Re-thinking geothermal

[Chilly807]

I don't know what the building codes specify in the US, but in Canada all new housing MUST have an air exchange system, most have taken it one step further and use one that has heat recovery as well.

It does make quite a difference, the house is never stale smelling, and stays remarkably cool and fresh in summer.

Sean

 

[eepete]

I think solar won't generate enough heat during the winter months at our latitude, when you need it the most it works the worst. I.e. short daylight hours and frigid temperatures.

Sean

Well, you're absolutely right on the short daylight hours. I see a big difference in the KWH output in January vs. June.

As for the frigid temperatures, the PV panels actually are more efficient when they are cold. My 7.7KW array had a peak output of 9200 watts the other day. A cold front came through, it was about 60 degrees out and very windy (so the wind cooled the panels), we were near the Zenith, and the humidity was very low.
A typical voltage change is about .08 volts per degree C, another manufactures says it is -.38 percent per degree C. And the resistance of the interconnect wire goes down as it gets cold.

Today, temps were about 68 degrees but the humidity was way up and we had little wind, and the peak output was only 8000 watts.

Regarding too tight houses, we noticed more odors when we moved into our house. We probably need the exchange, oh good another project :laughing:. One thing we did that helped was put a UV light in a duct that feeds the master bedrooms. The bulbs had a catalyst of some sort on them that supposedly gets rid of lots of VOCs. The UV lights do that on their own too. The "cat box smell" went down since uric acid (C5H4N4O3) is a VOC. The little bits of black mold at the bottoms of some windows where condensation accumulates in the winter was greatly reduced, some windows it just went away. We're trying to decide if we want to add them to the main part of the house too. It's hard to find a good place to put them where the UV won't damage the ducts and HVAC equipment.

Pete

 

[grsthegreat]

i can see that most of you like your geothermal systems.......my experience here in north Idaho have been mixed.

It must be the way they install it here, cause all 3 people that have had it installed that i have had contact with arnt happy with the systems.

The reason i have been involved is im there wiring in an electric water heater or boiler to supplement their winter heat.

There FREEZING. Maybe our subsurface temps are too cold????

 

[Chilly807]

i can see that most of you like your geothermal systems.......my experience here in north Idaho have been mixed.

It must be the way they install it here, cause all 3 people that have had it installed that i have had contact with arnt happy with the systems.

The reason i have been involved is im there wiring in an electric water heater or boiler to supplement their winter heat.

There FREEZING. Maybe our subsurface temps are too cold????

Proper design is a must if it's going to work right, and retrofits aren't easy to make work in some cases.

For example, hot water baseboard heaters don't work well with geothermal, simply because the water doesn't get hot enough. My hottest water temp at -20 C outside temp is just under 100 F. That's not hot enough for baseboard heaters to keep the house warm. It is hot enough for infloor piping, though.

If you already have infloor piping for radiant heat, what is the spacing? Mine is every 6", not 12" as is common with higher temp systems. We discussed it with the installers at the time we built the house, they were undecided if 12" spacing was going to be enough, so erred on the side of caution and went with 6" throughout, with the garage floor being the exception. It has 12" spacing, and is harder to keep warm. Mind you, it also has a 7x10 steel garage door with an R value of around 12, so that's a source of heat loss to begin with.

In my personal opinion, geothermal is a much better option for new construction than retro-fit, the cost is more reasonable since you're comparing the complete package price instead of simply adding a different thermal source. It'll never compare well with an oil furnace for initial cost.

Our costs were about $5000 more than anything else that was even vaguely energy efficient, for the whole project.

If I had to guess, I'd say there was a miscalculation when those systems you mentioned were designed, either in the size of the system, or in the application of the heat generated. Possibly in the heat loss numbers for the house.

We had three estimates, one was for a 5 ton system, the one we went with was a 3 ton. The 3 ton does a good job, so the 5 would have been overkill.

This is relatively new to most installers, I expect the knowledge base will get better with time and experience.

Sean

 

[Redneck in training]

Ladia,
That's interesting, how far is the pond from the house and how deep are the lines from the pond?
Rob

The lines are about 6 to 7 ft deep and about 200 ft from the house. My observation is that there is no point to obsess about few degrees of temperature. The overall heat gain will not change that much with greater temperature rise.

 

[Redneck in training]

i can see that most of you like your geothermal systems.......my experience here in north Idaho have been mixed.

It must be the way they install it here, cause all 3 people that have had it installed that i have had contact with arnt happy with the systems.

The reason i have been involved is im there wiring in an electric water heater or boiler to supplement their winter heat.

There FREEZING. Maybe our subsurface temps are too cold????

The heat accumulatoir in my system is also the water heater. The heater elements are wired in parallel for about 9 kW. I consider it as back up when the HP goes bad. I turned the breaker off from day one and never turned it back on.

 

[Rob-D]

Well, you're absolutely right on the short daylight hours. I see a big difference in the KWH output in January vs. June.

As for the frigid temperatures, the PV panels actually are more efficient when they are cold. My 7.7KW array had a peak output of 9200 watts the other day. A cold front came through, it was about 60 degrees out and very windy (so the wind cooled the panels), we were near the Zenith, and the humidity was very low.
A typical voltage change is about .08 volts per degree C, another manufactures says it is -.38 percent per degree C. And the resistance of the interconnect wire goes down as it gets cold.

Today, temps were about 68 degrees but the humidity was way up and we had little wind, and the peak output was only 8000 watts.

