Pond Boss Forums INTRO Questions & Observations Geothermal Heat Pump

Undersizing HVAC doesn't make long term sense for the consumer, but is common enough as some contractors (IME, YMMV) propose a system smaller than what should be used in order to submit a low bid.


I agree, but then that IS their business. All they can fix is their electric supply - not correct any sizing problems with the geothermal HVAC.

I agree with what you said Theo. However, the diagnosis was coming from the geothermal tech. MarkECIN said that the geo tech called the electric co. to arrange transformer upgrade that will handle the excessive draw caused by simultaneous heat source demand. I would think that a proper diagnosis would be to find out why the system is regularly demanding emergency heat (heat strips). The fix would be reducing or even eliminating that demand.

The math doesn't add up for purposely under sizing the geo unit allowing the emergency heat strips to take over in extremes. It takes four times the energy to run them. I guess that I could agree if the emergency heaters were activated only a few hours a season but I don't think that that is even close to MarkECIN's demand. The only other factor would be the additional cost of a properly sized system at the time of installation but I would be shocked if that cost is even close to what running heat strips on a regular basis year after year would be.

Once again, Brettski is right. Proper sizing goes way beyond sq. ft. of the house. Other things to consider but not limited to are house floor plan, multi-level, average outside temperature, average wind speed, insulation integrity, temp preference of the owner, shaded or full sun etc. etc. Unfortunately, many contractors don't take many of these factors into consideration when sizing and designing a system. It's the consumer who loses in the end.

One more thing my hubby was wondering about...the geo tech stated that the temperature coming into the unit was in the 20s whereas ground loops are much warmer coming in. The unit cannot build as much heat with 20 degree water. In essence this would make one think that ground loops are much more efficient contrary to all what I've read and heard that pond loops were. Thoughts? d

Ahhh. Now we are talking about potential root causes. First of all 20 degree water is frozen solid. If the fluid really is 20 coming in then I would question the length of the of the loop. Regardless, that has to be the major contributing factor to your issues. My non-expert understanding is that an open loop is more efficient than a pond loop and a pond loop is more efficient than a ground loop.

I'm starting to worry a bit about your geothermal tech. Like Blain said, the water is definitely not in the 20's. If you have a closed loop, it is on the bottom of the pond, so it is at least in the mid 30's or better. I disagree about the efficiency of an open vs closed loop though. In a closed loop you only have to circulate water, but in an open loop you have to lift water. Then there is the filtering problem.

I understand slightly undersizing the system. An undersized system is more efficient and costs less. That is up to the point where you cannot maintain comfort on all but the most extreme days. It sounds like you may be slightly undersized on cooling, but way undersized on heating. Why don't you unplug your heat strips (like I did) and see if the geo system can keep up on its own? Don't turn the thermostat down while you are away.

The company has done many ground loops and we're only their second pond loop, but they are a reputable company. However, I agree with you and believe there is some 'learning' happening here with the winter side of things (the unit was fine during the summer as far as I cold tell). Mark keeps throwing me questions to ask y'all. IMO the unit size etc and other than the problem with dimming we had, it is operating pretty close to correct. Like you said, without disconnecting the heat strips, I'm not convinced. I will dig up the literature on size etc; this may give you a better understanding of the unit itself (and that staging etc is SO over my head). Our house is well constructed with high R ratings in the walls and ceilings. It's been SO darn cold here this past month. I know it is 5 ton and we have 500' (5 loops) sunk in the pond for sure. I'll get back with more info.

It's possible the transformer was undersized. Need to measure amps and voltage drop to diagnose properly. The electric company would probaly do this before swapping the transformer.

Blaine has touched on this but I don't think it's been answered, do you leave the thermostat on one setpoint or is it programed?
Do you manually adjust the thermostat up and down based on activity or comfort level?

I have an air source heat pump that I installed a few years ago and had a very hard time convincing the wife to leave the settings alone.

They (HVAC Company) should have conducted a "Manual J" to determine the required heating and cooling load for your house. I bought some software and did this myself when I installed our system. It's a pretty good experience especially for an older home as you can change paramiters (like increased insulation) and see the effect imeadiatly.

