mfreund
Veteran Member
I vote for oversize too. Ours is a 4 ton unit with drilled wells for the ground loop. Wish it was 5 ton.
geothermal questions and possible DIY
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I vote for oversize too. Ours is a 4 ton unit with drilled wells for the ground loop. Wish it was 5 ton.
Pixguy
Elite Member
I am starting to look into geothermal for my next home and trying to understand how it works and understanding the technology.
Another challenge is learning if the forced air is similar to traditional forced hot air systems that are cold and hot, cold and hot and drying out the mrs's eyes and contacts.
Good luck, I'll be watching this thread closely.
Another challenge is learning if the forced air is similar to traditional forced hot air systems that are cold and hot, cold and hot and drying out the mrs's eyes and contacts.
Good luck, I'll be watching this thread closely.
JimRB
Veteran Member
I do not have backup heat unit in my house. It has gotten down below zero F and the house has stayed warm. Fairly well insulated house, thermopane windows, 1,100 sf daylight basement, 1,100 sf 9 foot ceiling first floor and 600 sf two bedrooms on second floor. Not the most energy efficient home construction from a floor space and design perspective. 3 ton unit with slinky ground loops.
I have 17 years of electric bills on a spreadsheet. I do know that my neighbors pay a lot more to heat or cool their houses.
My power co-op did the manual J calculation, I think it was manual J, off the blueprints. I believe they calculated 2.5 tons. Seat of the pants and rule of thumb is not a good way to size a unit. If you have a house with plaster walls and no insulation in the cavities is going to figure out different from a house with fiberglass insulation, or one with cellulose insulation, or one with sprayed closed cell insulation.
When you compare apples to apples remember that there are inexpensive air to air and expensive air to air. I do not know if there are inexpensive geothermal units. Two of my neighbors replaced their air to air units when they were less than 10 years old. My geothermal is 17 years old and is chugging along. Yes I had to have the coil replaced as it started leaking but I gather all coils did that back when my unit was made. If you shared the specs, brand and model of the air to air and the geothermal then someone might be able to make a more educated guess. It may be that your contractor is just tossing out ballpark numbers to a tire kicker.
As mentioned in a few articles, a geothermal tech will have another day or two of training over a regular tech. An air to air may take a half day to set up. A geothermal may take a day.
If you do some research you will see horror stories of loops not deep enough and freezing, leaks, improperly sized. I have been rather satisfied with my unit and installer. My house is not humid in the summer. It does not have hot or cold spots. My electric bill is not outrageous.
Geothermal Heat Pump Costs: Pros and Cons | QualitySmith
Cost of a Geothermal Heating System: Geothermal Heat vs. HVAC
I have 17 years of electric bills on a spreadsheet. I do know that my neighbors pay a lot more to heat or cool their houses.
My power co-op did the manual J calculation, I think it was manual J, off the blueprints. I believe they calculated 2.5 tons. Seat of the pants and rule of thumb is not a good way to size a unit. If you have a house with plaster walls and no insulation in the cavities is going to figure out different from a house with fiberglass insulation, or one with cellulose insulation, or one with sprayed closed cell insulation.
When you compare apples to apples remember that there are inexpensive air to air and expensive air to air. I do not know if there are inexpensive geothermal units. Two of my neighbors replaced their air to air units when they were less than 10 years old. My geothermal is 17 years old and is chugging along. Yes I had to have the coil replaced as it started leaking but I gather all coils did that back when my unit was made. If you shared the specs, brand and model of the air to air and the geothermal then someone might be able to make a more educated guess. It may be that your contractor is just tossing out ballpark numbers to a tire kicker.
As mentioned in a few articles, a geothermal tech will have another day or two of training over a regular tech. An air to air may take a half day to set up. A geothermal may take a day.
If you do some research you will see horror stories of loops not deep enough and freezing, leaks, improperly sized. I have been rather satisfied with my unit and installer. My house is not humid in the summer. It does not have hot or cold spots. My electric bill is not outrageous.
Geothermal Heat Pump Costs: Pros and Cons | QualitySmith
Cost of a Geothermal Heating System: Geothermal Heat vs. HVAC
dodge man
Super Star Member
I just had geo installed. We already had duct work. Our cost was 20k installed. It also included a new hot water heater and a tank that preheats from the geo. A regular furnace depending on efficiency was 6 to 9k.
We will receive about 5k back in a tax rebate and $500 from the power company. We also get the power at 8 cents a kWh instead of 12. They calculated our pay back in three years on power savings. Even if they were just trying to make a sale, I figure the payback at 5 years or less. Our old system was LP which is pretty costly to heat with these days.
