Central Heating Question

Beave

Hi there, in our home we have our rads and hot water run off our oil, we also have a wood burning stove which heats the water and radiators. When the stove was fitted the plumber told me not to have the fire up to heating temp and the oil on at the same time didn't say why, my question is why? What will happen if my stove is heating my water and then the oil comes on at the same time?

yoshytoshy

Pitching is the first problem ,then loads of air and then a filthy heating system. All depends on what way it was installed ,but more than likely you have two seperate pumps.

Beave

Hey yoshytoshy, thanks for the quick reply, sorry mine was so slow. I don't understand 'pitching'. There is a pump on the stove side that comes on at a set temp. So basically if the oil heating comes on when the fire is already circulating the water, then the oil side could 'drive' the water back down the 'fire' side and cause it to airlock? Is that it?

Billy Bunting

and also very likely that the hi-limit stat on the boiler will cut out and you will have no functioning boiler until you push the reset button.

yoshytoshy

Beave wrote: »

Hey yoshytoshy, thanks for the quick reply, sorry mine was so slow. I don't understand 'pitching'. There is a pump on the stove side that comes on at a set temp. So basically if the oil heating comes on when the fire is already circulating the water, then the oil side could 'drive' the water back down the 'fire' side and cause it to airlock? Is that it?

Excuse if this is a bit ott ,but it's how some systems work.

Pitching can happen when the flow of water in a heating system is too fast. In your attic there is a pipe hanging over your small expansion tank (open vent),this is where water will spit out if pitching is occuring.

On a dual system ,there is usually two pumps. One on each system and they are usually pointing towards each other (Flow >< Flow). This allows non return valves to be placed on the system to prevent either boiler heating up when not used.

If you can imagine two pumps ,pumping into each other. The water will rise up to easiest point ,which is your open vent in the attic.
If this happens for long enough ,you will get air in your heating system because of all the water getting thrown out through the open vent.
Aswell as all of this ,your heating system starts to corrode because of oxides etc.

Beave

That was a perfect explanation, thanks a million, now Ik now why the plumber just said don't do it, I thought the answer would be alot simpler.