HVAC II, which one?

[buckeyefarmer]

I've only done a handful of geothermals, so I'm far from an expert, but from what I've seen, as mentioned previously, geothermal is the way to go if done properly.

However...



Helped a buddy who is an HVAC contractor put a dual fuel system in his house this past winter, and so far, even when it was 30 F degrees outside, he still didn't need to run his gas furnace because his heat pump was keeping the interior at 74 F degrees no problem (R410A system, over 9.0 on the HSPF).

Numerous variables to consider as far as the interior conditions go.

What you quoted is not showing up, but Air to Air is not a geo system. A heat pump normally puts out air cooler than body temp, so it feels cooler to the touch, but it will probably be in the 90's and warm enough to warm the space.

 

[Richard]

There are different piping layouts. You will need one loop per ton of unit. The length of the loop depends on piping layout, depth, pipe size, soil type, location, etc... The designer will use software to determine the lengths. I would recommend 6 to 8 feet deep for horizontal, but the depth is included in the length sizing,

Thanks for commenting on the build of the brand and pricing!

Regarding buried 6 feet or more, that is also what they say. I asked them (and here it is for the crowd)

Since I can dig down to 15 feet, is there any additional benefit from going from 6' down to maybe 12?

Also... if the recommended length is 600' of underground tubing, is there any benefit of putting in 1,000 or is it just a waste of money?

In other words, is 600' the "minimim cost, minimim performance' standard or would that number (if the accurate amount) actually be the right amount?

If I use the field across from the house, I'd be veery able to add what I wanted to be positive it's ok. Might even lay a duplicate field of same stuff for my wifes uncle who lives next door so if/when his 15/20 year old system dies and he wants to convert to geo, he'll already have the hard part done.

They came out yesterday and looked around. Regarding doing any 'calculations', they didn't take any measurements, no window counts, nothing... just came and looked at what I had and the layout, noting we might need an adjustment here, slide the (basement) refrigerator over there for more room, punch a hole through house to take pipe outside over here... but not the first measurement.

Can they even give an accurate quote if they don't go through that process or are they simply relying on the unit I already have and their experience in the business? (this place has been around for a while)

 

[MarkV]

Richard I am following your thread with interest. We are do for a new system and have considered Geothermal. I personally can't see dumping that much water everyday unless it was being dumped back into the aquifer. Have you investigated the possibility of drilling another well to dump the water in? I don't know how that would compare to the trench and piping closed loop price wise yet may be worth looking into. I also heard, could be urban legend, that the EPA looking at stopping vertical closed loop system due to possible water contamination.

MarkV

 

[2manyrocks]

When my house was sized, I know they measured exterior walls, doors and windows. I also think the calculations took into account the estimated R factors of all those surfaces. They also asked me how much insulation was in the walls. And they gave me a copy of their calculations.

As far as burying pipe is concerned, I think there are some established parameters for ground temperatures at certain depths, and going 12' probably just means you've removing twice the amount of material for negligible gain. You just want the pipe deep enough to be protected from damage and to be in the earth deep enough to get the ground temperature needed for your system.

The amount of pipe in theory should be calculated based on how much surface area has to be in contact with the ground to make the system work properly. Too much is too much. Too little is too little.

 

[Reg]

Addition: the reason I'm leaning on a closed loop is simply, I abhor the idea of pumping out say, 2,500 gallons water per day, ever day of the year forever more. Dumping said water into ditch and adding cycles to my well pump which is already say, 10 years old.

A closed system simply seems the "right" way of doing it.

Plus, once a closed system is closed you have included any/every thing in it that will be in it.
i.e. you will NOT be sucking in a new load of whatever is in the ground and relocating it to the ditch, though eventually I guess it would find it's way to the aquifer (polluted).
You could (at least in theory) fill a closed system with something other than well water, e.g. some solution better able to conduct heat. (I didn't say "Glycol")

I would be interested in seeing tables of pipe length/diameter required for given materials (copper ?, plastics ?) and flow rates, or the basis of the arithmetic used to derive the tables.

