Why does my combi boiler lone fry dampen to the tap when the heat is on? I have a combi boiler that not long had a piece fixed...

I have a combi boiler that not long had a piece fixed as the hot water wasn't getting to the radiators (the hot wet in the tap was fine). Since later I now individual get hot dampen to the taps if I switch the hot wet to the radiators on as well. Any view why? Will this be due to a mistake the plumber made when he fitted the last sector?
Hvac boiler?
Answers:    Your boiler needs to state a minium water temp,so when cold sea flows thru the domestic water coil steam is transferred and the water is warm up.this water temp.setting is on the aquastat and it may hold been lowered .I would beckon the company and explain the problem.I think I would close to to have the boiler verbs 130 degree dampen for the domestic coil.