Hi, I am new to here and have some questions, first I'll say what I currently have.

I built my house in 1979, all electric, Comm Edd  had good rates (suck today) for all electric at that time (Northern Illinois). I installed a 30 kw furnace with a 2.5 ton heatpump.
My electric bills weren't bad untill 4 years ago when I had the outdoor unit changed. I told the heating contractor that it was a 2.5 ton unit, he replaced it with a 2 ton unit.  I was MAD!!!!!!!
  My unit was set up with an outdoor thermostat that shut the heatpump off at 15 degree out door temp and resistent heat took over. Now with a 2 ton unit I can only get down to 25 degrees outdoor and have to shut the unit down. There are alot of days and nights that the temp is between 15 and 25 degrees and I can't run the heatpump, this has greatly increased my light bills in the coldest months.

What I am planning is to try Geo thermo, add a Horizontal field and change the air heat exchanger in the outdoor unit to water heatexchanger.

What I am looking for:  is there any free software for figuring closed loop lenghts, pipe sizes, pump size and pressure drops

If you convince one or more local contractors that you are serious about this rather than a mere tire-kicking looky-lou, they will handle design for you and incorporate best local practices.

Within my combat radius I charge between $150 and $600 for an energy audit of varying depth and complexity. That gives rise to reasonably accurate estimates of likely savings / payback for various options. I charge for it because doing them properly takes time and adds value. Willingness to pay for value separates the serious from the curious.

I occasionally take on a long range consulting arrangement wherein I remotely evaluate competing alternative proposals.

Do not confuse economic balance point with system balance point. Though a 2 ton air source heat pump (obviously) has less total capacity than a 2.5 ton unit, chances are that a newer system has a higher COP at any given outdoor temperature than the unit it replaced. If that is true (details are available within manufacturers extended specification tables for the model in service) then it makes sense to operate the heat pump at lower, rather than higher, outdoor temperatures than was the case for the prior unit. Since the replacement unit is of lower capacity than the former unit, it MAY (but not absolutely certainly) require greater use of auxiliary strip heat at a given outdoor temperature.

I'm curious about the marriage of 30 kW strip heat within a two ton air handler. That's far more kW than I think can be accomodated by the airflow of a 2T air handler. If the various stages of strip heat are improperly sequenced that could lead to more strip heat use than needed.

Finally, I suggest investigating what investments might reduce house heating load before spending on expensive alternative sources. In my area I typically find that applying spray foam insulation under the roof sheathing and verifiably airsealing the attic drops required tonnage by 1/3 or more. Foam isn't cheap, but it is less expensive than buying and operating extra HVAC tonnage.

Smaller unit does not automatically require higher outdoor lock-out.
Converting ASHP to GSHP is very doable, but not necessarily practical when you copare a package unit minus tax credit + higher efficiency.
You need more information + good advice.
A ManJ heat load for the house is step 1.
j

My air handler is a Bard 3 stage 30kw electric furnace with a 2.5 ton slant coil in it.

When the outdoor unit was changed the heating contractor was told it is a 2.5 ton unit.
After he installed the new unit and I got the bill and saw he installed a 2 ton unit. I went to him and asked why he installed a 2 ton, He went and looked at my old unit and said “OOPS I miss read the #s on your old unit, sorry about that”. Guess who will never be called to my house to do service again.


When I built my house both Comm Edd and Bard together did a heat load study and that is why a 30kw furnace and 2.5 ton heat pump was installed. The original 2.5 ton heat pump would heat the house down to 15 degrees without the help of resistance heat, except 10 kw of resistance would come in during defrost mode. Now at 20 degrees the heat pump never shuts off nor does the furnace blower and the first stage of resistance (10kw) cycles on and off to maintain temperature. I think losing 20% of heat pump capacity would be the answer for this.

Conventional heat pumps have a defrost cycle which is an energy loss and the blower fan running 100% of the time, I guess the best question is : at what point is it no longer efficient to leave the heat pump run continuous?

I looked at changing out my furnace to a 95% efficient propane furnace and installing my slant coil in it, but with the price fluctuation of propane ($1.80 to $2.60) and after doing the numbers the pay back was to long and price dependent.

