Heating only works when hot water is on

[Dan2505]

Hi
My heating only works if my hot water is on at the same time!
Last year they worked separately perfectly fine!

Any idea why this could be?

Thanks

 

[Deleted member 120897]

Crystal ball alert! Can you provide more information? What type of system you have, combi, s plan, y plan, unvented hot water, electric boiler?

 

[Dan2505]

oil boiler
Y plan I think

 

[Deleted member 120897]

So it’s either always operated like this or your 3 port valve (if definitely y plan) has failed.