Why isn't my house really hot with GCH on so much?

Johnandabby

jennifernil wrote: »

That depends on whether the bypass in the boiler can cope, or whether there is a separate bypass pipe fitted instead/as well.

You don't want it to be possible for all the rads to be shut down if there is not a decent bypass fitted, whether you have a thermostat or not.

In fact it is even more important to have a decent bypass if there is no thermostat to turn off the pump as well as the boiler.
A small rad in say the hall, with no TRV, makes a good bypass.

No, bypass should be added at the boiler if the boiler bypass 'can't cope'. But combis have integral boiler bypass, and why wouldn't the manufacturer's bypass cope? Having a rad as a bypass (without room thermostat) is an outdated approach.

Norman_Castle

The radiators are scalding too so yes I think it'll have to be turned down a bit! It's like a greenhouse today in here but it is freezing outside tho so that's ok I guess!

Turn the TVRs down. They prevent the room being overheated. The halfway setting, Normally III, is 70 degrees. TVRs set between III and IIII Should be between 70 and 80 degrees which should be warm enough for anyone who isn't a reptile.

When my heating was fitted I was advised having the boiler output temperature at maximum was the most economical however this seems to give a very uneven room temperature. The room was either hot or cold making me want to turn the thermostat up. I've now adjusted the boiler output to 75 degrees which gives a much more constant room temperature.

DTDfanBoy

bridgedino wrote: »

Flow temp into your radiators should ideally be around 82 degree, 71 degree on the return back to the boiler. 11 degree loss

That sounds like the perfect way to run a condensing boiler as inefficiently as possible

If the OP had an old non condensing boiler replaced ideally new larger radiators would have been fitted at the same time, condensing boiler generally have lower flow and return temperatures, most are also designed for a 20c drop across the system.

blackshirtuk

please correct me if i am wrong, but from what i've read a condensing boiler doesn't work as efficiently when the return temp is above 55c.

Therefore if you are expecting a 10c drop across the rads then the max outflow temp should be 65c for best efficiency.

or am i missing something?

Which leads me to question with a newish condensing boiler, trvs, bypass, thermostats etc is it more efficient to run the boiler at a lower output temperatures or high temps and let the trvs, thermo's cut the demand?

lonestarfan

southcoastrgi wrote: »

then your expansion vessel needs re-pressurising, I don't want to seem rude but from your posts on here its not something I think you can do, get someone in to service the boiler & get them to do it at the same time

Know your limits I say so no it's not rude. That's why I pay British Gas Homecare 300 every month so I don't have to muck about with things I don't understand lol so I shall get them out to check it all.
Norman Castle - about the 75 degrees. - I can't set it at 75 degrees as its a dial - it's full turned up to max or turned to low or anything in between but no calibration.

Norman_Castle

^ Try about 80% on the dial.

bridgedino

blackshirtuk wrote: »

please correct me if i am wrong, but from what i've read a condensing boiler doesn't work as efficiently when the return temp is above 55c.

Therefore if you are expecting a 10c drop across the rads then the max outflow temp should be 65c for best efficiency.

or am i missing something?

Which leads me to question with a newish condensing boiler, trvs, bypass, thermostats etc is it more efficient to run the boiler at a lower output temperatures or high temps and let the trvs, thermo's cut the demand?

The condensing boilers performance within the heat exchanger recovers heat from the combustion process that's normaly expelled out through the flue to outside.

The products of combustion are cooled and begin to condense around 55 degree, not the water in the heat exchanger. The recovered heat is used to maintain a higher water temp. Therefore less energy is needed.

The drop in temp between flow and return is different between a condensing and non condensing boiler. Only around an 11 degree drop for condensing.

DTDfanBoy

bridgedino wrote: »

Only around an 11 degree drop for condensing.

I suspect you may have meant non condensing

bridgedino

DTDfanBoy wrote: »

I suspect you may have meant non condensing

Indeed :beer: