13,333 btus off 15mm pipe.

[Mgrant]

Hi I am putting the pipework in for a heating system and am left with 3 rads to pick up with 13,333 btus of heat needed for this 3 rads. After the last rad on the circuit before these 3. Is around 4 meters, I have ran 22mm from there. I plan on reducing down to 15mm around 300 mm before picking up the first of these 3 rads. Should that be ok?

 

[chris watkins]

What is your Design Delta T ?

 

[Mgrant]

Have ran 22mm to pick up the hole system these are the last 3 rads on the system

 

[Mgrant]

is a sealed system ran off a 30kw combi

 

[chris watkins]

What is your Design Delta T ?

What have you designed the flow / return water temperature to be ?

Only this relates directly to what heat you are able to get out of pipes.

 

[joni os]

If temperature difference across rad (Delta T) is 11C then you are within margin for 15mm, but for the sake of extra 300mm ,why not take 22mm to tails of first rad. then larger or extra
rads could be added in future.

 

[ShaunCorbs]

No it won't simple answer

 

[Neil K]

If you've ran 22mm for the rest of the system, why not just keep it that way, why create future problems with a system you've put in from brand new?

 

[joni os]

No it won't simple answer

Please elucidate. Flow rate of 0.084 litres/sec, normally acceptable.

 

[lame plumber]

can we please go metric or imperial and stop mixing it up, poor brain can't cope

 

[Best]

My old fashioned pipe limit on open vented is 20,000 btu on 15mm pipes.
That said, I would always try to have maximum only on very large rad coming solely from 15mm pipes.
Do no harm to take 22 mm to the last tee branch off for last two radiators unless they are very small rads. Better to be looking at it, as looking for it, as the saying goes, - especially when the customer decides later to add a little extension

 

[Neil K]

Better to be looking AT it than looking FOR it ^^^^^^^love it, very true.

 

[joni os]

can we please go metric or imperial and stop mixing it up, poor brain can't cope

Simple conversion:- 1litre weighs 2.2 lbs 1 degree C = 1.8 degree F
Therefore to raise 1 litre by 1degree C requires 2.2 X 1.8 BTUs Approx 4 BTUs for sizing purpose. The metric energy system of a Newton force for 1 metre does not have the same simple direct relationship with mass of water and rise in temperature.

 

[chris watkins]

No it won't simple answer

?

If temperature difference across rad (Delta T) is 11C then you are within margin for 15mm, but for the sake of extra 300mm ,why not take 22mm to tails of first rad. then larger or extra
rads could be added in future.

Where as if you designed at 20deg C difference (so 70 Flow & 50 Return as you should) then a 15mm will p*ss it = 11kW, which I think is around 37K of them very out of date, pre decimal thermal units, that are so difficult to work with. :6:

 

[joni os]

Dividing output in BTUs by 4 X (Delta T) to get flow in litres per hour is all my pre senile brain can manage.

 

[Mgrant]

If temperature difference across rad (Delta T) is 11C then you are within margin for 15mm, but for the sake of extra 300mm ,why not take 22mm to tails of first rad. then larger or extra
rads could be added in future.

So carry on in 22mm to the first rad of the 3, the reduce down to 15mm to pick up the final two rads with a btu rating of about 9000btu between them.

 

[Mgrant]

Would mostly likely use a 22mm,15mm,15mm tee to pick up this rad then go to 15m to the finale two.

 

[Mgrant]

the finale two rads are 2641 btu then 6507 btus