C/Htg-DHW Problem

[MikeJM]

Can anyone help me with this please?
Our boiler fired up this afternoon on auto as normal to heat the dhw but i noticed half an hour later that the c/h rads were hot even though the room stat was not switched on.
Could this be a sticking valve of some sort? The system is only two years old.

 

[picasso]

Could you give a bit more info ? what boiler you have, type of controls, 2 port or 3 port (as in the pictures) would help

honeywell 3 port

• picasso
• 18 Oct 2010
• 26

honeywell 2 port

• picasso
• 18 Oct 2010
• 31

 

[MikeJM]

Thanks for reply.
Boiler is Worcester Danesmoor oil fired. The valve is a three way Danfoss HSA3.
C/H system is pressurised while the dhw has a header tank in the loft.

 

[picasso]

The three way valve is passing, you could try changing just the head, if still passing then its a drain down to change the body of the valve.

 

[MikeJM]

Could the problem be linked to this?
I drained the system last weekend (before putting the c/h on for the first time this winter) to put cleanser/sludge remover in with the intention in a couple of weeks of draining it again and putting inhibitor in. I do this each year as the mains water supply is brown at times with rust from the old iron mains SWW supply pipe, (we live in west cornwall).
I drained the system from a different point this year which came directly of a pipe that feeds a rad, could this be the cause? The guage on the pressure vessel also now reads 1.5 bar when running whereas it used to run at 1.1-1.2 bar.
Grateful for any help.
Mike