In an earlier thread, docjenser said: "That is 1155 total (pumping motor watts)! That is crazy. Do a pressure drop calculation, with 3000 hours average run time, a new pump setup might pay for itself very quickly.  Or tell me your setup, I can run the numbers for you."

I thought I'd start a new thread here so that all can learn along side me from docjenser.

You need between 19-25 gpm of total system flow, including 7-9 gpm for the 3 ton and 12-16 gpm for the 5 ton heatpump.


I am not clear about your ground heat exchanger, may be you can clarify. Your WEL webpage says 8 holes with 300ft (is that borehole or pipe?) however your PD calcs say 1200 of pipe in 4 circuits.

Your flow rates indicate that you are wasting a lot of pumping power, way overshooting. A single 26-99 for each heatpump, each consuming 230 watts when running would do everything for you. With your runtime, this would get you down to 637 kwh/year.


Given your runtimes, it appears that your entire system is way oversized.
Or is one heatpump for the bedrooms, only running at night, and the other one for the main floor, only running during the day?


Depending on your loopfield config, even a single 26-116 might be enough to pump enough for both heatpumps. You might need a balance valve for the 5 ton pump. In order to determine that we would need the the exact configuration of your outside loopfield.

Sounds like pairs, 2 in series X 4= 8 bore holes

ChrisJ

Bill's webpage says 8 boreholes, 300 ft each, that is 4800 ft in my book. Even if he means pipe, that is 2400 ft. His pressure drop is for 1200...

Bill's webpage says 8 boreholes, 300 ft each, that is 4800 ft in my book. Even if he means pipe, that is 2400 ft. His pressure drop is for 1200...

Bill's webpage says 8 boreholes, 300 ft each, that is 4800 ft in my book. Even if he means pipe, that is 2400 ft. His pressure drop is for 1200...

Docjenser, thanks!  I'll have additional info for your tomorrow.  Bill

I'm working to understand the exact piping layout of my borehole field.  I need a little more time, please.

Thanks.

Bill

Bill,while you are at it please confirm that all the other measurements are totals, meaning supply and return length.
Thanks

Posted By docjenser on 16 Aug 2012 01:43 PM

You need between 19-25 gpm of total system flow, including 7-9 gpm for the 3 ton and 12-16 gpm for the 5 ton heatpump.

I am not clear about your ground heat exchanger, may be you can clarify. Your WEL webpage says 8 holes with 300ft (is that borehole or pipe?) however your PD calcs say 1200 of pipe in 4 circuits.

Your flow rates indicate that you are wasting a lot of pumping power, way overshooting. A single 26-99 for each heatpump, each consuming 230 watts when running would do everything for you. With your runtime, this would get you down to 637 kwh/year.

Given your runtimes, it appears that your entire system is way oversized.  Or is one heatpump for the bedrooms, only running at night, and the other one for the main floor, only running during the day?

Depending on your loopfield config, even a single 26-116 might be enough to pump enough for both heatpumps. You might need a balance valve for the 5 ton pump. In order to determine that we would need the the exact configuration of your outside loopfield.

Docjenser, a huge thanks so far.

I cleaned up the first posting, reviewing all details.


Design summary:

I didn't have any input into the design for the (3400 sf, single story) house.  One 2-speed 3 ton (Envision) unit for the (4) bedrooms, with a 385 watt loop pump, and with a 3 zone air distribution system.  One 2-speed 5 ton unit for the remainder, with two 385 watt loop pumps.  And an 8 hole loop field using holes 300' deep with 1" pipe to commonly serve both units.

I'm keenly interested in optimizing it where it makes economical sense.


Summary of exact configuration of outside loop field:

My ground heat exchanger consists of 1" pipe in 8 holes, each hole 300' deep.

I have no information about how my manifold was constructed.  I was not in town when it was constructed and thus have no pictures or diagrams.  Using the hydraulics information from the 3T unit by itself (5T not running) (earlier posting, 6.3 psi measured Pressure Differential, using WF chart to determine 13.5 gpm, using UP26-116 pump curve to determine 27 fh of pump head) and using actual pipe lengths and diameters, I'm guessing that every 2 holes are plumbed in series, and hence there are 4 circuits each of 300' * 4 (down & up twice) = 1200' at 13.5 / 4 = 3.375 gpm.

FOR THE 3T UNIT:

Posted By docjenser on 20 Aug 2012 10:34 AM
Bill,while you are at it please confirm that all the other measurements are totals, meaning supply and return length.
Thanks

Yes, correct.  all measurements previously noted are totals, meaning supply and return length total.

