Pennsylvania New system-Max efficiency??

Discussion in 'Maintenance and Troubleshooting' started by Drew H, Feb 16, 2019.

  1. Drew H

    Drew H New Member

    Hi all,
    We just replaced an open-loop geo system in our just-purchased 2,600 sq-ft Poconos vacation house. Our January electric bill was ~$150 when the temperature was kept at 50 for all but about 2 days. Basic conditions include:
    1. New system is a Trane T2GX064SLR14N1 - 2-stage, open loop with hot water generator
    2. Well pump is a Franklin Electric 2243019204 Super Stainless Water Well Motor 4 2.0 HP 230V 3-Wire Single-Phase that was installed (I think) in 2005.
    3. Two new 100 gallon well pressure tanks.
    4. Well provides water to household and Geo. Water table seems high.
    5. Electric hot water
    6. House was built in '96. Has cathedral ceilings and skylights but seems properly insulated (Anderson windows, etc).
    The tech assures me the system was properly installed (including setting the water flow) and we discussed possible reasons for the higher consumption.
    1. Too much Aux heat use ... The Sensi thermostat has been occasionally calling for aux heat. The old sensi T-stat was recalled due to a faulty C pin and I just replaced it. So far (2 days), I haven't seen the aux heat kick on, but it's been a bit warm outside. I'm hoping this solves the problem but not optimistic.
    2. Well pump runs to0 often. Well guy and I discussed replacing the pump, but he's not convinced one of the newer constant pressure will save me.
    So, here are the options (in order of aggressiveness) that I'm considering and would love comment on...
    1. Do nothing. $150/month isn't bad for January in the Poconos.
    2. Set the Sensi Heat Cycle Rate to Fast to prevent large swings that trigger the Tstat calling for Stage 2 or Aux heat.
    3. Install a W-lead switch to lock out the aux heat. This will be tied to a temp sensor that will automatically close if the house temp drops belows ~45 to make sure the electric coils (aux) energize if the main system fails.
    4. Add a pressure reducer to the water supply to limit water flow and reduce pumping.
    5. Split the water input and add a shut-off to each tied to each of the 2 stages. Full flow only happens when called for. The goal is to limit water flow (pump use) to what's necessary. Is there a variable-flow water valve that will accomplish the same thing?
    6. Install a new well pump. If so, what would work best in my situation? How do I determine how much actual electricity my pump is currently using?
    Am I missing anything here? Any thoughts about my options? Thanks for any help.
    Drew
     
  2. waterpirate

    waterpirate Well-Known Member Industry Professional Forum Leader

    Hi and welcome!
    150.00 a month for total electric usage for a house in the Poconos is not bad imho
    The devil is in the details as far as what the thermostat tells your unit to do, set the settings that work for you, not the default settings
    Variable speed water control valves are available, pricey to buy and adds complication to the operation
    A 2hp single phase pump consumes a lot of amperage, a variable speed 3 phase consumes only what is needed.
    Adding a pressure reducing valve will only effect the pressure, not flow and electric consumption
    Stage 2 is not be avoided or feared, aux heat or stage 3 is the killer of electric bills
    Hope this helps
    Eric
     
  3. Drew H

    Drew H New Member

    Eric,
    Thanks for your very helpful response. Sounds like option #6--new well pump--might be the best approach.
    Before replacing it, I'd like to confirm how much electricity the 2hp pump currently uses per day. I assume the large pressure tanks mean that the pump is not running with every cycle of the furnace--only when the pressure drops below the threshold. I thought about buying a clamp-on ammeter to monitor it but the cheap ones don't measure inrush--which I assume accounts for a lot of the actual KWH. There are other more expensive energy monitor gadgets, but I'd rather not blow the $s on something I'd use for a day or 2.

    Does anyone have any simple ideas for determining how much juice the well pump uses? Knowing this will help me calculate the ROI for a new pump.