Again, how could the electric company undersize a transformer for a house when the installed systems are designed to be more energy efficient than the norm. I doubt that they gather all of the energy efficient data for each house before they choose transformer capacity. If they did it wouldn't be an issue. MarkECIN, you don't have any out of the ordinary high energy draws outside of HVAC that would strain normal residential service do you?

TJ, Leave the thermostat in one set position. If you must adjust up or down, do so in no more than 2, maximum 3 degree increments. This will keep the heat strips or AC from kicking in for faster recovery.

Don't know Blaine, we built the house new 10 years ago, pond 3 years ago and put geo March08. We keep the thermostat at 72 constant. 2500 living area, two people, nothing connected to the house electrically that is out of the normal (washer/dryer/fridge, the like). Not unless the neighbor has a line coming to the house and stealing electricity (just kidding). Seriously, all the calculations for determining heating and cooling capacity were done beforehand; quite a lot of work (i believe this even had to be submitted back to the State for the geo rebate money)...I may have a copy of it.

Yesterday, when the tech spoke with the electric company, the electric company was out within an hour to put in the larger transformer. What I don't understand is why this wasn't part of the front end test to "force a failure" (i.e. dimming of lights) and the transformer issue would have been caught back in March.
You know that is bad on motors etc.

Fairly easy to undersize it I would think if the house had gas heat originally. Those heat strips are inductive so a fair bit of inrush comes with the package.

I know this may be comparing apples to coconuts, but I have a 5 ton WaterFurnace and over 5000 sq ft. The installer said the pond loops need to be 600' per ton, so I got 3000' of loop. If you really have 500' of pond loop, this may be your problem. You may want to make a call to your system manufacturer and see what they recommend.

My last furnace ran on natural gas, so the first thing I noticed about my geo system is that the air coming out of the registers is not nearly as warm, and the system runs a lot more. My installer told me to expect this from any heat-pump, not just a geo system. That's one reason why you want to leave the thermostat alone. I would still suggest that you disconnect your heat strips, set the thermostat, and see if this works for you. Of course, in single-digit weather, you may want to wait a few days to try this.

Jersey, I got the footage screwed up; your number more inline (cannot find the exact footage in my paperwork yet). But this picture gives you an idea how much was sunk. I have a Carrier GT-PX Geothermal Heating & Cooling System (Two-Stage Puron Series)/ AG Series Electric Heaters and ClimateMater Programmable Thermostat. I found all that other data (the analysis stuff, etc but that is SO out of my league). I think we are OK for now other than the heat strips. I may do as you say and call the manufacturer direct. Thanks. d

Inlet fluid temps in the 20s may point to inadequate insulation/burial depth of the lines from the pond to the house. How far is the pond?

30 ft most, pretty deep except for a small valley section by the house. In pic you see guy on left going downward, that would be the low area at the bottom of like the levee.

The temperature should be above 34F even in the winter. Return should be about 2 degrees less. Check the pressure in the loop. Pressure in my loop is about 60 psig in the winter and 80 psig in the summer. The pumps are designed for pressurized loop and if the pressure is low they might cavitate. Another possibility is that the loop wasn't properly purged of air. The guy who installed my loop brought different pump when they were filling the loop and explained to me that the circulation pump will not purge air out of the coils. I had small amount of air coming out of the loop for about six months after it was installed. I could hear the circulation pumps chatter every few minutes as the air bubble passed trough them. Therefore I decided to install air trap to bleed the air out. I replaced one of the elbows with a T and sweat in about 3ft of 1" vertical pipe with a small ball valve on the top. Then I kept venting the air until coolant came out. I repeated the process until the pumps got consistently quiet. I also used the new pipe for a pressure gauge installation.

Would you say the depth is below the frost line? Did you notice if they isulated the pipes?

I looked up the equipment you have and this is a very nice setup!
According to one source I found the heat pump is actually made by ClimateMaster. If that is correct, here's a link to the installation manual.
http://www.climatemaster.com/downloads/97B0045N01.pdf
And a programable heat pump thermostat
http://www.climatemaster.com/downloads/ATP32U03.04.pdf
If this is your t-stat you have a fair amount of control over the heat strips through this interface.

