Central heating layout

[Steelmasons]

Assuming a 20C differential, 15mm pipe can be used for the main pipe work and 6mm or 8mm for the connections to each rad.

......and then wonder why the system is a pig to balance

Take into account boiler hex resistance an it doesn't leave a great deal for index circuit resistance (some combi boilers have a 4 metre head hex resistance) , 22mm should be used from boiler to index circuit/part of.

Stick to giving controls wiring advice Mr hailsham.

 

[newbuildinstaller]

haha

20* deta T now, hes piping a small house with a combi (which will be banged on max 24/7) and wont be balancing the rads other than to say they are hot.

hoy some 22mm speedfit in and 10mm runs to the rads (increase to 15mm when comming out of the floor to look a bit better) Flow or return in either side of the rad and use bi directional TRVs. Then off to the pub....

ITS REALLY NOT ROCKET SCIENCE

pipe it in any way that means less pipe!!!

Oh you should zone the house as all new systems must be zoned (although the zone police rarely break into houses to check )

 

[newbuildinstaller]

any way Im off out to buy some 6mm pipe got a big job on monday!!!

 

[Steelmasons]

any way Im off out to buy some 6mm pipe got a big job on monday!!!

Make sure that system is clean newgas , we don't want any blockages through that 6mm tube , what size pump you gonna use for all those 8/6mm runs???????

 

[newbuildinstaller]

a hamster on a treadmill (they are carbon neutral) and can get up some speed once the candle is lit

 

[D_Hailsham]

......and then wonder why the system is a pig to balance

It should make balancing much simpler!

20* delta T now, hes piping a small house with a combi (which will be banged on max 24/7) and wont be balancing the rads other than to say they are hot.

Are you suggesting that the OP should not to do the job properly?

Running with an 11C differential will mean that the resistance of the Hex will be even higher than the 4m quoted by steelmasons.

Boilers with built-in pumps (combi and system) always quote the available pump head, so the resistance of the Hex can be ignored - assuming, of course, that you are running with the recommended delta T.

 

[newbuildinstaller]

Are you suggesting that the OP should not to do the job properly?

Im suggesting a DIYer wont/cant do it properly nor in this case will it make any difference. No need to complicate piping a small house....

 

[Steelmasons]

Boilers with built-in pumps (combi and system) always quote the available pump head, so the resistance of the Hex can be ignored - assuming, of course, that you are running with the recommended delta T.

....and....

Which leaves an available head of around 1.5 metres @ a deltaT of around 20c.


Have you seen the abortion that 6mm leaves at the rad valves? , not forgetting system has to be as clean as a whistle and be maintained that way? , any numpty installing 6mm tube needs to be shot , you obviously don't install and never have done mr hailsham

...so 1.5 metre available head left when utilizing a 37 kw combi? , add resistance of 15mm index circuit coupled with 6/8mm feeds to radiators and you got yourself a right bitch to balance.(no it is not easier to balance).

Google has a hell of a lot to answer too , haven't we been down this road before Mr hailsham?

 

[D_Hailsham]

Which leaves an available head of around 1.5 metres @ a deltaT of around 20c.

Where does this comes from?

 

[D_Hailsham]

...so 1.5 metre available head left when utilizing a 37 kw combi?

I've already pointed out that the proposed boilers are too big for heating as the OP only needs 7kw to heat the house. The fact that a boiler produces 37kW for DHW is irrelevant when sizing the CH pipes.

Running with a 20C differential instead of 10C/11C has a significant effect on the pressure loss over the index circuit. Taking my system as an example (13rads, 14kW) and ignoring the resistance of the hex you get the following results:

10C: 2.3m
20C: 0.64m

So a boiler with an available head of 1.5m would be unable to cope with running at 10C, but be more than adequate when running at 20C.

 

[Steelmasons]

The fact that a boiler produces 37kW for DHW is irrelevant when sizing the CH pipes.

Obviously not irrelevant as far as resistance of hex is concerned , a 24 kw combi would have more available pump head than that of a 37 kw when both @ similar loads.

 

[Steelmasons]

Twice.