Central heating By-Pass

[asalcedo]

The main flow and return 35mm pipes in the central heating of my home are connected by a 22mm By-Pass with a gate valve. This by-pass is near the boilers before any control valves.

I read that the purpose of the By-Pass is to prevent local boiling in the boiler.

I have two questions,

1. At the moment the By-Pass valve is fully open, the system seems to work well, but, wouldn't it be more efficient if it were closed, assuming no boiling appears?

1. I am replacing the current 10year old Vokera boilers with new Worcester High Efficiency condensing boilers. For these boilers, is it better to have the by-pass valve open or closed?

[Malcolm]

I had a house with a by-pass because all of the rads had TRVs. This meant that in a worst case scenario all of the TRVs would be coused an there would be no way of circulating water around the system while the boiler cooled down, leadind to potentioa damage to the boiler.

My present house was set up so that there were TRVs on all rads except the bathroom, so this was used as a by-pass. It also meant that the bathroom was always very hot when the heating was on. When I had some work done on the system I talked to the heating engineer about this and he fitted a by-pass with an 'automatic valve' (sorry, no more info than this) an a TRV to the bathroom rad. This system has worked well for the last 4 years.

I would guess that all you need to do is to partially close the gate vave to abou a quarter open so that there is always an alternative circuit to prevent hot water accumulating in the boiler if all the rads are closed

Malcolm

[dennis]