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Series Loop for Cast Iron Radiator

L. P.
L. P. Member Posts: 10
Thank you for the information.


  • Confused_6
    Confused_6 Member Posts: 5
    Series Loop Piping

    I am going to be working with a contractor on converting my old oil boiler (173,000) to a new Weil McLain gas CGI-6 (167,000) piped for two zones (one for first floor and other for second).

    We are also going to replace the 78 year old two, three and four inch black iron pipes with new 3/4" or 1" copper lines. The heating/plumbing contractor, my friend's son, who is allowing me to buy everything direct from a supply company and just charging for his labor, would like to do a series loop for the new piping (two loops for each zone). When I expressed concern about about the water temperature entering the cast iron radiators at the end of the loop, he mentioned that if we are heating the water at about 180 degrees, then it will be close to 180 all the way around and that there would minimal temperature loss in the radiators at the end of the series loop for each zone. Attached is a layout of my first floor. Are you able to shed any light on this matter? Since the loops are piped from the basement, I am especially concerned about the water traveling up to the first radiator on the second floor and then back down to the basement and then back up to the second radiator on second floor and back down until it travels through all five radiators on the second floor.

    He mentioned that my current two pipe design was for my old gravity system and is not really used with new units with circulators and new 1" copper piping for two zones (each zone consists five or six radiators around a 900 sq ft area).

    Again, I appreciate any comments that you may have offer.
  • Uni R_2
    Uni R_2 Member Posts: 589

    Unless, you're in Siberia with bullet ridden walls and are missing your window glass, I can't see why you'd need a CGI-6.

    What was the heatloss calculation, or did the contractor do one?
  • Tom Hopkins
    Tom Hopkins Member Posts: 554
    no series

    Don't do it ,don't pipe them is series it's a bad decission espically for raditors there will be no way to balance them ,do either a mono flow tee system or maybe a home run system with manifolds which can be done in 1/2 oxygen barried pex tubing ,do it the way i mention leaves you open to easier balancing and possibly later installation of TRV to fine tune room temp.the one thing for sure is do a complete heat lose so as not to over size your boiler and learn more about what you can do given your opitions like maybe a modulating condensing boiler and lower water temps for those cast iron rads .Go to the resources section on his site download the heat lose program and check out the hot tech topics
    .I would opt to do mono flow tee and install thermostatic raditior valves on each raditor and use a small condensing modulating boiler with a outdoor reset and one system pump ,with the trv each rad becomes it own thermostat your will have to install a dpv peace and good luck clammy
  • Gene_3
    Gene_3 Member Posts: 289
    some things to consider

    That drawing is for the 1st floor, assuming the 2nd is the same you have 1800 sq ft. You say the home is 78 yrs old, does it have new windows,doors,insulation, these would all make a big difference.

    The temp drop across a cast iron radiator is huge so series is out of the question. I had an old house and what I did was split into many zones, with 2 rads on a zone tops due to my homes layout, I even zoned the baths which is truly wonderful in the morning.

    You have to split off the zv's and feed each radiator seperately or you will have severe temp control problems around the home.

    Don't forget to insulate all the pipes.
  • Gene_3
    Gene_3 Member Posts: 289
    please note

    that as the hot water enters the rad all of that rads cold water will come out the back and feed the next one, and so on, and so on

    what he thinks will happen will not
  • bob young
    bob young Member Posts: 2,177
    find a pro

    you have the wrong installer. you will be either freezing with off the chart fuel bills or doing the job at least twice. you need a real heating contractor & that will cost you cash but be well worth the results.
  • Weezbo
    Weezbo Member Posts: 6,232
    I happen to live in Americas version of Russian Siberia....

    i too , find that entire strategy to be a bit off.

    have the ladd do some reading in a spare moment at this site....that way you can "keep it in the family" and you will both have a major benefit to the success of your endeavours.

    save a penny pay a pound is a bad idea.
  • yourchizzler
    yourchizzler Member Posts: 10
    can the ham contractor

    dude, all those rads series NO WAY!!!agreed mono or buildmaifold with pex runs to each rad, I lost a job to a contractor who sounds like the guy in your house. ( do you live in westchester?) LOL. Also when you do your job and install a new boiler and hope you mono or maifold the system runs,don't forget something called a thermal bypass so you don't shock the boiler with cold return temps when the system cycles, It will be in any boiler piping install instructions but always overlooked. Good luck and you did come the the right place for good advice. god speed to you.
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