Geothermal - Waterfurnace 5 review

[gitmo234]

On my second month of Geothermal install, wanted to post some details here. Facts up front:

cost of electricity: $0.1403 per KWH
House size: 2700 square foot, Rancher, vaulted ceilings, poorly insulated, poor ductwork system installed, lots of large open space, hard to heat. 1/2 of the house was an addition by the previous owner, that had about 8-10 runs flex duct, over 30 feet long, zip-tied together, hanging with lots of slack, frequent zip ties for choking, etc. Lots of duct work errors ( found a duct to nowhere, just venting into unconditioned space, looks like someone tried to close it by smashing the end of it shut).

Previous fuel:

Propane: 1 year on this crap. Paid $3.50 a gallon to fill a 1000 gallon tank. Went through that in 5 weeks. Paid out the nose that year for heat.

Pellet fuel: Switched to pellet furnace and pellet stoves (duct work was poor and the house is too long/high ceiling to be heated efficiently). Keeping the harmon pf-100 going and supplementing the super cold areas with two pellet stoves meant the house being warm (except the master bathroom, it was around 50 degrees with a space heater going), but the air was dry and we were burning through 4-8 bags in a 24 hour period. Had to have someone keep the heat running when we were away for the weekend, etc. I think we went through 8 tons of pellets last year during the shortage.

Finally I had enough one day and that night after having a bottle of wine with my wife I said "I think I want to get a quote on geothermal". That was that.

Cost breakdown:

drilling 3 x 150' vertical holes, and running the loop in the holes and in a trench to the basement: $10k
Waterfurnace 5 series, 2x water heater (desuper heater) system, hook up, humidifier, new thermostat: $13k

Ripping out half the houses duct work, adding additional ducts, resizing ducts to proper sizes for rooms, locating two returns that were covered up by previous owner, repairing old duct work in rest of the house, etc, itemized bill, labor by the hour. $22k

Total: $45k. All rooms except 3 had work done to them somehow. I know this is a premium but I actually followed up with what was done daily, had it explained how it was neccessary and did my homework. Bottom line my house was built in the 70's and had a HVAC system (not the propane furnace, but the duct) installed and was about half the size of what was needed. The propane furnace was receiving 1/2 of the return air it needed to function correcting and was double the size needed for the house, while the duct was half the size needed.

I paid a premium no doubt, but its done f@#$ right. It came with a 10 year performance guarantee. Most importantly, thats the cost to pay so my wife doesnt gripe all winter about pellets, pellet dust, how heavy bags are, etc.


Performance review:

Average winter electric bill running 2 pellet stoves and a furnace (and eveyrthing else) $330 (average pellet bill per month: $400-$600ish)

First geothermal bill: $568. Caveat to this: 3.5 days of this bill were running "emergency heat" on the furnace, which is basically a gigantic space heater with a blower.... incredibly expensive. I analyzed the day by day usage (my electric company lets me view usage by the hour), and these days cost me approximately $120.

At first I had a bit of sticker shock. Then I decided to break down the cost, and take a look at the system. I also did a day by day comparison of temperate compared to cost (PECO also monitors this). It's been exceptionally cold this past month, the day I did the cost comparison, the wind chill was -6, when the normal average temp is normally around 40 degrees. Its 18 degrees as I type this.

First, with the cost shock, what we're really seeing is propane water heat, and the cost of wood pellets rolled into one bill. It appears large, but its still a reduction in overall cost.

Second... we had recently taken in a foster dog and my wife started sleeping with the TV on all night...TV running all day to keep the dog calm, and one going all night... adds to the bill (this habit has been corrected).

Third. The auxiliary heat in the furnace was set to operate anytime the thermostat reads below 35 degrees. I did some testing and the geothermal alone keeps up and maintains a temperature just fine somewhere between 20 and 25 degrees. Below that it requires auxiliary heat. Geothermal itself puts off a more constant but lower temp heat from the vents. Auxiliary kicks it up a notch temporarily. When the thermostat was showing that outside the temperature was as low as 8 degrees (lowest I saw), the aux was running all the time with it. I reset the system to not turn on aux heat until 25 degrees.

Fourth... the thermostat was set to wake up time at 5am, temp is 70 until 8 am. Then it drops to 68. At 4 pm it goes to 70, and drops back to 68 at 10 pm. I reset this to 68 all the time except between 5pm and 10pm its at 70.

Next months bill will be lower, and I expect it to drop again after it when I dont have a few days of constant aux heat. However, with the savings, there is still some costs of pellets and that electricity that would still be rolled up into the electric bill raising it some.

When I did the math, despite the $560 electric bill, I'm actually still very much ahead for the month and to meet (not exceed) the savings predicted, I'm due for a handful of higher than average bills, that are still lower than when the costs were separated.

