Hi, I'm a cold climate (Minneapolis/St Paul) resident in a 27 year old 4 level 3100 sq ft home with a 27 year old 60% (estimated efficiency) forced air gas furnace - 137k BTUh...  My total heating/cooling/lighting energy bill runs about $2500 annually and we use CFL bulbs and set back the thermostat to 63º at night or weekday periods when we're not home.  Occupied hours we bump it up to 68º and use an auxilary gas fireplace when it's really nippy out.

I had lived in the mild climate of Seattle/Tacoma (note how I like "dual" metropolitan areas?) and retrofitted an air source heat pump.  They do work well in temperate climates.

Thanks to our gov't kicking up the Federal Energy Tax Credit to $2k I decided against upgrading to higher efficiency fossil fuel heat plant and took a good hard look at ground source heat pumps.

I solicited bids from dealers marketing Econar, Geocomfort and Waterfurnace, compared technical features and contacted current customers of each.  I settled on the Waterfurnace - a 4 ton dual stage foced air unit with the desuperheater option using 4 vertical closed loops.  The equivalent units from competitors were similar but WF seemed to have a tad bit higher efficiency numbers and a solid warranty.  The customers I spoke with seemed pretty content with their investments.

The local dealer is one of WF's "gold" dealers.  I was told the Econars are backordered 6-8 weeks out but WF can get one in a week.  I just applied for the well drilling permits and that will be another 2 weeks.

Hopefully the system will be online by early December.

What range to you geo folks keep your thermostats set at?  Is it necessary to set back drastically as I do now or just set it and forget it?

All the vendors projected an annual heating/cooling/hot water cost of around $750.

My 2cents -

Thermostat set backs are more controversial with geothermal systems. One of the reasons is that you will no longer have 137K BTU of muscle anymore, so re-heating time will be significantly extended. Think 8 cyl Hummer replaced with a hybrid. Another reason is that your new system will probably have an electric resistance heater in the plenum as an extra 'stage' for those realllly cold periods. I live near Ottawa Canada, I know realllly cold. Anyway if the morning re-heat kicks in the electric resistance heater you've now spent significantly more energy than you saved with the setback. In summary many (most?) geo types recommend set it where you're comfortable & forget it.

RE set back thermostat, I agree, set and leave it. If you are used to cold sleeping temps, it would literally be cheaper to open the window.
I can't help wondering why you are the one pulling permits for the install, why is your contractor not responsible for this?
Joe

Existing total energy bill sounds pretty mild for the climate and size and age of home. Getting $2500 down to $750 sounds like a bit of a stretch.

You might still save a few dollars (not many) with judicious use of setbacks, but the above comments are good. What you must absolutely avoid is the situation where recovery from a setback includes using the electric resistance heat strips your system will likely include. Some thermostats purport to control this but it can be tricky. Best advice may be to set it and forget it.

I hope that both good load calculations were done and that the desuperheater will be piped to its own fairly large preheat tank.

Also, temperature control and ductwork in a 4 level home could be tricky - was a room by room load calculation done and compared with available flow from existing ducts? Is present system zoned and / or will the new system be zoned?

If your 4 ton WF unit is of the Envision series, then it's right in between the 3 and 5 ton units that I have - closed loop water-to-air 2-stage variable speed GSHPs.  And if you want to see performance information for these WF Envision units, it's available at http://welserver.com/WEL0043/ .

I have found an ideal tstat set back range is 4°.  But, I live in a warm climate (Dallas) where I don't even have an aux heater to worry about tripping on.  And I have an instrumentation system (above paragraph) that I used to determine how much is too much for set back.  A 4° set back, or for that matter any set back, for your climate, may not be cost effective, without first doing some experimenting to find ideal range.

Best regards,

Bill

Let me put it this way:  This is our 2nd home.  First residence was a 1600 sq ft 3Bdr rambler in western Washington state which was a new spec home and came with gawd-awful Cadet electric resistance heating units in each room - all on their own thermostats.  We never could keep the house comfortable and the heaters had a high failure rate.  That was when we opted for a central air exchange heat pump.  I was able to sell the remaining Cadet units to my neighbors who also had a miserable experience with them.

My current 3100 sq ft 4 level home is not zoned so the upstairs bedrooms are typically cold in the winter and warm in the summer months.  The finished basement is on a concrete slab.  We compensate by manually closing some of the registers on the lower floors.  With a horrendously oversized 137k BTUh fossil furnace, it doesn't run long enough to evenly distrubute the heat.  If I keep the fan blower on, then the manual humidifier pumps a bit too much moisture into the house.

I had a furnace dealer quote an 80% gas furnace with automatic humidity control and electronic air cleaner upgrade last year.  I gagged when the quote came in at $12k.  That included the replacement of the outdoor air coil for cooling though...

The WF dealer uses a pretty sophisticated software program which maps out heating/cooling load requirements for each temperature range we encounter here in MN (-30 to +97).  It is based on the whole house and not the individual rooms.  They show we'll engage the 2nd stage of the Envision ND049 unit at +25ºF and the resistance heat comes on at 0º.  The Twin Cities is in southern MN so we have only a few weeks each year at the most where we have to deal with sub-zero conditions.

