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do i need a check valve? (BPHX loop w/ electric tank)

I'm basically doing what is shown here: brass nipple in drain bung at bottom of electric tank, couple of tees, cold water feed in, boiler drain, recirc loop with BPHX. The drawing shows a check valve after the circ but I can't figure out why it needs one. What am I missing? (I don't like spring check valves....)

Comments

  • hot_rod
    hot_rod Member Posts: 14,748
    check valves prevent un-wanted flow. Flow on the opposite side of a HX can induce flow on the other under certain conditions. No harm in adding that check.

    What circ pump are you using? Must be brass or stainless if that is potable water in the tank. Most small circs have check valves included in the box now a days.

    I'd use a spring check, soft seat, low pop pressure. A hydronic design spring check seals "bubble free" swing or weighted checks do not.

    Here is an example of the checks that ship with circa these days.

    I'd imagine a small DHW type recirc might be enough for that application.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • varadhammo
    varadhammo Member Posts: 27
    The Circ is a stainless steel 006 threaded ends, no flange. I have an extra check valve from an alpha that I didn't need, I don't suppose that would work with the 006...?

    Also, I have a 008 already that I'm planning on using for the boiler side. It's a non IFC model, will one of these pop in style checks work?
  • hot_rod
    hot_rod Member Posts: 14,748
    most of the new circ pump volutes are machined out for those checks to snap in. Look inside the discharge port for the clue. Or contact the manufacturer. There are a number of checks you can sweat or thread into the piping. Some prefer to have checks downstream of the circa a few inches.

    Be sure it snaps in tightly or it could end up in the piping somewhere.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • icesailor
    icesailor Member Posts: 7,265
    edited December 2014
    You need the check.

    That is a more difficult way to pipe that.

    Do everything as shown. but connect the cold to the top of the tank at the cold water inlet. The hot water from the HX will share the connection. It also will restrict the flow of the 006 pump. Leave the dip tube alone. Cutting off the dip tube like they have will decrease the amount of available stored hot water.

    That schematic will give you full pressure through the tank. Unlike some drawings I have seen. But connecting the cold into the top is easier and works just as well. Probably better.

    Use brass nipples and brass screw fittings for the circulator and a union. You don't want to be dealing with copper fittings if you have to change the pump.

    Electrical:

    Leave the bottom thermostat where it is and leave it alone. That piping arrangement might cause the circulator to cycle more because the cold water enters just below it. HELLO? If you have a newer foamed tank, enjoy moving the thermostat through the foam. They tell you how to wire the pump to make it run. They neglected to tell you that you will need a control to tell the boiler to run if you get a hot water call. You need to use something like a Taco ZR 501 and use the dry contacts to start the boiler. Or at least a smart Sparky that understands. There are almost as many ways to wire this as there are priming a shallow well water pump.

    OBTW, should you decide that the developers of this idea are smart and I'm not, they neglected to mention that there are two black wires buried in the foam, directly in line with the top of the tank and the lower element and thermostat.

    And that "special drain tee" that they might supply, few fittings have been developed for plumbing than can compete with the uselessness of that one. Just ask them at PEX Supply or your local supply house if they hade a faucet washer for that drain if it starts to leak. They won't. Not ever. Its easier to use a 3/4" brass tee and a 3/4" IPS boiler drain. When that hateful valve leaks, it has a washer with a larger hole in the middle and it is held in place by a brass post that I can only describe it as appearing like a circumcised dink. You can take a proper sized heat proof washer, hold it with a pair of pliers and use your favorite dead battery drill and make a larger hole in the washer. If it is a convex washer, you need to file the top of the volcano off. Then force it on to the post. Like a condom.

    After you have done it a few times, you can do it ahead of time and catch the change on the fly, loosing little water and not draining the tank. If the washer is bad, often the O-Ring on the stem is bad and will leak. SO, putting a hose cap on the hose threads doesn't stop the leak.
  • varadhammo
    varadhammo Member Posts: 27
    icesailor said:

    You need the check.

    That is a more difficult way to pipe that.

    Do everything as shown. but connect the cold to the top of the tank at the cold water inlet. The hot water from the HX will share the connection. It also will restrict the flow of the 006 pump. Leave the dip tube alone. Cutting off the dip tube like they have will decrease the amount of available stored hot water.

    That schematic will give you full pressure through the tank. Unlike some drawings I have seen. But connecting the cold into the top is easier and works just as well. Probably better.

    Use brass nipples and brass screw fittings for the circulator and a union. You don't want to be dealing with copper fittings if you have to change the pump.

    Noted. After thinking about it for a second, I think I agree with you about the cold inlet sharing the top port with the HX loop and not shortening the dip. "Check" on the brass nipples and unions for the 006, already sitting on the work table :)
    icesailor said:


    Electrical:

    Leave the bottom thermostat where it is and leave it alone. That piping arrangement might cause the circulator to cycle more because the cold water enters just below it. HELLO? If you have a newer foamed tank, enjoy moving the thermostat through the foam. They tell you how to wire the pump to make it run. They neglected to tell you that you will need a control to tell the boiler to run if you get a hot water call. You need to use something like a Taco ZR 501 and use the dry contacts to start the boiler. Or at least a smart Sparky that understands. There are almost as many ways to wire this as there are priming a shallow well water pump.

    I'm going to use a tekmar 156 (on/off differential setpoint control). After looking into a "simpler" way which would involve two aquastats and some relays, the 156 ended up being more cost effective, simpler to wire, and programmable (I can decide on the required deltaT between storage and DHW for the pumps to run). The heat source is wood boiler storage, I'll have one sensor in a well in the GARN storage, one sensor up against the water heater tank. Got a RIB 30A rated DPDT relay that the 156 will trigger, I'll wire the water heater electric elements through the N/C poles, HX circs wired through the N/O poles so the electric is disabled whenever the 156 decides to pump heat from the GARN, otherwise if storage is cold the WH tank's built in aquastats will just do their thing. The 156 relay will also trigger a RIBU1C which closes a RIB dry contact relay on the primary storage loop circ.
    icesailor said:


    OBTW, should you decide that the developers of this idea are smart and I'm not, they neglected to mention that there are two black wires buried in the foam, directly in line with the top of the tank and the lower element and thermostat.

    Noted.
    icesailor said:


    And that "special drain tee" that they might supply, few fittings have been developed for plumbing than can compete with the uselessness of that one.

    Yes I didn't even know what that special tee thing was and why it would exist, I took one look at it and thought "brass tee + boiler drain" :)

    Thanks for all your help!
  • icesailor
    icesailor Member Posts: 7,265
    We have a thing in sailboat racing. KISS. Keep It Simple (but don't be) Stupid.

    If you are in to technology for the sake of technology, that's one issue.

    If it is cost savings, you won't live long enough to pay back the extra cost. Cheaper isn't always bad.

    There was an old 1960's Folkie Group, "The Limelighters". They sang a song "Charmin Betsy".

    Rich gal drives a brand new Rolls
    Poor gal drives a Model A
    My gal uses her thumb
    But she gets there, just the same.
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