First off, thanks to everyone who shares their expertise here. I've learned a lot just through lurking (I am not a mechanical/technical person). My husband and I are a crossroads where we have to decide whether or not to continue to use the geothermal system that was installed in the Fall of 2010. It's been extremely problematic and unreliable, and on top of that has not saved us any money...and we are using much more electricity than we did before, which I think is worse for the environment than the natural gas we heated with before.

I won't go into all the problems, but the latest problem caused me to really push our contractor for an explanation of what we should expect for usage. They have been out to our house literally every 3-4- months replacing or rewiring something. Right now we are waiting for a new blower motor for the Spacepak.  I asked him to re-do the System Summary that he provided as part of the sales cycle, which had shown how energy efficient the new system would be. I now have that, and would like your expert opinions on whether geo was just a bad choice for us. We have an 1898 3 story Victorian that had/has radiator hw heat.  We're currently heating with all gas while we wait for the new blower motor.

I'm attaching the new system summary, which now comes with the following caveats from our dealer/contractor:

1. The system displayed in the analysis is a forced-air furnace with a geothermal split system. The system installed is a hi-velocity system. The blower for a hi-velocity system draws more amps than a traditional furnace.

2. System design assumes 2 pumps for the loopfield. This is a default parameter. The system installation has an additional pump, which utilizes approx 1000 kWh per year.

3. The Carrier Geothermal Design does not have a parameter for humidifier operation, which includes: the fan on the humidifier, the fan on the air handler, the water heater blower motor, and gas to run the water heater.

4.The system required the use of a condensate pump to pump the condensation created during AC season and the excess moisture from the humidifier to the laundry room sink.

I would like your expert advice on whether we keep having them fix the geo, or whether it would be better for both our pocketbooks and the environment if we went back to heating with natural gas. Thanks!

The first lines of the first attachment are eye-popping!

A 98,122 BTU/hr heating load at a 65F difference? Really?

Is there ANY insulation in that house, ANYWHERE?

How's about glass (at least in most of the windows :-) )?

I know it's 3 stories tall, and over a century old, but I've seen 3 story houses that vintage with half that heat load after all of the low-hanging air-sealing & insulation fruit was taken care of. (And at the upfront expense of geo systems, it's usually worth going after some of the higher-hanging goods too.)

If that's what the designer came up with a heat load, my competence-alert moves immediately into the orange zone between yellow & red. The only way the heat load could be that high would be if it's a VERY large Victorian with lots of heat leaks, many of which could/should be fixed economically.

The ~14K+ of average internal heat gains are also on the high side, unless you use heat lamps as night-lights (or maybe you have 5 freezers in the basement where you store 3 years worth of venison & fish?), but that explains the relatively low 61F balance point. But seriously, I'd like to know where the 14,260 BTU/hr of average internal gains is from- that's over 4000 watts of continuous power, even after subtracting off 500 BTU/hr for a pair of sleeping humans.

And the heating setpoint of 70F is 82F above the -12F outdside design temp, or an 82F difference, but only 77F above the presumed balance point. So it looks like they were designing the geo for 65/77 or about 85% of the heat load beyond the internal gains, which is reasonable, if the raw numbers for load were correct.

Using difference between he 70F setpoint and their calculated balance point of 61F and heating setpoint on their 14,260BTU/hr internal gains number you get 14,260/(70-61)= 1584 BTU/degree-hour. Projected linearly to a 65F delta that's over 98KBTU/hr, more like 103K (but what's 5KBTU/hr between friends? I'm not quite sure how their modeling works...

Bottom line, you may or may not have a system worth fixing, but the original installer is probably not your best resource on that. But if the heat load calc reflects the true condition of the building, it's probably worth spending some money tightening up the place before re-designing the geo system to make it actually work reliably.

If you have a mid-winter billing period where the gas-burner was pulling 100% of the load, the boilers input BTU & DOE output BTU, along with your zip code (for weather data purposes), the fuel use, and the exact dates that the billing covers, it's possible to calculate an excellent ball-park number on the true heat load using the boiler as the measuring instrument.

