central heating design

[gregd72002]

Where did you get the flow rate of 18.6 litres/min from?

The rads add up to 39101 BTU, which is 11.46 kW. With a 20C differential the flow rate is 11.46/(4.18 x 20) = 0.137 litres/sec or 8.22 litres/min.

I am assuming that the rad outputs shown are actual values, i.e they take into account the flow and return temps, and not those quoted in the manufacturer's literature.

Are the pipe lengths shown the total, i.e flow plus return, or do you have to double the number to give the total?

the flow rate is provided by the boiler manufacturer

rad max outputs shown are provided by rad manufacturers

pipe lengths shown are 1 way, so should be doubled for total

 

[doitmyself]

Make and model of boiler?

The flow rate quoted by the boiler manufacturer is that required for max output, which I calculate to be about 26 kW. Obviously it will never run at that output as there are only 11 kw of rads, so the flow rat will be lower.


The rad outputs will be about 15% lower due to the 20C differential, i.e about 10 kW.

 

[gregd72002]

Thanks!

the boiler is logic vogue 32kw

i was told there is no problem with having more powerful boiler than needed.

I understand the 15% lower and Im fine with this.

From what I saw the big radiator in living room was delivering around 10deg less heat than others. Hence the redesign.

 

[doitmyself]

The boiler is logic vogue 32kw

I was told there is no problem with having more powerful boiler than needed.

From what I saw the big radiator in living room was delivering around 10deg less heat than others. Hence the redesign.

You need 32 kW to provide instant hot water, but you only need about 12kW to heat the house. Your boiler provided a max of 24kW for CH, which is twice what you need. Your boiler does modulate down to about 5kW, but it starts of at max output and then reduces it as the flow temperature increases.

Do you find that the boiler is continually going on and off, i.e cycling? If so, this could account for the large rad never getting up to temperature.

I know you said the system has been balanced. How far open are the lockshield valves (min and max)?

 

[Worcester]

Irrespective, there is no need to call the original "plumber" back.

He should be made to pay for his mistakes.

Go to trading standards tomorrow and start a small claims court action, this will (eventually) at least get you some of the costs back to put it right. DON'T use the bailiffs to enforce, use the sheriffs, they have a LOT more power as they are court officials.

 

[Ermintrude]

I love conservatory teed off 8mm droppers on a 1800 700 dpx that never gets hot