Last winter my bill in January was for 29 days and used 4500kw. Most of the month was resistance heat due to the severe cold. To see how my house would compare with other fuels I made a spreadsheet and used 4000 of the 4500kw as heat load and figured using a 95% efficient propane or natural gas furnace. I figured GEO Thermo at 3x input energy 4x and 5x input energy. My house is a ranch 1560sq ft. I'm sure you will correct me if i'm wrong


4000kw = Natural Gas 140.3 therms cost $111
4000kw = propane 154 gal cost $2 gal = $308 cost $2.40 gal = $370
4000kw = electric $369
GEO Thermo 3x = 1334kw cost $138.50
GEO Thermo 4x = 1000kw cost $109.50
GEO Thermo 5x = 801kw cost $92.26

I live in the country and natural gas is not available

First thing would be to see if you could reduce the load by 20%. Lowering the load to make the 2 ton work might be the least expensive thing for you to do.
Average geo COPs will be 3.5 to 4 so it certainly would save, but if you can get 2 ton to do it for average (counting resistance heat) of 2.0 and save 5 figures on installation you would still be ahead for the first 50 years or so.
j

What joe.ami said. In a circa 1979 house there are usually many ways to lower the load by a half ton or more for short money compared to a GSHP conversion.

Code mins on insulation were pretty skimpy back in the day, and air sealing was all but unheard of. Start there first- air sealing is usually the lowest hanging fruit, with the most rapid payback. Fix all of the obvious air leaks, and get blower-door tested to find & fix the rest.

Is there a full basement? If yes, has the band joist & foundation sill been spray-foam sealed & insulated? That's typically the single largest un-treated less-obvious infiltration in most homes that haven't had a full round of air sealing. Insulating uninsulated foundation walls is usually a double-digit improvement on heating energy use while providing higher comfort levels. (But needs to be done right to avoid moisture issues.)

Pressure testing and rectifying duct leakage can also often get you into double-digit savings for short money as well.

Do you ever experience ice damming/icicles on the roof? That's a symptom of heat leakage, but sometimes takes some sleuthing to figure out the source.

Geo COPsof 4+ are pretty rare, when all pumping & air handler power is factored in. In your calculations don't count on hitting better than 3 unless you have a very diligent designer and optimal conditions. Surveys of existing geo systems in New England puts the average COP around 2.5 for total system power. Mind you this isn't all latest-greatest equipment. But while newer equipment is more efficient than older stuff and the average system designs may have improved, average new systems are definitely not 2x more efficient, (and probably 1.5x more, even if some are.) For sub-3-ton heat loads in my area (central MA) there's a trend toward ductless mini/multi-splits, since they hit near-geo seasonal efficiencies (~2.3-2.7 ) at lower risk & cost, but it's not the right solution everywhere. (Open floor plans, fewer rooms, and a tolarance for the visual aspects all factor in.)

Thank You joe and Dana for your imput

In 1979 I insulated the house for electric heat.
Walls are 2x4 , with glass bats, 1" Thermax foiled on both sides with seems taped,
Ceiling 8" bats with 12" on cellulose on top,    might blow some glass on top to raise R factor higher 
Windows are Anderson thermopane        have upgraded a couple , plan on doing a few more
have never had ice damming problem, snow sits up there forever, Winters are toooo damn long here

band joist & foundation sill have not been spray-foam sealed ,      will look into that

have a Fluke Thermal Imager at work, will have to bring it home and play with it
pressure testing the house is not hard to do, have had this done at work to control rooms to make insurance company happy for
fire suppression systems
spray foam insulation under the roof sheathing and airsealing the attic drops NOT IN THE PICTURE, to costly and can cause major problems when selling a house (I believe it is a code violation)

Posted By art1976 on 23 Aug 2011 07:12 PM
spray foam insulation under the roof sheathing and airsealing the attic drops NOT IN THE PICTURE, to costly and can cause major problems when selling a house (I believe it is a code violation)

Not sure about the code point, but if you want to see costly, try buying a geo system.

