How many rads from a 22mm pipe?

[srobbo180]

I am planning to add a radiator in a shower room. I am able to access the 22mm flow and return pipes that run through the room. The pipes end in manifolds that currently feed 4 radiators. Am i ok to tap into the 22mm pipe before the manifolds to feed 1 rad or will this have an adverse effect on the remaining 4 rads.

Thanks

Simon

 

[cr0ft]

It depends on several factors. Does your boiler have enough power to heat the new radiator? How big are the other radiators? A 22mm pipe will feed a lot of radiators as long as the boiler is up to it. You may well find you have to rebalance the remaining radiators after you install the new one though.

 

[srobbo180]

There are 2 44 inch doubles, 1 19 inch double and 1 38inch single

 

[diamondgas]

Pinched this from another site ... I knew there was some data somewhere regarding what heat a pipe could carry!!! So it's not how many rads but how much heat is needed... I have no idea whether the info is true but it sound good here you go:-



"The heat carrying capacity of a tube is limited by the maximum velocity that can be accepted for noise reasons. This is generally taken as 1.5 m/s. The other key factor is the temperature drop of the system which is generally taken as 20°C for a condensing boiler, although greater or lesser temperature drops could be specified.

For 1.5 m/s and 20°C temp drop, the carrying capacity of each pipe size is as follows -

8mm = 4.5 kW, 10mm = 7.3 kW, 15mm = 18.1 kW, 22mm = 40.2 kW and 28mm = 67.5 kW. "

 

[SimonG]

Pinched this from another site ... I knew there was some data somewhere regarding what heat a pipe could carry!!! So it's not how many rads but how much heat is needed... I have no idea whether the info is true but it sound good here you go:-



"The heat carrying capacity of a tube is limited by the maximum velocity that can be accepted for noise reasons. This is generally taken as 1.5 m/s. The other key factor is the temperature drop of the system which is generally taken as 20°C for a condensing boiler, although greater or lesser temperature drops could be specified.

For 1.5 m/s and 20°C temp drop, the carrying capacity of each pipe size is as follows -

8mm = 4.5 kW, 10mm = 7.3 kW, 15mm = 18.1 kW, 22mm = 40.2 kW and 28mm = 67.5 kW. "

Interesting that, they seem a bit on the heavy side, this is old money, I was always taught 15mm carried just over 13,000 btus. But its a long (long, long ) time since I did all that.

 

[SafeGasInstall]

will be ok ,mate! just drain system dawn and pick flow and return !

 

[diamondgas]

Looking at my last post I thoughtthey were a bit excessive so I did a bit more delving ... The table below looks a bit more realistic! I've put a link to the web page also ... Blinkin DIY not.com!!!

Nominal Pipe size Internal Area (m2) Water flow rate (litres/sec)Maximum theoretical heat flow rate. (Ignoring resistance)
(Kwatts )

8mm - 2.5kW
10mm - 4.2kW
15mm - 10.3kW
22mm - 23.4kW
28mm - 39kW

That looks a bit more realistic

Central heating pipe sizing

 

[Blackcatgas]

It will be fine, just connect it up, you might have to rebalance a few rads but I doubt it.

 

[srobbo180]

Pinched this from another site ... I knew there was some data somewhere regarding what heat a pipe could carry!!! So it's not how many rads but how much heat is needed... I have no idea whether the info is true but it sound good here you go:-



"The heat carrying capacity of a tube is limited by the maximum velocity that can be accepted for noise reasons. This is generally taken as 1.5 m/s. The other key factor is the temperature drop of the system which is generally taken as 20°C for a condensing boiler, although greater or lesser temperature drops could be specified.

For 1.5 m/s and 20°C temp drop, the carrying capacity of each pipe size is as follows -

8mm = 4.5 kW, 10mm = 7.3 kW, 15mm = 18.1 kW, 22mm = 40.2 kW and 28mm = 67.5 kW. "

The total wattage for the rads I have on that pipe is 6178 if i am correct that is 6.178 KW so that gives me plenty to play with?

 

[diamondgas]

Interesting that, they seem a bit on the heavy side, this is old money, I was always taught 15mm carried just over 13,000 btus. But its a long (long, long ) time since I did all that.

They did to me too SimonG hence the bit more research... Dodgy plumbing websites full of nonsense!! lol

 

[SafeGasInstall]

last year i fitted 3 P+ rads on 15mm ,in total there was 18 i think ! I thought customer is going to work but just about !
he was happy to go for it so I did it ! re balanced the system and it worked but it needs one more exp vessel !
I think this winter will be new boiler for him ! as old one it was only 28cdi the old wb !

 

[Billy Bob Bob]

I am planning to add a radiator in a shower room. I am able to access the 22mm flow and return pipes that run through the room. The pipes end in manifolds that currently feed 4 radiators. Am i ok to tap into the 22mm pipe before the manifolds to feed 1 rad or will this have an adverse effect on the remaining 4 rads.

Thanks

Simon

you should not have any issues,but what system do you have combi or conventional?

 

[srobbo180]

Hi, sorry for the delay. i have a WB Heatslave 19/25 combi boiler

 

[Billy Bob Bob]

should work fine off a combi