We recently installed a 4 ton geo. unit in our MN home, and we're seeing water (about 8-16 oz./day) seeping out of the base of the unit and pooling on the floor. The installers have been out three times and indicated that this is just ice from the compressor melting and running off. They indicated that it's not hurting anything (there's no electrical components nearby), however I wonder if this indicates a problem with the compressor. The condensation problem seems worse when it's above 20 degrees outside. We're not seeing any significant savings in our heating cost, which also makes me wonder if the unit is functioning correctly. Any suggestions?

That doesn't sound right, though I doubt the problem is with the compressor.

Tell us more about the system:


Type (package or split)
environment it sits in - temp and humidity
before and after energy bills
entering and leaving water temps

8-16 oz is a LOT of water to attribute to condensation

The (package) unit resides in our basement, humidity = 39%, temp. = 62 degrees. Jan energy bill (before) = 36.2 kwh/day, (after) = 92.4 kwh/day. Avg. Jan. temp was 13 degrees in both years (before and after). Entering/leaving temps = 33/29. He pressure tested the unit, and indicated that it's not leaking or losing pressure.

Sounds like a lot of run time with frost/ice built up on loop and/or refrigerant lines inside unit.

I'm not a pro. In cooling mode, it is my understanding that coils can freeze up due to improper refrigerant charge or improper air flow possibly due to a dirty air filter or closed registers or dampers. It is possible that any of this can affect components when in heating mode?

Thanks for your thoughts.

The filter is clean, the registers are open. The tech did check the refrigerant charge, and he said it was okay. FYI, the difference in my heating bill with geo (2010) vs. w/o geo (2009) was $50 (the Jan bill was $360 in 2010 vs. $408 in 2009, same avg. outdoor temperature 2009/10; indoor temp. = 68 degrees in 2010 vs. 64-68 in 2009).

Actually, using data from the St. Paul airport, December 2009 was approximately 8% less degree days than December 2008, so it seems that you are correct when you said your average temps are the same as last year. Something appears to be wrong with your system, or maybe some settings are not correct, since your bills are, for all intensive purposes, the same. I would expect much more savings with geothermal.

You've been great at providing answers to questions. Here are some more.

When (month) was your loop installed?
What is the Manufacturer and Model of the unit?
What is the Make and Model of thermostat? Any zoning?
What type of loop do you have? Please include feet and pipe size.
Did you maintain 68 degrees for the entire month of December 2009? Did you use setbacks at any point during the month (if yes, how much and how often)?
Was your installer experienced with geothermal, and did you check references?
Have you experienced any system lockouts?
What was your old heating system?

I wonder if your auxiliary heat is coming on too much. I assume your auxiliary heat is enabled, (breakers on, etc.) and can turn on when "appropriate"?

The unit is a WATERFURNACE MODEL #NDV049A111CTL. The thermostat is a SimpleComfort Pro 5812, and the entire house is operating on a single zone. We have a closed loop system, with 4 200 foot wells. I'm not sure about the pipe size, but I would guess 1.5" diameter(?). We did maintain a temperature of 68 degrees for the entire month of December (no setbacks- the installer said setbacks are not recommended). The unit was installed in the first part of September, and our old furnace was powered by natural gas. I am not aware of any system lockouts (all lights on the unit indicate that it's functioning properly). The auxiliary heat did come on a few times in December (as indicated by the light on the thermostat), but only when the outdoor temperature was more than 10 degrees below zero, and the aux. power did not appear to stay on for any extended length of time. The geo. heat was actually a tiny bit more expensive in Nov. (than our previous natural gas furnace), however Nov. 2009 was slightly cooler than Nov. 2008. I did get one reference for the installer (not enough, I know), and they have been installing geo. systems in the area for many years. I should have been more diligent in checking their track record. I truly appreciate the feedback on this problem!

Maybe your electric bill is in line for your area. I hope not since you don't seem to be saving with geo compared to natural gas. What are your gas and electric rates? I hate to ask, but are you including electric and gas in the $408 heating cost for 2009?

The only other thing I can think of is a possible wiring issue where your aux is engaging at the same time as your compressor, and aux is not indicated on your thermostat. I believe I read about this happening to someone in another thread.

Checking the refrigerant charge is the LAST thing a Tech does. Did the Tech perform a heat of extraction/rejection on the unit? If not, your contractor is not well versed in geothermal service.

Bergy

Bergy, can you explain this.  I have heard of this, but don't know how it is performed and what it may indicate.  Thanks!

CFM, GPM, and airside + waterside delta Ts. Throw in amps and static pressure while you are at it and you have a fairly complete set of vitals. If your tech can't or won't perform these checks, find another.

