Geothermal Parallel well installation

[jongig]

Thanks for reading.

I am a licensed water operator with plenty of experience with wells and piping. I am building a house and hired a contractor to install my HVAC system using a loop configuration consisting of two wells, each well is 300 feet deep. My system is a 4-ton system.

My question is about head loss. The two wells are 15 feet apart and the 1.25 inch pipes from one are mated to the other in parallel and then two pipes enter the house using the same size 1.25 inch pipe. In the parallel connection they used two T connections and two elbow connections. They placed the straight side of the both T connections on the same well making it a straight shot from house to the first well. They then used the side out of the two T connections followed by two elbows to the second well. In simplest form this means the first well has a straight shot to the house and the second well has 4 elbows.

I would think a balanced flow is important in this type of situation and if they had used one sideout T on one well 1 and one on well 2 they would have achieved balanced flow from both wells.

Can someone please tell me if this should be an issue or not? Will the flow rate differ between both wells? Since the ditch is still open should it be changed?

I spent a lot of money on this system to achieve a efficient system and I don’t want to see it not work as well as it should just because of this.

Thanks,
John

[tecman]

Parallel wells is common. The major point is to have the correct circulator flow. The well tubing should be the same length and and diameter. Fitting losses are most likely insignificant in your case.

paul

[jongig]

Thanks for the post but I really need a definitive answer. I’ve attached a picture. Some of my reading suggests that the flow being the same among the wells is important. I may have to sit down and do some math but I don’t know enough about these systems and the pipe to make a lot of sense from the math.

[crash11]

Those lines coming off the "T" going vertical in the picture......... do they both go into the same well? If so that's wrong. If they go to seperate wells then you'll get equal pressure drop through each well.

My concern is the fact that you used 1 1/4" for your two loops. To get peak efficiency you'll need to push 18 gpm through your loop to get proper turbulence in each parallel loop (9 gpm each). Your heat pump probably only needs 10-12 gpm though. What kind of flow center are you using?

[jongig]

2 lines from the sideout T and through the elbows go to one well. The other well has a straight shot.

[jongig]

Here is another picture which shows the piping and the wells as the pipe goes into them.

I'm very tempted to have them run all 4 pipes into the basement and then header them into the pump. It seems since I'm so close to the house it might be nice to monitor temperature from both wells.

Thoughts please!

John

[jongig]

Those lines coming off the "T" going vertical in the picture......... do they both go into the same well? If so that's wrong. If they go to seperate wells then you'll get equal pressure drop through each well.

My concern is the fact that you used 1 1/4" for your two loops. To get peak efficiency you'll need to push 18 gpm through your loop to get proper turbulence in each parallel loop (9 gpm each). Your heat pump probably only needs 10-12 gpm though. What kind of flow center are you using?

Just the information I'm looking for.

The flow center is a black module looking thing which is just two pumps mounted together with barbed fittings. I didn't get the pump info but I will. As I recall them saying that the pumps are attached going out and comming in to the house, push/pull configuration.

Even if you're right and I need 18 GPM there can not be equal flow through both wells due to the piping.

Can someone that knows this pipe do the head loss math and let me know the difference?

Thanks,

John

[tecman]

After seeing the picture, you're fine. Since the majority of the pressure drop is in the actual vertical loops, any small pressure drop difference from the main line to the bore hole is insignificant. The sizes step down from the main header to two equal sized lines.

paul

[jongig]

After seeing the picture, you're fine. Since the majority of the pressure drop is in the actual vertical loops, any small pressure drop difference from the main line to the bore hole is insignificant. The sizes step down from the main header to two equal sized lines.

paul

The picture does look as though the pipes are smaller going into the wells.

The pipes are smaller from the T to the wells. it drops down to 1 inch.

[arc8]

I,ve looked at your picture.
I prefer to see a header instead, but it still can work with what you got!
Question:
are the loops the same length?

If so, you should had one tee on each side, not the same side; like a reverse connection! This will make sure you get the same amount of resistance and water flow!

[crash11]

This is true (in response to tecman). The flow rates through each loop will only differ by 10% at the most I'm guessing. Also, with a 2 pump flow center you should be able to get the flowrate you need (do you know if they are Grundfos up26-116 or up26-99 pumps?), but the problem may be that to get good heat transfer in your loop you won't be able to get good heat transfer in your unit. Does your unit have 1" fpt ports? I have a 4 ton Florida Heat Pump unit and it came with 1" ports. Flowing that much (~18 gpm) through those ports is risky because of erosion.

If you do plan to bring the 4 lines into your basement, you may as well cut those t-fittings out and re-route them while you're at it. However, it's not imperative.

[jongig]

I had to get in the ditch and measure the pipe and the pipe to/from the house is 1.25" and the pipe from the T connections is 1". As was said earlier this makes it a much better situation. I still would have rather seen the pipes run differently but this certainly is acceptable.

My unit is a 4 ton unit with 1.25" connections. I didn't note what the circulators were but I will and let you know.

The unit gets turned on tomorrow and I'm sure it will work just fine.

After all the money I've spent on this I really want low monthly bills to make up for the extra cost. My wife was never completly on board with the extra money and I sure would like to show that it was worth it.

Thanks,

John

[crash11]

I had to get in the ditch and measure the pipe and the pipe to/from the house is 1.25" and the pipe from the T connections is 1". As was said earlier this makes it a much better situation. I still would have rather seen the pipes run differently but this certainly is acceptable.

My unit is a 4 ton unit with 1.25" connections. I didn't note what the circulators were but I will and let you know.

The unit gets turned on tomorrow and I'm sure it will work just fine.

After all the money I've spent on this I really want low monthly bills to make up for the extra cost. My wife was never completly on board with the extra money and I sure would like to show that it was worth it.

