It turned out to not really be a choice. I took what I could find on a holiday weekend which turned out to be UP26-116F 230 VAC 1. 75 A. That works out to 402 watts per pump.

One is still overkill according to the calculations kindly provided by geodean.

Sorry I'm late to this thread as loop pump selection and sizing is one of my pet peeves in the residential geo world. You got good advice from geodean and it sounds like things worked out for you. I'll just throw out a few points:

-from what I've seen oversizing of loop pumps seems to be extremely common. I think this comes from a combination of things. There is a fairly limited range of pumps to choose from. Many geo contractors from the forced air side of the biz and have no clue about fluid dynamics or how to size a pump. I'm afraid that sounds condescending but I don't mean it to be. There is a huge body of knowledge required to be a good geo designer installer, and I don't think you can expect everyone to be an expert in every aspect (don't ask me to design ductwork!). Unfortunately many of the geo manufacturers are also deficient in this field and as a result a lot of the training info available is over-simplified or just not that clear. It's far worse to have too little loop flow than too much, so it's natural that most installers will err on the side of caution. A couple hundred watts of extra power use vs potential system failure, callbacks, etc. I know what I'd do if I was an installer!

-You can't calculate pump power consumption from the HP of the motor or the nameplate amps. These are spec'd at specific conditions that generally have little to do with normal operation. In your case you might be in the ballpark with 402 Watts - the 26-116 will draw somewhere between 310 and 530W depending on flow. At 15gpm or so you should be around 330W.

-Pump power will generally increase as the flow increases. The realtionship will depend on the shape of the pump efficiency curve. You lucked out, at around 15gpm you're right in the sweet spot for efficiency for the 26-116. Which brings me to my next point...

-The efficiency of the 26-116 at it's best point is... a whopping 22%! That's right, you're drawing over 300W to do 60W worth of pumping work. This drives me nuts. Big industrial pumps can achieve over 90% efficiency and evein in this size range 50-60% should be easily achievable. I'm not picking on Grundfos, either. Pretty much all the wet-rotor circ pumps in this size range are this bad or worse. The 26-99s are actually a bit better - they get up to 30%.

-The only pumps I've found at a reasonable cost in this size range that approach decent efficency are the Armstrong E-series. Most of them are in the mid-40s for efficiency so they are a step in teh right direction. They are dry-rotor pumps that have a mechanical seal so there is the potential of the seal wearing out and they do seem to be a bit noisier. I was able to use a single E-9 instead of 2 26-99s which saves me about 2-300kWh per year. Since the Armstrong's were the same price it was a no-brainer for me. I have had one bearing failure, but it was in a pump that I had picked up form a surplus company so it may well have been compromised somehow before I bought it. The pump I got new has been running fine for a year.

cnygeo, your above posting is very helpful.  Thanks!

I think you're right - there's a limited range of pumps to choose from.  In my case, I have 3 Grundfos 26-116 pumps - over 1000 watts just for pumping water when both of my GSHP units are running.

And you're right - I'm way over pumped.  So far so, that I'm off the (WaterFurnace) pressure drop versus water flow charts (running 21 gpm through a 5 ton GSHP and 14 gpm through a 3 ton unit).

With 22% efficient motors - yuk!

For my residential application at least, and since my GSHPs/pumps reside up in an attic where I just can't afford to increase my risk of a water leak, it doesn't look like there's much alternative, from your comments.  Perhaps I've misunderstood, though, and you can further comment.

My question is, what's the alternative for me, again noting I can't change to other pumps with higher possibility of leaking?

Thanks!

Best regards,

Bill

cnygeo, are the 3 speed Grundfos pumps any more efficient on low speed?