FWIW: The local grid sources in MN are moving toward a higher fraction of wind & combined-cycle gas, and the coal fraction is beginning to dwindle (it can't compete on fuel price & efficiency with cc gas) and at the current mix even resistance heating may be close to par with heating with #2 fuel oil. If the geo is averaging a COP of even 2 it's probably greener (if more expensive) than heating with gas in an 80% efficiency burner.

Yes, we have windows! The house is a bit drafty and the insulation is not the best. Ceilings are high.

I wondered about the heating load numbers in the new analysis.

The analysis we received back in 2010 had the following:

Heating Load:  90,000 Btu/Hr
Htg Load Temp Diff:  80 Def F

Thank you for the reaction and advice. I am relieved to hear that at least we might not have increased our carbon footprint. You've given me some things to investigate, and it is helpful to validate our thought that we should bring in a neutral expert to take a look.

Oh, by the way, the house is not huge. It's 3100 sq feet above ground, and the basement is ~1400 sq feet. There was no heat in the basement, now we have 3 of the 35 ducts going there. Can I use gas therms/day to calculate BTUs? I've looked at some old energy bills, and the highest gas therms/day I found was 14.7.

(and I got the third part of the analysis to attach finally)

What is "extremely problematic?" What were the problems.
I think you need another expert in there.

I think you're both right that we need another expert. I don't see anyone listed in the Twin Cities (on this site).

Joe, remember you asked for it...Here are some of the things that have happened since our install from Aug-Oct 2010. Each of these required one or more visits from the installer, and they've even volunteered to visit our home daily while we were out of town several times because they couldn't guarantee the equipment would reliably heat the house (we've now got a thermostat you can access remotely, put in as much for the installer's convenience as for ours) :

1.  Sept 2010: System shutting off when there was still a call for heat, hi temp unit back ordered, when it comes it is damaged but damage is deemed only cosmetic.
2.  Nov 2010: Puddles in the basement from geo units several weekends in a row (response: the installer placed the drain tube too far into the tank, which caused the float not to turn on the pump)
3.  Nov 2010: Radiators heating up when there was no call for heat (response: the only way to prevent this is to add an electric zone valve which will provide 100% shut off until a call for heat)
4. Thoughout November 2010: multiple fault codes on the unit, unit faulting out approximately weekly
5. Faulty pump replaced
6. System rewired after we expressed concern that gas was kicking in before geo.
7. Nov 2010: Warm weather shutdown error messages on unit
8. Dec 2010: While working on the system, they blew out some type of special transformer
9. Dec 1, 2010:  We're told Carrier has decided there is a faulty sensor causing the E2 and E4 ongoing error codes
10. Dec 2, 2010: My husband arrives home to find the house at 58 degrees
11. Jan 2011: High energy costs blamed on "soft fault", nevertheless, installer agrees to install a dual fuel meter which will allow us to track the geo's energy usage separately from the rest of the house, and make us eligible for a lower electric rate. Throughout all this we are told that fine tuning the system will allow us to see energy savings.
12: Feb 2011: "Final adjustment" made on high temp unit to discontinue lock out that was occurring.
13. March 15, 2011: We have no geo heat. (response: the zone panel didn't have power)
16. June 2011:  We discover on a call for cooling we are only getting room-temp air (pressure had to be increased in the loopfield)
17.  2011-2012:  Lots of times we have had tepid air blowing with calls for cooling or heat
18. TXV in Spacepak needed replacing last summer during the heat wave. Took more than 3 weeks to get it with the other part it is soldered to.
19. New tech FINALLY realizes that the wireless thermostat is no communicating consistently with the controller(?). Pulls wires and installs a wired thermostat. In the meantime we have had 5-7 thermostats.
20. Now Spacepak blower motor has been on order since late Feb, and we are running totally on gas.

I'm sure some of this just comes with the territory, but I feel a little cursed....

Posted By tamar on 21 Mar 2013 05:38 PM
Oh, by the way, the house is not huge. It's 3100 sq feet above ground, and the basement is ~1400 sq feet. There was no heat in the basement, now we have 3 of the 35 ducts going there. Can I use gas therms/day to calculate BTUs? I've looked at some old energy bills, and the highest gas therms/day I found was 14.7.

