DIY Doctor UK DIY Forums

Strange problem on a system as follows:

Ideal Classic NF40 boiler

room and tank stat seem ok and MV but (all with boiler stat on highest setting)

Call for HW only boiler flow is at 78degs (about right per spec)

Call for HW & CH or CH only boiler flow is always 50degs but if some rads off on the TRV's then flow temp increases.

Result cold house and not very hot water and pump keeps going trying to heat the house with 50deg water!

any ideas

Hi Darren,

Check pump is not 'sticking'
Could be CH stat on boiler?

A bit more progress last night! Effectively what is happening is that the boiler is cutting out before reaching flow rate temp (as if the thermostat is cutting in) and in my limited knowledge I see that it should work like say a kettle i.e keep going until temperature reached.

So last night and in the traditional way I would give the control box a small "wack" each time the boiler cut out and lo and behold it would come back on again!! Using this method I managed to get the flow temp up to about 75 degrees. A bit low compared to spec but 20 degrees higher than i was getting!! So I suggest that some electicrical connection (of sorts) in the control area is problem, any ideas. (please note I have to wack it each time to get it going, one wack is not a long term fix!

Thanks to all that have tried to help!

Hi,

Giving it a whack to get it to work points obviously to an electrical connection.
My money is on a relay on the PCB.
Does it click a lot after whacking it?