 

[moeh1]

I looked real hard at geo a couple years ago and would have had to go open loop.
Hard on your well
Hard on your pump
Hard on the heat exchanger if you have the wrong stuff in your water
Not all second wells have enough capacity to "sink water" as fast as they can pump water.
Open discharge is outlawed in many areas due to wasting water.
The cost of systems eventually drove me to a high end air source unit that does great done to about 10F, then I have to switch over to a backup system.
If you go closed loop, no advantage to going deeper once you get to a stable ground temp. They have some "slinkly coils" that might reduce the actual distance you have to trench. There are some past posts here. Techman? did an install in Pa.

 

[buckeyefarmer]

He guessed that the incremental cost from the pump/dump to a closed loop system (me doing the digging & backfilling) would be about $2,500 upcharge. By the way, the speculated price for a Climatemaster TSV-030 (Tranquility 27 series) was $6,000. He corrected that today saying it would be about $6,682 as a pump/dump install and if I added the closed loop, it would then go to about $9,182 with me doing the digging and backfilling.

This is the single speed model, the dual is the TT line which will run slightly more in cost, but could offer some long term energy savings

 

[Sigarms]

What you quoted is not showing up

Apologies, what did I quote, and where is it not showing up?

but Air to Air is not a geo system

Understood.

A heat pump normally puts out air cooler than body temp,

In heating mode, yes, a R22 unit will usually have discharge air at the registers in the mid 90's range. Not always so with a R410A unit.

Apologies, off topic.

 

[buckeyefarmer]

Since I can dig down to 15 feet, is there any additional benefit from going from 6' down to maybe 12?

Also... if the recommended length is 600' of underground tubing, is there any benefit of putting in 1,000 or is it just a waste of money?

As an Example:
(repeat, this is only an example) For my area, with **K heat load and **K cooling load, the TS036 would need 625'' of trench at 6' deep in damp silt/clay soil. At 12' it would need 510' trench. this is for a horz 2 pipe spaced 24" apart.
If I use Knoxville TN bin data, at 12' it is 570' and at 6' it is 705' trench.
A slinky, 8 ft/ft, 3 ft coil at 12' would be 355' and at 6 ft would be 440' trench.

This is just an example to show how the depth can shorten the trench & pipe somewhat, and different pipe layouts make a difference.

More pipe is OK, as long as it is not drastically longer. you will need to have an antifreeze in the pipe, which slows the flow, so the longer the pipe the more pump you need. There comes a point the longer pipe does nothing but add to the cost, as it increases the pump size and causes more circulation pump electric usage. The main point is 1 loop per ton, the loops MUST be the same length, and use a reverse return header. One common mistake is to use the wrong soil conditions, and you can easily be 50% undersized, if your soil turns out to be drier etc...

Yearly heat cost, at $.10 per khw is estimated at $440, cooling $289, another $269 for hot water generations (I included desuperheater in the estimate). 12' deep saves only $18 /yr on the projected total cost.

Again, just an example using some made up heat and cooling numbers. you need the manual J calculation to determine these numbers.

 

[buckeyefarmer]

Sigarms: When I quoted you, and you had quoted someone previous, what you quoted didn't show up in my posting. It's a problem with the BB software apparently.

 

[2manyrocks]

It would be great to see a geothermal system figured out here on TBN that beats the contractor's design. Even better if the homeowner installs the ground piping with photos here, too.

 

[buckeyefarmer]

It would be great to see a geothermal system figured out here on TBN that beats the contractor's design. Even better if the homeowner installs the ground piping with photos here, too.

You will when I get mine done. Although the same principal, each design is almost unique. Look on youtube for some nice geo videos. Also one of the HVAC Boards has documented installs that people have done themselves..
one is www.ricksgeo.com

 

[2manyrocks]

That's a good read on that link. If he had his own backhoe to work at his own pace, I think he could have saved himself some of the headaches he mentions. But it's a very good link. thanks.

 

[irvingj]

I've had a water-source (what geothermal used to be called) heat pump in my house since its construction in 1986. It's still ticking away, and has saved gobs of money over its life. I'm currently researching some on replacements, as it may be coming to the end of its useful time....

