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Stiebel Eltron recirculation pump Model No. CP3S15-62FC

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I have an open system from my home built water heater. 250 gallon LP tank with burn chamber welded in. Filled with water and fire built it heats about 200 gallons quick and holds the heat well.

My problem seems to be the pump. It is installed correctly and is about 12" above the water level. I cannot get the pump to prime and continuously pump my water.

Question: Does this pump require head pressure to work? Will it not draw water up twelve inches once primed?

Has a built-in check valve which seems useless in a system that would require head pressure?

If I am using the wrong pump what brand and model do you recommend? I don't need a bunch of system this and that. I simply need a pump that will move 5-15 gpm.

Thanks.

Comments

  • Big Ed_4
    Big Ed_4 Member Posts: 2,785
    edited February 2022
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    Pump or circulator ? Looks like a Grunfos circulator .. Which is not a self priming pump , it creates a pressure drop to move water . Why a open system ?
    I have enough experience to know , that I dont know it all
  • hot_rod
    hot_rod Member Posts: 22,147
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    Move the pump below the water level. Outdoor wood furnaces always have the pump at the bottom of the tank, they are also open systems

    Or stick a high temperature sump pump in the tank😉
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Csmith1967
    Csmith1967 Member Posts: 12
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    ty bob. I was wondering if gravity feed was enough.
  • hot_rod
    hot_rod Member Posts: 22,147
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    The old gravity systems worked because of the large diameter piping. The hotter water would rise up in the large pipes that had very low flow resistance, cooler water would fall down. Systems that are piped with 3/4, 1 , 1-1/4" sized piping generally need a circulator to cause the flow to move. It provides the energy to move the fluid.

    The typical small wet rotor circulator needs about 4 psi pressure at temperatures around 180- 190F. placing the pump as low in the system as possible should provide enough pressure to keep the pump working properly. A. centrifugal type circulator will not lift water out of an open container.

    The water will stay in the piping above an open boiler as long as you do not have any auto air vents up high point.

    It is possible at high temperatures to pull a vacuum in the system, if you have piping a story or so above the water level, running 180F or lower should be fine.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • GroundUp
    GroundUp Member Posts: 1,907
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    It is not installed correctly- as Bob mentioned, it needs to be below the water level. Lower equals more head pressure which is better.
  • Csmith1967
    Csmith1967 Member Posts: 12
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    I moved the pump down near the floor and piped it. There is about 2' of standing water above it. Pump comes on but still doesn't move anything.

    So I have two 1" lines running to the basement. One feeds hot water and the other returns it. They attach to six valve manifolds that segregate my zones.

    I am looking for a different pump. Ideally I'd like a 12v recirculation pump. 3-6 gpm.

    Anyone have any suggestions.
  • hot_rod
    hot_rod Member Posts: 22,147
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    I moved the pump down near the floor and piped it. There is about 2' of standing water above it. Pump comes on but still doesn't move anything.

    So I have two 1" lines running to the basement. One feeds hot water and the other returns it. They attach to six valve manifolds that segregate my zones.

    I am looking for a different pump. Ideally I'd like a 12v recirculation pump. 3-6 gpm.

    Anyone have any suggestions.

    Did you purge the air out of the circuit and all the loops? if there is an air bubble that pump, any pump, will not circulate.

    B&G has a 12VDC Eco Circ, but it is a fairly small, low performance circ
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Csmith1967
    Csmith1967 Member Posts: 12
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    Im not familiar with B&G. What company is that.

    Yes on purging. The pump was below the water level and filled with water when I opened the valve. It just will not pump any water.
  • hot_rod
    hot_rod Member Posts: 22,147
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    3 things you need to know to select a circulator
    fluid type
    gallons per minute
    head or pressure loss of the circuit

    Here is the Bell & Gossett eco 12VDC it will do 3 gpm or so, depending on the pressure drop.

    As for pressure on the pump, if there is water at the suction and discharge, regardless of a check valve, then the distance of the water above the circulator is the pressure on it. If your water level is two feet above, you have 2' head. It is seeing the pressure from the suction side if there is a check at the discharge

    A few reasons that it is not circulating

    air lock
    not spinning, jammed rotor, installed backwards
    a closed valve somewhere, obstruction in the piping, are all the manifold ports open??
    sized too small to overcome the head, or pressure drop, doubtful

    disconnect a loop at the manifold, see if it is circulating that far, or take a short piece of pex and jumper from a supply to return.

    Those pumps with internal checks sometimes get air locked right in the pump body. Loosen the flange bolts on the discharge side to burp that air bubble.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Csmith1967
  • Csmith1967
    Csmith1967 Member Posts: 12
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    Im getting surgery this week then off to Mayo for ten days so not going to do much more.

    Brand new pump. Actually, have two.

    I ran a 5' line from bottom of boiler tank to the pump that was below the tank then a 6' line back into the top of the tank. An 11' open circuit with pump below water level and not pushing any pressure. Still nothing.

    No valves or obstructions.

    The steibel eltron is the recommended pump. I let the water gravity from the tank through the pump then plugged it in. Starts and hums, but it doesn't move water. The pump is turning. I'm baffled.

    I order a 12v self-priming 3.1 gpm pump I will hook to our battery bank with wind/solar When I am back.

    ty all for the help.
  • GroundUp
    GroundUp Member Posts: 1,907
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    If it's not flowing water, there is an obstruction. Most likely that obstruction is air. Simply filling the lines is not a purge- you need to actually force water through the loop with an external source of pressure such as a transfer pump or using your garden hose
    Csmith1967
  • hot_rod
    hot_rod Member Posts: 22,147
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    Im getting surgery this week then off to Mayo for ten days so not going to do much more.

    Brand new pump. Actually, have two.

    I ran a 5' line from bottom of boiler tank to the pump that was below the tank then a 6' line back into the top of the tank. An 11' open circuit with pump below water level and not pushing any pressure. Still nothing.

    No valves or obstructions.

    The steibel eltron is the recommended pump. I let the water gravity from the tank through the pump then plugged it in. Starts and hums, but it doesn't move water. The pump is turning. I'm baffled.

    I order a 12v self-priming 3.1 gpm pump I will hook to our battery bank with wind/solar When I am back.

    ty all for the help.

    As Groundup mentioned, it is all but impossible for the circulator to not cause the water to move.

    Assuming it is installed properly, arrow pointing the correct way
    Sized properly, sounds like it is
    No obstructions in the pump or piping

    Is the impeller spinning or just the motor? It fairly easy to break the ceramic shaft in those circs, if they are dropped, for instance.
    Remove the 4 allen bolts and confirm it is spinning, or look in the end on the bench when powered up.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    Larry Weingarten
  • Csmith1967
    Csmith1967 Member Posts: 12
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    I will definitely check that Bob, ty.