Hello: Great forum, looks like there is a ton of knowledge here. As I mentioned in another post, I am thinking about installing a GHP in 4-5 years, but since there are alot of options I am curious what would be recommended for my situation. I have a 1600 sq ft bungalow (ranch) with a finished basement below, and a 850 sq ft attached garage. The house has average insulation (R20) and the basement walls have none. The garage is also insulated with R20. Both attics are R40. The house is currently heated with a 80,000 BTU high efficiency propane furnace (93%). It is a 20 year old Lennox Pulse and while it works fine it is loud and irritating. I have no A/C but wish I did for the few weeks of the summer that is actually hot up here (Northern Ontario). The garage has a commercial style hanging furnace that is 100,000 BTU but I seldom use it since I installed a small woodstove, as the furnace is very inefficient. The garage is only heated when I am working in it which is about 1 day a week in the winter. What I would like to have is some type of GHP that will heat and A/C my house, and also put heat into the attached garage. For the garage all I want to do is keep it from going below freezing, as currently it can go as low as 0F/-16C if the outside temps are -35F/-30C for a week or more. I am not interested in installing in floor heating in either the house or the garage, so for the house I would want to reuse/augment the existing ducts, and in the garage I expect I would have to install some type of water heated radiator similar to what is used with a boiler system. The other things I don't know are, should I attempt to size a system to heat my house down to -40F/C (which it gets here every winter for about 2 weeks) and get rid of my propane furnace, or should I design it to retain the furnace and use both as required. Any info is appreciated. I realize there are lots of details I am probably leaving out, but at this point I just want to know if my goals of heating the house and garage are achievable and realistic, and what my options are. Thanks Michael

I don't think installing a geothermal system in a garage is a good idea. Geo is a gradual heating system, the air the vent puts out is a luke warm air.  Although it runs very efficiently, it takes a long time to get up to temperature (without AUX heating to assist it).  It works most efficiency when maintaining the temperature in the heated space.  Although there's been some study's were a modest setback in the temperature can save energy, the setback are only a few degrees.

Basically to make things simple, your not going to be able to open the garage door, pull a car in, turn on the geothermal system and work on the car in any reasonable amount of time. It's going to take 8 hours at the very least, perhaps days to get the temperature up to comfortable levels when the heats been off for any length of time. (without AUX heat) Your far better off with a propane/oil/gas/electric heater for the garage.

   

Thanks for the reply. What I actually want to do is keep the garage at a constant 5C of 40F just to keep everything from freezing. I would still use the woodstove or propane furnace as required when working out there, and then when the garage is idle it could cool back down to the 5C/40F temperature.

The house would of course have to be maintained at 20C/70F for comfort.

Does this clarification change my options at all?

I am kinda surprised I haven't received more responses...are my goals unrealistic?

Thanks

Michael

a water to water and go hydro air inside , and modine heater in the garage ( maybe 2 they will be very derated )
http://www.google.com/products?sourceid=navclient&rlz=1T4TSHB_enUS288US288&q=modine+hydronic+unit+heater&um=1&ie=UTF-8&ei=lUYoS_O9FZS4lAfVi7WeDQ&sa=X&oi=product_result_group&ct=title&resnum=4&ved=0CCoQrQQwAw

Normally they are very helpful on this site, My guess would be because you misspelled several words in your topic header, they dismissed you question entirely.  I know I almost didn't bother to look at it.  

As for what you want to do, using extra heat from the geothermal system to heat the garage, I think it could be done.  But I see a few problems, with no return, the garage room pressure would build up, there by allowing less heat into the room as the ducts have to blow against higher room pressure.  I have a similar problem with one of my bedrooms in the house, the return is in the hallway, and if i shut the door for any length of time, the room becomes colder in the winter and hotter in the summer.  I believe this is cause by the lack of an air return.  If you were to install a return in the garage, the system would suck in very cold air, making the rest of the house colder as the air is pushed through the system, making the geothermal system work harder (and less efficiency).  I guess the solution would be have a way for the air in the garage to escape to the outside, but not too large of a draft as to allow too much cold air in.

Is the garage insulated?

