How to refill a single zone, oil fired hot water boiler for baseboard radiant heat

Discussion in 'Boiler Forum' started by McG, Dec 2, 2011.

  1. McG

    McG New Member

    Messages:
    33
    Location:
    CT, RI
    Concord, Dec 1, 2011 006.jpg

    Please help me understand this system and how to get it up and running again. I had to lower a pipe, so I drained down the system (don't know if I did this properly) cut the pipe and lowered it. Now I need to get the boiler running again.

    I think I need to flush the pipes first to remove any solder/flux, dust from the repair job and to check that my joints are holding. What direction is the water going to flow, which valves to open and which to close. Any help would be greatly appreciated.

    Here are a few pictures. I'm not a pro so please do not use pro lingo or abbreviations. Thanks.

    The make-up water enters the system from behind the expansion tank.

    Attached Files:

    Last edited: Dec 2, 2011
  2. Gary in NJ

    Gary in NJ New Member

    Messages:
    90
    Location:
    NJ
    Open the valves, open the autofill (so it is unregulated) and bleed the air out of the zone. Once the air is purged you can put the autofill in its operational position and start the boiler.
  3. Dana

    Dana In the trades

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    Location:
    01609
    BTW: That foam between the joists (rafters?) needs an ignition barrier to meet code. (Pretty clean looking job!) Half inch sheet rock makes it, as does half inch ply or OSB.
  4. McG

    McG New Member

    Messages:
    33
    Location:
    CT, RI
    Thanks. Is the "autofill" the cold water supply, that here enters the system above the expansion tank and below the spirovent? What is the autofill's operational position? Half open, closed, or open?

    When I was draining down the system, I heard what sounded like the expansion tank filling up with water. I realized then that the supply water was still open. The hissing stopped when I closed that valve which I guess is the autofill valvle. Is this something I have to address? Like by draining the expansion tank. If so, how do I do that?
    Last edited: Dec 2, 2011
  5. McG

    McG New Member

    Messages:
    33
    Location:
    CT, RI
    Thanks, it has a coat of fire retardant paint on it. The installer said their special paint sold only by foam distributors, satisfied fire codes. Drywall or plywood would be more attractive and an additional fire retardant, definitely.
    Last edited: Dec 2, 2011
  6. Tom Sawyer

    Tom Sawyer In the Trades

    Messages:
    3,268
    Location:
    Maine
    Concord, Dec 1, 2011 003.jpg

    keep the water flowing until all the air is gone. At least a couple of minutes or so
  7. McG

    McG New Member

    Messages:
    33
    Location:
    CT, RI
    Tom, Thanks! The labels help a lot! Couple of questions: If I follow your instructions, the water will not flow through the boiler chamber itself but only through the baseboards, is that right?

    This will purge the air and clean the debris that might be in the pipes. I can keep running the water until no air bubbles appear in a five gallon pale with the hose outlet submerged in it. When the bubbles stop, close the drain, remove the hose, open the lower valve (allowing the water to flow into the boiler).

    I guess the pressure should read about 12 psi, or whatever the pressure is coming off the well pressure tank. Then turn on the boiler and the pressure will increase to about 18 psi, am I right?

    Should I drain the expansion tank? How to do this?
  8. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,270
    Location:
    New England
    First, while handy, it can be messy with a valve between the hot water pipes and the expansion tank. If you leave it closed during operation, you WILL end up dumping water from the high pressure relief valve each time the water heats up (if you have the autofill open). You can leave the autofill valve open...it should be adjusted to fill your system to the proper pressure. This is often around 14-16 pounds. It is adjustable. The pressure should not increase during operation...that is the purpose of the expansion tank, to hold the pressure - it gives the heated/expanded water a place to go, otherwise, the pressure would rise radically, and then get dumped by the relief valve.

    While you have the system bleed down, it's a good idea to check the precharge on the expansion tank. It should be the nominal design pressure of the system. The water needs to be off, that valve above it open, and at least one other valve in the system open, or you'll be measuring water pressure, not the air pressure. There's a Schrader valve on the bottom of that tank, just like one on your car tires. Check the pressure the same way, with the same gauge. If you get water out of that, it's shot, and must be replaced. If good, pump it up, if required.
  9. McG

    McG New Member

    Messages:
    33
    Location:
    CT, RI
    Thanks Jim. I'll do that. I guess I can pump up the expansion tank with a bicycle pump if need be. So with the water turned off and the valve open and at least one other valve I should get "the normal design pressure" which I assume is between fourteen and sixteen psi?
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,270
    Location:
    New England
    Yes, unless you have an unusual situation, most residential boilers run at nominal atmospheric pressure 14-16psi.
  11. frozen

    frozen New Member

    Messages:
    7
    Location:
    Michigan
    I just looked at my system. As old and poorly designed as it is, someone at some point thought to splice in a fill/supply line from a cold water run. For me it's pretty simple. Just open the vavle and top off.
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