Radiators getting hot without pump

[the_big_1]

Hi Guys,

I have noticed that when I have my boiler on, its a Powermax, the central heating radiators get hot. The pump isnt running, I know that for sure, I undid the power to it.
There doesnt seem to be any flow valves etc, the pipe exits the tank, to the pump, then out of the boiler to the heating.
Is water ment to get past the pump if its not running or is it faulty or some other part?

 

[picasso]

There is nothing wrong, its just one of the foibles of these boilers, a check valve on the flow stops the rads heating up.

 

[the_big_1]

Hi,

Do you put it on the flow or return? what type, any links that could help me find one?

 

[picasso]

Single check valve on the flow as near to the boiler as you reasonably can.

http://www.screwfix.com/p/22mm-single-check-valve/61237#product_additional_details_container

 

[the_big_1]

How does it work? is it harder for the flow to open the check valve without the pump running? I guess fitting the valve with the arrow away from the boiler?

 

[picasso]

The check valve stops convection but opens easily when the pump starts.

 

[the_big_1]

Great stuff so the arrow (Flow direction) is away from boiler?

 

[picasso]

Yup

 

[the_big_1]

Many thanks!!!!!!

 

[the_big_1]

I Fitted the valve today, still the same :0(

 

[the_big_1]

Any other ideas?

 

[andytw]

Any other ideas?

I have 2 of these in let properties and definitely had hot rads in one of them. I did the same as you have just done.
It didn't fix the problem. Sorry I didn't see your post earlier.
To fix the problem I put a zone valve in the flow from the boiler to the radiators. This is normally closed.
The room stat normally controls the CH pump, so instead I used the room stat to control the zone valve and used the microswitch in the now open zone valve to control the CH pump.

Some more info and pics here...

//www.diynot.com/diy/threads/gravity-valve-on-powermax.315148/

andytw

 

[the_big_1]

Hi ya,

I gues then when the valve is powered, it opens, closed by spring when power removed? Microswitch closes when valve is ope?

Cheers!

 

[andytw]

Hi ya,

I gues then when the valve is powered, it opens, closed by spring when power removed? Microswitch closes when valve is ope?

Cheers!

Correct, the spring holds the valve closed so no gravity flow. When the room stat comes on and calls for heat the room stat sends power to the valve which now opens. When the valve is fully open an internal microswitch in the valve sends power to the central heating pump.
When the room is up to temperature the room stat turns off. There is now no power to the valve which closes under spring power. As it closes the internal microswitch in the valve opens and turns off power to the pump.

andytw

 

[the_big_1]

Great stuff!
I will have to find a cheap zone valve!