So far now, I will say that the house is evenly heated and the most comfortable it has ever been. I sleep better with humidity at 40% and I dont have to worry about carrying in pellets or a shortage.

I kept my two stoves as back up and sold the PF-100 for $2500.

So far, I think I'm getting what I asked for. Its efficient, especially when you factor in that the temp has been in single digits or below freezing virtually all month. If we were at average temps of 40, I'd be in smooth sailing. The peace of mind and freedom is probably the best part. It can be that cold outside and I'm still walking around in shorts inside my house and have no idea how cold it is outside without checking, and there's no maintenance to it.

 

[moey]

Im confused why you would have aux heat come on based on outside temp? It should come on based on the system not being able to maintain a setpoint. I think waterfurnace has other options for controlling the AUX heating. I would expect it to come on somewhere between 5F and 15F depending on the sizing of your system.

When you use setpoints you need to be careful to make sure AUX heat does not come on trying to recover. Otherwise your shooting yourself in the foot. We keep our house at 69 or 70 with our geo system. If I used setpoints below 20F it would never recover and eventually AUX heat would come on. Its debatable if setpoints even save you any money with a geothermal system. You have to extract more heat from the ground in a rapid fashion resulting in lower water temps coming in which degrades performance slightly.

Last month our geothermal portion of the electric bill was 2200KW about $330 thats for heat and hot water. We had about 1300 HDD days last month. This is for a 2700 sq/ft house.

Id look into how your AUX heat is setup and make sure your not having AUX heat come on using your setpoints.

 

[gitmo234]

I should correct my terminology - its AUX heat lockouts. I have a honeywell IAQ thermostat, and it has two fields in setup mode relating to aux heat, aux heat lockout and compressor lockout.

Aux heat lockout is the temp that regardless of circumstance, the aux heat cannot come on until the temp is below.
Compressor lockout is the temp at which point the geo stops and it focuses on all electric heat. (I set this to zero)
The temps in between is when both run as needed.

So I've set the aux lockout from 35 degrees to 25. When the temp was 30-35 degrees sometimes the aux heat was kicking on for a few minutes when it wasnt needed. Maybe I'm reading it wrong and the furnace was kicking it on to keep the cycle short.

Right now, during the day, Aux heat isnt coming on with my new lockout temps.

 

[gitmo234]

Oh wait a second...you mean temperature setpoints...as in I should pick a temp and leave it that way all the time... I get you now.

Yes, aux was kicking on to recover. Do you think its more efficient to maintain one temp all the time?

 

[laynes69]

Have you ever had an energy audit done on the home? It sounds like you have a decent heatload. I considered geothermal in the past, but I was told by many companies if the home isn't tight or insulated properly, you will still have high energy bills. I couldn't see spending $25,000 dollars or more to still have high energy costs.

 

[gitmo234]

The energy audit was what resulted in the extra $25k in work. The gentlemen spent 1.5 days here and identified a list of things to do. He just incorporated what he could into his work. There was some he couldnt do (windows, in ceiling lighting, etc), but no blower door test, be he did use heat gun and some infrared.

EDIT: Also.... without Geo I was have spent $250-$300 on electric plus about $400-$600 on wood pellets, so as far as high bills go, its cheaper than otherwise: $568 vs $650 (minimum)

 

[moey]

Oh wait a second...you mean temperature setpoints...as in I should pick a temp and leave it that way all the time... I get you now.

Yes, aux was kicking on to recover. Do you think its more efficient to maintain one temp all the time?

Yes it is definitely more efficient to maintain one temp all the time if the axillary heat is coming on trying to recover. Not just a little more efficient a lot.

 

[moey]

Ive never heard of the lockout scenario your describing it sounds like something for air source heat pump not a geothermal system. You may want to ask some questions on geoexchange.org about your thermostat maybe its normal. I dont know.

I have mine set to maintain to 1/2 degree if it can not maintain to 1/2 degree after 2 hours of trying electric auxiliary heat will come on to supplement.

 

[CRE10]

With geo you do not want to set back your tstat. Leave it and forget it. I would shut the breaker off to your strip heat unless you are out of town given that your loop field was designed properly. We design for 100% geo here.

 

[sloeffle]

Im confused why you would have aux heat come on based on outside temp? It should come on based on the system not being able to maintain a setpoint. I think waterfurnace has other options for controlling the AUX heating. I would expect it to come on somewhere between 5F and 15F depending on the sizing of your system.

My aux heat ( not hooked up ) is only called for when the setpoint of the thermostat and the temperature of the house has a 5 degree spread. It might come on after x amount of hours of straight run time, but I have not noticed it. We have an Aprilaire thermostat.

Our house is a 2200 sq ft ranch ( climate zone 5a ) and the only time I have seen my aux heat kick in is when temps are below 0. The 2nd stage of the geo can keep up pretty well until then. Our geo is 4 ton 5 Series Waterfurnace with approximately 2400' of pipe in the ground. What is the size of your unit ? At temps below 20F I generally run our woodburning furnace anyways because I hate the idea of making the electric company any richer than what they are.

