Central heating pipe sizing.

[Reltub]

Evening guys,

Been to quote a big house that needs a new boiler, looking to fit a regular boiler as they dont want to replace radiators etc. so dont want to cause any leaks or have pressure issues. There are 13 radiators with approx 28Kw of out total then there is the 450x900 cylinder on top. I have measured all rads and compared them to the outputs of modern rads not 100% accurate but it gives me a good idea. Looking at quoting for a 30Kw worcester regualar boiler and upgrading to fully pumped and 'S' plan. So will a 30KW boiler be sufficient and will I need to put any 28mm pipe in? I have the treloar book but the calcs are frying my brain. Will a 15-60 pump be sufficient? any advice and guidance would be appreciated as I want it to be bang on.

Regards

 

[Ermintrude]

30kw will fly through 28mm upto the zone valves and pump then provisionally 22mm if nice short runs. Calcs not that hard once head round it. Upload a drawing

 

[Reltub]

will i need to upgrade to 28 or will 22mm do? Haven't got a drawing of the whole property i suspect some of the heating pipework is undersized but i want to make sure my work is correct, they have said all the radiators work but I will be putting a disclaimer in my quote regarding this.

Thanks for reply

 

[Ermintrude]

I would run all the primary stuff in 28mm as a minimum. So boiler to valves and pump set

 

[josh]

The outputs of the old rads will be a fair bit less than the new so your probably a bit oversized,
Depending on the temp drop you allow makes a big differance on the pipe sizing to.
Using the treloar work it out with a 10c drop then a 20 and youl be surpirised of what youl get away with.

 

[AWheating]

you will need to upgrade the primary to 28mm pipe, as 22mm is approx. max 24kw at a 20 degree diff.

 

[AlexGas]

Evening guys,

Been to quote a big house that needs a new boiler, looking to fit a regular boiler as they dont want to replace radiators etc. so dont want to cause any leaks or have pressure issues. There are 13 radiators with approx 28Kw of out total then there is the 450x900 cylinder on top. I have measured all rads and compared them to the outputs of modern rads not 100% accurate but it gives me a good idea. Looking at quoting for a 30Kw worcester regualar boiler and upgrading to fully pumped and 'S' plan. So will a 30KW boiler be sufficient and will I need to put any 28mm pipe in? I have the treloar book but the calcs are frying my brain. Will a 15-60 pump be sufficient? any advice and guidance would be appreciated as I want it to be bang on.

Regards

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