DIY Home Improvement Forum banner
1 - 20 of 33 Posts

· Registered
Joined
·
19 Posts
Discussion Starter · #1 ·
I know this is a question which may not be easy to answer....or if it can, more info is needed. But here it is:

I am new to this 8 year old home. It has the benefit of being heated by both a 'pump and dump' geothermal in floor heat system as well as a typical forced air propane furnace system. I have been heating the home primarily using the in floor geothermal system and using the propane furnace only as a backup in case the geothermal can't keep up. Currently, I am having a problem with one bedroom zone not heating properly. As I try to figure out why, it struck me that perhaps with propane prices being much lower now than a few years ago, perhaps I might be better off using that system as the primary heat source this year.

What do you think? Is there a way to figure out which is most economical to run?
 

· Registered
Joined
·
16,341 Posts
There is so much price gouging going on with propane and the cost so erratic we might have better luck putting tooth paste back in the tube than attempting to calculate a cost comparison. Example: wholesale propane is around $0.36 at present in some areas with retail being anywhere from $0.86 to $2.80 / gallon.
 

· Registered
Joined
·
19 Posts
Discussion Starter · #5 ·
you would have to post your fuel prices, heatpump model number, propane furnace efficiency rating.
fuel prices:
Propane prices in our area are: $1.19/gallon. Electric prices in the winter are: .0677/KWH

heatpump model number:
There are 2 heat pumps. One is Florida Heat Pump WW036-1USC and the other is Florida Heat Pump WW048-1USC.

propane furnace efficiency rating:
It is a York Affinity 9.S which I believe has a rating of 92%.
 

· Civil Engineer
Joined
·
5,832 Posts
You already have the systems installed from the sounds of it, so the comparison is much simpler than computing the life cycle cost of a new installation. You just need to calculate the cost per BTU for each system, and compare them.

For the propane, you need to know the net efficiency, which is the percentage of the heat content of the propane actually delivered to your house by the furnace. The figure of 92% is pretty high, you might get that with a condensing furnace, but typically you are only going to get perhaps 85% of the lower heat content of propane, which is 84,250 BTU/gallon (see http://www.afdc.energy.gov/fuels/fuel_comparison_chart.pdf). So you can calculate the cost per BTU based on the local price for propane, and if you use 85% efficiency for a non-condensing furnace, you would get about 71,600 BTU delivered to your house per gallon of propane, which you say is $1.19 per gallon, so your cost per BTU delivered to your house for propane is 1.19/71,600 = about 1.66 cents per thousand BTU.

The cost for the heat pump is harder to determine, since heat pumps move heat from one place to another, and their efficiency varies with outside air temperature. Best to check your historical records to see how much electricity you use to heat with the heat pump, then you can compute the cost per BTU delivered to the house based on electricity costs and the amount of electricity you need to operate the heat pumps. Your installer can probably help you to figure how many kwh you need per BTU, which will vary with outside temperature, unless you have a groundwater heat pump, in which case the cost per BTU is relatively fixed.
 

· Banned
Joined
·
14,538 Posts
unless you have a groundwater heat pump, in which case the cost per BTU is relatively fixed.
It's geothermal. That usually means it's ground water.

The geo is almost always cheaper. Of course that all depends how much electricity is in your area.... that should be checked.

It's nice to have back up heat in case of problems but with a proper geo system you shouldn't need it at all. I live in Manitoba where we get down to -40 f pretty regular in the Winter, and those with geo are doing just fine with no back up at all.

I would consider simplifying things and getting rid of the propane altogether and just going with an electric air handler. I doubt you'd be using it anyway if your geo is sized right and well maintained.
 

· Registered
Joined
·
19 Posts
Discussion Starter · #8 ·
Correct, it is groundwater heat pump. Up to now, they have been working great. As for switching to electric air handler for backup, that wouldn't be the route to go. Since I have propane for the backup, the electric company gives me a reduced rate of .0677. If I removed the propane, the rate would go to .0997.

And yes, we didn't incur the cost of the GSHP since it was in the house when we bought it. That was a big factor in choosing this house over another.
 

· In Loving Memory
Joined
·
42,671 Posts
If that's your rate then geo is definitely the way to go. It's going to be cheaper than propane.

Too bad you can't get rid of the propane..... it's just more maintenance which most likely won't be used enough to warrant it.
A little propane generator can run that furnace during a power outage.

It would take a 30 KW generator to run both of those heat pumps, fridge, some lights, and a TV during a power outage.

FHP OEM parts are cheap, and with the set up he has, not much in the way of less expensive after market parts available.

