Boiler sizing allowances

[TFGplumbing]

After you have your final heat loss calculation how much percentage do you allow for pipe runs & intermittent heating allowance?

For example

I am pricing a project atm on a 5 bed country house

Whole house heat loss is 22kw

With rads it's 23.5 *rounded up to slightly larger sizes

That's not including any heat loss for pipe or intermittent heating.

Essentially it's a toss up between a WB HS 18/25 set to 25 KW or a WB HS 25/23 set to 25 KW.

Whats your take?

Thanks

 

[ShaunCorbs]

10% and round up to next size

24 kw so 27kw so around 28-30kw would be fine

 

[TFGplumbing]

Thanks Shaun

 

[ShaunCorbs]

Thanks Shaun

have you added they cylinder ? the only reason i ask i was looking today stnd 900 x 450 cylinder want 10kw (17kw max) unvented require about 15kw

 

[TFGplumbing]

They requested a combi

 

[ShaunCorbs]

They requested a combi

oooooo for a 5 bed house ?????????

if they really want it size it on hot water demand not heating

 

[TFGplumbing]

The place has got sweet dynamic pressure too.. shame really unvented would be awesome

it's only got 1 bathroom though

 

[ShaunCorbs]

The place has got sweet dynamic pressure too.. shame really unvented would be awesome

it's only got 1 bathroom though

sounds ok i would go for a viessmann 222 it acts like an unvented if you have the space

or if they want a worcester go for a highflow

 

[TFGplumbing]

Got to be oil, putting in a heatslave