Why is my heating so poor?

[slimwallet]

To be fair this is not a new problem but my wife and I are fed up with feeling chilly when the frosty weather arrives.

Prior to 7 years ago we had a lovely warm house heated by a 22 year old boiler that never needed any repairs, never cost anything in routine maintenance, but was almost certainly very inefficient.

Seven years ago we had a complete overhaul of the system by a well recommended competent guy. A Glowworm Flexicom 30HX boiler (30kW) was installed, new pump, control gear and hot water cylinder. For some reason he reversed the old water circuit flow. Basically since then we have never felt that the heating is effective.

The house is smallish 4 bed detached, fully double glazed, full 8 inch roof insulation and mostly cavity wall insulated. The system has 13 radiators but two are out of use as, with the kids left home, 2 bedrooms are out of use.

Because of the poor heat problems, we had a complete 36hr+ chemical flush 18 months ago to clean any sludge in the system and also a Magnaclean filter installed. A new Wilo Pico 25/1-6-130 pump was installed at the same time. We still got poor heating performance but no problems were identified this Autumn when we had the annual service. I keep checking everywhere but I cannot see anything wrong. The motorised valves are working fine, the pressure relief bypass is not passing but the boiler never seems to run anything like flat out, more like barely ticking over!

I have increased to output temp setting to 82degC to try and make house warmer but it has no effect. For example our heating came on at 6.30 a.m. this morning and has been on continuously as it has not yet reached target thermostat temperature (21dedC). The boiler outlet temp almost 12 hours after it came on is only 72degC.

I believe, by design, the boiler will only give a 10degC "boost" to the circulating water and that does seem to be borne out by my readings so the boiler is doing the maximum it's parameters allow it to.

Should I have a larger pump? or does anyone have any suggestions.

Thanks..

 

[dilalio]

In addition to above... it may be that your rads need properly balancing so that the heat from the system water is fully drawn out by them and the return to the boiler is cool enough for it to be able to fire more heat into it!
What are the temp differences like between the flow and return pipes to the rads and boiler? There should be a noticeable "to the touch" difference.

 

[slimwallet]

Rads feel quite hot by now but they take hours to get to that state. I can hold my hand on them. I don't find any cold spots on any of them and all have been bled of air.

I don't understand the d.0 setting or how reducing power output could make the house warmer.

 

[dilalio]

Reversed system flow!
Hmmnn, wonder if there's an old NRV somewhere on the primaries, as a hangover from a gravity system!

 

[Doggit]

If the plumber reversed the flow, did he readjust the valves at either end of the rads, and are there thermostatic valves fitted.

 

[slimwallet]

Thermostatic valves were fitted with the new boiler. There were none before. Supposedly the system has been balanced twice now. In the visble piping I cannot see any NRV's

 

[snb]

Are you certain that the boiler has not been installed and it has the flow and returns connected the wrong way round at the boiler. Won't be the first time. Worth checking as this would cause the boiler output to be reduced

 

[jackthom]

Some photos of the boiler and pump layout would be interesting. Is the pump set for the maximum head / speed?

 

[Doggit]

If there was an NRV in the system on the wrong part of the flow, then nothing would get through, so that could be discounted. If the TRV's have been fitted with the new boiler, then the flow and return being reversed is nullified. If the boiler is over specified, then it would heat the system quickly, but then cycle frequently, so I think that aspect can possibly be discounted, but Jimmey seems well genned on that aspect so I may have to defer to him. The systems been flushed, so that confirms no blockages, and the rads have been balanced, but are they allowing enough flow through in the first place. If you know the first rad on the system, try opening up the return valve a turn or two, and see if it gets hotter.

But why haven't you called the installer back with your concerns.

 

[AGAS]

I don't understand the d.0 setting or how reducing power output could make the house warmer.

what is your D.00 set too ? has anyone been playing with the settings ?

 

[dilalio]

Bypass left somewhere?

 

[AGAS]

slim wallet that don't sound good

 

[Doggit]

This is how you check the D.00 settings.

Range Rating The boilers are fully modulating, therefore it is not necessary to range rate them, however, if desired, you can adjust the boiler in 1kW increments between 10 and maximum output of your appliance, as follows:
a) Press and hold the ‘MODE’ and “+” button for 5 seconds. The display will change to flashing ‘0’.
b) Use the ‘+’ or ‘-’ button to scroll to 96.
c) Press and hold ‘MODE’ 5 seconds to confirm.
d) The display now shows a flashing ‘d. 0’.
e) The part load setting is displayed in kW. Press ‘MODE’ the max rate will be indicated, to change the value to the desired setting, use the ‘+’ or ‘-’ button.
f) Press ‘MODE’ for 5 sec to confirm the new setting has been saved.
g) Press and hold ‘MODE’ and “+” to exit.

 

[muggles]

@slimwallet I'd start by investigating the flow direction to find out why it was reversed from the old boiler and whether it is now correct. It's not unheard-of for old systems to be circulating backwards, so the reversal may have been the correct thing to do

How big is your house? How many radiators? Can you remember what the old boiler was? 30kW is quite a big boiler - my own 1970s 4-bed semi uses 12kW, for example. It may be that your boiler just can't get the heat away fast enough, and range rating it as described above might help in this situation. I wouldn't be surprised to find that the boiler is running at minimum rate because its dT on the flow & returns is exceeding 30°C

Check the pipes coming out of the boiler. Is the flow (right hand of the two coming off the top) hotter than the return?

When you say it was flushed for 36 hours, was this with a flushing machine or just chemicals added to the system? Did the rads get noticeably hotter during the flush?

 

[Nige F]

What about the rule ( return from cylinder last before boiler ) If it's actually circulating the wrong way ? Or is the water "just" going through the boiler the wrong way ?