New central heating - could I ask for some help please

We have just had a new central heating system installed to replace the old warm air and wondered if anybody could offer some advice please. It has a Worcester Bosch 8000 Life combi boiler, Easy smart controller and 12 radiators. My question is about the temperature that the radiator water is set to. The heating company said it should be set to 75 degrees but it is taking around 2 hours in the morning for the heat to rise from 16 to 20 and it then seems to struggle to get much hotter. The boiler goes up to a max 88 degrees so I tried it at 85 and it heats much quicker. I spoke to another Company who said it was fine to leave the temperature higher because the smart controls and boiler will adjust the water temperature as required. Does this sound correct. We are trying to work out if we have been given undersized radiators that should be heating the house quicker with the water at 75, or whether we should be setting the boiler higher. Thanks for your help.

 

Flow is way too high, 80c really should only be on HW cylinders, 65-70 on CH, when smart WC is installed it can modulate it lower as needed.
Did they fit weather compensation smart controller?
Was this all new piping?
What size combi is it?

 

What type of house is it, size, walls, insulation etc

 

Almost certainly undersized radiators. Target flow temperature for a new system should be no higher than 70°C, with a return of 50°C. If you're running at 85, your boiler won't condense, which means it loses a huge chunk of its efficiency. It effectively becomes a standard efficiency boiler at around 80-85% efficient rather than the high efficiency 92-95% it should achieve.

Gas boilers should be set up to have a difference between their flow & return temperatures of 20°C, with a return of no more than 52°C, in order for condensing to occur. The lower you can go, the better it will be (to a point).

Think you've got a good case for saying the system was incorrectly specified and needs to be rectified.

 

Hi
Thanks for the replies.
It is a 4 bed 70's detached house (typical box with another box on the edge for the garage!). Boiler is 35kw Combi. All brand new piping and radiators. It has EasyControl where it picks the weather via the internet; it does not have a separate outside whether sensor. Walls are brick cavity with no insulation, loft is insulated, concrete downstairs floors so three pipe drops from upstairs. Upstairs gets hot very quick and it is hot downstairs too but just seems to take a while to heat up. Have checked a couple of online calculators, one shows the radiators being the right size but the stelrad calculator shows a couple being undersized. We have radiators in the bathroom and cloakroom that do not appear to be so effective as the others. Could it be that it needs better balancing. The water goes upstairs first and then drops back down. Thanks

 

You may need the boiler ranged, check that the correct heat curve is set on the smart controls and system is correctly balanced first before going further.
Incorrect curve can lead to greater heat loss than boiler is generating.
Boiler ranged incorrectly can make flow temp rise too quickly and trip out
Incorrect balancing can lead to return flow temps being too high as it loops around the closest radiators to the boiler and boiler modulating down.

Set temp to 65c, then balance all the rads, close all lockshields and open them up 1/4 turn to start, you want all of them to warm up at the same time, but to do it properly you need a IR or contact thermometer to check each side of the rad pipes for delta.

Did you see the piping all done, was it 22mm from boiler then 15mm branches?

 

Thanks for coming back. Yes the piping was 22mm from the boiler and 15mm branches. It was only installed a few weeks ago but I do not recall them doing anything with thermometers but I may have missed it. Thanks

 

A lot of the online calculators are still based on old theory of non-condensing boiler system design, so will give inaccurate radiator sizes for modern systems

 

Reminds me of the Old Days when BG were getting into the CH market - packages of heating Rads - just random sizes. All the same few sizes. Sub contracted out . I always remember a customer ( a copper) quizzing me , and being when I told him the way it worked . (it was subbed to my boss, I was on the cards) @ least the guy got a good install even if he didn't get the rads sized+ situated correctly. Then Maggie sold it all off - Tel Sid

 

One of the advantages of warm air heating is (was!) the very quick warm-up from cold, compared to water-filled radiators.

 

There's no reason why a properly specified & installed wet system shouldn't provide similar performance

 

I stand by my statement, but I have no desire to argue with such a respected, experienced, and helpful member of these forums as yourself. Best wishes.

 

Warm air will definitely heat a house from cold faster then a wet system

Next fastest us a thermalstore as the rads are almost instantly hot with conventional rads coning after that.

Of course a warm air house will cool down significantly faster as well...

 

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