Replies

1. 
   Marson | Oct 03, 2009 07:07pm | #1

   I recently did that exact thing--had an old gravity system piped in 2-1/2" (up to) pipe that I converted to pex. I went to a manifold system where each radiator is on it's own loop back to the manifolds. I did it on the cheap, as usual. I'm not a heating guy, just a general contractor with a few years in the trenches.

   It was a heck of a lot of work. I remember I had to take an extra day off work because I couldn't get it done in one three day weekend. The hard part was tying into the old steel pipes. Really got some respect for the old timers who put it all together. Probably if I had to do it over, I'd go all the way back to the radiators with copper (except for the upstairs radiators). Took about a million trips to the hardware store. I think I used every fitting made for converting anything from 1/2" to 1 1/4" IPS to copper to pex.

   I air tested my system and it held 40 pounds, but when I started running water in it, I still found leaks. I found out from an old plumber that it doesn't work to air test old iron. He claims the rust blocks the leaks. I have a boiler drain on each manifold (which is just a cheap Souix Cheif manifold by the way) for ease of draining, so I wound up just running water at full pressure from the tap into the system via a garden hose and finding leaks that way. (Had to cut the boiler out of the loop because the PRV would blow). Never had problems with any new-to-new connections.

   The system does work fine. All the radiators get hot. One big thing that I didn't factor in was the amount of radiation in the basement from all those big steel pipes. My basement got colder after the conversion, and that meant my floors got colder. So I am just completeing phase two, which is to run pex under the subfloor (with insulation below) to temper/heat the floor. (The water for any given radiator first goes under the floor, then supplies the radiator).

   I had problems with air entering the system. I'm not sure why. I had a few minor leaks which I fixed, but I'm still in the diagnosis phase--just got this up and running last winter. Either I have a leak somewhere like the PRV valve or something, or else maybe it's some kind of fluid dynamic thing because I am now pushing the water through all that 1/2" pipe. I'm going to to get a Spiravent.

   I am using the same old POS boiler.

   The other thing you should be aware of is boiler shock--that is caused by too low of a return temperature.

   All this advice is worth what you are paying for it. Others will probably advise professional help, and they won't exactly be wrong.

1. 
   cameraman | Oct 03, 2009 07:15pm | #2

   Did the same thing a couple of years ago.

   I also never factored in the output of the lagre iron pipes.

   Now wife complains of cold floors and I have cold basement!!

1. 
   DanH | Oct 04, 2009 03:59am | #3

   Same thing happened when we replaced our old GFA furnace (cast iron heat exchanger) with a new 96% unit. The utility room went from being the warmest place in the house to the coldest. (It helped that the crew that installed it really tightened up some of the old ductwork that the jackleg builder installed.)
   As I stood before the gates I realized that I never want to be as certain about anything as were the people who built this place. --Rabbi Sheila Peltz, on her visit to Auschwitz

2. 
   USAnigel | Oct 05, 2009 06:28am | #5

   Thanks for the info, I think I'm going to leave a "fitting" to add basement heating if needed.

1. 
   Jeff_Clarke | Oct 14, 2009 07:28am | #6

   When we went from a 1964 American Std. boiler to a 2007 W-M Ultra III I had sections of fin-tube placed in-line in the basement above each basement window.   Works well and didn't cost much.

   Jeff

2. 
   dreadlock | Oct 05, 2009 05:45am | #4

   shark bite and pex.  Great stuff.  I own alot of rentals and they have gotten me home for dinner on time several nights.