(and I got the third part of the analysis to attach finally)

The therms/day have to be correlated to the average temperature on that day to come up with a heat load.  A single-day's use has very large margins of error, but a full mid-winter month's usage against the heating-degree-days for that month typically stays within a 5% window.  With the boilers input & output BTU numbers you can then convert the input-BTU/day at the average temp to a BTU/degree-hour, which is the slope of the line.  If you set the zero at an appropriate balance-point temp, the heat load grows by the same BTU/hour for ever degree below the balance point. (Using 65F is the typical default, but they 61F as the balance point in that attachment. I'd use 65F, not 61F, unless your non-heating electricity use before installing the geo was something like 3000 kilolwatt-hours per month or more, which seems unlikely.  The national average is something like 900-1000kwh/month, and people with just one refrigerator and only high-efficiency lighting typcially come in between 450-750kwh/month.)

A 3100' house with almost ANY insulation should have a heat load less than 90K at a difference of 65F, even counting the 1400' of basement.

If the basement has no foundation insulation and the foundation sill & band joist haven't been air-sealed & insulated, that should have been in the top 5 on the "before investing in geo" list.  A 3 story house has a significant stack effect driving infiltration, and the two best ways to cut that down to size is to air-seal the bottom against air entry, and air seal the top-floor/attic against rising air escaping. Air sealing can be the absolute CHEAPEST way to take a significant chunk out of the load.  Duct/plumbing/flue/electrical chases that run from the basement to the upper floors or out the attic need to be air-sealed at the bottom & top too, since they are otherwise low-impedance bypasses for stack effect infilrtation.  Balloon framing and even partition walls that often had not top plates back in the day also need to air sealed.

For yuks, let's assume that 14.7 therms/day peak happened on a day where the average temp was 12F (the high might have been 22F, the low, +2F.) And lets assume your boilers steady state efficiency is 80% (output BTU divided by input BTU/)  Let's also assume your house really balances somewhere around 65F, not 61F.  The base-65F heating degree days (HDD) for that day was then:

65F-12F= 53 HDD

And the BTU of the boiler's output burning through 14.7 therms was then:

0.8 x 14.7 x 100,000= 1,176,000 BTU

So the BTU per degree day is:

1,176,000 BTU /53 HDD= 22,189 BTU/hdd

With 24 hours in a day, converting  that to per hour it becomes:

22,189 BTU/ 24= 925BTU/degree-hour.

Remember, the zero is 65F, so the heat load at -12F (about the 99% outside design temp for Minneapolis) is:

65F- (-12F)= 72F heating degrees

So the heat load at the 99% condition is going to come in around:

72F x 925 BTU/deg-hr= 66,600 BTU/hr.

But this is just an example using a fictional average outdoor temp- run the math on the real numbers.  If you have a date or dates for an all-gas heating period, you can download a spreadsheet covering that period with base-65F HDD data from a nearby weather station using degreedays.net sources.

If you're heating hot water with gas, that will peel a bit off the final heat load calc, but if you're using overnight setbacks on the thermostat it will add a bit. They don't exactly balance- it depends on how deep the setback and how much hot water you actually use, but they do counteract each other.  Whatever the number comes out to be, the true heat load is going to be within 20% of that even on a single-day's measurement unless you were in Hawaii that day, with the thermostat set to 50F.  On a month long estimate the error bars will be inside of 10%, barring unusual circumstances (like your geo system actually being functional for a few days out of that billing period, overnight setbacks to 50F where it actually GOT that cold indoors, etc.)

Thank you for providing that detailed explanation, Dana1.  I think I will be spending some quality time with my calculator this weekend.

Just to make sure I'm on the right track, I will figure BTUs with average therms per day and average heating degree days. We have been using strictly gas boiler for heat since Feb 1  (and at the end of January we often were in auxiliary mode), and I have the following info from Xcel:

Jan 22-Feb22
Days: 31
Usage (Therms or MCF): 213
Usage per day: 6.9
Heat factor content: 1.0246   (does this factor in?)
Heating degree days: 1475  (47.58HDD/Day)

Here's what I come up with. The average temp for my Jan 22-Feb 22 bill was 19 degrees. The new boiler installed with the geo is supposedly 96% efficient, but I'll use 90%. Caveat that I was out of town for a week and husband works long hours so set the heat down to ~64 degrees for much of the day/nights, and we have started using the setback feature (to 65 degrees) for all nights since geo has been inoperable.

