Need help optimizing geo setup for open loop

Discussion in 'General Discussions' started by reb214, Mar 1, 2017.

  1. reb214

    reb214 New Member

    I'm building a new home in central PA, it is a ranch with a full finished walkout basement. 2200 sq ft first floor, 1700 sq ft finished basement. We are doing geo, selected WaterFurnace 7 series, and are leaning open loop (if well works out right). WF GeoPro dealer did full calc for the house and came up with a little over 4 ton load, so we are doing the 5 ton WF 7 series.

    My question is regarding the open loop configuration we are hoping to utilize. I teetered back and forth over closed/open loops, but there is lots of water here, and I need an irrigation well for sprinklers, so I thought killing two birds with one stone would help. Cost savings of just having to do two wells versus three wells (and taking into account the deeper wells and extra cost of closed loop install) was about $11k. My only hesitation is I know you have to take into consideration the operational costs of the well pump. That's what I need help with.

    The supply well is drilled 180' deep, provides almost 100 GPM, and the pump would be set at 100' with static water level at 40'. Well is about 100' from the house too.

    My needs are this: Irrigation needs 48 psi and 12 GPM. The WF 7 I've been told needs about 15 GPM at only about 10 psi, but I've also seen that you only need 1.5-2 GPM/ton for open loop? Anyone able to help? Does the WF7 need 3 GPM/ton?

    Either way, I need normally 10-15 GPM only at 10 psi, and for a couple months of the summer, for a few hours a day, I need an extra 12 GPM and pressure of about 50 psi.

    Geo dealer only cares about his water, so this part has fallen back on well provider. That's why I need advice. He recommends a 2-tank, VFD setup as follows:

    Gould's pump (2 hP or 3 hP)
    Franklin Electric Motor - 3 phase, 230 V
    Pentek Intellidrive VFD
    2 small bladder tanks, PIT, and FS, and leak sensor

    Basic operation would be pumping through 1st bladder tank to a setpoint of 10 psi for geo, thus reducing power consumption of VFD and saving operational cost. Whenever irrigation is called for, and flow past FS exceeds 1.5 GPM, the Pentek would kick up to setpoint of 50 psi. There would be a check valve then another bladder tank and the FS on the line to the irrigation system.

    My main questions are:

    1) How much water does my WF7 need for a 5 ton?

    2) Will the two pressure setup help to keep operating costs reasonable? Or is there another option that is better?

    3) Will the WF7 be able to handle dual pressure feeds? 10 psi and then 50 psi periodically? I'm assuming the flow control valve will just respond accordingly during higher pressure periods right?

    4) Main question: Any input on size pump to get? 2 hP looks to be borderline, especially if we'd draw down to close the 100' level, if at the same time at peak water demand, but on the other hand I'd hate to oversize and jump to the 3 hP without good reason.

    Advice is appreciated!! Thanks in advance.
  2. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    In central Pennsylvania, your water temps should be around 50F. Waterfurnace specifies 1.5 gpm/ton for EWT above 50F, and 2 gpm below 50F.
    But that specification in the real world is a moving target, if your EWT is 49.9F, you don't have to have 2 gpm.
    Now, the 7 series dos not need 1.5 gpm/ton all the time, only in the highest stage (12), which it really almost never runs in, most of the time it will be in stage 1-6, and would need between 2-4 gpm. The modulating valve will regulate this. You just don't want leaver water temps to be below 40F.

    Get a symphony system for it, so your installer can remotely optimism flow etc.

    I would not get 50 psi through the heat exchanger. You are better of using a separate dedicated small variable speed pump.

    Keep in mind, due to the modulating capability of the 7 series, it will have very long run times, about 6500 hours annually, where it will need very little water. The pump should be smaller rather than larger. 2 or 3 HP sounds way to much.

    Your holy grail for efficiency will be the amount of piping power you use.
    Last edited: Mar 3, 2017
  3. reb214

    reb214 New Member

    Thanks docjenser. I guess I'm trying to minimize the size well pump I need. Seeing that my cooling load in PA is less than my heating load, and that I'd be watering the lawn (big lawn, several zones) in off peak cooling times at that, it sounds like my geo water use during those early morning or late evening hours may only be 2-4 GPM or so. That would make my peak water demand only be 14-16 GPM including irrigation, so I could probably make out with a smaller hP pump looking at the curves. The well guy was telling me 3 GPM/ton (so 15 GPM) + the 12 for irrigation, so peak of 27 GPM. That's a totally different ballgame there.

    I'll ask my contractors about a second pump option and see what the feedback is. If we proceeded with there recommendation of the two pressure setup (maybe smaller pump though), would putting a pressure regulator in the line to the geo make any sense? Say slightly higher setpoint than normal operation so it wouldn't normally have to reduce anything, but would kick in to reduce the pressure down during periods of higher setpoint with the irrigation going on?

    I'm really excited for the WF 7 as I hear it is great, but I just worry I'm not thinking of everything to optimize it's performance and operating cost that will bite me in the rear later.

    Thanks for your help!
  4. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    If the `dual usage occurs in summer only, you have some more room. Your water will still be 50F EWT, and it does not matter if you discharge it with 60F, 70F or 80F. Plus your cooling load will likely be half you heating load.
  5. IronOak

    IronOak New Member

    I’m certainly a novice concerning Open Loop systems but I did enough research to know it was rather iffy at my location because of water quality and local conditions, so we decided not to tempt fate and went Closed Loop. I do however have considerable experience with researching the overarching Technology, vetting Contractors, then purchasing and now using our GSHP system for a little over a year here in Southcentral PA.