    Thanks,
    Drew
     
  4. arkie6

    arkie6 Member Forum Leader

    2.0 HP seems like a lot for a well pump unless you have to lift the water hundreds of feet or have huge gpm demands.

    I would look at the actual water table and critically review your actual water demand in gpm, then use that to select the appropriate well pump. Open loop generally only needs ~1.5 gpm/ton which is around 7.5 gpm for your 5 ton geo unit. Add another 10 gpm for home use for a total of ~17.5 gpm. One way to further reduce the well pump size is to reduce the head or lift that the pump has to overcome. Your geo unit doesn't need high water pressure to operate, it just needs flow. If you took your new appropriately sized (using pump curves) well pump and supplied one of your pressure tanks and geo unit with relatively low pressure water (10-30 psi), and then installed a second 1/2 HP booster pump to take a suction on this low pressure source to supply the second pressure tank and your home needs at higher pressure (say 40-60 psi), this would allow a reduction in size for the well pump. So rather than pay to run a high HP well pump all the time that your geo unit runs, you run a lower HP pump for the geo unit and supplement it with the booster pump the relatively few hours per day/month that the extra pressure is needed.
     
  5. Drew H

    Drew H New Member

    Thank you! This makes sense if I'm going to replace the pump.

    I have a few questions...
    1. I assume we're still talking about a standard rather than constant pressure pump.
    2. Will I need new pressure tanks for this differential pressure setup? We just replaced the tanks with 2 WellXtrol 302 tanks -- 86 gallon capacity, 23 gallon drawdown at 40/60 psi.
    3. Is there anyway to calculate the savings?
    4. Is this a standard configuration my well service folks will understand?
    By the way, I just timed the well pump and came up with these stats...
    1. Pressurizing the tanks from 40-60 psi without any water running takes 1:30; with the Geo running it takes 1:45.
    2. With the Geo running, it takes between 6:40 and 7:30 minutes to go from full pressure (60 psi) to where the pump kicks in (40 psi). (This sounds right if the geo draws 7.5 gpm and the 2 pressure tanks have a combined 46 gallon drawdown)
    So, the pump is running about 15% of the time the Geo is running. Does this change the calculation?
     
  6. arkie6

    arkie6 Member Forum Leader

    1. Yes, a conventional constant speed pump rather than a much more expensive variable speed pump.
    2. No. You just need to adjust the air bladder pressure to ~2 psi above your pressure switch cutoff.
    3. Probably, but not enough data has been provided to make any sort of prediction, i.e. your home's heat loss/gain, typical number of hours/month with setpoint at 50F vs 70F, etc.
    4. I'm not sure about a standard, but it is a pretty simple pumping configuration I described above.

    Second 1. Off-hand, I would say from that info that your existing well pump is more than adequate if not oversized.
    Second 2. Assuming your pressure tank air bladders are set per the manufacturer's recommendation, 2 x 23 gallon drawdown = 46 gallons / ~7 minutes = ~6.6 gpm which is in the ballpark of where it needs to be.

    It would help if we had running amps on the well pump and geo unit to see what kind of potential gains could be had, but given that run time it would likely take a long time to pay back the cost of new pumps. How long does your heat pump run to maintain temperature? If it is running 50% duty cycle in 1st stage (12 hours per day), that is ~2 hours per day the well pump is running. 2HP = 1.5kW x 2 hours/day = 3 kWh/day for the pump not counting motor inrush amps (~6 times motor running amps) which can add up if the pump cycles on every ~7 minutes. What is your cost of electricity? What is the cost in your area to replace a well pump and add a second booster pump?
     
    Last edited: Feb 16, 2019
  7. Drew H

    Drew H New Member

    I would love to know the running amps but don't know how to measure this without some expensive new tools.

    My Sensi stat app emails monthly run times. To maintain 50 degrees (all but 3 days) in January, the system ran 364 hours; 12 of those were Aux hours. This was before replacing the recalled stat. Unfortunately, Sensi doesn't provide a way to download this info more frequently. So your 50% duty-cycle estimate seems spot on for 50 degrees. PPL electricity is $0.07039--not too bad compared to some. I'd have to get an estimate for the upgrade cost.
     
  8. Clifford Allen

    Clifford Allen Joe Homeowner

    2019-03-27 21.07.09.jpg There is a way to get the pump power consumption using you electric meter.I have attached 2 pics of the calculations performed on my GHP when installed in 1996. The calc starts on pg 1 para 5. thru 6.
     

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