In addition, we did have some geo usage during the first 8 days of the period, but because the blower motor was on the way out of commission, I suspect we were just eating electricity and mostly blowing room-temp air around.

65F-19F= 46 HDD

BTU of boiler's output is:  .9 x 6.9 x 100,000 = 621,000 BTU

So the BTU per degree day is 621,000/46 HDD = 13,500 BTU/HDD

Divide by 24 hours 13,500/24 = 562.5 BTU/degree-hour

Here's where I get confused, when you say zero is 65, but using your example:

65F - (19F) = 84F heating degrees

heat load at the 99% condition  84F x 562.5 = 47,250 BTU/hr

Did I do this right?

Posted By tamar on 22 Mar 2013 05:27 PM
...snip... I have the following info from Xcel:

Jan 22-Feb22
Days: 31
Usage (Therms or MCF): 213
Usage per day: 6.9
Heat factor content: 1.0246   (does this factor in?)
Heating degree days: 1475  (47.58HDD/Day)

Just to clarify...
Natural gas can be sold in various units. For residential applications, it is usually sold in hundreds of cubic feet (CCF) or in therms (a measure of energy content, with one therm = 100,000 Btu), and they are about equivalent. The actual conversion factor depends on the natural gas composition, which is mostly methane, but with some ethane and other gases that vary with the source. A typical conversion is CCF x 1.024 = therms. In your case, it looks like the conversion factor is 1.0246 (therms/CCF).

But MCF is thousands of cubic feet of gas, so gas usage in MCF = gas usage in CCF / 10. So when you state that your gas usage is 213 therms or MCF over a month, I am guessing that it is 213 therms or CCF, which are roughly equivalent, but not 213 MCF which would cost about $2,130 at $10/MCF.

Quote:I think you're both right that we need another expert. I don't see anyone listed in the Twin Cities (on this site).

Try a different site

Joe, remember you asked for it....

Can't help much without specifics

Each of these required one or more visits from the installer, and they've even volunteered to visit our home daily while we were out of town several times because they couldn't guarantee the equipment would reliably heat the house (we've now got a thermostat you can access remotely, put in as much for the installer's convenience as for ours) :

At least they covered there incompetent butts by making sure your house didn't freeze

1. Sept 2010: System shutting off when there was still a call for heat, hi temp unit back ordered, when it comes it is damaged but damage is deemed only cosmetic.

I don't know what "high temp" unit is. Are we talking a modulating boiler?

2. Nov 2010: Puddles in the basement from geo units several weekends in a row (response: the installer placed the drain tube too far into the tank, which caused the float not to turn on the pump)

Are we talking about a condensate pump on a modulating boiler?.....Installer error

3. Nov 2010: Radiators heating up when there was no call for heat (response: the only way to prevent this is to add an electric zone valve which will provide 100% shut off until a call for heat)

Boiler 101 hot water moves......Design error

4. Thoughout November 2010: multiple fault codes on the unit, unit faulting out approximately weekly

Means nothing without detail

5. Faulty pump replaced

Condensate pump?

6. System rewired after we expressed concern that gas was kicking in before geo.

Installer error

7. Nov 2010: Warm weather shutdown error messages on unit

I think this means unit wouldn't run because of an outdoor temperature lock-out....Installer error

8. Dec 2010: While working on the system, they blew out some type of special transformer

Technician error

9. Dec 1, 2010: We're told Carrier has decided there is a faulty sensor causing the E2 and E4 ongoing error codes

If true- heat pump's fault

10. Dec 2, 2010: My husband arrives home to find the house at 58 degrees

...and....

11. Jan 2011: High energy costs blamed on "soft fault", nevertheless, installer agrees to install a dual fuel meter which will allow us to track the geo's energy usage separately from the rest of the house, and make us eligible for a lower electric rate. Throughout all this we are told that fine tuning the system will allow us to see energy savings.

Why wouldn't you have startede with the lower electric rate?- Design error

12: Feb 2011: "Final adjustment" made on high temp unit to discontinue lock out that was occurring.

I don't know what you mean by high temp unit, but "adjustment" means- Installer error

13. March 15, 2011: We have no geo heat. (response: the zone panel didn't have power)

What caused it?