Here's the detail behind the totals for the 5T unit for example:

8' of 1" HDPE pipe to pump (in attic)
22 ' of 1.5" pipe to header pipe 'T' (in attic)
76' of 2" pipe to manifold (from attic to yard)
1200' of 1" pipe down/up/down/up 2 holes back to manifold (in yard)
76' of 2" pipe to header pipe 'T' (from yard to attic)
22' of 1.5" pipe to pump (in attic)
8' of 1" pipe to unit (in attic)

Many thanks!

Best regards,

Bill

If you indeed have 21.3 gpm flow at the 5 ton (5 ton on, 3 ton off),


(2) 26-116 in series at 21.3 gpm are pushing 40ft/head.

Your configuration with (4) circuits of 1200ft at 21.3 gpm would be 55ft/H, whereas (8) circuits of 1" pipe each running 600ft would give you 37ft/H, so you appear not to have 2 holes piped together, but (8) 600ft circuits.


Plus it is unlikely that someone went the extra mile with 1.5" and 2" pipe, and then puts in 1200ft long loops in only 4 circuits for an 8 ton system.


Now, if both your units running with 30.2 gpm total, and given your configuration, your are pushing 38 ft/head. However, you only need between 19-25 gpm flow for both HPs, and then your system PD is between 15.2-25.4 ft/H. A single 26-99 would do this for both heatpumps (16ft/H at 20 gpm) if you are willing to take the current ones out and put in a 26-99 into the 2 inch pipe before it splits up into the 1.5" and 1" inside.

You have about 2700 hours of runtime, but there is some overlap, where a single pump I would assume runs 2000 hours total serving both heatpumps. A single 26-99 would consume 42$/year, saving you about $75/year. Of course a WILO STRATUS WOULD TAKE THAT PROBABLY DOWN TO $20/year, which I would put in if designed from scratch. The least you can do is throwing out a 26-116 out of the 5 ton circuit.
Alternatively your can replace the (3) 26-116 with (2) 26-99s which should cut your running costs down in half.

Posted By docjenser on 21 Aug 2012 03:24 AM

If you indeed have 21.3 gpm flow at the 5 ton (5 ton on, 3 ton off), (2) 26-116 in series at 21.3 gpm are pushing 40ft/head.

Your configuration with (4) circuits of 1200ft at 21.3 gpm would be 55ft/H, whereas (8) circuits of 1" pipe each running 600ft would give you 37ft/H, so you appear not to have 2 holes piped together, but (8) 600ft circuits.

 ... if both your units (are) running with 30.2 gpm total, and given your configuration, your are pushing 38 ft/head.
 
However, you only need between 19-25 gpm flow for both HPs, and then your system PD is between 15.2-25.4 ft/H. A single 26-99 would do this for both heatpumps (16ft/H at 20 gpm) if you are willing to take the current ones out and put in a 26-99 into the 2 inch pipe before it splits up into the 1.5" and 1" inside.

You have about 2700 hours of runtime, but there is some overlap, where a single pump I would assume runs 2000 hours total serving both heatpumps. A single 26-99 would consume 42$/year, saving you about $75/year. Of course a WILO STRATUS WOULD TAKE THAT PROBABLY DOWN TO $20/year, which I would put in if designed from scratch. The least you can do is throwing out a 26-116 out of the 5 ton circuit.

Alternatively your can replace the (3) 26-116 with (2) 26-99s which should cut your running costs down in half.

Docjenser, thank you very much.



I measured 64.0 and 54.4 psi at PT ports just outside 5T unit (3T off) for a pres dif of 9.6 psi.  I'm pretty confident of the measurements, as I used a pretty good 4" measuring instrument.  I then used the WaterFurnace supplied chart to translate to 21.4 gpm (4.0 gpm/ton for the 064 Envision unit).

I rechecked the Grundfos pump curve for (2) 26-116 pumps: 21.4 gpm = 40 fh = 17.3 psi.



I found a piece of paper drawn by the installer showing information about the borehole field.  I added to it pipe information from the purge ports up through the attic to the 2 units.  The drawing is shown  here.

Looking at this, I think you're right.  I probably have an unknown sized trunk line, serving each hole as it goes across the yard, with each hole connected to it.  I.e., (8) 600 ft circuits.  And thus, perhaps, the trunk line is gradually reduced in size from 2" to 1", with no manifold.

You can see a picture of the 2" header pipes going to the attic, and the 2" HDPE purge ports here.  A general idea of the borehole field is here.  And here's an image of the trenching - the pipes visible are the unconnected borehole pipes.

For the 16' of 1" pipe connected between the push-pull configured pumps and the 5T unit, and the 44' of 1.5" pipe, here's a picture.  And here's a picture of the 2" header pipe in the attic separating off to the 1.5" line going to the 5T unit and the 1" line going to the 3T unit.  And lastly, here's a picture of the 1" pipe connected to the single pump for the 3T unit.