There are two possible modes (algorithims) for the control loop, "Proportional Integral" or "Differential". Proportional Integral is the default mode. The installer would have set this option.
If the control loop is very "tight" there will be very little deviation from the set point but the system may need to use third stage to keep it in the loop in the time alloted by the algorithim. This may be what you're seeing since your electricity use seems very resonable. I'm thinking the heat stips may be energized for a vey short amount of time to keep it in the loop.

You have a two speed compressor so low speed is stage one, high speed is stage two and high speed with the heat strips energized is stage three.

You can control the amount of time the system has to meet the heeting demand with the heat pump cycle through the "Smart Heat Staging" option. I would try increasing the time interval to see if the system can meet the demand with stage two of the heat pump cycle.

"SMART HEAT STAGING
This will control how the thermostat to engages 3rd stage or auxiliary heating when needed. Options are ON or OFF. Default is OFF. When the option is set to ON, the time range for this option is 5-120 minutes in 5 minute increments, if set to ON. 5 minutes is the default time. This is the minimum amount of time after temperature conditions for activating auxiliary heat are met, before the electric heat is engaged."

Hi everyone. Nice discussion! I'm in N. Central Indiana, about 30 miles SW of South Bend. I had a company last Fall come out and quote a Geo system for the house, and I'm not 100% confident in their service. It took them a bit over 2 months for them to come back with a quote, and I'm wondering who else in N. Central Indiana I could call. My biggest concern is the electrical rates and the actual payback time. I have Nipsco as a supplier, and just got a notice from them about an upcoming 16% jump in rates.

While the savings seem substantial over the Natural Gas heat/standard air conditioning syltem that I have now, I'm still not 100% convinced because they didn't ask to see my electric/natural gas usage, they used their standard formula.

1700 sq. ft. 100+ yr. old farmhouse, no basement (crawlspace), counterflow furnace (all ductwork is in crawlspace, and is not insulated). There is a 6 yr. old 90% effeciency furnace in the house now, and I installed a fireplace insert built by QuadraFire
this Fall. I just got the utility bills last week and it said:
Natural Gas:
1-21-2009 Average temp 21.6, # of days 34, Units used 97.7
vs. last year
1-22-2008 Average temp 29.8, # of days 33, Units used 195.2
$138 for the 1-21-2009 usage
Electric:
1-21-2009 572 kwh used, average daily usage 16.8
1-22-2008 767 kwh used, average daily usage 22.6
$86 for the 1-21-2009 usage

Looking back at last years electric usage during the summer, in July I used 1114 kwh, at a cost of $167 strictly for A/C.

I installed a Bosch whole house tankless hot water heater in the Spring of 2008, which replaced the 30 yr. old Rheem 40 gallon water heater.

I was quoted between $9500 and $12,800 for an open system using a Bosch FHP. This quote did NOT include the Well and the water drainage systems, humidfier, or hot water option. From the house to the pond is approx. 200 feet, and the soil sand down to 12'. My well is new as of Spring 2007, and with the current pump it pumps 28 gpm. The well driller said that with a by changing the well pump I could pump in excess of 100 gpm.

They estimated a payback in 4 to 5 years, but I don't see it.
So, I'm wondering if switching to Geo will be worth it.

Thoughts, comments??? Any suggestions on someone esle to contact for a quote? This quote was from Geothermal Specialist, Inc. in LaPorte, IN.

Thanks!

My 2c worth:

I would start with insulating the ductwork in the crawl space. This should be done whether you change to a geo system or not. You have a huge heat loss there.

Next, look into any tax rebates on installing a geo system.

Last, I question why you would use a well and the electricity to run a well pump when you have a pond.

Don't let anyone try to sell you a "passive" water heater for your geo system. They cost 5 times as much as a standard electric water heater, which will work just as well. You can just not wire it up, or wire it for emergencies and cut the breaker off.

I agree 100% about insulating the duct work in the crawlspace. I hesitated to do that this Fall because of the water supply pipes running in there as well. (old galvanized pipe) I bought the tools and most of the supplies to change all the supply plumbing to PEX, I just have to get 2 manifolds and the PEX tubing itself.

