He had done quite a few and was highly recommended by WaterFurnace, who even called him "our fireman," meaning they brought him in when the situation needed a real expert. But he was definitely off on this one. I would like WaterFurnace to understand that a recommendation from company HQ carries a lot of weight with a consumer. We only chose this contractor because we thought that WaterFurnace was careful about its products and reputation. So far, WF has been no help at all. And as I said in my first post, the installer has retired or something and is nowhere to be found.

Another number I can share: at this point our EWT is 25.6 and LWT is 21.2. Those numbers seem low, but then again it has been frigid for a number of weeks and we're not setting the thermostat above 66 degrees.

Without wanting to offend others, most of these posts (other than joe.ami) are a waste of time.
Please see my original post as well.

SR

Yep, that's unfortunate.
Are there other WF dealers in your area?
Among the problems with this are we have little data about what your bill should be, and while the design is questionable to say the least, most waterfurnace dealers are not commonly rookies.

We need some thoughts from somebody standing in front of the system.

Look up the closest WF dealer to you and you might get some help there. WF can't help you if there is no local rep.

j

and we're not setting the thermostat above 66 degrees.

Why are you setting the thermostat low? Has the system frozen up or locked out in the past?

Posted By Princeton N.J. on 07 Feb 2011 08:40 AM
No we're in New Jersey! But I believe the discrepancy is that the designer counted inside closets, some of which are large (this place was built in the 70s -- houses and energy were cheap), and may have allowed for more sf because the house sits up off the ground on piers, for weird drainage reasons. So if the house is in total closer to 3000 sf and has an underside exposed --- would 8 tons still be way too much?

Closets are counted as part of your homes square footage - anything inside the insulated outer walls counts as square footage for calculating heating and cooling loads. 

So it appears that your home is actually ~3000 sq ft rather than 2200 sq ft as originally stated?

The fact that the home sits up off the ground on piers should not affect the square footage calculation.  Whether or not you have an exposed floor with or without insulation under the floor should be reflected in the Manual J calculated heating and cooling load, but this will not change the square footage number.

Posted By Princeton N.J. on 07 Feb 2011 08:31 AM
Is 8 tons possibly too much -- or too little?

8 tons looks about right given the heat load and water temperatures you posted.

Assuming (and that is a big assumption at this point) your calculated heating load of 75,917 Btuh is correct or close, the heating capacity of two (2) 4 ton WaterFurnace Envision units is pretty close to what you need given your cold water loop temperature.

1 ton = 12,000 Btuh.

75,917 Btuh / 12,000 Btuh / Ton = 6.32 tons.  But this doesn't tell the whole story.

I looked up the specs for a WaterFurnace Envision Series model 049 which has a nominal 4 ton (48,000 Btuh) rating.  However, with an Entering Water Temperature (EWT) of only 32 deg F at 12 GPM, the heating capacity of this unit drops down to only 37,400 Btuh.  Two of these units should be producing ~ 74,800 Btuh at ~32 deg F EWT.  The problem is that your water loop temperature is way below 32 deg F, most likely due to being insufficiently sized for your application.

Here is the WaterFurnace datasheet that I referenced:  http://www.waterfurnace.com/literature/envision/SC1000AN.pdf

Fact is that you are pulling way more heat out of the ground than 765 ft of vertical borehole support. Usually 765 of 1.25" pipe support 5-6 tons of load in rock. Your EWT is too low, indicating more of an 8 ton load. Obviously you pulled a lot of heat out of the ground.
Too many people are very focussed on manual J, they do not consider them to be off, your building being exposed from underneath can make all the difference.
So it appears that your heatloss is off, your building needs much more heat than anticipated, your 8 ton heatpump capacity seems fine, but your loop is on the edge, especially when your thermostat was only at 66F. Is your building insulated from underneath?

Posted By fsq4cw on 07 Feb 2011 09:53 AM
Without wanting to offend others, most of these posts (other than joe.ami) are a waste of time.
Please see my original post as well.

SR

Posted By fsq4cw on 05 Feb 2011 08:15 PM
It does sound like your system is over sized – WAY over sized and your ground loop WAY undersized for 8-tons! You should be able to comfortably get by with 1 4-ton HP and you probably would have PLENTY of ground loop (765ft) for 4-tons.