We have a 1900 sq ft house in west central Illinois. Our estimate for power including hot water will be about $1000 per year. Of that 300 is for hot water. The number that impresses me is the AC cost. $100 for the entire year.
How does it work? I think it heats more evenly as far as different room temps go. Less cold and hot spots. I think this is due to the fact it runs more but uses less power when running. It's also best not to change the temp by much. If you turn up the temp more than 1 ot 2 degrees the electric back up kicks in using more power.
They install took just three or four days. They directional bored the tubing in and shot it into our basement.
Hope the info helps.
We will receive about 5k back in a tax rebate and $500 from the power company. We also get the power at 8 cents a kWh instead of 12. They calculated our pay back in three years on power savings. Even if they were just trying to make a sale, I figure the payback at 5 years or less. Our old system was LP which is pretty costly to heat with these days.
We have a 1900 sq ft house in west central Illinois. Our estimate for power including hot water will be about $1000 per year. Of that 300 is for hot water. The number that impresses me is the AC cost. $100 for the entire year.
How does it work? I think it heats more evenly as far as different room temps go. Less cold and hot spots. I think this is due to the fact it runs more but uses less power when running. It's also best not to change the temp by much. If you turn up the temp more than 1 ot 2 degrees the electric back up kicks in using more power.
They install took just three or four days. They directional bored the tubing in and shot it into our basement.
Hope the info helps.
JimRB
Veteran Member
One problem with oversized units at least in the summer is dehumidification. My house is comfortable in the summer and winter without huge temperature swings when the unit is running or not. The delta T of the discharge air is enough to warm or cool the house but not enough to freeze or boil you if you happen to be close to a supply vent.
Country Geek
Gold Member
I've got another thread going on my geo install, no DIY on mine. In NC, there is a 35% state credit on top of the federal tax credit. Kinds of makes it a no-brainer, IMO. Of course judging from prices quoted here we pay more so some of the extra rebate is probably just going to the installers. I'm looking at about $31K for a 5 ton system with a propane furnace backup. The propane backup is likely not needed but I want to be able to heat my house with a generator during ice storms that take the power out. The ground loop subcontractor also said that he thought my ground loop was very overengineered.
OP
LD1
Epic Contributor
Same thing the contractors always try to push.
To size the unit for proper dehumidification, makes the unit too small to heat in the winter without back-up heat anytime the temps drop much below 30. Of course you probably dont see much of that in GA, and down there AC is probably more important than heat. Up here Heat is the primary goal.
As far as being too big to dehumidify....well right now the house has no AC at all. So a unit that is too big is still going to dehumidify the house more-so than it is right now.
mfreund
Veteran Member
Ours is too dry in the summer. You almost need to turn on the humidifer. Yes we needed to add a humidifer our installer said that it was not needed, but we do in the winter because of the back up heat.
Stimw
Elite Member
I have installed 2 in two different properties. They were both FHP Units. (Florida Heat Pump)
I used ground water (65*) discharged on lawn or drainage ditch as needed.
They are VERY efficient! I checked register temp with room at 70* and heated air coming out of vent was 20* warmer.
The last unit was a 3 ton and was rated at 23 amp and on a 30 amp breaker. Water pump was on a separate breaker, 8 amp 220 V.
Duct work isn't hard if you have sheet metal experience. Duct board isn't bad to work with either. Both are easier with the special tools.
I used ground water (65*) discharged on lawn or drainage ditch as needed.
They are VERY efficient! I checked register temp with room at 70* and heated air coming out of vent was 20* warmer.
The last unit was a 3 ton and was rated at 23 amp and on a 30 amp breaker. Water pump was on a separate breaker, 8 amp 220 V.
Duct work isn't hard if you have sheet metal experience. Duct board isn't bad to work with either. Both are easier with the special tools.
71bronco
Gold Member
Our installer said an oversized unit was as bad as an undersized one. I turn the breakers for the backup heat off so they can't turn on. Set the thermostat at 70 and it stays at 70 even with last winters -15 temps.
We had our pipes linebored with one extra run than usual for our size unit. This way there's hardly any mess, only a 12' ditch where the pipes go into a manifold and a small spot to go thru the basement wall. Our lines are actually under our septic system around 20' deep.
We really like ours and have had it around 3 yrs.
Jeff
We had our pipes linebored with one extra run than usual for our size unit. This way there's hardly any mess, only a 12' ditch where the pipes go into a manifold and a small spot to go thru the basement wall. Our lines are actually under our septic system around 20' deep.
We really like ours and have had it around 3 yrs.
Jeff