Foaming the underside of the roof deck isn't necessarily a code violation (even if it sometimes is)- meeting code on an unvented roof is all about the R- ratio of air-impermeable to air-permeable foam for the climate, and the vapor permeability of the foam layer. (With closed cell foam you can be fine even if the R-ratio doesn't meet code, but that's irrelevant in your case. See: http://www.buildingscience.com/documents/reports/rr-1001-moisture-safe-unvented-wood-roof-systems )

But since you have a foot of cellulose atop 8" of batts there's almost nothing to be gained there- you're already above R60. Forget about blowing more on top of that too- not anywhere near as cost effective as treating to the heat leaks in the basement. The fact that you have no ice damming is evidence of relatively good thermal-tightness of the roof.

Air-sealing the attic floor/upper floor ceiling from the conditioned space is definitely not a code violation, it's become a code REQUIREMENT. (Air-leaky recessed lighting fixtures in that location would be a code violation in some states- gasketed air-tight insulation-contact rated fixtures are now required.) If you have a bunch of them and they leak like crazy under blower-door conditions you may want to reassess the cost-effectiveness of replacing them, or at least sealing up as much of the leakage as you can from below with a fireproof caulk/tape, etc. Boxing over them is a standard (but laborious) retrofit method, but under 20" of insulation I can see why you might not want to bother. The 12" of cellulose is moderately air-retardent- it'll slow (but not stop) the flow.

The 2x4 walls with R13 batts + an inch of iso adds up to ~R16 for a whole-wall R (thermal bridging factored in), which is better than 2x6 framing w/R21 batts, provided the batts were installed with meticulous care, no gaps or compressions. Taped seams on the foil facers also improves the air-tightness, but a blower door test (with the IR imaging) is still worth it to nail down the all of the easy leaks and find any insulation gaps, thermal bypasses, etc.

But if your foundation and foundation sill/band joist aren't insulated that's a fairly significant heat leak in your climate. An inch of (unfaced) XPS glued to the wall with taped or mastic-sealed seams, then trapped in place with a 2x4 studwall w/ UNFACED R11 or R13 batts brings the whole-wall R of the foundation wall up to a healthy ~R15 (thermal bridging factored in) without introducing mold/rot potential. The XPS is over 1perm, and allows ground moisture to dry toward the interior rather than rising higher to rot the foundation sill and the R5/R13 R-ratio is sufficient to limit condensation to where it won't raise the humidity of the new studwall to rot or mold levels in winter, as long as you put a coat of standard latex paint on the interior of the wallboard. (Half inch min. gypsum is required as an ignition barrier for the rigid foam, and is a handy place to apply the ~2-perm paint as the semi-permeable interior vapor retarder.)

See case-4 in this paper:

http://www.buildingscience.com/documents/reports/rr-1003-building-america-high-r-foundations-case-study-analysis

Note, the hygric analysis was for a Minneapolis climate, which is several degrees colder than northern IL, so if it works there, it'll work even better for you. If you're uncomfortable with that, use only R11 batts, and go with 1.5" XPS or 2" of unfaced EPS. But truly, the R3 of the stud with R5 between it and the above-grade portion of the foundation wall means the cold edge of the stud will not be below the dew point of the interior air for extended periods and won't accumulate winter moisture, and at center cavity condensation on XPS does no damage and doesn't affect the thermal performance even during those hours where the interior surface of the XPS is below the dew point of the conditioned space air.

Put 1" of XPS between the bottom plate of the studwall and the slab too, as insulation and a capillary break. If you should ever finish out the basement and fully heat it there's an argument for adding 1" of XPS under a sub-floor when you do, but that's a much lower magnitude heat loss than what you're losing out the top half of the foundation wall and band joist.

After you seal & insulate the band joist & sill to the new rigid foam on the foundation wall with 2" of closed cell foam (R12-R13) and you're pretty much done. Given your high-R roof, moderate-R walls, and decent windows, it wouldn't surprise me if the uninsulated foundation & band joist accounts for more than 25% of your total heat load, even if you're not fulling heating it. (Retrofitting my own foundation peeled between 15-20% off the total, but I have a lower-R roof, lower R walls and crummier windows than you do.) It will almost certainly pull the heat load down to within the output of your 2-ton unit at +15F, and even if it's not a DIY it'll be far cheaper than a conversion to geo.