I really noticed the difference in heating the house when I ran the blower on the furnace to suck the hot air from the living/dining room that was accumulating there from the insert to circulate it thru the rest of the house. The Master bedroom is the furthest room away from the living room, and it's 20*F cooler than the living room without running the blower on the furnace. With the fan running, the temp only climbs 4*F, but the temp in the living/dining room will drop 10 to 12*F.

The floors are cold as well, and after I switch to PEX I want to get the bottom side of the floors covered with foam insulation. If the PEX pipes do freeze, at least they won't break. I'm planning the piping so that there won't be any fittings in the crawlspace, with the exception of where the well supply line transitions to PEX from beneath the ground. (the bladder tanks are in an old underground milk room that is insulated and heated). I'll make sure that I have heat tape on the copper pipe.

I upgraded the windows in the house 3 years ago, and before last Winter I blew 18" of cellulose insulation in the ceiling. This Summer/Fall I ripped two layers of siding off of the house and covered the outside with OSB, calking all of the seams. Old Man Winter caught me before I could get the Tyvek vapor barrier up.
Every wall cavity that I checked had fiberglass insulation in it, and I couldn't get hardly any more cellulose insulation in the walls. There was the origional shiplap siding, a layer of clapboard siding over that, a layer of fiberboard/asphalt granular siding with the exposed siding being aluminum. I ripped all the siding off down to the clapboard. When I replaced the roof 2 years ago I added a temp/humidity controlled power vent.

The duct work is the older galvanized tin. What insulation works better, the bubble/foil wrap or the fiberglass/plastic faced?

It is below the frost line and the pipe was insulated. Once we get out of these terribly cold weather I would like to maybe disconnect the strips or such.

The company that did the actual sinking in the pond to house are considered the best in Indianapolis area--highly reputable. Thanks for the links, I'll be sure to go see what the thermostat one says that is different from the papers that came with it. I think all of you are giving me a wealth of information (that I'm trying to absorb). We knew when we put this geo in that it is a complex system to learn about and understand (and we are trying to). The HVAC company is reputable, our unit was an updated model. I read some notes they put on receipts and there was a note about the 'stat maybe not staging properly'. Mark did not ask him about that when he was here this past week to check why the lights were dimming (the tech was to get a hold of ClimateMaster). Huummmn? I think I will do some checking at the links you noted and makes some calls.

WOULD I RECOMMEND GEOTHERMAL? - You bet! It's nice to be warm, not worry about what the thermostat is on, and not have those $1,000 LP bills coming at me. No regrets, worth the up front costs--payback 5 years--well worth it and an investment in our home. I do appreciate all the info sharing; great site--this Pond Boss for my geo and pond information.

The foil/bubble paper R-values aren't great when contacting what it's insulating. Fiberglass is likely better if you're just plannng to wrap the ductwork. Keep in mind that the vapor barrier belongs on the HEATED side. About 90% of the DIY crawlspace insulation jobs I've seen have been installed wrong.

I think I saw an Owens Corning pamphlet one time that said you lose like 40% of your heat through the floor.

Esshup: $160 for gas doesn't sound all that bad....I guess it depends on how much wood you're going to burn and the cost of wood. If you could save $100/mo on heating and cooling...that's still only $1200/yr and would take quite a while to recoup you're costs...possibly as long as the life of the system. Burning wood in addition to using gas is kinda a wild card that is hard to put a value on.

Blaine, I got my electric bill covering the coldest temperatures here in 30 years. It was $267.34 for 24 days. Honestly, I don't think that is bad at all, about $100 more than what I had last year (before geo). We're going to wait until next week and try to turn off the strips and see if we can see any difference.

Mark, I'm trying to follow the cost savings of Geothermal here, so your electric bill went up about $100 for 24 days, and you mentioned not having a large propane bill. Any idea how much money you are saving per month or is it too early to know yet?

Myself and I suspect Brettski are following this thread.

...with interest

Thanks for the update Markecin. My huge bill may have been caused by a faulty water sensor scheduled to be fixed Monday morning. I may never know but $480 for one month was more than double the amount that I expected. I will definitely be keeping my eye on it though.