repipe old CI radiators, My customer now has a new boiler

G Lyons

My customer has a new Dunkirk boiler and baseboard radiation in the addition to his home. He is heating the old part of the house with the original cast iron radiators, which he likes. I would like to repipe the radiators so as to get rid of the large volum of water the pipes hold. How should they be piped. Can I pipe them in series as the baseboard is done, or will I have to use monoflow tees. There are only 6 old radiators to pipe to. I hope not a supply and return from each radiator. Help Please.

Mike T., Swampeast MO

With the possible exception of adjacent radiators in the same room standing iron should never be connected in simple series. If you must use one-pipe, then use monoflow/diverter tees. Two pipe systems generally give better control possibilities.

If you connect them in simple series you will have terribly uneven heating.

Don't forget that when piping a monoflow system you must size the radiation for the lowering supply temp after each radiator. An existing two-pipe system will NOT be sized with that in mind!

While the big, old mains do hold lots of water, it's usually not a problem if you insulate the piping.

G Lyons

Re; new piping to old CI radiators. Thank you Mike T.

I see what you mean. I will leave the piping configuration the same but install 1" cu or pex in place of the large old iron pipe that is also taking up head room. I could supply and return from the large radiator with 1" and 3/4 inch the smaller radiators. Would that work?

kevin coppinger_4

you know....

if you set the system up as a manifold you could run a seperate line of 1/2" pex to each radiator as a supply and return.......kpc

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jeff_51

just a note

CI rads and baseboard must be on seperate zones if you dont manifold or you will get very uneven heat

kevin coppinger_4

CI rads...

and copper fin tube baseboard that is....kpc

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Dave Stroman

I use reverse return. No diverter tees needed and you can turn off or balance any number of radiators without interfering with the flow to the others.

Dave in Denver

G Lyons

Whats reverse return ? Thank you for the help.

I can see that a header would work fine.. I will run 3/4 to the large rad in the living room and 1/2 to the other 3 rooms. There are 4 rads in all not 6.

Wayco Wayne_2

Kevin!

You beat me to it. For several years now I have been replacing large gravity pipes with a manifold and 1/2 in PEX. I usually use Multicore for this. People around here on the Wall refer to it as a "Home Run" system. Homeowners love to get more ceiling space in their basement. (especially the tall people, clank!.. Doh!) Most want to finish off the space for a play room of some sort. I use Wirsbo Brass manifolds with the flow sensors so I can balance the loops separatly. It's easy to run the pex up into a joist bay out of the way. I usually set them up for constant circulation too. Bring the constant circ loop on with an outdoor stat or tie a relay into the B terminal on the sub base of the House tstat so that when they switch to heat it turns on the circ. :P WW

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Constantin

Sometimes, a picture speaks a thousand words...

... see below. Basically, reverse return ensures that each circuit gets about the same amount of water by making all the flow-resistances as similar as possible. Naturally, this works best for manifolds where all the attached piping is the same length, etc.

G Lyons

Revers return

Thank you Constantine, for the reverse return primer, I have heard this called "first in last out" and used on water heaters and softeners when installed in a bank (group).