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Pump away on the return side

walnut
walnut Member Posts: 9
I am using an electric hot water tank as my heat source.

I have a grundfos alpha 2 on the return side and just before it an expansion tank.

The concern I have is that if the water is heated and expands it will have to travel up to my manifolds through the loops and back the return to pressurize the expansion tank. I don't think the water can pass through the alpha 2 in the reverse direction. There probably is very little chance that one of the zones won't be open when water is expanding.

I have two 1" pex loops off the hwt that end at a 4 and 3 port ss manifold with actuators before going through 5/8" pap loops that vary between 204 and 278 feet.

Any other thoughts? Thanks for looking !



Comments

  • HVACNUT
    HVACNUT Member Posts: 5,752
    What's the factory charge on the extrol? It looks like an ST-12 domestic tank.
    walnut
  • dko
    dko Member Posts: 562
    Probably a Watts ETX-30

    I'd support the air and dirt separator better. The pex on the right of the pump is also stressed, i'd support that entire line better so it's straight. You don't want sharkbites especially stressed on one side.
    walnut
  • Jamie Hall
    Jamie Hall Member Posts: 22,934
    Not to worry about how the pressure gets from here to there. Unless you have some pretty formidable check valves arranged to isolate the tank, it will get there.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
    walnutEdTheHeaterMan
  • HomerJSmith
    HomerJSmith Member Posts: 2,395
    edited February 12
    This electric hot water tank doesn't provide domestic hot water does it? Not connected to street water? Solely used to provide hot water to heat emitters in a closed sys ?
    walnut
  • walnut
    walnut Member Posts: 9

    This electric hot water tank doesn't provide domestic hot water does it? Not connected to street water? Solely used to provide hot water to heat emitters in a closed sys ?

    The tank doesn't provide domestic water. It is connected to street water before the PRV before the check valve.


  • walnut
    walnut Member Posts: 9
    HVACNUT said:

    What's the factory charge on the extrol? It looks like an ST-12 domestic tank.

    Flexcon PH5. I pressurized it to match my hydronic pressure at 25psi.
  • walnut
    walnut Member Posts: 9
    dko said:

    Probably a Watts ETX-30

    I'd support the air and dirt separator better. The pex on the right of the pump is also stressed, i'd support that entire line better so it's straight. You don't want sharkbites especially stressed on one side.

    Thanks! I'll add some more supports.
  • hot_rod
    hot_rod Member Posts: 21,868
    The expansion happens everywhere in the piping and tank, it doesn't travel with water flow.
    That looks like a domestic water pressure reducing valve? Those typically only go as low as 20 or 25 psi.
    ideally you should have a listed backflow devise instead of a swing check on the fill water.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    walnut
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,590
    Are you using PEX with an oxygen barrier?
    If not, then you need to use all nonferrous metal parts including the pumps. I can't tell if that pump is an iron body or not.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    walnut
  • GroundUp
    GroundUp Member Posts: 1,868
    7 loops of 5/8" PAP at 204-278' and only 15,000 BTU to heat it with? How's that all working out?
    walnut
  • walnut
    walnut Member Posts: 9
    hot_rod said:

    The expansion happens everywhere in the piping and tank, it doesn't travel with water flow.
    That looks like a domestic water pressure reducing valve? Those typically only go as low as 20 or 25 psi.
    ideally you should have a listed backflow devise instead of a swing check on the fill water.

    It is a zurn 70xl range is 70-25psi. I have it set to 25psi. What would you recommend for a listed backflow device, are you implying a reduced pressure zone or dual check valve?
  • walnut
    walnut Member Posts: 9

    Are you using PEX with an oxygen barrier?
    If not, then you need to use all nonferrous metal parts including the pumps. I can't tell if that pump is an iron body or not.

    The red pipe is oxy barrier. My manifolds and the grundfos alpha2 are stainless. The white pex is standard pex b but is limited to what you see in the image.
  • EdTheHeaterMan
    EdTheHeaterMan Member Posts: 7,590
    edited February 13
    walnut said:



    The red pipe is oxy barrier. My manifolds and the grundfos alpha2 are stainless. The white pex is standard pex b but is limited to what you see in the image.