The Econar dealer emphasized their "cold climate optimized" single stage Vara unit handles sub-zero temps with no added source.  That tells me they oversize their installs and I would lose overall efficiency.  He quoted a 4 ton unit as did everyone else.

As far as the permits, yes, the dealer submits that but asked if I could provide the legal property data for him.

Quoted price for the entire system will be about $22k and I will get the $2000 energy tax credit for 2008.  The state has a subsidized energy loan available after I have our energy supplier conduct an energy audit.  The state requires I adopt at least one of the audit findings for my project.  The loan is secured by my mortgage which makes the interest payments deductable.

We started doing aggressive setbacks with the old furnace since it's so inefficient.  I wouldn't have an issue keeping a geo unit set at a constant 68-70 setting.  For cooling, we'd probably opt at 78º or so.  As long as the humidity is kept in control, we find we really don't need any more than that.

I project the immediate benefit will be increased comfort followed by quieter operation and finally, energy savings and resale value.  Getting rid of a major fossil combustion risk inside the house also is a big factor.  And I just replaced all my smoke/CO detectors...

Maybe Mrs. Kravitz recommended he do his own permits like he told me to do.

I predict that your projection will be fully realized.  I am impressed with your understanding of the many nuances of a geothermal system.

You may find the operating cost savings so substantial such that you can rationalize setting the tstat at 69° or even 70° when running in heat mode.

This is what happened for me, in cooling mode (Dallas cooling-centric climate).  The geo operating cost savings were so substantial we decided we could affort setting our tstats to an occupied temp of 76°, increasing our summertime comfort, versus the 78° we used to use with conventional A/C.

Best regards,

Bill 

The question I have is why not ask to go up to the 5 ton 2 stage unit and eliminate the need for any resistance heat.  Unless your ductwork cant handle 5 tons 

First obvious reason is a 5 ton unit is larger and more expensive than a 4 ton unit.

Second reason is my current, oversized pre-1986 fossil furnace simply runs too briefly to maintain any degree of comfort or efficiency.  All three contractors sized a 4 ton unit for my home.  I'm likely to have less than 100 hours of sub-zero weather per year to justify a larger unit just to handle those 100 hours.  And, if it does get that cold for an extended time, we still have a gas insert fireplace to supplement any extra heat load.  I've also read with oversized GHP units used during the cooling season, humidity control becomes a problem.

I equate the above analysis to buying a car with a large V8 so I can safely accelerate up to speed while merging onto a freeway.  That acceleration, while nice to have, comes with a penalty of increased fuel comsumption, more pollution, higher insurance, larger tires to replace.  My driving habits don't really justify buying that added power to put to use in a very limited portion of my actual driving.

Our current vehicles are a 19914 cylinder compact pickup, a 1992 4 cylinder 4-door sedan and a 2007 hybrid 4-door sedan.  I don't need to be able to beat my neighbor in a 0-60mph drag race, but it is certainly nice to pass him up at the gas pump.  And, since the hybrid doesn't start up until I'm almost out of the driveway, I pump ZERO Carbon Monoxide emmissions into the garage - would then could infiltrate into my attached home.

I WANT to get off fossil fuels.  I WANT to decrease my greenhouse emmissions (although some independent analysis show residential Geo installs may actually increase overall emmissions).

I NEED to replace a 28 year old inefficient gas furnace.  I've done my homework and that tells me my $20k initial investment in Geo technology will net me a better overall return than other HVAC alternatives and give me better comfort, safety, resale value and economy starting instantly.  Do I care that my cash flow will be negative for the next 5-8 years?  Perhaps, but I need the benefits of geo NOW.  The cash flow situation will rectify itself many years after I've began to enjoy the instant benefits of the Geo retrofit.

What is the Manual J heating and cooling loads for the home that the contactor calculated?

Heating load = 51,000 BTUh
Cooling load = 30,000 BTUh

... if I understood what "J" loads are.

And all the bidders projected cost data based on an 80% gas furnace. My current unit is considerably older and less efficient that that.

Sounds like a small load for 3100sf. How much of that is basement (below grade).
Also stunned that 12K was price for fossil system.
J

Quite a bit of our basement comprises the 3100 overall square footage.  I'm guessing 1100 sq ft is below grade?  Highest heating/cooling loads are the upper level where the 3 bedrooms, a full and 3/4 bath are.  Figure standard sized rooms.  Around 700-800 sq footage upstairs?

 

Status update:

State and city health permits for four vertical closed-loop earth loops applied for.  Depth to be 150-180 feet.  Contractor says it takes about 2 weeks to get the permits approved.

I also scheduled an infrared energy audit for early December by our energy utility - Xcel (www.xcelenergy.com).  I intend to secure a low interest state energy loan for the project.  Funds require an energy audit and adopting at least one of the findings.