vertical loop opnions wanted.

I am installing a Geo system. I have already worked through the processes of sizing my unit, but I want other opnions on my vertical loop requirements.

Geo will be a 2 stage, 2 ton unit, with deheater, and AUX heat.
Building load 1700 cooling, 2500 heating.

Using Geodesigner 3.3 I enter my numbers, and it tells me 250' loop with 1.25" pipe is my requirements.
everyone local (that I have talked to) designs for 150' vertical loop per ton for residential.

I already have 1 265' deep drinking water well I will be converting over to Geo (we now have city water).
Using this is using current well, then adding 1 new well deep enough to cover below loops (loops will be same length in each well)
all with 1.25" pipe. 2 parallel loops (1 in each well), manifold outside, (plus 75' each way to the house which will be average 6' under ground which is not in formula below)

Which size would you go with?


2X 150' loops = 300'
Geothermal source
max cool 81 deg
avg cool 63 deg
Avg heat 44
min heat 33
Min freeze protect 13 deg.
Heat 3.54 COP
cooling 19.4 EER
Aux balance point 9 deg (my design low is 11 deg for my area).
cost per year $712.00

2X 200' loops = 400'
Geothermal source
max cool 72
avg cool 59
avg heat 47
min heat 37
min freeze protect 17
Heat 3.66 COP
cooling 20.6 EER
cost pear year $698
aux balance point 5 deg.
(adds 30% to well cost over 2x 150 loops)


2X 250' loops
geothermal source
max cool 67
avg cool 57
avg heat 49
min heat 40
min freeze protect 20 deg
Heat 3.74 COP
cooling 21.4 EER
cost per year $691.00
(adds 60% to well cost over 2X 150 loops)

I don't think I should quote actual prices but 30% cost is more then 1 years operation cost.

Thanks again for your opinion.

 

Hi and welcome,

What is the diameter of your existing water well that is no longer being used? Is it cased? Where are you geographically and what soil type did you input for your design work? Design software is a wonderfull tool, but it is not the end all for design work. If your local looper has a solid track record doing geo, I would bank his opinion and reccomendation over software any day of the week.

Have you spoken with anyone local about useing the existing water well bore? Or are you just spitballing the idea here?
Eric

 

Diameter is 6" I think. Need to measure it to be sure (covered with snow right now)

Cased with Steel to bedrock.

Geology maps show my ground as
Chickies formation
Light-Gray, Hard, Massive, Scolithus-bearing quartzite and quartz schist; thin, imterbeded dark slate on top' conglomerate (Hellam member) at base

In geodesign software I used "average rock"

Yes, were using original (265') well. Software shows its enough size, but driller says 150 per ton, so were adding 1 well and putting 1 loop in each.
I cant use pump and dump since I live near a super fund site. If I pump much water, I can draw the contamination towards my house, EPA monitors contamination spread.

I am just showing the results of each depth. 300' total is requirements, but if it was you, would you go deeper for better water temps as shown above?
I also just relized that if instead of drilling a new 150' well for 2 loops (total of 300') I could extend my current well to 300, or even 400'

 

If you have a six inch well in rock to 265', I would be very interested in what the software says about putting 2, 1 inch loops in that 1 bore you have and grouting it shut with thermally enhanced grout to match the conductivity of the surrounding bedrock. 2 birds with 1 stone. Well got grouted shut and you got somewhere to put your loops without any extra drilling. In my OA we typically use 1" x 300 for 1.5 ton of load in silts and sand. The TC for bedrock may good to go for 265' = 1.5 ton of load. Just saying

Eric

 

1 250' loop of 1.25" pipe"
geothermal source
max cool 89
avg cool 66
avg heat 43
min heat 30
min freeze protect 10 deg
Heat 3.47 COP
cooling 18.6 EER
aux bal point 7 deg.
cost per year $692.00

2 250' loops of 1.00" pipe in same bore
geothermal source
max cool 85
avg cool 64
avg heat 44
min heat 31
min freeze protect 11 deg
Heat 3.51 COP
cooling 19.0 EER
aux bal point 5 deg.
cost per year $688

I made the mistake of posting this same question on 2 websites. You answered both posts. thanks.
But this info might be helpful to someone else, so I left it in both places.

 

What is you solution going to be? Those numbers look good to me when compared to anything that is not geo. If you are going to pay to have additional drilling done, " the brotherhood thanks you, our kids need shoes too ".
Eric

 

Maybe I missed it somewhere. But why are yo only doing a 250'loop inside your 265' well?
why not install the loops to the bottom, why are you stopping 15' short?

 

Because the software will not do a odd number, or that is the standard size at the loop store? If it is a standard thing, buy the 300' loop and cut it off rather than lose 30' per loop.

Hey Dan,
I forgot to congratulate you for your pro status at the other place. They are a weird bunch. But it is good that you would not let them black ball you for being a " dirty well driller ". lol I wound them up pretty good!

Eric

 

And of course your driller knows best because he monitors and checks the loops he installed to insure that they perform the ways they are supposed to!