So keeping the furnace is a good idea.
 
  • Like
Reactions: supers05

· Registered
Joined
·
17,805 Posts
only a fool would run a heatpump on a generator, that would make zero sense. burn the fuel directly, the gensets are inefficient as hell. internal combustion engine is like what, 20%? 25?

Being able to heat without power is great, have a gas fireplace and the generator won't be needed.
 

· Banned
Joined
·
14,538 Posts
A little propane generator can run that furnace during a power outage.

It would take a 30 KW generator to run both of those heat pumps, fridge, some lights, and a TV during a power outage.

FHP OEM parts are cheap, and with the set up he has, not much in the way of less expensive after market parts available.

So keeping the furnace is a good idea.
Maybe it's different in the USA but in Canada you have to spend money on propane tank inspections.... You have to keep a full propane tank, fully operational CO detectors.... yadda yadda. It's not worth it if you're not using it. The ONLY advantage I see with propane heat in his circumstance is he's getting a break on the electrical rate. Now THAT is worth it.
 

· Registered
Joined
·
17,805 Posts
depends on if the geothermal system can carry the heating load on it's own without supplemental.

A 3 ton or lower machine won't do it in many houses. you do not want to resort to resistance backup heat.
 

· In Loving Memory
Joined
·
42,671 Posts
Maybe it's different in the USA but in Canada you have to spend money on propane tank inspections.... You have to keep a full propane tank, fully operational CO detectors.... yadda yadda. It's not worth it if you're not using it. The ONLY advantage I see with propane heat in his circumstance is he's getting a break on the electrical rate. Now THAT is worth it.

We don't have any of those requirements here.
 

· Banned
Joined
·
14,538 Posts
depends on if the geothermal system can carry the heating load on it's own without supplemental.
Never seen one that can't. What's the sense of going to all that extra expense of a geo system if you have to rely on a back up of some kind? May as well just do a plain jane air to air heat pump.

We have schools and other large buildings installing Geo here in Manitoba with no back up heat whatsoever. In fact I'm losing one of my contract buildings (a school) this next summer. They're ripping out the boilers in order to finalize a geo install. There will be no back up heat. With a properly sized geo system there simply is no need for it.
 

· Registered
Joined
·
15,740 Posts
Never seen one that can't. What's the sense of going to all that extra expense of a geo system if you have to rely on a back up of some kind? May as well just do a plain jane air to air heat pump.

We have schools and other large buildings installing Geo here in Manitoba with no back up heat whatsoever. In fact I'm losing one of my contract buildings (a school) this next summer. They're ripping out the boilers in order to finalize a geo install. There will be no back up heat. With a properly sized geo system there simply is no need for it.
Seen a resort freeze a small lake to the bottom last year.... They barely made it to spring. Talk about taking things right to the edge. Might not be so bad this year though. That was a loop at the bottom of the lake instead of the ground, but same principle. It is possible to have one very large ice cube. (all the more crushed ice for us i guess) But when properly sized, the coldest years still have plenty of capacity to spare and are relatively cheap to operate. (expensive to install)

Cheers!
 

· Banned
Joined
·
14,538 Posts
Seen a resort freeze a small lake to the bottom last year.... They barely made it to spring. Talk about taking things right to the edge. Might not be so bad this year though. That was a loop at the bottom of the lake instead of the ground, but same principle.

Cheers!
Not at all the same.
The idea of a "GROUND" loop is that the earth (beyond the frost layer) is constant heat source/sink which stays at pretty close to the same temp at all times. That concept can not be applied to a lake which is open to the atmosphere. It doesn't take a brain surgeon to figure out water happens to water if you make it cold enough.

At the end of the day I would call that setup a unthought through, 'poor man's hacked up geo install' as opposed to a properly sized/installed geo system.

I would also call it an environmental hazard..... I pity any fish who lives in that water!
 

· Registered
Joined
·
19 Posts
Discussion Starter · #20 ·
Glad ours is a 'pump and dump'. Have the beauty of constant temperature input with the well water and then it just dumps it back on the ground in the woods. We live out in the country on lakefront property and this type of system is still allowed. Quite a few of these systems in our area. Very few closed loop ones. I've read they are a bit more efficient than the closed loop too but I don't know that for sure.

I do know they are expensive to install but we lucked out with that as well since it was in the house when we bought it. This past spring the 4 ton unit gave out on us.....the compressor seized up. Lucked out there though since the system has a 10 year warranty and it only cost us the labor. He said the compressor unit itself cost about $2,000.
 
1 - 20 of 33 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top