Copper to Pex Conversion for CI Radiator System?

Calypso

Hello Everyone,



I have a NTI Trinity Ti200 condensing boiler that is connected to 20 some odd radiators on a single zone in a 1907 3 story brick in Minneapolis. The system provides great heat as is, but one of the supply/return loops in the basement has old gravity piping still in place. I would like to remove this large stuff to get some headroom in the down there.



The boiler is plumbed with 1 1/4 copper. I have a Grundfoss 26-99 pressurising the primary side of the boiler, and a Grundfoss 26-64 downstream of the above when the zone is active. These two pumps then feed into a 1 1/2 inch check valve, then split into two loops of 1 1/4 copper. One of the loops (Call it loop A) has had the gravity pipes removed, and the radiators on loop A are fed with 1/2 inch copper - all is good.



The loop B is fed with 1 1/4 copper that is then mated up to the large gravity supply and return. This loop then feeds all radiators with original steel pipe.



So here is the question: I want to delete the large gravity pipe. I then want to connect 1 inch pex to the 1 1/4 copper and run it to a suitable manifold. I then want to feed all the CI rads with 1/2 pex. Will this work?



I'm worried about the smaller ID of the pex, compared to copper, and the possibility of not enough volume reaching the CI radiators. Thanks in advance.

Ironman

Proper Calculations are Needed

Do your know the heat loss for your house? Has a detailed load calc been done? This is the first step in determining the sizing of any and everything in a hydronic system. I realize that you're talking about existing pipes and rads, but now you want to change the size and number of cars on the train that carries the btu's. That will require specifics: how many btu's? How many gpm? We also need to know the EDR (output) of each rad.



!/2 in pex (02 barrier) may be sufficient for some rads and not others. The manifold is a good idea as it allows you to adjust the flow rate to each rad, but how much does each one need? Simply putting larger tubing (5/8 or 3/4) won't solve the balancing issue either.



Believe it or not, those old gravity pipes were carefully sized and configured in a certain way to get the correct flow to each rad. Yes, the dead men did load calculations and engineering to design the system to work correctly. Changing it to forced flow and decreasing the pipe sizing will require that, too.



You can download a simple load calc program from Slantfin and do the calculations yourself. Just be careful to get the correct info to enter into the program.



I've attached radiation tables to calculate your EDR; use a 150 multiplier x the square footage. I believe there's a more detailed one under one of the tabs above.