    It only takes a little bit of oxygen to foul up a system over time. If there are any nonferrous fittings in that system, that little bit of PEX b will allow enough O² in the system to make that part disintegrate in a few years. So if there is an iron plug or a cast elbow hiding in the system somewhere behind the plywood, or in the floor, or behind some sheetrock, then expect a leak sometime in the next few years.
    Edward F Young. Retired HVAC ContractorSpecialized in Residential Oil Burner and Hydronics
    walnut
  • hot_rod
    hot_rod Member Posts: 21,868
    Oxygen ingress is also related to the temperature in the tube. Below 140 f you will have very low potential. For piece of mind you could squirt in some Rhomar or Fernox conditioner.

    A vented double check would be a good addition, especially if you add chemicals. This backflow prevents the system water from mixing with your potable water.
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    walnut
  • walnut
    walnut Member Posts: 9
    GroundUp said:

    7 loops of 5/8" PAP at 204-278' and only 15,000 BTU to heat it with? How's that all working out?

    It is running off a low boy 3500 watts non simultaneous. I am probably going to swap it over to simultaneous for 7000 watts. I put the circulator on a ST-01 and have it run 30m on and 30m off over 24h but the primary switch for the circulator having power is the tekmar which won't run unless one of the zones calls for heat. I set the water tank to 90F and my water comes back 80F so delta T of 10F. The 30 minute rest period allows the tank to get the water back up to temperature. At the end of the 30m period if all zones have been calling for heat then my delta T is really low 82F to 78F or something. I was wondering if I might be able to use an aquastat to prevent the circulator from running if the temp of the water at the water tank is too low. Maybe use a contactor with a 24v coil with power feed from the tekmar.

    That said it is working fairly well. Had some recent 5F weather where the system struggled but only had a little of the supplemental active. I have supplemental heat - electric radiant and electric baseboards of 7000 BTU but they are off for the most part. The house is close to passive so heat losses are pretty limited. My modeled heat loss at design temp of 25F is 16,500 btu for ~4000sq feet. Generally we don't reach design heat so 99% of the time with very minimal supplemental heat running the system does a good job.

    Been thinking about possibly installing an air to water heat pump but the heat demands are low enough that I am not sure putting money into a heat pump is a worthwhile idea. I am probably better off putting the money into PV to offset my electrical usage. The 40 gallon low boy was $350 and I figure worst case I could just buy a couple more of them if the BTU demand exceeded what it can deliver.

  • walnut
    walnut Member Posts: 9

    walnut said:



    The red pipe is oxy barrier. My manifolds and the grundfos alpha2 are stainless. The white pex is standard pex b but is limited to what you see in the image.

    It only takes a little bit of oxygen to foul up a system over time. If there are any nonferrous fittings in that system, that little bit of PEX b will allow enough O² in the system to make that part disintegrate in a few years. So if there is an iron plug or a cast elbow hiding in the system somewhere behind the plywood, or in the floor, or behind some sheetrock, then expect a leak sometime in the next few years.
    Fortunately nothing like that. The only ferrous components are the expansion tank and the water tank. I should be able to monitor the dirt mag and see how much debris I get. Was thinking of putting in a powered anode to make the water tank last longer.
  • walnut
    walnut Member Posts: 9
    hot_rod said:

    Oxygen ingress is also related to the temperature in the tube. Below 140 f you will have very low potential. For piece of mind you could squirt in some Rhomar or Fernox conditioner.

    A vented double check would be a good addition, especially if you add chemicals. This backflow prevents the system water from mixing with your potable water.

    That's good to know. I am running at 95F at the tank. I thought about adding a reduced pressure zone but you have to test them yearly and when they do vent you end up with a flood. I should probably turn my water supply fill valve to half off? Really I should have zero water leaving my system so not much point in having the valve open? I am going to avoid chemicals - I tried for lead free components as well but couldn't find a dirt mag in lead free. Annoying that they add lead to brass so that they can lubricate the machine that fabricates the fittings hopefully it all goes away as code changes to require LF on all potable fittings and fabricators upgrade their machining gear!
  • hot_rod
    hot_rod Member Posts: 21,868
    You can easily run a 5500 w element on a 30 A circuit 18,755 btu/hr

    actually you can find 6000 watt elements also

    6000 divided by 240v = 25 A

    Although the wiring inside the he tank gets toasty with a 6kw load
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
    walnut
  • RickDelta
    RickDelta Member Posts: 179
    dko said:

    Probably a Watts ETX-30

    I'd support the air and dirt separator better. The pex on the right of the pump is also stressed, i'd support that entire line better so it's straight. You don't want sharkbites especially stressed on one side.

    ....... agreed! HomeDepot has those little split ring + shorty allthread + shoes to support this piping manifold.

    Those plastic straps are doing very little.