Thanks,

John
Now we're talking. Now the ideal flow rates for the unit and the loop match (~12 gpm) so all you have to do is set up your valves to achieve that 12 gpm (I may go a touch higher just because of the slight difference you'll have between each loop........maybe 13 gpm). Does your unit have pressure curves? Mine came with a little table that tells you what pressure drop you get at various flowrates through the condenser. I plotted the data in Excel to form a curve. Then I hooked up some pressure gauges on either side of the unit to read my pressure drop so I could back-figure what kind of flowrate I had.

[fsq4cw]

I spent a lot of money on this system to achieve a efficient system and I don’t want to see it not work as well as it should just because of this.







This is just my own personal opinion, however, your ground loops could/should be designed differently if efficiency is what you desire – and geothermal is all about efficiency!

First of all, you’re using 150ft/ton, fine, if that’s the required length per ton. I would strongly suggest that you have only 1-loop per ton, 4-150ft boreholes (4-ton) separated by 15 ~ 16 feet minimum, 3/4in HDPE pipe down hole (properly grouted) and PROPERLY designed reverse return headers with 1.25inch runouts.

What I see in your pics looks sloppy, poorly designed and amateurish. I hope this is not what you ultimately end up with.



IMO

SR

[jongig]

This is just my own personal opinion, however, your ground loops could/should be designed differently if efficiency is what you desire – and geothermal is all about efficiency!

First of all, you’re using 150ft/ton, fine, if that’s the required length per ton. I would strongly suggest that you have only 1-loop per ton, 4-150ft boreholes (4-ton) separated by 15 ~ 16 feet minimum, 3/4in HDPE pipe down hole (properly grouted) and PROPERLY designed reverse return headers with 1.25inch runouts.

What I see in your pics looks sloppy, poorly designed and amateurish. I hope this is not what you ultimately end up with.



IMO

SR


Yes, that's what I've ended up with. The unit is powered up and heating the house. I've not had the best relationship with my contractor and I have to trust that this will work. I will sandwhich the pipes in between 2 inch dow-board with closed cell expanding spray foam for insulation and protection. The unit is working but by no means done and my house is ready to move in except the heat/ac is still unfinished. The electric was strange because my electrician thought he should run 50 amps to the lower part of the unit but I was told to have him run 50+25 amps to breakers in the top of the unit. The unit of course wouldn't work because as it turns out the two breakers at the top of the unit are for auxillary heat. This unit has three circuits totalling 130 amps and all at 240 volts, yikes.

I would love to figure out how this thing is working and the efficiency of the system.

[fsq4cw]

Thank-you for not taking terrible offence to my comments.

I think you may have to wait till later in the season to access efficiency. You will have some idea as to how well you’re doing by determining at what temperature the backup comes on at and compare this to the winter design temperature for GSHP systems in your area.

Another simple method requiring nothing more than a thermometer, would be to record LAT & EAT at the supply/return plenums, then:

HC (heating capacity) = CFM (manufacturer’s spec) x (LAT –EAT) x 1.08 = χBTU. Then compare this to the manufacturer’s specs.

Hope this helps, have fun & good luck!

SR

[jongig]

Thank-you for not taking terrible offence to my comments.

I think you may have to wait till later in the season to access efficiency. You will have some idea as to how well you’re doing by determining at what temperature the backup comes on at and compare this to the winter design temperature for GSHP systems in your area.

Another simple method requiring nothing more than a thermometer, would be to record LAT & EAT at the supply/return plenums, then:

HC (heating capacity) = CFM (manufacturer’s spec) x (LAT –EAT) x 1.08 = χBTU. Then compare this to the manufacturer’s specs.

Hope this helps, have fun & good luck!

SR

I sure do't mind doing math but please explain it better such as what is LAT and EAT? I'm guessing this is the loop temperature in/out f the house. I did see them place a probe on the brass fittings into the unit. I am surprised that the unit doesn't have a readout.

I would like to keep track of how the unit is working and if you'd please explain to me how to do that. It also seems that having a couple temperature probes and a program to monitor data would be nice. You'd have to have a program that would aslo monitor the on and off of the unit or you'd get a lot of useless temperature readings.

john

[fsq4cw]

Hi John,

HC = Heating Capacity (Total Output) in BTUs, CFM (Cubic Feet Per Minute, fan capacity), LAT (Leaving Air Temperature at the supply plenum), EAT (Entering Air Temperature at the return plenum) = xBTU (whatever your answer is in British Thermal Units). From there convert your answer in BTUs to kW (BTU x 0.000293), divide this answer by energy input to run your HP (kW) and you should arrive at a COP (Co-efficiency Of Performance).

Just run the HP long enough, continuously, to achieve full operating temperatures. Then measure the air temperatures at the supply & return plenums long enough to get an accurate reading on your thermometer and do the math. If need be you can even use a meat thermometer from a grocery store to get an idea of the air temperatures.

Good luck & keep us posted!

Steve

[larobj63]

Another residential geo system with back-up resistance heat....

Sigh... :o

[jongig]

Another residential geo system with back-up resistance heat....

Sigh... :o

Yes I'm not sure what to think about the extra 19,200 watts of resistance heat. This unit has 3, 240-volt circuits, 2 are 50 amp and the third is 30 amps. The heat pump is 50 amps. I would like to buy a backup electrical generator and no way am I buying a unit to run those three circuits.

Next issue and I've not found anything on the Internet that gives me information about loop temperature. I permanantly placed a thermometer on both sides of the geo-loop, moving in/out. The temperatures of the loop have gone down to a low of 32 degrees going out and 38 comming in. Seems rather cold but I really don't know.

Does the unit know the return temperature and only remove a certain amount of heat or does it just take what it can?

john