Was a Manual J load calculation done on your home?

Do you have anything in writing where WaterFurnace suggested this installer (whether they’re still in business or not), even an e-mail?

There is the possibility, as ‘Looby’ alluded to, that your system could be reconfigured by abandoning 1- 4-ton HP, redoing your duct work, maybe adding zoning, and using all the ground loop on the remaining 4-ton HP.

You may be able to recover most, if not all your costs by selling the surplus HP.

I don’t think you need more borehole.

Keep us posted & good luck!


SR

You have to be careful with comments like that, now it turns out that his load might be much larger than anticipated, at least the ground loop cannot keep up with it. In addition, going from (2) to (1) heatpump does not change the BTU load of the house and would not change his high electric bill. Oversizing heating capacity do not result in significantly higher electricity consumption, they would just cycle more and cost more to install upfront. The problem from the beginning here were high electricity bills. It might turn out that the house simple has an unusual high heating load, being exposed exposed from underneath. For sure the Loop temperatures, given its size, suggest that.

Posted By arkie6 on 07 Feb 2011 11:27 AM

Posted By Princeton N.J. on 07 Feb 2011 08:31 AM
Is 8 tons possibly too much -- or too little?

8 tons looks about right given the heat load and water temperatures you posted.

Assuming (and that is a big assumption at this point) your calculated heating load of 75,917 Btuh is correct or close, the heating capacity of two (2) 4 ton WaterFurnace Envision units is pretty close to what you need given your cold water loop temperature.

1 ton = 12,000 Btuh.

75,917 Btuh / 12,000 Btuh / Ton = 6.32 tons.  But this doesn't tell the whole story.

I looked up the specs for a WaterFurnace Envision Series model 049 which has a nominal 4 ton (48,000 Btuh) rating.  However, with an Entering Water Temperature (EWT) of only 32 deg F at 12 GPM, the heating capacity of this unit drops down to only 37,400 Btuh.  Two of these units should be producing ~ 74,800 Btuh at ~32 deg F EWT.  The problem is that your water loop temperature is way below 32 deg F, most likely due to being insufficiently sized for your application.

Here is the WaterFurnace datasheet that I referenced:  http://www.waterfurnace.com/literature/envision/SC1000AN.pdf

Geothermal heatpump sizing, especially with water to air units, is not done with 12,000 BTU/ton. We usually size for 97-98% of the total load, and supplement with resistance heat to temperature spikes. 76kbtu/h would call for a 5-6 ton system. Apparently, the manual J might be off here.

I freely admit that I am no expert with your situation. But there are experts here that may be able to offer suggestions to lessen the heat loss on your home (as well as obviously helping with your geothermal system.) Are there walls around the perimeter of the piers keeping the wind from blowing through below the house, or is it totally open? I have seen houses both ways.

Posted By Princeton N.J. on 07 Feb 2011 09:34 AM
He had done quite a few and was highly recommended by WaterFurnace, who even called him "our fireman," meaning they brought him in when the situation needed a real expert. But he was definitely off on this one. I would like WaterFurnace to understand that a recommendation from company HQ carries a lot of weight with a consumer. We only chose this contractor because we thought that WaterFurnace was careful about its products and reputation. So far, WF has been no help at all. And as I said in my first post, the installer has retired or something and is nowhere to be found.

There might not be too much wrong with your system, other than your house loosing too much heat, which is not the fault of the geosystem. Lets not judge prematurely before we know all the facts. You telling us what the loop temperatures are changed everything here.

Posted By docjenser on 07 Feb 2011 12:20 PM

Posted By arkie6 on 07 Feb 2011 11:27 AM

Posted By Princeton N.J. on 07 Feb 2011 08:31 AM
Is 8 tons possibly too much -- or too little?

8 tons looks about right given the heat load and water temperatures you posted.

Assuming (and that is a big assumption at this point) your calculated heating load of 75,917 Btuh is correct or close, the heating capacity of two (2) 4 ton WaterFurnace Envision units is pretty close to what you need given your cold water loop temperature.