I would highly recommend you get a blower door test done. You only pay to insulate your house once vs paying a higher bill every month for not insulating.

 

[jebatty]

I can see where ground source may work and be economical in some areas, but I doubt that it would make any sense in a cold MN climate.

 

[moey]

I can see where ground source may work and be economical in some areas, but I doubt that it would make any sense in a cold MN climate.

There are geothermal systems in Alaska. They are designed for about 30F inlet temp in the winter and about 90F in the summer. You would never see 90F in a cold climate. Plenty cold where I live we have had several days in -20F and the system works. I dont think its been above freezing temps in 3 or 4 weeks. Obviously it costs more in a cold climate then a moderate climate. You also need more pipe in the ground to maintain that 30F incoming water temp. There is plenty of heat in 30F water to heat your place its the magic of moving heat.

Our system only costs a couple thousand more dollars then if I had a new conventional system and A/C unit installed.

 

[CRE10]

There's a whole lot of gshp's in Canada too.

 

[Highbeam]

I can see where ground source may work and be economical in some areas, but I doubt that it would make any sense in a cold MN climate.

Oops. Gshp only makes sense in cold places.

 

[gitmo234]

Honestly I dont remember the tonnage, and I'm not sure what the "turn around time" is, or how long it takes to catch up.

I dropped the Aux cutoff to 5 degrees over the weekend and gave it an hour or so to move up a degree. The geo was running constantly during that time but there was no change in temperature.

Woke up this morning with the outside temp around 10 degrees and watched it a bit. Seemed like geo was running by itself for 4 out of 5 minutes. Aux would kick on, the fan would run harder, run for 30 second to a minute, then the blower would slow down it would be geo only for 4 or 5 minutes.

 

[jebatty]

Oops. Gshp only makes sense in cold places.

Chuckle...chuckle. A few GSHP people I've talked to have indicated that as the long winter drags on, and as the water returned to the ground loop gets colder along with the surrounding ground in the loop, they notice a significant increase in kwh usage by the system. Where I live, based on EPA data, shallow ground water may start out at about 40F, deeper ground water 45-50F.

Another question for a chuckle, maybe, but is it really possible to extract more than about 8F from 40F water before freezing occurs in the water? In the ground through which the water flows? Or more than about 15F from deeper water before freezing? Is this an issue with closed loop GSHP? How does that impact the economics of installing a GSHP system?

 

[gitmo234]

I'm waiting on a call back from my contractor to determine my balance point.

In broad terms, with temps in the single digits (wind chills below that), is it to be expected for the aux heat to kick on in conjunction with the compressor, for a minute or so every few minutes, when maintaining a temp?

 

[moey]

Chuckle...chuckle. A few GSHP people I've talked to have indicated that as the long winter drags on, and as the water returned to the ground loop gets colder along with the surrounding ground in the loop, they notice a significant increase in kwh usage by the system. Where I live, based on EPA data, shallow ground water may start out at about 40F, deeper ground water 45-50F.

Another question for a chuckle, maybe, but is it really possible to extract more than about 8F from 40F water before freezing occurs in the water? In the ground through which the water flows? Or more than about 15F from deeper water before freezing? Is this an issue with closed loop GSHP? How does that impact the economics of installing a GSHP system?

Closed loop systems will start out the year warmer and as winter goes on reach a steady state around 30F. Properly designed they will stay at roughly that temp. The units are rated at 30F for closed loop systems they expect the water to be that cold. They still deliver COPs of 3.5 to 4. Ive never seen that much of a difference on my monitoring statistics when the water gets colder. Its there but its not significant.

Closed loop systems are treated with antifreeze protection to about 15F. The system will lock out below that. It would only get that cold if the installer did not put enough pipe in the ground for your area.

 

[gitmo234]

I dug up the analysis, there are two fields (both of which demonstrate how bad our house is):

Heating load: 59,696 Btuh
Annual Heating Load: 90 million BTU


Long story short, set the auxiliary heat lockout to 15 degrees, and set the thermostat to hold 69 degrees constantly. We'll see how that works. Did some other research...57k BTU for a heat load would be the load (as a general rule) for a house with an additional 1000 square feet.

 

[CRE10]

Ask the installer for his Manual J calculations and what percentage he designed the geo to account for.

The loop temp will be coldest in March and warmest in say August. It's all about the loop sizing for efficiency. Water temp is a huge deal. Most people here freeze protect to 25. I have a super loop on mine so my water temps are basically unheard of for horizontal applications.

 

[sesmith]

I


Long story short, set the auxiliary heat lockout to 15 degrees, and set the thermostat to hold 69 degrees constantly. We'll see how that works. Did some other research...57k BTU for a heat load would be the load (as a general rule) for a house with an additional 1000 square feet.