16. June 2011: We discover on a call for cooling we are only getting room-temp air (pressure had to be increased in the loopfield)

Not the likely culprit, but adding pressure to a loopfield in cooling system is not uncommon

17. 2011-2012: Lots of times we have had tepid air blowing with calls for cooling or heat

Again means little without specifics

18. TXV in Spacepak needed replacing last summer during the heat wave. Took more than 3 weeks to get it with the other part it is soldered to.

Based on the information here this is the 3rd part failure

19. New tech FINALLY realizes that the wireless thermostat is no communicating consistently with the controller(?). Pulls wires and installs a wired thermostat. In the meantime we have had 5-7 thermostats.

5-7 thermostats suggests installer incompetence

20. Now Spacepak blower motor has been on order since late Feb, and we are running totally on gas.

I'm sure some of this just comes with the territory, but I feel a little cursed....End Quote

Yeah you are cursed- by an incompetent installer/designer and 4 actual part problems on 3 seperate appliances in 3 winters.

Hydronic and high velocity geo require a better than average installer/designer. You need help. Check with local building department to find out who in your area has done geo-hydronic (and done it well). For repair work your local heating inspector will likely make a referral.

"I don't know what you mean by high temp unit...."

I am pretty sure this is the GT-PW W2W heat pump. It was presented to us as one of the only W2W heat pumps that could get the water hot enough to allow us to heat with some geo before switching to gas when the radiator heat was needed. I think if nothing else, this was a mistake, because the hw heat is so slow to make a temp different that only in shoulder seasons will it keep us from needing the gas heat on top of it. We were led to expect that auxiliary heat would kick in "only on the coldest days" which we interpreted to mean single digit days, but the aux kicks in when it drops into the high 20s.

Shame on us for not asking more questions and requiring more documentation. We went with a well known installer in this area who said they had hundreds of successful geo installs....

Posted By tamar on 22 Mar 2013 06:14 PM
 
...

65F-19F= 46 HDD

BTU of boiler's output is:  .9 x 6.9 x 100,000 = 621,000 BTU

So the BTU per degree day is 621,000/46 HDD = 13,500 BTU/HDD

...

13,500 BTU/HDD / 3100 SF = 4.4 BTU/HDD/SF (from above).

This (4.4) seems awfully high.  As Dana asked, do you have much/any insulation?

For comparison, my residence, constructed in the early '90s and doesn't have anything special WRT insulation, windows and doors, and has a lot of glass, is 3400 SF and uses 6900 BTU/HDD (see 'Structure Energy Efficiency' chart at http://www.welserver.com/WEL0043 ).  That's 2.0 BTU/HDD/SF.

With your your structure at 4.4 BTU/HDD/SF, that's 2.2 times less efficient than an average house.

Best regards,

Bill

Bill,

You are comparing a house built in 1898 with a house built in the 1990's. I would expect the house built in the 1990's to have significantly lower heat losses than a house built in 1898.

I do not accept that 2.0 BTU/HDD/SF represents the heat loss for the average house in the U.S. There are some benchmark data for housing stock in the U.S. as of 1997 provided at homeenergy.org at one time, and these results are shown in the table below.

from http://www.homeenergy.org/show/article/nav/consumerinformation/page/2/id/825

Range of Energy Use..... Relative Frequency
Under 5.0 BTU/HDD/Sq.Ft. ..... 12.2 percent
Between 5.0 and 10.0 BTU/HDD/Sq.Ft. ..... 39.4 percent
Between 10.0 and 15.0 BTU/HDD/Sq.Ft. ..... 23.9 percent
Between 15.0 and 25.0 BTU/HDD/Sq.Ft. ..... 14.7 percent
Over 25.0 BTU/HDD/Sq.Ft. ..... 9.8 percent

13,500 BTU/HDD / 3100 SF = 4.4 BTU/HDD/SF (from above).

This (4.4) seems awfully high. As Dana asked, do you have much/any insulation?

We don't have much insulation except for third floor. We rushed into Geothermal because we needed a new boiler and we were remodeling the kitchen, so we did not do as much due diligence as if we could take our time and spend another winter with the old boiler heating the house.

I didn't think, anywhere in my wildest dreams, that heating with geo could possibly cost more than heating with a 40-50 y.o. boiler, even with a drafty house.

