28mm pipe boiler flow/return

[PEDANTICVINDICTIVEMAN]

Some Suprimas have 22mm pipes off the boiler but have to be changed immediatley to 28mm if you read the installation instructions, so I would leave well alone.

 

[ChrisR]

Quite. The reason in that case is that the boiler has to dump excess heat into water very rapidly and get it out of the boiler. So it's the volume of water which is important there.

If you do the sums with pump size, pipe resistance, temperature drop etc you find that at 80,000Btu/hr 22mm isn't enough for anything but very short lengths of pipe, you really need 28 in most systems. If the pipes are too small and you avoid overheating, other problems can be flow noise, condensation = rusting in the boiler, and increased insulation requirements. If you avoid all those, it still means you won't get all the energy you could, out of the boiler.

 

[lonspwi]

Thanks for all your excelent replies.
While I'm moving the cylinder, do you think it is worth replacing the existing 22mm diverter for a 28mm one ?

 

[ChrisR]

The effects are individually quite small, so it's hard to pick one. If you have a lot of 22mm AND the rads add up to anything approaching 80k then swapping some easy-access lengths of pipe might be worth it IF you find the rads struggle in v cold weather.
WHat sort of cylinder will you be using - some of the quick-recovery ones can absorb 80,000 all by themselves! Again. would recovery time be critical?

For the CH, if the house is detached and not especially well insulated, work out the volume in cubic metres, which when miultiplied by 48 - 50 should give a rough guide in Watts
so eg 10 x 9 x 5 hi = 450, 450 x 50 = 22.5kW, 22.5kW x 3412= 76700Btu/hr
If your house is only50kBtu then it won't be critical!

 

[ph]

ChrisR you ****in muppet! Its got sod all to do with the size of the boiler more like if you had an 8 bedroom mansion you would probably use 28mm circs!on the whole every boiler works off 22mm circs irrespective of what boiler it is as long as it is piped up right. There is always the option of increasing pump sizes! ANYWAY GO BACK TO COLLEGE or GO TO COLLEGE as you sound like youve never been!!!!!!!!!!!!!!!!11111

 

[wilhelm]

get the bouncers!

 

[doitall]

ChrisR you **** muppet! Its got sod all to do with the size of the boiler more like if you had an 8 bedroom mansion you would probably use 28mm circs!on the whole every boiler works off 22mm circs irrespective of what boiler it is as long as it is piped up right. There is always the option of increasing pump sizes! ANYWAY GO BACK TO COLLEGE or GO TO COLLEGE as you sound like youve never been!!!!!!!!!!!!!!!!11111

And just where did you learn muppet, back of a fag packet.

Just shut up if you dont know what the hell your talking about.

 

[lonspwi]

So what do I do ?
I have a house with 3 floors, size (in metres) is 7x10x8.5 plus a conservatory 10x3.5, so it seems like the 80kbtu boiler is inadequate, I would need a boiler in excess of 100kbtu going by ChrisR's calculation.

Boiler aside, I am redeveloping the upper floor (2nd), 3 rooms, 15kbtu required. So do I use 28mm or 22mm for the circuit ? The circuit will be extended from the first floor, which uses 22mm.

 

[kevplumb]

bigger wont hurt

as for the other muppet

pro WHAT

 

[doitall]

Then split 22mm to each floor

 

[kevplumb]

hope thats not a compression stop end under the board's

 

[doitall]

hope thats not a compression stop end under the board's

Yes it is m8.

temporary capped pipe while the work is in progress

 

[kevplumb]

 

[oilman]

lonspwi, the info here was fine until ph (short for p155 head) opened his halfwit mouth. Rule of thumb to support what ChrisR was saying is 22mm is OK to shift 13 to 14kW, and 28mm to shift 20kW or so. If you have 2 lots of pipes then you can shift twice the heat. The reason most installations have 22mm pipes is cos it's cheaper. It's the reason most boilers are forever starting and stopping as well. The pipes just can't shift the heat.

 

[doitall]

cause you could always doitlike this and run 22mm to both floors.