You may want to consult with your installer to help with the tstat settings. Proper setup can make or break efficiency. On the lockouts, you say you have 2. The outside temp lockout, you figured out right. It locks out aux above whatever temp you have it set at. 20-25 degrees might be a reasonable #. The compressor lockout, I don't think you would use. I believe that would be for a system that uses another fuel (like a gas furnace) for backup. That would lock out the geo below a certain temp, if it couldn't keep up, and switch over to gas, I think, but not sure.

Your tstat probably has differential control...you set a droop temp that causes second stage operation, then another temp that sets aux. So you might set it up with a 70 degree set point, a 1 or 2 degree droop, so second stage doesn't come on unless the heat pump can't keep the temperature up with first stage. Then you set a temp setting even lower (maybe 2 or 3 degrees) so if the heat pump is in second stage, and can't keep up, aux will come on to help. The heat pump should continue to run in second stage when aux comes on (ie, not lock out the compressor). Aux just comes on to help...your heat is still coming mainly from the heat pump operation, and aux will cycle off as soon as it brings the room temp back up to the set point. One other setting that may be of interest may be called the anticipator, or sensitivity. A higher # usually would make the tstat less sensitive, a lower # more sensitive. If the tstat causes the system to shoot over the set point, adjust it to be less sensitive. If it under shoots, set it more sensitive. This setting can cause aux to run more if the system is constantly trying to overshoot.

If your tstat has a proportional control setup algorithm, it works a little differently as it uses run time as well as temperature to figure out when to stage and stay at the set point. That's the way ours is set up, but we are using a climatemaster tstat. There would be settings to hold off aux for a set time period (that you specify) when the system can't keep up. This holds aux off until it is really needed.

Hope some of this helps.

 

[Seasoned Oak]

45K for a $560 a month heat and hot water bill, wow. I spend about $850 annually for heat and hot water for 3000 SQ ft of poorly insulated 3 story house with a coal boiler. No one month is ever more than $170 for 25 million BTUs . For that much cash you should be able to super insulate and heat the place with a candle. Installers around here require that you upgrade the insulation levels dramatically before they install anything.

 

[moey]

I dug up the analysis, there are two fields (both of which demonstrate how bad our house is):

Heating load: 59,696 Btuh
Annual Heating Load: 90 million BTU


Long story short, set the auxiliary heat lockout to 15 degrees, and set the thermostat to hold 69 degrees constantly. We'll see how that works. Did some other research...57k BTU for a heat load would be the load (as a general rule) for a house with an additional 1000 square feet.

I would strongly suggest you control your AUX heat by setting a differential it will come on if the temp drops X degrees below a setpoint. Or if it can not maintain a temp for a certain period of time. The way your controlling its usage makes no sense. So what happens on a sunny day? A windy day? Your running your system like a air source heat pump. It sounds like your thermostat isnt even meant to be used on a geo system. Sorry to sound harsh..

 

[sesmith]

Chuckle...chuckle. A few GSHP people I've talked to have indicated that as the long winter drags on, and as the water returned to the ground loop gets colder along with the surrounding ground in the loop, they notice a significant increase in kwh usage by the system. Where I live, based on EPA data, shallow ground water may start out at about 40F, deeper ground water 45-50F.

Another question for a chuckle, maybe, but is it really possible to extract more than about 8F from 40F water before freezing occurs in the water? In the ground through which the water flows? Or more than about 15F from deeper water before freezing? Is this an issue with closed loop GSHP? How does that impact the economics of installing a GSHP system?

This is where good engineering and system design comes into play. Geo loops drive the ground temperature down in the winter and up in the summer. You have to have enough loop in the ground, and deep enough for the system you are using and the design load of the building. Some soils transfer heat better than others, so there's a consideration there, as is the amount of moisture in the soil. That said, you can use a geo system in Alaska if it's designed right. The higher the heat load of the building, or the longer and harder the heating season, the more money you will save in operating costs over other fuels.

During the heating season, incoming water temps might start out at close to 50 in the fall, and be down as low as 30 at the end of the winter. Geo systems can handle the low end without any issues or real drop of efficiency. Currently, my system is running about 35 degree incoming water temps. and heating our house, with very little aux use, with outside air temps hitting 5-10 below zero lately, and wind chills down to the -20 and -30 range. You just won't do that effectively with an air source heat pump.

 

[gitmo234]

The tstat is Honeywell Visionpro IAQ. As far as the Aux heat setting, that's the only real way to control it. When I took a better look at the paperwork, my balance point is 15 degrees. So the Aux heat should have been locked out at 15 degrees vs 35. I reset it to 35 now and its still keeping up okay. I've heard the furnace go through 2 of its stages here and there. The electricity monitor is also showing a dramatically lower draw.