Combi Boiler Question

PiKe

PiKe

PiKe

Caporegime
Joined
18 Oct 2002
Posts
25,287
Location
Lake District
Just had a new Worcester Bosch combi installed which replaced a 20 year old swift flow.

The new boiler has separate controls for the water and central heating temperature.

How do I work out what the central heating temperature should be set to in order to avoid it short cycling? It's set to 4 which equates to approx 60c.

My house has 8 radiators, 5 of which have TRVs on.
 
I dont really understand what you mean by short cycling?

Dont you have 2 thermostats on front of boiler for how hot your heating is going to be? (oops just read you already mentioned controls)

You will then have a room thermostat which is basically just an on off switch to try and regulate the temp of its environment. (You shouldnt have a TRV on the radiator in this area iirc)
 
PiKe said:
Just had a new Worcester Bosch combi installed which replaced a 20 year old swift flow.

The new boiler has separate controls for the water and central heating temperature.

How do I work out what the central heating temperature should be set to in order to avoid it short cycling? It's set to 4 which equates to approx 60c.

My house has 8 radiators, 5 of which have TRVs on.
Click to expand...

Does your boiler have the ability to set a range of heat output? For mine (a Vaillant) to stop heat cycling, I reduced the power output from the default 20kW to about 13, and I can set the temp without the boiler always heating up hard and then over-running and chucking heat out the chimney. I got that number by entering the details of my house/rads/windows into one of the online calculators. That should give you an idea of how much heat your rads can shed from the boiler, and then you set the boiler to that.

So rather than control the short cycling by lowering the temp of the rads (because you will want them hot), you adjust the energy the boiler is trying to put into the rads so it matches what your rads can output.
 
I don't know how I can change the power output, there is only a dial for CH water temperature and hot water.
 
Set it low as you can and still heat the house up. Probably have to adjust it as we get into winter.

Mine adjusts the temperature of the flow itself dynamically based on the heating requirements. So when it first comes on it will flow at 80c then ramp down to about 35c and just tick over there.
 
Building on previous answers, you want it as low as possible while still being able to heat the house, as well as that you want the TRVs has open/high as possible without overheating rooms or being wasteful by heating unusued rooms. Its not good to be having the TRVs doing most of the work in controlling it much better to run with a lower flow temp have the TRV not need to do a great deal.

Ideally the return at the boiler wants to be about 55C to allow it to condense the flue gases properly, the flow will be about 20C hotter than this
 
You must log in or register to reply here.
Back
Top Bottom