When mine was installed, it was originally going to be a pump and dump system, but I really didn't feel good about that, for all the reasons stated already. The designers of the system, a couple of NH engineers, then came up with an elegant solution:

1. They created a manifold with an on-site PVC (?) welder that split the 2" line coming from the house into two 3/4" loops, with welded return bends on the ends of each.

2. They fashioned a large wire spool (4' diameter) on a stand so it could rotate.

3. Using the spool, they wound up my well pipe, with pump on the end, and removed all the plastic spacers I had so carefully positioned when I put it in.

4. They then fed the four 3/4" lines (2 loops) back down the well hole (std. 6"), along with the pump and water line. The loops effectively replaced the plastic spacers. They weren't able to get it back down as far as it had been, but still got about 200' of loop into the well (with the water pump below that); static's at 80'.

5. Welded up the manifold to the two loops, connected to the 2" lines going back into the house, installed two Grundfos circulators in series, and I then had an 8-1/2 gpm recirculating loop. All lines were 8' or more below the surface, so it's all just water, no need for A-F.

As it was a closed system, the water in the loop was filtered well and then treated. It's hooked up to a valve inside so I can replace and/or flush the loop when needed. Twenty-three years and counting.... Still has the original Grundfos pumps, still runs @ 8.5gpm with a 6 degree+/- TD on the loop. I do augment with a wood stove; we have the coldest tap water in the state, I think, in the winter!

It ain't real pretty sitting in my basement, but it sure does work. I envy you guys who have the newer systems-- mine uses R-22 and has a 3.25 COP; I'm drooling over the new ones with a COP of 5!!

In all those years, I've replaced both TXVs, all 3 check-valves ("cheap" Singers/Gemlines), one reversing valve, and repaired a couple of leaks. Not bad, methinks. Oh- it also makes hot water... and in the summer can take house heat and put it directly into DHW. Clever, those NH engineers.

 

[2manyrocks]

irvingj, how many square feet does your unit serve and BTU capacity does your unit have? I am curious what size you have because your system has successfully run on a 200' loop in your well?

 

[buckeyefarmer]

mine uses R-22 and has a 3.25 COP; I'm drooling over the new ones with a COP of 5!!

Thanks for sharing your experience!
You've done good. I know a guy who got over 30 yrs with his homemade Geo system. He just replaced it with a new waterfurnace, only because of the age and the rebates.
A COP of 3.25 isn't bad. Most will not get 5 out of the new systems. The TT Tranquility 27 spec sheet shows COP's ranging from 3.6 to 4.0 at full load. At partial load, they run from 3.9 to 4.6. They all advertise their best numbers, but actual situation will be a little less most likely.

COP is the performance of the unit for the heat cycle. If you use electric heat, for every 1 KW (3413 btu) of electric used you get 1 KW of heat, or a COP of 1. You will never get better. For Geothermal with a COP of 5, you are using 1 KW of electric to get the equivalent of 4 more KW of heat from the ground, for a total heat output of 5 KW from the 1 KW used.

And all the free hot water you want in the summer with the desuperheater option.

Great systems, can't wait to get mine done.

 

[irvingj]

2manyrocks (sounds like NH!): My house is a post and beam, built like a walk-in cooler; exterior is foam panels with sheathing in & out, foam is 10". R-39 all around, walls & roof.

House is about 1800 sq ft, heat pump is a ... 3 or 3-1/2 ton, if I remember correctly. Design heat loss @ 0 degrees is around 20KBTU. Sounds impossible, but I heated the whole house --and basement-- with an electric 17.5KBTUH heater the first winter when I ran out of wood (heat pump wasn't hooked up yet). Ran pretty much constantly for a few days, but it did the job. The electric bill was horrendous, however!

The heat pump was sort of hand made by these two guys, a one-of-a-kind. Has a desuperheater coil plumbed in to DHW with a single Grundfos, as well as a dedicated DHW heat exchanger, whose extra water line opens via a HP regulator after second reversing valve cuts in. This is in addition to the usual refrigerant-to-water well loop heat exchanger and air coil. The extra DHW refigerant-to-water coil is that "bump" sticking out in the front bottom.

