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Can boiler be run for domestic hot water when heating pipes are drained for repairs?

NassauTom Member Posts: 51
edited November 2014 in THE MAIN WALL
I am draining the pipes and radiators in my hydronic heating system down to about 6 feet above the basement floor to cut out and replace a pipe near the basement ceiling. The boiler also supplies domestic hot water. Is it safe to run the boiler to heat domestic hot water while having the circulators turned off?


  • Docfletcher
    Docfletcher Member Posts: 487
    Wait for a pro's answer to be sure...

    I'm no pro, but I would say not safe or good for the boiler because the water in the boiler jacket will not circulate, causing a rapid increase in water temperature (short cycling).

    I am assuming you are speaking of hot water supplied by a coil in the boiler as opposed to an indirect water heater with it's own circulator.

  • billtwocase
    billtwocase Member Posts: 2,385
    I can be done by a pro. The system needs to be full, closed, and expansion tank not isolated. Feed and returns capped off, low water cut installed hopefully.
  • ww
    ww Member Posts: 282
    edited November 2014
    is this a result of that cracked radiator you had?

    when i replaced a circulator as well as did some top floor radiator work i drained the system down to reach the top of the boiler. i made sure the thermostat was off and no call for heat would happen. i lowered the hi limit on the aquastat since i wasn't using the circulator and a 20 degree differential didn't matter.

    my situation involved having no circulator for a month or so for which i utilized a bypass pipe in place of circulator. at the time the expansion tank was drained too. i didn't need heat anyway during that time.

    i got plenty of hot water every day with no problem.

    if this involves that broken radiator and all the other pipes are good below the floor just bypass the radiator with a couple of elbows, some nipples and a union in between and you can have heat also with the radiator out of the circuit as well...or just cap it off for now...if you just want hot water..if heat then bypass it.

    just remember this is what i did. i looked at it and saw this would work and it did. others may say it won't work. but all i can say is i needed to do this..it worked..and had no problems during or after...and it worked for me.

    i also would cap off the return and supply pipe while i was getting the bypass pipe ready or the other radiator depending what i was doing.

    just get a couple of big wrenches..maybe pipes if needed for leverage...measure what you need and account for thread depth. if you can. i personally wouldn't use copper for that job..it costs too much and it's not as strong if radiator moves around in my opinion.

    you will have to open some of the bleeders when draining to prevent air lock. make sure you close them all before putting the boiler on.

    sometimes things can be done by a homeowner. if things get too hard to do or you don't have the basic skills to figure things out after gathering information from everyone and have to be guided for each and every detail then it may be time to consider someone else to do the job for you. if you feel confident,have a plan and enjoy doing this then go for it.

  • NassauTom
    NassauTom Member Posts: 51
    ww said:

    is this a result of that cracked radiator you had?

    Hi WW. Yes, it is. And, thanks for sharing your experience. I am replacing the return pipe from the radiator which is about one foot of vertical and two feet of horizontal pipe up near the basement ceiling. I drained the radiators and pipes down to just below this point, so there is still water in the boiler. I have obviously turned off the thermostats and the shutoff for the circulators for good measure. I have actually had the heat shut off for the zone that addresses the main portion of the house for two weeks since the radiator shattered. And, the system drained itself to some degree through the gaping hole in the radiator. :-)

    I am using copper in my repair, mostly because it is less stiff. I have come to the conclusion that the root of the misalignment and perhaps even the shattering of the radiator were due to the settling of the house combined with the stiffness of the iron pipes. Most of the iron pipes leading to the radiators in this house had already been replaced with copper (perhaps due to more severe settling in other parts of the house?). Only this and one other radiator were still supplied entirely by iron pipe.

    Oh, and yes. The copper is a very expense solution!! Wow. Luckily, I'm not putting in that much.

    I've never worked on any heating system before, and, while I consider myself pretty handy, this is not the type of job I would pick to do for fun. But, I am currently unemployed and can't afford to bring in a plumber or heating contractor. So, as it is said, necessity is the mother of invention. I will learn what I need to learn to get this fix done. I truly appreciate the help and insights you and many others have provided along the way.

    Well, I have to get back to work. The pipe is cut. I need to pull it out, practice threading on it and then thread the pipe that I will be joining the copper to. Then do the copper work and, with any luck, I'll have my heating system back together.
  • ww
    ww Member Posts: 282
    ok...that sounds great...i do all this stuff myself just like you...ok...i'm sure you've reviewed how to sweat pipes or done them before...i'm sure this will work out fine and i see you have to work around this house settling problem too.

    the plumber on this old house tv show uses a flexible line and special fittings with tool to crimp them to avoid soldering..who knows..in the future..

    with all this settling you might want to look into that. with the flexibility of this material it may be right up your alley. i haven't used it but have seen it and it must work or he wouldn't use it.