the boiler keeps switching off and doesn't let the radiators get hot enough.

 

[bengasman]

How many pipes at the m/v?
How did you know the m/v is at OUTPUT side of cyl?
How did you check that when dhw is off, it REALLY is off?
Does the lever feel different when the heating is on compared to off?

 

[tifano]

bengasman, thanks for your help so far !

- I have 3 pipes on the m/v
- the m/v has to be at the output of the cylinder as the pipes are very hot at this point and the return pipe seems to enter the bottom of the cylinder. This return pipe is cooler.
- not sure if hw (as appose to dhw) is off.
Lever feels the same when heating is on. Very loose and easy to move.

I think I'll start looking at voltages of the various coloured wires and see which ones show voltage when off / hw/ ch and ch/hw.