Heating works only when hot water is on

[Pez6791]

Hello

I have underfloor heating, which only seems to work when the hot water is on.
The temperature settings are all set correctly. However, the temperature starts to drop and the only way to get it warm again is by turning the hot water on.
The person i bought the house off told me that the hot water and heating work independently.

The boiler works off oil.

Can anyone give advise ?

Thanks

 

[crashndie]

hi mate what type of time switch do you have? it sounds like a wiring fault to me, can u just have hot water only on?

 

[kevindgas]

agree it is most likely wired as a hot water priority system rather than a Y or S plan
ideally you should have an S plan+ system with independent timing for each section HW/HTG/UFHTG. although a lot are wired to a 2 channel timer with the 2 heating zones using the same time control and switching via the stats.

 

[MANDATE]

Thats the type of problem you get with a 3port motorised valve.
Either the valve is not moving beyond mid position (where you get both CH and HW for short period) or if it does a faulty micro switch prevents the boiler from lighting. So look to see if you have such a valve just after the pump. It's called a 'Y' plan/system. The valve takes up any of the 3 positions according to demand.
The answer may be to replace the actuator head of the valve, that is assuming it did function correctly at some time.
It is possible the valve was never wired correctly from the start. It has been known for the required wire from the HW OFF terminal on programmer to be omitted.

 

[Pez6791]

Thanks for the replies.

It's a Tower 2 port zone valve.

There is a small arm that sticks out. Should this be set to manual, auto or half way?

 

[MANDATE]

I can't see how a 2port zone valve is related.
On a 3port the lever should be left on auto. It is only when draining and re filling when lever is put on manual(which is half way)