Pump selection for GeoCool 4 ton inverter heat pump
The documentation states 5.3~19.8 GPM, and also has a note:
There should be a ten degree temperature difference between incoming and outgoing water.
Based on those requirements, is the Taco 007 VDT a good choice? It can track the 10 degree differential and follow the variable output of the inverter HP.
https://www.supplyhouse.com/Taco-007-VDTF5-007-Variable-Speed-Delta-T-Cast-Iron-Circulator-Pump-115V
Comments
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Can't tell anything without knowing what sort of system the pump is pumping through — how much head it has to operate at.
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England1 -
is this a geo heat pump? If so the loop size needs to be part of the pumps requirement.
You need to know the fluid, required gpm, and pressure drop of the circuit.
Usually the manuals give you pump spec options.
Many newer hp use variable speed pumps, that are controlled by the hp, via a 0-10 or PWM signal.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
The HP manual has no other pump info other than " the pump should be less than 600 watts", and system pressure between 25 and 50 PSI.
I have two sets of loops that can be operated together or alternately, 3/4" PEX
3x500' ~2.5 Tons
4x500' ~3.3 Tons
These are home runs to the equipment room, connecting to 1" manifolds with individual valving.
I can give it any multiple of 500' of loop.
The loops are -3' to +3' as referenced to the equipment room floor. Pretty flat situation.
With the individual valves we should be able to burp it loop by loop easily.
Fluid is going to be 20% glycol.
Looking at the diagram, the HP will power the pump directly L1 L2 . I'll have to use one for the 115V Taco if I go that route.
It really has no other data besides the GPM range, differential, and wattage and I just figured out that is because it is supplying the line power through an internal relay.
This system will be for a brief summer cooling season, and the house has hydronic for the heating.
Unfortunately my hydronic heat pump is on backorder so I will get occupancy with this unit, and test and commission the hydronics with a water heater as discussed in that thread.
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Here is a pressure drop calculator for plastic tube of all sorts. Enter all the info. Type of tube, size, length, fluid, temperature and gpm. This give you the pump head for the loop field. Generally you need 2-3 gpm per loop. Just guessing 500' per ton of horizontal loop.
A GEO system should be calculated to the location, soil type, equipment requirement, load size, etc. There are software programs to do this.
Somewhere you need the info for the HP flow requirement, and related pressure drop. That needs to come from the manufacturer.
It sounds like you are just spitballing the design? :)
Here is a graphic of the components.
So you need the flow info and then calculate the pressure drop in the loop field, the piping from the manifold to the HP and the pressure drop of the HX in the unit. That pump is generally a 240V, operated from the HP control, as you suggested.
I doubt an 007 will be even close to the pump you need.
Look at typical GEO pump modules here, they start at Grundfos , generally 240V pumps to wire to the HP 26-99
\
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
I registered at Geo-flo and used a single unit calculator, and got 21.3 Ft of total head at a nominal 10 GPM on
all 7 loops.
The Taco 013 charts at ~16GPM at that head.
The Taco 012 looks like it could do the trick too.
I was WAAY out in the weeds with the Taco 007, thank you!
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"It sounds like you are just spitballing the design? :)"
Kinda Sorta, you got me.
I built my fields and headered them that way so I can alternate fields to feed the hydronic HP and let one recover. I am intentionally over-looped.
They home run into the room, a few feet away from the hydronic HP and 10' of pipe away from this air handler/HP.
The installation manual only mentioned the things I have listed.
I go to a sales brochure and get "7.93 GPM" in both full load and part load. That sounds bogus, and nowhere do I find a mention of pressure drop across the HP.
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again, just a WAG, 4 loops for 4 ton@ 2.25 gpm per ton= 9 gpm.
I would go with a Grundfos 26-99
With 3 speeds you have some adjustability
Speed 2 at 9 gpm you have 18’ head
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
Thank you Bob. you would not bother with a pump that tracks a Delta T then.
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there are variable speed GEO specific pump stations with the larger sized pumps. That 007 isn’t going to work.
But some control, usually in the heat pump control board, tells the pump how to vary its speed.
If you plan on running this for cooling, you will need to insulate the pump and piping. These GEO pump centers are tightly insulated so the don’t sweat.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
this video explains how the variable speed pump and controller work on the loop field. In this example they choose two different flow rates as it is a two stage hp that it connects to. He mentioned 3 gpm per loop on this application.
If you want to spend the money for a variable speed pump, and there is now control interface on your unit, this package makes sense to dial in all the parameters and monitor performance
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
This HP does not have a PWM out, it just has a relay and supplies power to the pump so it can sequence it to start prior to the compressor.
That is why the TACO that comes with sensors and a way to set up a Delta T seemed like a good deal. HP turns it on, then being an inverter with a wider range of capacity it could track that and vary the flow as needed.
In cooling mode, the ground loop piping and the pump will get warm with the rejected heat, so sweat on that unit is not the issue.
It will be a thing on the hydronic HP. I am insulating everything in the room, and I also have a Heat pump water heater in there with a condensate drain, which will keep that room pretty low humidity. I will take whatever help I can get.
The backordered hydronic HP does have a PWM out to the pump.
