potterton promax 15 he

chris23ab · 29 Sep 2009

Hi.
I am new to here and am gas safe registered.
I am having a problem with the above boiler on an unvented system.
Boiler fires up and runs on hot water ok.
When central heating is running ( not for long ) there is a sloshing noise where water is entering the heat exchanger, the flow sensor drops out and boiler and pump stop then there is a backfill of water and air bubbles back up the return pipe.
I have bled the system and vented it as much as possible.
The flow sensor is doing what it should.
Pump is working ok. Pressure it at 1.5 bar.
Can anyone help please.
P.S
The boiler has worked fine for the past few years.

twgas · 29 Sep 2009

What system do you have (y or s plan)?
Does CH work when HW is also on?
Join the combustion chamber for more detailed boiler stuff.

chris23ab · 29 Sep 2009

Hi.
Its on s plan.
will not work or stay on when on both.
Heating 2 port valve is working and operating as normal.
Its like the circulation it emptying the heat exchanger of water then when the boiler / pump stop it re fills up again.
Cheers.

ajstoneservices · 29 Sep 2009

Check the flow/return temperatures, flow should be 84c max.

chris23ab · 29 Sep 2009

Flow not even managing to get hot.
Near enough cutting out straight away as it seems the h/e is being cleared of water leaving the air to shut off the flow sensor.
Then when the boiler and pump cut off the h/e fills back up with water.

twgas · 30 Sep 2009

chris23ab said:
Flow not even managing to get hot.
Near enough cutting out straight away as it seems the h/e is being cleared of water leaving the air to shut off the flow sensor.
Then when the boiler and pump cut off the h/e fills back up with water.

this doesnt make sense. The flow sensor is activated by the pump (moving the water through it) and so, if the flow switch deactivates it will cut off the boiler but the pump will continue to run. If the pump stops the power to it must be disappearing, This could be caused by the end switch in the MVs going open circuit, this is unlikely as you say it happens when both HW and CH are on but earlier you said HW is ok on its own so that valve must be working and it would keep the pump on.

powell30 · 1 Oct 2009

Detatch the flow sensor wire and loop it so you have a continious circuit. If boiler stays lit but noise continues it has to be airlocked (doubtful) or one of the portvalves or pump is the problem. Careful not to leave boiler lit for long......ali heat ex and they will melt.......

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potterton promax 15 he

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