You guys may want to check out this site and talk to Roy. I've been using his pumps for about a year now. He has a very good selection of pumps and very good pricing for 3 speed B&G pumps that can be dialed in to exactly your required flow rates.

http://www.flowcenterproducts.com/

Roy is the owner and very helpful. I run pressure drop calcs on all of our loop fields and minimize the watts used and have had very good response from owners.
Dan

I thought our pumps (one in and one out) were sort of redundant. Our contractor outright told me running just one pump would fall right at the lower end of the flow requirement for the geo unit. He said he does this and then doubles the pumps which puts the flow slightly above the recommended flow, but that way if one pump fails the system will keep working and hopefully during an annual inspection they would catch it. I am torn, I almost wish I had two smaller pumps or one sized to handle the flow required for KWH consumption reasons, but I really like the redundancy as well.

For the heck of is I did meter just one pump on and it was pulling 540w or 2.25 amps. With both pumps running they were pulling 1.75 amps each or 420w each or 840w total. So it's not a whole lot more and I am guessing the increased flow might help a tiny bit with the overall COP might make up the added power consumption, maybe?

I haven't seen efficiency curves for these (efficiency ratings for small pumps in general are hard to come by, probably because they're so pitiful) but I don't think so. I believe they're still the wet-rotor type which will limit their efficiency. However, if they give you the flexibility to better match the flow to the system, that's certainly a plus. Wilo makes some very efficient variable speed pumps - those might be worth a look. Also, I believe the Grundfos Alpha pumps are available in North America now or will be shortly. They were too small for my system, but for a smaller unit they might work well. the variable speed aspect of these is really overkill but the efficiency of these is very good over most of the flow range.

One other thing - pump power is not voltsXamps - the motors have power factors somewhere between 55% and 85%, so unless you actually use a power meter that is capable of accounting for this your reading will be high. The same goes for compressor motors. The "kill-a-watt" plug in meters will do this and are pretty cheap, but you have to plug them in series with the load (I'm assuming your pumps are hard-wired).

I second the observation that amps X volts doesn't tell the whole story. Unfortunately, typical central geo units don't lend themselves easily to measurement by "Kill-aWatt", or similar. I'm on a quest for accurate PF values for compressors - I need something tighter than 55-85...

I'm using a WattNode made by Continental Control Systems ( http://www.ccontrolsys.com ) along with non-split toriod transformers, and high speed sampling (300 Hz), to get highly accurate True RMS power measurement.

Best regards,

Bill

I doubt you'll be able to find a single power factor number that will be accurate enough - doesn't power factor change with load as well? I could certainly be wrong - I'm no EE. That said, one potential source might be Copeland's compressor sizing software - if I remember it has both watts and amps, so you could calculate a PF for various compressors from that.

dunno - I'll check into the Copeland tool

I took the real wattage on the 48 v DC side of the power in to the inverter feeding the pumps. I just take a reading then turn on what ever load and get a new reading, so I really calculated the amps backwards from total watts consumed. It is amazing the odd power factors on these motors, some are in the 80's some are in the 20's.

So does this table tell me that no matter how many pumps or no matter the size of the pump i can not exceed 13 GPM on 1" Sch 40 Pipe?

No....more pumping pressure will give you more flow.

So if my current system has two Grundfos 26-99F's and is producing 10 GPM if i switch to two Grundfos 26-116F's i should be able to exceed the Florida Heat Pump ES049 required 12 GPM?

Steve....from your other post the delta T of your loop is 4-5°. This is well within specs for your heat pump. More flow through your loop will not make your system any more efficient.

How important is meeting the required 12 GPM?

Steve Step - I don't think I'd sweat it too much.

I just skimmed the WaterFurnace Envision spec catalog's performance tables for their 049 model (likely very similar to FHP) and the performance tables include flows down to 5 GPM in low stage and 6 GPM in high stage unless your entering loop liquid is down around 20.

What is the ideal EWT for maximum heating effeciency? What is the ideal EWT for maximum cooling effeciency?
What is the ideal delta T for EWT and LWT?
What is the ideal delta T for the RAT and SAT in heating? What is the ideal delta T for the RAT and SAT in cooling?