I don't understand how (8) 600' 1" circuits, connected to a trunk line flowing 21.4 gpm, results in 37 fh.  Can you help?  If the 2 pumps are producing 40 fh, and the 8 600' circuits are consuming 37 fh, that only leaves 3 fh for everything else.  Yet we know the coax HE is using 22 fh because we measured 9.6 psi (* 2.31 = 22 fh).

Wish I was smart enough to figure this out.



When both units are running, as I wrote earlier, the measurements were:

5T: 63.1 In, 55.0 Out, 8.1 delta psi = 19.4 gpm through 2 pumps (from WF chart)
3T: 67.9 In, 63.5 Out, 4.3 delta psi = 10.8 pgm through 1 pump
Total flow out to borehole field = 19.4 + 10.8 = 30.2 gpm



Overall, replacing three UP26-116F pump motors with one UP26-99F (inserted into the 2" header line) would be very attrative to do.  Please help me understand how it would work - this is a pretty dramatic reduction in flow volume.

Where on the pump curve would the 3 scenarios operate (3T/5T units On, 5T On only, 3T On only)?

From your comments above, it looks like you're saying:

3T/5T On:

20 gpm = 2.5 gpm/ton
pump produces 16 fh (from UP26-99F curve) at 20 gpm
16 fh / 2.31 psi/fh = 6.9 psi = total of all friction loss in system, including 2 coax HEs in parallel


5T On / 3T Off:

? gpm
pump produces ? fh (from UP26-99F curve) at ? gpm
? fh / 2.31 psi/fh = ? psi = total of all friction loss in system, including 5T unit's coax HE


3T On / 5T Off:

? gpm
pump produces ? fh (from UP26-99F curve) at ? gpm
? fh / 2.31 psi/fh = ? psi = total of all friction loss in system, including 3T unit's coax HE


Meanwhile, I'll look at my log data to determine what the new scenario's pump operating hours are.  With one UP26-99F pump for the system now, the new 'On' time (hours) will be whenever either unit was on.

Many thanks!

Best regards,

Bill

That covers the benefit, now what's the cost?
The price of the pump and install if you don't do it your self could make or break this deal.
Whatever else, once again Doc has put something new on my radar.........
Now I gotta rethink that too!

Posted By joe.ami on 21 Aug 2012 11:34 AM
That covers the benefit, now what's the cost?
The price of the pump and install if you don't do it your self could make or break this deal.

...

Joe, here you go:

Just finished computing annual runtime for any time at least 1 pump was running: At least 1 pump running runtime = 2419 hrs annually

From before:
3T pump runtime = 1678 hrs annually

Posted By joe.ami on 21 Aug 2012 11:34 AM
...
Whatever else, once again Doc has put something new on my radar.........
Now I gotta rethink that too!

I looked at the Wilo Stratos variable speed pumps.  Wow!  Nice units!

A Stratos model that could give me 20 gpm at 16 fh (1.25x3-25) would cost me $1305 list.  It consumes 120 watts operating at this point on the pump curve.

The next size up, still at 20 gpm / 16 fh, would cost me $1845 list.  It consumes 100 watts.

Existing setup: $118 annually

Using this variable speed pump: 100 watts * 2419 hrs = 242 kWh * 9.1¢ = $22 annually

Savings = $118 - 22 = $96/year.

Impressive operating cost (100 watt pump, $22 annually).

Not sure it makes sense economically in what's now a retrofit situation.  Looks like variable speed pump is something that's got to be designed in from the beginning, like docjenser does.

Best regards,

Bill

Now if someone would just make similar pumps for 1/2 the price.

Is it reasonable to demand a 3 year payback on a project such as this?

The expected life of the asset and alternative investment choices should both figure in, unless you plan to sell the home in 3 years.

Many options. Obviously iif you plan things from scratch, things work out fine financially. You can actually save money, in your case buying 1 pump instead of 3 for the original install. The take home message is that we need to go away from putting standard loopfields in, and then choosing the pump(s) to get enough flow. We must take the most efficient pump, and then trying to design the loopfield to fit the efficient pump. Look at this example, 8 tons of capacity possible with a single 26-99.


You have many choices. First, you can take a 26-116 out of the 5 ton circuit. Another option is to not buy a 26-99, but use one of your existing 26-116 to power the whole loopfield.
Higher operating costs, but lesser up front money.
For the Wilo, keep in mind that when only one heatpump is running, it will rev down, using much less than 100 watts! They are amazing pumps!

Posted By jonr on 21 Aug 2012 08:26 PM
Now if someone would just make similar pumps for 1/2 the price.

You can get them at good suppliers for 1/2... http://bostonheatingsupply.com/2085590.aspx