Got to scratch your head here. A single 265' borehole with 530' of 1.25" pipe with a 0.4 grout in your kind of rock will nicely support a 2 ton system. You can go with a higher grout, but you don't have to. You also simply have no manifold.

Pipe length is not everything. You need to make your pressure drop calcs as well. You might should decrease the pipe diameter size if going with 2 circuits. Keep in mind that the 2 ton only needs 6 gpm of flow. But again, why bother. Just make sure your load is correct

Did you say 2500 heating load, 1700 cooling load? Is that in BTU/hour?

 

One of my mantras is "never too late to spend more money". So what if you try it with one well and you find it doesn't perform perfectly? Could you not then spend more?
Eric you crack me up...."kids need shoes too".......

 

heat gain (BTUH) 17,463
Heat Loss (BTUH) 22,831

the well guy is coming over tomorrow (thursday) and we will discuss different options.

 

What is to discuss?

As some folks here harp on, run heat of extraction numbers.

Slip a pair of .75" pex, (CPS), or a pair of HDPE SRD11 down the hole and go.

Take them to the bottom.

Drill later.

Mark

 

Pressure drop is very high with one 0.75" pipe, 530' of pipe alone at 6 gpm would have 46 ft/hd. Add the inside and out side pipe to the borehole, and the heatpump, and you would need a 2 pump flowcenter. 1.25" pipe going down will work the best and give you 10% more performance than 0.75". A 265' will nicely support 23000 BTU heat loss. I agree with MArk, there is nothing to discuss, except may be going with high conductive grout.

 

Sorry, Doc is correct on the pumping. Use bigger pipe.

Mark

 

Thanks for the help so far. Sorry to keep everyone in suspense but I had to postpone my meeting with the well driller until Monday morning.

As far as the pump, I am looking at the climatemaster Tranquility 30 with internal pump(s)

 

I do not know where the missing stuff goes on the internet. The post I typed was auto-back up until I went to look at page one of this thread.

How does ClimateMaster know that I am going to tell you to drop a pair of 1" HDPE loops down that well to the bottom? The watts to water number can be very important to the total power usage of a system. So if we tie these two 1" X 530' loops to a manifold we only count one of the loops like in Doc's essay. We add that to the amount and size of the pipes supplying the heat pump we only need X feet of head times 3 GPM per ton.

Now we know what we need to pump so why buy a pump that uses three times the energy we need to buy to move the water we need to heat your home? We are looking at 66% more than we need to do the job times the number of daily hours times the life of the pump.

I, again do not have numbers for the supplied by ClimateMaster you can now do the math. If they supply a pump curve and you do two 1" loops down the hole let me know and I will help with the arithmetic.

Mark

 

the unit uses an internal variable speed Grundfos Magna 25-140 pump. Speed is controlled by unit based on delta you set in thermostat.
I was told by supplier that this will use less energy then an external "on/off" flow control center.

Geodesign software shows for 1-1.25" pipe loop
Average heating EWT is 45.
coldest heating day Min EWT is 31 Deg.

at Min EWT of 31 deg, the GPM is 6.0 with WPD psi 3.1 and FT 7.1
on Average heating day is 2.3 to 4.5 GPM flow.

the pump chart shows for 6.0 GPM the Head(ft) rating is 47.1

For 2 - 1.00" pipe loops, both heating Min and Average EWT is only 1 deg higher.
cooling might be 3 deg lower.

for cooling, it looks like the unit will never get out of stage 1 with a flow requirement of 2 to 3 GPM

I think I am reading the charts correct.

 

What you are missing is the resistance of the pipe. That is measured as feet of head.

I like ECM pumps and what they can do. I did not spec a ClimateMaster unit because the pump supplied unit cost me $1,000.00 USD more than the same machine without a built in pump. The pump I needed, ECM and all was only $300.00. So I make an extra $700.00 because I know what I am doing? Not.

Mark.

Mark

 

Ok, I follow. I only compared the built in pump to the QT Flow Center, and the price difference was around $100.00 more for built in pump.
Now that was earlier in the game when I thought I needed an 3 ton unit (and the QT flow center had 2 pumps).

I bet the savings would be greater based on the 2 ton unit with built in pump VS the QT flow center with 1 pump.
I do like the concept of the QT. It would save me even more money during install because I don't own a purge cart (or have I found 1 for rent).
I have not done much of research on flow centers, and am always open to recommendations.

 

Since you are hearing me I will continue.

I like John Manning, but I disagree about push/pull flow centers for the same reasons I do not want a manufacturer picking my pump curves. I like pressurized systems, but that was what I was taught.

I do not own a purge cart. Someone gave me a self priming pool pump which is all I need to purge the system I design and build. If I need to have a cart strong pump, I sub-contract the work.

With a 25/140 I could move Lake Erie to Utah.

What I would do is buy a lower priced unit without a pump then buy just enough of a pump to make the heat transfer between the home and the loops IF it is all designed correctly.

Mark