    Just to be upfront I will not use company names (here or via PM, e-mail, post card, Morse code or bribe) to talk about those I did not use!

    Don’t let GeoPro or ABC or Elite or Certified, or WeBeGeo&Stuff or Uncle Ted designations be the sole (or even major) determining factor on finalizing a Contractor, real/actual loads, equipment manufacturer or size selected. The bulk of the companies that I had the unfortunate opportunity and displeasure to talk with (GEO imposters & wannabes and they all had some sort of designation) had little to no clue of local Geology, Hydrology and conducting and interpreting a Manual J!

    I noticed that you do not specifically use the term Manual J and I’m wondering if that was an oversight on your part in the writeup or was one not performed? Walking around and counting windows and grilles/registers and pulling out a tape measure while carrying an official looking clipboard & company logo No.2 pencil may seem impressive----buyer beware! A Manual J is so much more than windows, supply/returns, number of Bedrooms, house orientation and square footage! Hey they may even use a Laser Measure device and we all know you’ve got to be distinctly qualified (to sell something??) if you have one of those puppies!

    I’m sorry for being a little facetious but my early “getting-pricing” experience still bothers me some. Okay, I’m really just now starting to believe again that humanity has a slight chance!

    Did you or they have your water tested? If the GEO company didn’t bring this up/demand it for an Open Loop system, pooch punt um right now…lots of borderline (GEO quality) water here in Central PA! If they decided to forgo this test based on experience “in your area” that’s not a good sign either. My neighbor’s (~210 yards away) water source is from a different aquifer and the quality is much different than mine.

    Also, I think wells & well water have a revenue target on them and you may find that having (not just using and consumption) a well will eventually become more expensive than just the pumping cost (and system cleaning cost if it’s the bad stuff that causes fouling), as more & more regulations creep in and other revenue sources fall short. Private and/or grandfathered may not mean private and/or grandfathered as we know it forever!

    Who knows they may even want to tax the Btu’s we are taking out of and rejecting back into the ground someday – don’t laugh!

    Anyway, I do wonder a little about your 5-ton choice considering the overall size, approx. location and newness of your home just based on my research and experience with our GEO system thus far. So, do yourself a large favor, double-quadruple check their numbers and just make sure you are only rounding up to the next full ton and not 2!

    Variable Capacity, Dual Stage & 2-Stage types are smarter choices if you need/want/plan to be oversized. So, you are good there.

    If you do plan on adding some square footage to your home in the future a 5-ton system will most likely handle it. Subsequently, the 5-ton size becomes a wise(r) choice today…Open Loop maybe not so much in the long-haul!

    Best of luck on the new build and the GEO system.

    Warm Regards,

  6. Is your home on a well? Cant you use your home's water supply to supply the wshp and dump the water down the irrigation well. Keep it super simple kiss.
    My neighbor installed a open loop, and it worked for about 11 months, after that efficences were terrable. The water was high in minerals, something the installers overlooked. He says ever 6 to 12 months the heat exchanger needs replaced, and he also uses firewood most of the daylight hours. So I would sugest a water mineral test.
  7. reb214

    reb214 New Member

    This is a new construction. Domestic water will be public water, so no need to figure in domestic in the equation thank goodness!

    The open loop equipment is not purchased yet, as they just drilled the well and are still figuring out it's suitability for the application. As to hardness, that is a concern I agree, but 3 of my neighbors have geo (2 of them open loop) and have ran that way for 10 years each so far. You do have to get the heat exchanger acid flushed periodically though due to these concerns, and also have to be sure to get upgraded materials (CuNi I think?) for the heat exchanger for open loop.

    As to the Manual J, I've had both a Climate Master and WF dealer provide this sizing as 4+ tons, so both spec'd five ton. I just liked the WF 7 better than the CM 30 offering, that's all. I saw the report from the Climate Master dealer, the WF guy provided a GeoLink report summary, so I can't 100% confirm he did a Manual J, but the numbers are very, very similar to the Climate Master guy.

    I'm definitely open to suggestions though. I just don't think closed loop is an option to be honest, unless I have no choice and have to do horizontal. The extra required depth of wells and changes to equipment were quoted as $10k option. I can pay to pump a heck of a lot of water for $10k, so long as the performance of the system as a whole is OK. Especially considering I need to pay for an irrigation well anyway for watering 1.5 acre lawn, I thought open loop had more pros than the possible cons. Perhaps I'm not thinking about things I'm not familiar with though, so I'm not 100% sold on it as final answer. Thanks for the help so far, and keep it coming!
  8. docjenser

    docjenser Well-Known Member Industry Professional Forum Leader

    What is wrong with a horizontal loop field?
  9. reb214

    reb214 New Member

    Nothing is wrong with horizontal technology. It's just the cost. Since I needed a well anyway, I wanted to explore vertical. Open loop was the better option economically at the time. Now that I've went down that path though, I really would hate to have to divert to horizontal and incur that expense on top of having already drilled. That's all. That is indeed what we will do though if the well doesn't prove to be a good supply well. Thanks!

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