The height of the ceilings figures into the equation, too, right? We have 10 ft ceilings on the first floor, and a large staircase open to the second floor.

Given the information I've provided, do you think there's any value in testing the different components in line with a test meter to see if they are drawing electricity in accordance with factory specs? We had asked for the in Dec 2010 after our first scary Xcel bill (highest we'd ever had by over $100), but to my knowledge it was not done. Of course we'll have to get the blower motor installed first so that we can turn the system back on.....

Posted By Lee Dodge on 23 Mar 2013 12:52 PM
... There are some benchmark data for housing stock in the U.S. as of 1997 provided at homeenergy.org at one time, and these results are shown in the table below.

from http://www.homeenergy.org/show/article/nav/consumerinformation/page/2/id/825

Very helpful.  Thanks!  Bill

As someone who lives in and loves old houses, they are quirky when it comes to everything. A installer with a good pedigree for normal projects, does not even get them close to the " this old house caliber " trades people. IMHO your system was botched so badly from the start that your only option is to start over from zero gathering data on your homes real needs and wants. After collecting that data and compairing it to what you have the things that will need to be fixed will be obvious. At that point you can do a cost breakdown on what it will cost to fix it, or abandon it based on economics. Is your initial installer/designer feeling any culpability for your current dillema/issues? Personally I would want a pound of flesh from someone over this mess. My website has a story entitled " when bad things happen to good houses ". It is my personal story. The geo clinic portion will allso get you up to speed as to how to address your issues.
Hope this helps
Eric

As a side note, just because a house is old, it has no correlation to quality. IMOA some of te victorians were built by ships carpenters for wealthy sea capt.s others were built by carpenters, and some were built by drunk brothers in law. They are all victorian homes that were built turn of the century, yet very different.

I found this info from 2/2/2012 (I requested this info based on your sticky on this site)....I think these numbers are okay, right?

Carrier 50YDS (Hi-Velocity Split Unit): WATER IN Pressure: 40psi WATER OUT Pressure: 36psi Pressure Drop: 4psi WATER IN Temp: 37 degrees WATER OUT Temp: 30 degrees Temp Difference: 7 degrees

Carrier 50YEW (Hi-Temperature Unit): WATER IN Pressure: 32psi WATER OUT Pressure: 30psi Pressure Drop: 2psi WATER IN Temp: 39 degrees WATER OUT Temp: 32 degrees Temp Difference: 7 degrees

Posted By waterpirate on 23 Mar 2013 04:50 PM
...IMHO your system was botched so badly from the start that your only option is to start over from zero gathering data on your homes real needs and wants. After collecting that data and compairing it to what you have the things that will need to be fixed will be obvious. At that point you can do a cost breakdown on what it will cost to fix it, or abandon it based on economics. Is your initial installer/designer feeling any culpability for your current dillema/issues? ...
Eric

Thank you, Eric.

Our installer continues to say they will do "whatever it takes" to make us happy. This thread is an attempt to try to figure out what we should be asking for. What would make us happy is to not have to be in almost constant contact with them.

On Monday, we will get our replacement blower motor installed. My plan is to not turn the geo on until after Xcel issues another bill, so that I will have a full billing cycle of heating totally with gas to calculate the BTUs/hour. Hopefully then we can go over the numbers with someone neutral and figure out if the equipment configuration we currently have can be used more efficiently.

I'm unhappy with the Spacepak, which has had 2 repairs in the past year, both of which required a significant wait for the right part to be available. I'm also not sure we are buying ourselves anything with the W2W geo unit. When we asked for that unit to be installed, we thought that our first stage heat would be water, with the hi-velocity air as a back up. There was some serious miscommunication on this, and we ended up without a radiator in our new kitchen (except for a very small one under the sink that does not warm the room).

If we switch the order of the stages now, we will have to install a radiator in the kitchen. Not the end of the world, so that is maybe an option.

Another option is to upgrade the Spacepak to newer technology that is more efficient (the AirCell).

And, we will make other improvements to our house as suggested here to try to get to a happy place with our heating bills. The good news is that during the times when everything has been functioning, the house is comfortable; even a little on the warm side upstairs with the stat set a 69. And the basement is warmer than it previously was, though certainly not the same temp as the rest of the house.