It's complex, but it's held up pretty well. Guess I did also replace a couple of octal-base relays, now that I think about it. It has no electric back-up resistance heat- I didn't want it installed, it's still sitting somewhere in the basement...

Here's a couple of views of the house, south & north sides.

 

[2manyrocks]

thanks a bunch. I'm in middle TN and have no idea why I'm blessed with so many rocks. They ooze out of my garden every time I till it.

The R-39 panels explain a lot of how you're able to heat with only 3-4 tons in NH. You're heating a very tightly insulated house.

Sometimes homeowners think they are heating 1800 SF for example, but their house is so leaky, that they are effectively trying to heat the great outdoors. I remember talking to one engineer who shocked me because he refused to size any structure without running a blower door test to determine how leaky it was before he would size a system.

I'm still amazed that your loop is 200' for your system. What kind of pipe is used in your loop?

Your system appears to have been so well thought out that it may be a challenge to find a replacement. Are those engineers that designed your system still around?

 

[irvingj]

I don't know where the engineers are now... the heat pump was part of a package deal with a now-defunct outfit called Northern Energy Homes based in Norwich, VT in the 80s.

The house was obviously built to be super insulated and tight; the white PVC pipes visible on the north side of the house are from an air-to-air heat exchanger which was also part of the deal. Incoming outside air is heated (an aluminum heat exchanger) by exhausting air. Efficiency is purported to be in the 95% range, and, assuming I keep it clean (1X per year), it'll bring in fresh outside air at 48-50 when it's -20 outside and indoor ambient is 70. Exhaust air is drawn from the bathroom vents and one between the laundry room & kitchen. Drips water pretty well when it's cold out, and it is equipped with a freeze-stat which turns off the intake fan while leaving the exhaust on for defrosting. I highly recommend it- Boss-Aire is the manufacturer. (Others use a single fan motor on a double-ended shaft, which require a motorized damper for closing off intake during defrost.)

Northern Energy Homes died when the 80s went bust, along with a lot of other companies; last I heard those heat pump designers went to work with one of the major players in the then-new water-source heat pump industry; I certainly hope they did!

The loop pipes are a black plastic, somewhat flexible; I don't know if they're PVC or a polyethylene type. A long length can easily be flexed, but a short piece could be used as a weapon, it's so hard! Pretty tough stuff.

The hope I have is that, when it comes time for replacement, the loop will simply remain intact and be hooked up to the new inside unit. I don't see why that wouldn't work. However, it appears that, other than a desuperheater, I may have to forego a dedicated DHW circuit. I can live with that--- It's really not that effective in the winer heating season anyway, as once the water's up to temp on DHW, when the system switches into house heat the head pressure's low enough that it takes heat OUT of he DHW loop (via the desuperheater)-- condensing temp's around 90, so if the DHW's hotter than that....

What happens is that the machine goes back & forth between DHW and house heat without ever stopping. I've circumvented that by dropping the dedicated DHW t-stat to it's lowest setting (85?) so it never comes on. Because of the desuperheater, however, when it's cold and the unit's cranking for house heat, it'll keep my 80-gallon electric hot water heater right around 90; if I want hot water, I just switch on the upper electric element and I have 125 in about ten minutes or less, then switch off the electric heater after morning showers or laundry.

I grew up in a 200-year-old cape, and lived with that leaky, frosty, drafty, oil-sucking, constantly-in-need-of-repairs behemoth.... decided I didn't want to go through that again! My house was relatively expensive at the time ($120K in 1985), but I bit the bullet and never regretted it. (Well, maybe once or twice in the early years....) Now, it's really nice to "boast" about how efficient it is!

 

[Richard]

Another angle on the ground loop system for a Geothermal setup...

It dawned on me that if I did one of these, there might be some merit in laying one of those magnetic tapes over the top of it so it could be located in the future if need be.

1. Prudent?
2. Where do you get this stuff?
3. If used, what do you use to FIND this stuff once buried?
4. Any other way to mark it better than the magnetic tape?
5. Given the power company uses it, would you be "allowed" to use it since it might imply power is down there instead of water?