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Thread: I Discovered What is Needed To Bleed a New Heating Loop

  1. #1

    Default I Discovered What is Needed To Bleed a New Heating Loop

    Patience.

    I decided to turn on the heat in the newly completed upstairs (former attic space) that I've been working on this summer. I went down to the basement and checked that my valve controller was calling for heat (which it was) and listened to make sure the circulator was running (it was). Then I felt the pipe going upstairs to confirm it was hot (it was) and then the return to make sure it was hot. It wasn't.

    I went back upstairs to check the first baseboard in the system and it was stone cold. Back downstairs with a 5 gallon bucket in hand, I closed off the return valve and opened the bleeder. I got about 8 oz. of cold water and the pressure gauge went from 20 to 0. Well I never did bleed the system when I connected it to the boiler several months ago, so now was the time.

    I went upstairs and opened the bleed valve that was installed mid-loop at the highest point and got a lot of air, and then a dribble of cold water. I closed the valve and went back downstairs and opened the bleeder. Once again, about 10 oz of cold water and a complete drop in pressure. This upstairs/downstairs circuit was repeated about 10 or 12 times before I finally got hot water from the mid-loop bleed valve. With each cycle I checked the base boards and the hot water was starting to move through the loop.

    With hot water past the upstairs valve I started to get more and more water from the bleed valve on the boiler. And then finally, after a significant amount of time, I got hot water from boiler bleeder and then a long push of air from the schrader valve on the expansion tank.

    A trip upstairs to touch the last baseboard in the loop confirmed that hot water had finally made its way through the loop. At first the water movement was very noisy; so much so that I started to wonder if there was a leak - I knew there wasn't because I did a 90 day air pressure test - but it makes you second guess yourself for 30 seconds.

    Then it all went quiet and I could smell all of the stuff that collected on the fins burning off the baseboards. I had heat.

    By the time I got back downstairs to collect my bucket the pressure was back to 20psi. I stood there looking at my boiler and I felt damn proud of the plumbing projects I tackled this year. This year I:

    - Installed a 300' heating loop upstairs and added a zone valve to my boiler
    - Installed a full bath upstairs including all vents and plumbing for the shower, toilet and two sinks.
    - Ran the waste lines for the above and connected it to my main waste line.
    - Replaced my indirect hot water heater that was improperly installed 10 years ago (causing it to fail).
    - Installed a Honeywell thermostat for the heat and AC for the upstairs.
    - Added a Taco ZCV404 Zone Controller to control all 4 zones (3 heat, 1 DHW)
    - Replaced a flaccid relief valve on my boiler and replaced the T&P gauge
    - Replaced the expansion tank
    - Replaced a damaged media tank (my fault, don't ask) on my Fleck 5000 twin-tank water softener.
    - Helped a friend with a emergency Sunday install of a new hot water heater including all new wiring back to the panel.

    On all of the above, not a single leak. The information contained in these forums provided me with almost everything I needed to know. The few times I couldn't find the answer in a search, a direct answer was always just a question away (usually responded to in just an hour).

    My boiler that was a complete enigma to me just a year ago is now like an old friend. I now feel that I can handle just about any plumbing project that my hose throws my way.

    And all it took was patience.

  2. #2
    DIY Senior Member BobL43's Avatar
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    Did you ever try bleeding the entire new loop at the boiler with the makeup water pressure regulator in the "full open" position? You can't put it on full pressure with the system closed, but if your drain valve is open, you can. The highest pressure you mentioned is 20 PSI, so I guess you did not put in in full pressure mode. The water goes through the system MUCH faster when unregulated than when it is in normal mode. that's a lot of running up and down stairs by yourself. The circulator does not have to run to do this as far as I know, but the zone valve has to be open if there is one for the new loop.
    I am definitely not a pro plumber, but I am a pro crastinator

  3. #3

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    I did attempt to open the makewater valve but it didn't easily move and I didn't think it wise to force it. Otherwise I may have added a new repair to my list. It was nice to confirm that the makewater valve did return the pressure to 15psi each time, so I know that is working properly.

    I did open the manual valve lever on the Taco 571 valve and left the circulator running as I wasn't sure whether or not it should be engaged.

  4. #4
    DIY Senior Member BobL43's Avatar
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    Anyway, glad you got the air out!
    I am definitely not a pro plumber, but I am a pro crastinator

  5. #5
    Retired Defense Industry Engineer jadnashua's Avatar
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    You mentioned the valve at the expansion tank...that air pressure needs to be set when the plumbing system is NOT pressurized. If you opened that valve and didn't restore the pressure, it is not set properly, and you are liable to get an overpressure situation, especially if all zones are calling for heat and you get all of the air out of the system. If you're nominal pressure is 20# (14-16 is more normal, but 20 may be called for depending), then the expansion tank should be just under that pressure as a precharge. Once the system is pressurized, the expansion tank will read the same as the system water pressure....but, you need to set up the precharge properly, or there'll be no room for the water to expand.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

  6. #6
    DIY Senior Member BobL43's Avatar
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    Quote Originally Posted by jadnashua View Post
    You mentioned the valve at the expansion tank...that air pressure needs to be set when the plumbing system is NOT pressurized. If you opened that valve and didn't restore the pressure, it is not set properly, and you are liable to get an overpressure situation, especially if all zones are calling for heat and you get all of the air out of the system. If you're nominal pressure is 20# (14-16 is more normal, but 20 may be called for depending), then the expansion tank should be just under that pressure as a precharge. Once the system is pressurized, the expansion tank will read the same as the system water pressure....but, you need to set up the precharge properly, or there'll be no room for the water to expand.
    Good point jim
    I am definitely not a pro plumber, but I am a pro crastinator

  7. #7

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    The nominal pressure was 14-15psi. It was only after the boiler went from 140 degrees to 200 degrees that the pressure increased to 20psi.

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