1 ton = 12,000 Btuh.

75,917 Btuh / 12,000 Btuh / Ton = 6.32 tons.  But this doesn't tell the whole story.

I looked up the specs for a WaterFurnace Envision Series model 049 which has a nominal 4 ton (48,000 Btuh) rating.  However, with an Entering Water Temperature (EWT) of only 32 deg F at 12 GPM, the heating capacity of this unit drops down to only 37,400 Btuh.  Two of these units should be producing ~ 74,800 Btuh at ~32 deg F EWT.  The problem is that your water loop temperature is way below 32 deg F, most likely due to being insufficiently sized for your application.

Here is the WaterFurnace datasheet that I referenced:  http://www.waterfurnace.com/literature/envision/SC1000AN.pdf

Geothermal heatpump sizing, especially with water to air units, is not done with 12,000 BTU/ton. We usually size for 97-98% of the total load, and supplement with resistance heat to temperature spikes. 76kbtu/h would call for a 5-6 ton system. Apparently, the manual J might be off here.

If 12,000 Btuh/ton is not used for sizing water-to-air geothermal heatpumps, then what is used? 1 Ton = 12,000 Btuh is a recognized standard conversion.

97% of 75,917 Btuh = 73,639 Btuh.  That's still 6.14 tons. 

The problem I see in this situation is that a 4 ton nominal rated geothermal heat pump won't produce but ~ 3 tons of heating with 32 deg F loop water.  Even less capacity is produced when the water temperature is in the mid to low 20 deg F range.

Yes - 25 EWT in central Jersey is a smoking gun.

Forgive me if it has been asked / answered, but how old is this house? 8 tons for 2200 SF...did Washington sleep there enroute to Trenton? has the chinking fallen out from between the logs?

Seriously - I'd recommend taking a step back and concentrating a bit on the house - perhaps start with a blower door test.

...

Posted By arkie6 on 07 Feb 2011 02:00 PM

Posted By docjenser on 07 Feb 2011 12:20 PM

Posted By arkie6 on 07 Feb 2011 11:27 AM

Posted By Princeton N.J. on 07 Feb 2011 08:31 AM
Is 8 tons possibly too much -- or too little?

8 tons looks about right given the heat load and water temperatures you posted.

Assuming (and that is a big assumption at this point) your calculated heating load of 75,917 Btuh is correct or close, the heating capacity of two (2) 4 ton WaterFurnace Envision units is pretty close to what you need given your cold water loop temperature.

1 ton = 12,000 Btuh.

75,917 Btuh / 12,000 Btuh / Ton = 6.32 tons.  But this doesn't tell the whole story.

I looked up the specs for a WaterFurnace Envision Series model 049 which has a nominal 4 ton (48,000 Btuh) rating.  However, with an Entering Water Temperature (EWT) of only 32 deg F at 12 GPM, the heating capacity of this unit drops down to only 37,400 Btuh.  Two of these units should be producing ~ 74,800 Btuh at ~32 deg F EWT.  The problem is that your water loop temperature is way below 32 deg F, most likely due to being insufficiently sized for your application.

Here is the WaterFurnace datasheet that I referenced:  http://www.waterfurnace.com/literature/envision/SC1000AN.pdf

Geothermal heatpump sizing, especially with water to air units, is not done with 12,000 BTU/ton. We usually size for 97-98% of the total load, and supplement with resistance heat to temperature spikes. 76kbtu/h would call for a 5-6 ton system. Apparently, the manual J might be off here.

If 12,000 Btuh/ton is not used for sizing water-to-air geothermal heatpumps, then what is used? 1 Ton = 12,000 Btuh is a recognized standard conversion.

97% of 75,917 Btuh = 73,639 Btuh.  That's still 6.14 tons. 

The problem I see in this situation is that a 4 ton nominal rated geothermal heat pump won't produce but ~ 3 tons of heating with 32 deg F loop water.  Even less capacity is produced when the water temperature is in the mid to low 20 deg F range.