Regarding too tight houses, we noticed more odors when we moved into our house. We probably need the exchange, oh good another project :laughing:. One thing we did that helped was put a UV light in a duct that feeds the master bedrooms. The bulbs had a catalyst of some sort on them that supposedly gets rid of lots of VOCs. The UV lights do that on their own too. The "cat box smell" went down since uric acid (C5H4N4O3) is a VOC. The little bits of black mold at the bottoms of some windows where condensation accumulates in the winter was greatly reduced, some windows it just went away. We're trying to decide if we want to add them to the main part of the house too. It's hard to find a good place to put them where the UV won't damage the ducts and HVAC equipment.

Pete

Pete,
I have UV for my water purification system. The bulb lasts a lot longer than the year they specify it for but I'm waiting for LEDs to be designed that run the right spectrum, so far, no good. We're using a Berkey system now after the water filters. If any of you are interested in a simple solution to pure water yuo should investigate these. They use them in disaster areas around the world. Low tek but super good, we're finicky about our water.
I like the idea about the bulbs in your system, I'm thinking you guys are right and an exchanger is something I should definitely investigate.

Rob

 

[Rob-D]

Proper design is a must if it's going to work right, and retrofits aren't easy to make work in some cases.

For example, hot water baseboard heaters don't work well with geothermal, simply because the water doesn't get hot enough. My hottest water temp at -20 C outside temp is just under 100 F. That's not hot enough for baseboard heaters to keep the house warm. It is hot enough for infloor piping, though.

If you already have infloor piping for radiant heat, what is the spacing? Mine is every 6", not 12" as is common with higher temp systems. We discussed it with the installers at the time we built the house, they were undecided if 12" spacing was going to be enough, so erred on the side of caution and went with 6" throughout, with the garage floor being the exception. It has 12" spacing, and is harder to keep warm. Mind you, it also has a 7x10 steel garage door with an R value of around 12, so that's a source of heat loss to begin with.

In my personal opinion, geothermal is a much better option for new construction than retro-fit, the cost is more reasonable since you're comparing the complete package price instead of simply adding a different thermal source. It'll never compare well with an oil furnace for initial cost.

Our costs were about $5000 more than anything else that was even vaguely energy efficient, for the whole project.

If I had to guess, I'd say there was a miscalculation when those systems you mentioned were designed, either in the size of the system, or in the application of the heat generated. Possibly in the heat loss numbers for the house.

We had three estimates, one was for a 5 ton system, the one we went with was a 3 ton. The 3 ton does a good job, so the 5 would have been overkill.

This is relatively new to most installers, I expect the knowledge base will get better with time and experience.

Sean

Sean,
My radiant is from Radiantec(?) in Vermont. The tubes are 6 x 200 foot loops on three zones. They are about 12" apart and use aluminum plates to disperse the heat. The trouble is that the floor is 1-1/2" thick and there is a slow rise in the evenings when the sun goes down. We expected this in the design so it's not a problem and compensated for.
I designed a temperature regulator that keeps things about 108F to compensate for the extra floor thickness.
It's a very efficient system and we can keep the room temp much lower with the floor being warm.
To keep the mean temp at 108f I'm concerned that the geo won't be able to reach the 115~120f top temp to maintain the system.

Rob

 

[Lt CHEG]

I like the idea of geothermal myself, especially if I don't go with modular construction of my new house. My big problem is that I have access to natural gas on my land and it is so darn cost effective that I think the pay back time of geothermal would be too long and I'd probably benefit more from investing the extra from geothermal into another energy saving measure. By the same token I will be renting an excavator for my uncle to use to construct the foundation for my house. So since I'll already have the excavator the extra cost for excavating for the geothermal loops would likely be minimal and that may really bring the cost down too, since my uncle ( a former full time GC) is helping us for free. Since I plan on running central air conditioning this may be a real money saver in that area. I'll be keeping my eye on this thread carefully as I live less than an hour north of the Catskills and my conditions are likely pretty similar to Rob's.

 

[Rob-D]

I like the idea of geothermal myself, especially if I don't go with modular construction of my new house. My big problem is that I have access to natural gas on my land and it is so darn cost effective that I think the pay back time of geothermal would be too long and I'd probably benefit more from investing the extra from geothermal into another energy saving measure. By the same token I will be renting an excavator for my uncle to use to construct the foundation for my house. So since I'll already have the excavator the extra cost for excavating for the geothermal loops would likely be minimal and that may really bring the cost down too, since my uncle ( a former full time GC) is helping us for free. Since I plan on running central air conditioning this may be a real money saver in that area. I'll be keeping my eye on this thread carefully as I live less than an hour north of the Catskills and my conditions are likely pretty similar to Rob's.

LT,
Hi neighbor!
If I had to do my house again I would do modular. I've seen some really nice designs and I've read that you can submit a plan and have it built for you. Everything is put together in a factory , all the beams are cut on jigs and then dropped on your foundation.
The most labor intensive part of geo is running the tubes and the tubes are relatively cheap compared to the compressor. You might want to think about running in the tubes and dead ending them in the house. You could run a dual system with the gas as a backup or the geo as backup. The initial expense would be higher but it might pay dividends down the line.

Personally I like the idea of having the oil burner intact and adding the geo. After 18 years the expense of the initial system is no an issue. The other thing i would consider is radiant floor heat. It's the best system I've ever lived under. No noise, warm floors, no radiators taking up room space, etc.
Just make sure if you build hardwood floors that you keep the top lay as thin as possible. I wouldn't do hardwood again. I bought "TrafficMaster" from Home Depot for my new office and this stuff is great! Water proof, looks like wood, goes down easily and is perfect over radiant. At ~1/8" thick it keeps your subfloor under an inch thick so your radiant response time is much quicker.

Good luck with the new house, I know the excitement of building a house.

Rob