Heating only working when hot water required

[M Mannas]

I have a Danfoss 75 controller for a Ideal Classic LXFF & FF Fanned flue gas boiler.

I can get HW any time I want but when requesting Heating I can have it as long as I also request HW. The problem comes when the HW tank is full as the heating then goes off. From then on every time I switch on the heating it starts then goes back off. I can run the HW for a while then try again but it trips back off when HW tank is full again.

I have two motorised values
1 - Honey well f-8 and this seems to be controlling the HW - I have taken off the cover and when HW is requested it moves from one position to the other. I have noticed on the back it is on the Manual setting.

2 - Barlo 2PV-2 - Seems to be for heating. When Heating requested I can see the switch (Which is on top) move from one side to the other. Someone said I should just put this to Manual but it does not seem to have this setting. I can move the switch on top when HW is not requested but when it is the switch becomes rigid.

 

[EliteHeat]

Sounds like your Barlow 2PV is not making the microswitch to fire the boiler.

I have no idea if a replacement head is available for this unit, but someone else probably will.

 

[M Mannas]

Thanks for the reply. I am very new to all this and just getting my head round how this works.

Does it make sense that I am getting heating when water is on? The strange thing is that it works until HW is not longer required.

 

[EliteHeat]

Makes perfect sense. The valve is actually opening but is not making the contacts. Therefore, if there is a demand for HW then the CH will remain working as long as the HW demand exists.

 

[M Mannas]

So...
If I am able to get a replacement head is this something I can replace myself or are we talking about calling a plumber?

 

[bobbo85]

The actual body must be gone if its moving across but not opening ,with the head off cant you turn the valve yourself,if so is it stiff,get some cleaner and throw it in the h/tank and draw it in,and give it some wd 40 see if its the outside thats stiff

 

[EliteHeat]

So...
If I am able to get a replacement head is this something I can replace myself or are we talking about calling a plumber?

If it's replaceable then DIY it - no draining involved.

 

[ChrisR]

Barlow 2PV

Nasty old ACL.
Replace the whole valve - means getting wet.

Honeywell f8 I don't recognise, except on a camera lens.

Meantime, if you turn your cylinder stat up, your boiler stat down, and your heating on, the boiler will stay on trying and failing to heat the hw up to the temp you set, and you'll get warm rads.