97% of your annual heat load! not your peak load at design temperature. It does not much economical sense to install a heating capacity all the way to design temperature (lets say 0 degrees) and have a large portion of the system run at idle the rest of the time. Thus you design the heatpump size down to lets say 15 degrees. Below 15 degrees, you use supplement electric heat to supplement the heatpump. The heatpump still makes most of the heat, so you only use a small portion of the heat from electric resistance. That way you might pay $30-50 per year for aux heat but it save you usually 2 tons in oversized equipment, a few thousand $ lesser upfront cost, the smaller equipment will actually run more efficient the rest of the year, usually saving you more than you pay for resistance. It will also not short-cycle as much, and most importantly, dehumidify the air much better in the summer time in heating dominated climate.

Doc,

I don't disagree with your sizing methodology. I was just confused by your statement "Geothermal heatpump sizing, especially with water to air units, is not done with 12,000 BTU/ton."

6 tons total or two (2) 3 ton units might make better economic sense in this situation ASSUMING the actual peak heat load is ~76,000 Btuh AND the water loop is properly designed for that 6 tons to maintain ~32F EWT, or at least not let it drop into the mid 20's. The WaterFurnace 3 Ton Envision Model 038 has a capacity rating of only 27,000 Btuh with 32F EWT. That's 54,000 Btuh total for two units or ~71% of peak load.

Another consideration in this situation is that the owner has the two stage Waterfurnace heatpumps which somewhat compensates for oversized units under light load and cooling situations.

Regarding vertical geothermal wells, typical in my area (mostly 5' to 50' of clay then sandstone or shale) is 150' to 200' of bore hole depth per ton of heating/cooling capacity. For the owner's existing 8 ton system, that would be 1200 to 1600 ft of borehole. Seems like he was probably shortchanged with only 765' of borehole. Assuming he only needed 6 tons capacity overall with electric heat strips making up the difference during design conditions, that's still 900' to 1200' of borehole.

The owner's calculated heat loss, even for 3000 sq ft, seems high to me, but I'm in the south and 4 to 5 tons of capacity would typically be sufficient for that size home down here. The best approach to this situation might be to get an independent home energy audit done to find out where all of the heat loss is going, then focus the $$$$ on fixing that. Then, if the two existing 4 ton units could operate mostly in 1st stage to maintain temperature (31,000 Btuh @ 32F EWT x 2 = 61,000 Btuh or ~5 tons), the existing 765' of borehole might be sufficient.

Posted By engineer on 07 Feb 2011 02:07 PM
Yes - 25 EWT in central Jersey is a smoking gun.

Forgive me if it has been asked / answered, but how old is this house? 8 tons for 2200 SF...did Washington sleep there enroute to Trenton? has the chinking fallen out from between the logs?

Seriously - I'd recommend taking a step back and concentrating a bit on the house - perhaps start with a blower door test.

Yeah, something isn't right here... either really bad heat transfer in the loop or the house is leaking alot of air.  Have you looked into tighten up the house some before installing the geo?   

I wish Washington had made a stop. Maybe the souvenir sales would pay for the heat. But two things: first, I was wrong about the sf. Looking at the manual j calcs I see that it's more like 3,000 sf. Second, the house was built in 1970 or so, when energy was cheap. It's up on piers (a joke the zoning commission played on the builder, something about "drainage") and has many glass windows and doors. We've had a full energy audit and found that yes, it is leaky. Although not as bad as you might think.

I'd like to find a way to raise the EWT without having to dig another well (which we couldn't do anyway bc of the price). Any hope of that? Thanks.

Thank you for all this info. Our heat loss is likely because our 70s-era ranch house is up on piers (a zoning demand when it was built bc of local drainage issues) and also bc like most 70s places, it has lots of windows, glass doors, high ceilings, and three skylights. We had a pro energy audit last year that suggested doing more insulation -- and maybe even insulating the bottom of the house.

Are you suggesting that perhaps with a "tighter" house, our loop could handle the load? It wouldn't help the EWT, would it?

Another thing I've read on this thread is that some people think the problem might be that we only keep our house at 66 degrees (because we don't want to waste energy and also it's just comfortable for us at that temp). Does the interior temp of the home affect the EWT and LWT?

Again, I appreciate your help.