With my old (now removed) indirect system I was told the rule was no more than 2 rads to be fed off 15mm pipe and that the main 22mm should run front to back of the house, teeing down to feed each rad or pair of rads.
Now things may have changed with modern combi boilers but I would like opinions on whats just been fitted below from some of you who do this for a living, to me it seems just too much is being asked of the 15mm supply pipework. Am I right ?
From the new greenstar 28i boiler fitted in the front porch the supply is in 22mm, tee'd down to 15mm for the hall rad (2081btu), a riser from the boiler in 22mm is tee'd to 15mm to feed bed 3 rad (2498btu) then tee'd again off that to drop to the lounge rad (3483btu), then tee'd again to go to Bed 1 rad (6278btu). Total btu's on this 15mm run is 12259btu and from what I read the design limit for 15mm is around 13600btu* So all should be well on this circuit so far.
The 22mm riser then goes to the back of the house under upstairs floor where it tee's to 15mm to feed the towel rail (1000btu), another tee then the bath rad (1532btu), another tee then the drop down to the lounge 2nd rad (3924btu) which then tee's downstairs to feed the dining rad (6278btu). the upstairs underfloor tee's one last time to feed bed 2 rad (6278btu). The total btu's on this 15mm run is 19012btu which is well over the design limit of 13600btu for 15mm pipe.
* 15mm pipe design limit is an average because other factors contribute like the amount of tee's on the polypipe runs, the water pressure and pump flow curve as well as pipework length.
Now things may have changed with modern combi boilers but I would like opinions on whats just been fitted below from some of you who do this for a living, to me it seems just too much is being asked of the 15mm supply pipework. Am I right ?
From the new greenstar 28i boiler fitted in the front porch the supply is in 22mm, tee'd down to 15mm for the hall rad (2081btu), a riser from the boiler in 22mm is tee'd to 15mm to feed bed 3 rad (2498btu) then tee'd again off that to drop to the lounge rad (3483btu), then tee'd again to go to Bed 1 rad (6278btu). Total btu's on this 15mm run is 12259btu and from what I read the design limit for 15mm is around 13600btu* So all should be well on this circuit so far.
The 22mm riser then goes to the back of the house under upstairs floor where it tee's to 15mm to feed the towel rail (1000btu), another tee then the bath rad (1532btu), another tee then the drop down to the lounge 2nd rad (3924btu) which then tee's downstairs to feed the dining rad (6278btu). the upstairs underfloor tee's one last time to feed bed 2 rad (6278btu). The total btu's on this 15mm run is 19012btu which is well over the design limit of 13600btu for 15mm pipe.
* 15mm pipe design limit is an average because other factors contribute like the amount of tee's on the polypipe runs, the water pressure and pump flow curve as well as pipework length.
