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Water Boiler Piping

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Ziggy
Ziggy Member Posts: 1
I replaced my oil-fired boiler and the unit I am putting in has no hookup for an expansion tank. What is it's purpose and do I need it.

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  • Dave E.
    Dave E. Member Posts: 9
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    Water Boiler Piping Question

    I'm rearranging the near-boiler piping of my Weil-McClain 268V water boiler. The main reason is to add B&G Flo Control valves to the supply and return. It was overheating uncontrollably. There's currently a galvanized 1.25" curved piece from return tap to circulator. Most of the old supply and return piping is 1" iron or steel of some sort (diverter tee radiator system). Between the circulator and the return line is 1" copper. I really hate to solder, so I don't expect to use any new copper. I removed a 1.5" copper pipe from the supply tap at the top of the boiler to the supply main. (I also removed some pipes to long-demolished out buildings). I thought I might as well also move the circulator to the supply side now. I expect to replace any changed pipes with 1" black iron.

    Question #1: Should I use galvanized instead of black iron?

    Currently make-up water is from a 1/2" copper pipe horizontal to gate valve, then elbowed down and elbowed horizontal again to a B&G model FB-38 reducing valve, through another gate valve to a 1/2" tee. One leg goes straight down and is bushed out onto the 3/4" tap at the top of the boiler, which the W-M manual says should be for an automatic air vent, when using a diaphragm-type expansion tank. The other leg goes straight up, zig zags through two elbows (to avoid a joist) and then connects to a Watts model ET-15 expansion tank with diaphragm.

    Question #2: Is the arrangement in the above paragraph acceptable, or should I install an automatic air vent, and pipe 3/4" from a tee in the supply, above the newly relocated circulator, to the expansion tank?

    Thanks for your consideration.
  • Timco
    Timco Member Posts: 3,040
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    You really should be reading up on this before repiping the near boiler piping. I would suggest 'Pumping Away' and 'Primary / Secondary piping made Easy' in the online store. Black pipe is what you want, but copper is 100X's easier to fit & run. There are MANY factors in how the piping is designed, manifold size and pump / ex tank location. Really hard to type someone through a job like this...

    Tim
    Just a guy running some pipes.
  • Dave E.
    Dave E. Member Posts: 9
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    (moved posting)

  • Dave E.
    Dave E. Member Posts: 9
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    Thanks, Timco. I have a copy of "Pumping Away", but I didn't remember it addressing the questions I had. I'll read it again today, since it may help with the work, and I haven't read it in a while. My brother also has a 68 series boiler with a similar expansion tank connection to the boiler, and it doesn't seem to have caused a problem. Piping 3/4" from the top tap to the expansion tank is what the Weil-McClain manual recommends for a "closed type expansion tank" but not a "closed diaphragm pre-pressurized expansion tank".
  • Timco
    Timco Member Posts: 3,040
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    Could you post some pictures? What do we mean by 'overheating'? and by 'return trap'? A closed tank can be diaphram or steel, just closed. That's why in Pumping Away Dan explained both in detail. Diaphram is more modern and better when using air-removal devises, although I have had great success with steel type tanks and an airtrol fitting. I like having pumps and ex tank on supply side, and fill ties into them there as well. Pumps pump away from that. Have you thought about bypass or boiler protection? Is your boiler a CI unit or mod / con? I can send you pics of typical installs and show the typical layout of near boiler piping looks for reference...What type of emitters do you have?

    Tim
    Just a guy running some pipes.
  • Dave E.
    Dave E. Member Posts: 9
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    I'll look into posting some pictures.

    My "overheating": Since I moved into the house in October, 2004, the oil burner would continue to fire, and the radiators remain hot, regardless of the thermostat setting, and even if the thermostat was disconnected. (I should have tested to see if power was supplied to the circulator when there was no call for heat, but I didn't. I'll do that as soon as the system is filled with water again, or maybe disconnect the power to the burner and test sooner. I couldn't find any professional in my area that seemed to know about piping boilers.

    The boiler is a cast iron unit, probably about 15 to 20 years old. The boiler supplies water only to seven cast iron radiators on the first floor of a one bedroom house with a finished attic (a second bedroom for short people only). The attic is heated only by a heat pump, and has no hydronics. At one time the system supplied hot water to radiators in about a half dozen motel cabins also, but these were probably demolished before the present boiler was installed. The boiler is rated at 86 MBH DOE heating capacity, 0.70 GPH in I=B=R burner capacity.

    I've just taken another look at "Pumping Away", and seen that my current make-up water and compression tank arrangements are not as recommended in the book.

    I'd like to repipe to something like the illustration on page 48 (but one zone, not two), but I have a few questions:

    1. Is "boiler drain" above the boiler an actual fitting sold by that name, or a sillcock opened to allow air in when draining the boiler?

    2. The "air separator" is shown as two black boxes. Is the smaller one an air vent, and is it included with, or part of, the air separator?

    3. Is the air separator pictured on page 48 still recommended if the boiler has an air vent like the one pictured on page 57?

    4. I was going to put a ball valve also on the return for possible future maintenance, is that a good idea?
  • Timco
    Timco Member Posts: 3,040
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    First, a 'runaway boiler' is typically a control issue. Something is telling the boiler to make hot water, and it may be migrating through the system with no pump (gravity) if the piping is wrong. Does it fire often?

    As for the questions, 1) This is for purging air from the boiler, not actually draining. I do not use this. The air will rise into the zones as the system fills. The supervent or spirovent will allow air to escape. I like purge stations on the returns. 2) This is a scoop with a float type vent on top. If water is moving too fast, it will not remove air very well. I prefer a microbubbler like a spirovent or honeywell supervent. All one unit. 3) The boiler is where the water is the hottest, and a great place to catch air, but again if the water is moving too fast, it will not get it. The spirovent goes as the first item in line on the supply side and this way gets all water that comes out of the boiler at nearly it's hottst point. The fill line and ex tank tie into the bottom of the spirovent, and you pump away from that. Will not hurt to leave the boiler vent and add the spiro. 4) Purge stations will let you isolate the zones and purge the zones. I will post pics in a second from my other computer. These take the place of the boiler fill in question 1.

    Hope this helps...This is a lot to take in and do well. Do yourself and insurance a favor and check / replace your relief valve with a new 30# unit while the boiler is drained. Maybe even replace the gauge to know it is right.

    Tim
    Just a guy running some pipes.
  • Timco
    Timco Member Posts: 3,040
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    I sent an email with return purge station pics...

    Tim
    Just a guy running some pipes.
  • Dave E.
    Dave E. Member Posts: 9
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    Thanks, but I'm having problems accessing that email account now, so I've changed the one I'm listed with for this site. Could you possibly forward the email to me at proactivedave@yahoo.com? Thanks!
  • Timco
    Timco Member Posts: 3,040
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    done...

    T
    Just a guy running some pipes.
  • Timco
    Timco Member Posts: 3,040
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    Yes, you need it and it ties in at the air seperator on the supply side, if you have one. If not, it tie in downstream of the circulator so you are 'pumping away' from it. If you start a new thread and include some near boiler piping pictures, we can help....
    Just a guy running some pipes.
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