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With geo and modulating unit, the pump will be running most of the time. There is pretty quick ROI to go for an ECM, the issue you run into the high head ones tend to be spendy. Probably something like a 0026E is in the ballpark. A delta T (assuming it will track properly) would help reduce pump power under low load, so if you can get one for reasonable price, might be worth a shot, worse case you can run it in fixed speed mode.
You can also see if you can put two cheap ECM circs in series but might be low on GPM still.
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Is it a two stage HP? That would be another reason to use a Flow Center that modulates with the compressor as that video explains.
This kit is for GEO hp systems that do not include the control, a plug and play unit.
I think if you price these components separately this price my not be out of line.
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
It is an inverter HP ,with more than two speeds.
It only lists a partial and a full load set of numbers like a two stage.
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Looking at that site, it shows the same at low and high…..7.93 GPM.
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And the 4 and the 5 ton. I am a bit skeptical.
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You need the IOM.
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Here is the IOM
geo-pulse-installation-manual1.pdf
Very Vague!
I also see it's a sideline of MrCool. Bottom of the line mini splits.
I wouldn't touch it!
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Too late for that.
I have a call into their tech support for those answers.
I got an email back with somewhat less than satisfactory results that conflict with the O&M.
He said 3 GPM per ton so 12 GPM, and a 4~8 temperature drop. I can buy their spitball of 12 GPM, but it puts me in a bigger pump and I am going with that Taco 013 variable and set it to track 7 Delta T.
My other Geo resource had a hard limit of 10 on the Delta T for his installs. I dug the loops for that one back in 2011 for my brother's system.
It seems foolish to bump 10.
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My Mr Cool system has been great, and coincidentally it was a GeoCool water to air heat pump that I installed in my Connecticut house and that thing was very nice.
Mine was a single vertical well, but just in case it helps you, this is the ground loop circulator that I used. It performed great, and this company (Ingram) that supplies it is very good in my experience. They have great customer support and welcome DIYers
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el1 -
Thank you Paul, I purchased the heat pump from Ingrams as well.
My system needs to be pressurized between 25 and 50 PSI. We will charge it to 25 PSI after fill and test.
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ok gotcha. That pump I linked is atmospheric so forget that one! 😅
NJ Steam Homeowner.
See my sight glass boiler videos: https://bit.ly/3sZW1el0 -
3 gpm/ton is standard for any wshp imho. Its the same flow you use for a water cooled AC also known as "tower tons". 2-21/2gpm on the chilled water side of a chiller and 3 gpm/ton on the heat rejection side. With a HP your reversing to heat with it so 3 gpm /ton is the safe #
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Thanks ED.
I am ordering a version of the 26-99 that Bob posted above. We did some head scratching on my loop headers too.
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We are charging the loops today with glycol and I am wiring up the units. I have most of the return air done, and will get a local shop out to make the transition as I had posted about in the other thread.
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Real world performance:
All 7 loops with pump on high = 10+ GPM
4 loops = 8 + GPM
3 loops = 7+ GPM
We stacked the air handler up, installed the return air and I started working the wiring.
Return air outlet was 10x20. I got a short way bend, a long way, and chunk of duct, and an 8x30 to penetrate the bearing wall.
We brought the condensate out to the right edge it is hiding there in the shadows but easy enough to pour a glass of water in.
Not a lot of working room, once I observed the 36" electrical code on the panelboards.
Flanged the 8x30 to the outside wall and I may put a pair of 16x20 cheap filters out there in a site build adapter. The inline one is an oddball 22x22x1 and if I can I may use that pair of MERV 5 to catch the bulk of the stuff.
My limited understanding is you want a couple of bends on a return air like that for noise. The short and long way and that short section is what I will start with.
Plumber formed the lineset better than I could.
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is the lineset photo sideways or did they really coil the lineset vertically?
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That is the space available, about 9" between wall and units.
If you have some 4th dimension available feel free to use it. :)
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What circulator did you end up with and how many tons?
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It is a ups26-99f
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I am buying two more pumps today, and working from the observed performance of the Grundfos 26-99, we are going with the Taco 0034E -f2. The 0026E is a little light on maximum head by our estimation.
We figured out the 15-58 Alpha was a little light for the hydronics, but that 26-99 may be just right.
So the 26-99 moves to hydronics, both heat pumps get the Taco 0034e for loop pumps, and that 15-58 Alpha would do the pump-to-buffer nicely if we add a buffer tank. We are going to give no-buffer and ODR a really good try though.
If not I will find it a home.
The hydronic heat pump has a PWM out on both inside and outside pumps that is an option. Of course the 26-99 is just the 3 speeds but that Taco could either use the PWM or I could build a 10VDC control for it.
Fun stuff and thanks for all the help along the way.
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Most 0-10V device can take a 12V PWM output. If the pump is hunts, you can add a simple RC filter (1k resistor with 10uF capacitor) to generate DC from PWM.
Sketch what you are piping up. There should be one high head loop pump and two small pumps for each geo unit.
There is also a B&G smaller 0-10V pump (ecocirc+ 20-18). The + is important as it means 0-10v control.
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It's already piped, I'll take a picture next week when we connect the hydronic unit up.
Each unit gets a Taco for the ground loops. and the hydronic gets that 26-99F 3 speed.
Most of the time it is either one or the other, but I set it up so I can get some HVAC alongside the hydronics on special occasions like birthdays and holidays. :)
With enough pump I can run alternating loop fields and see how much the ground can recover.
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