Another problem I see is the entire system would have to be designed to account for the heat loss for the garage.  You would want enough heat flowing into the garage to keep it above freezing, but with no way to regulate the temperature, it would be tough to keep the garage any reasonable temperature when it gets too cold. The garage is at the mercy of when the house is calling for heat. (assuming one zone) I guess you could have a separate zone just for the garage, but that's really outside my expertise. Not that I have all that much to begin with.
   

I get lost and lose interest in posts consisting of one big paragraph.

Designing geo to meet 100% of load in a heavy heating climate is generally uneconomic. You could keep the propane for coldest days but an easier solution is likely to be geo plus electric strips.

Not a good idea (and against code) to integrate garage and house in same duct system.

Consider freeze protecting the garage with electric resistance - maybe via baseboard style electric heaters set for 5C. Keep the hanging furnace for the days when you work there

Tough crowd! LOL!! I actually had several paragraphs when I typed my original questions, and for some reason when I submitted the post it showed up as one big paragraph. I also realized I mispelled several words AFTER I submitted the post but couldn't figure out how to correct it. My bad. Seems the older I get the worse my 2 fingered typing gets....

Garage is insulated (R20 walls, R40 ceiling). I don't want to duct the forced air from the house into the garage, I want to use forced air in the house using the existing ducts, and some type of water heated radiator with a fan (like what would be used with a boiler) to keep the temps above freezing.

Thanks for the info so far.

Michael

Not anywhere close here to what you can receive on HVAC-Talk.

There are many professionals and very knowledgeable experts, here, who understand that you can get everything in life you want if you just help enough other people - the opposite credo of many on HVAC-Talk where knowledge is power.  This forum here is one of the finest placest to get geothermal related HVAC help.

Stick with all of the helpful people here - you'll learn a lot, and, get a good amount of help.  Especially if you answer promptly and to the point, when Joe asks questions (just don't get too excited about zoning).

Best regards,

Bill

So your thinking that a Geothermal system will function like a boiler where radiators with hot water running through them would heat the room? The systems are not compatible, Geo water doesn't get anywhere near hot enough to use a radiator, geo radiant heat runs under the entire floor to heat the room. I guess you could add piping to the existing garage floor and pour cement over it, making the garage floor higher, but it would be somewhat expensive to do.  

Have someone generate the numbers to see what airflow CFM it will take to  hold  the  temp you select for your garage using  ~78 F air.  You will quickly see  that the space  will  be  somewhere between drafty and a dust storm.  Not a practical solution for storage, certainly not to work in.

I base this on my own install, 3 geo loops: 1/2 of a 2200 sf ranch house is radiant, the other 1/2 uses an air handler (existing ducts) and attached 1000 sf garage which is radiant heated. A single GSHP makes  100 F water for all three. The air handler runs more often to heat the house to 71 F than either radiant loop. Garage is set  @ 64 F,  fine for working. It's ~ R-36 construction so adding a 1000w flood light will heat things up to 67 after about an hour in still air.
I'm in N GA where it's 40 F today.

You can heat your house with a GSHP and a new water coil air handler but not w/o  careful if not considerable upgrade of your existing duct system. If your climate will call for AC in the summer be SURE you buy an AH w/ Variable speed blower. I have a stepped blower and need more range between heat & AC. (Some of that is because Dampers close for heating the radiant space.)

If your garage floor can stand another 4" topping put in the hydronic, otherwise as others have said, put in a blast heater as the low air temps and air movement of any geo won't make you happy after the $$$$ outlay.

Dick

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So your thinking that a Geothermal system will function like a boiler where radiators with hot water running through them would heat the room? The systems are not compatible, Geo water doesn't get anywhere near hot enough to use a radiator, geo radiant heat runs under the entire floor to heat the room. I guess you could add piping to the existing garage floor and pour cement over it, making the garage floor higher, but it would be somewhat expensive to do.  

You can most certainly use a Modine style heater with a hydronic geo system. For that matter, radiators will work fine as well, they will just have far lower output than they will with higher temp water. I have steel panel radiators in several rooms. The output at 110F is about 30% of their listed rating, so you need to bear that in mind when sizing them.

In your case you might be even better off if you don't need to keep the space at 70F. You might get more like 50% of the rated output in that case.

Not a bad idea at all, just be sure to oversize as needed.