Refrigerant gauges should stay in the truck unless specifically indicated, especially in the case of a package unit.

40% RH in basement suggests fairly low potential for condensation, so I remain skeptical. I suspect a slow water leak. If the system incorporates a desuperheater for domestic hot water, that's a whole set of additional leak points.

I have the same system you have which was installed for us last year.  First - I don't see any condensation problem from the compressor area as you are.  I "do" see a bit of frost/condensation on the brass elbow fitting where the returning loop solution connects to the cabinet.  That's to be expected and there is never more than a few grams of water below that fitting.

It's difficult to compare a direct cost saving over several years.  When we had our antiquated 60% efficient gas furnace, we kept our afternoon/evening thermostat down around 67º F and had the night/daytime setting down around 64º F.  We were always chilly.

Now that we have the ND049 system, we keep our afternoon/evening thermostat set at 70º F and only set back at night to 67º F.  The immediate benefit is we are much, much more comfortable in the winter.  My overall savings (without factoring in our KWh costs are higher this year than last) is running around 10% over last year.

The HUGE savings is realized in the summer.  We used to only run our AC when we were sweltering during the high temp/humidity periods we'd get several times each summer and the thermostat at 80 - and it'd take half the day to cool down the house to that level.  Now, we keep the unit on auto cool around 76º and I'm seeing an easy 25-30% savings.  I also have the desuperheater option.

I haven't had the techs out yet to perform the post-installation checkup but called them last week to schedule one.  The only issue I have right now is my pressure gauges on my loops.  The return gauge is now reading around 0.  The other day we had an outdoor temp of 22º F and our Honeywell 3000 Tstat said we were in emergency heat mode.

I didn't buy our system for merely a cost savings over the fossil fueled systems but wanted a modern, dependable solution where we could live in greater comfort, increased safety and remain environmentally responsible.  So far, we're meeting those goals and saving a bit on energy as well.

We certainly are more comfortable with the geo, but the lack of savings coupled with the moisture lead me to believe that something is wrong with some part of the unit. Maybe the two aren't related. When the tech. came, we did look at the coil. It has a layer of spray-on insulation, and there was a layer of ice on the insulation that was melting and dripping into the bottom of the unit. He was clearly surprised by the amount of water, but indicated that it was truly water (not refrigerant), and that this was not a leak. His manager had initially asked him to somehow better insulate the coil, and he scoffed at that notion, indicating that nothing he would be able to do would improve the insulation on the coil.

When I call them next, I will ask about FM, GPM, and airside + waterside delta Ts, amps and static pressure. If they aren't able to control the runoff, do you think it's reasonable to ask that they start replacing components of the system?

the issue would seem to me to be the water temp is way to low or the refrigerent temp and pressure where to low , also the slim possiblity there is an issue with the expansion device . Dont start replaceing parts untill you get a clear diagnosis
coming from NG the savings are going to much less then other fuel sources but with out kwh rates and and NG rates you cant even guess at if this indicates a problem or not. Water on the floor is another story

The heat of extraction/rejection is done via the P/T ports of the loop field. With the desuperheater shut OFF, the following information is needed...

Water temp IN
Water temp OUT
The difference is the "Delta T"

Loop pressure IN
Loop pressure OUT
The difference is the "Delta P"

In the unit's specification manual you can look up the pressure drop (Delta P) at the incoming water temperature and find the GPM flowing through the unit. The same page will show what the heat of rejection and heat of extraction should be.
The last bit of info needed is the brine factor... 500 for pure water and 485 for anti-freeze.

The formula is (Delta T X GPM X Brine factor) If the calculated Btu's are within +-10% of the book value, the unit is operating properly and NO guage set should be connected to the refrigerant system.

Bergy

Bergy, this is great. Thank you!

If the insulated coil is so cold that the insulation ices up then yes, I believe there is an issue with the system.

First thing to look at would be leaving water temperature. TXV (expansion device) can cope with some percentage of undercharge, but a substantial undercharge could cause both icing and poor performance, leading to both the icing and excessive, expensive use of aux strip heat.

If charge is low then amps should be low, and the heat transfer should be low. A heat balance calculation can be done and compared with mfg specs

Bergy, when you say "500 for pure water and 485 for anti-freeze." is the 485 figure used for anti-freeze regardless of the water/anti-freeze mix? Thanks

Bonnie - my theory from afar is that there may be an undercharge or other refrigerant side issue causing both the coax to get cold enough to condense water through insulation and thus the unit capacity to be really low, requiring heavy use of more expensive aux strips to keep you warm.

But that's just a theory, limited by the internet. A competent tech may find other details that blow my idea out of the water.