Posted By joe.ami on 18 Dec 2014 09:38 AM
Ok while the geo is a more efficient air conditioner, it likely conditioned more space. If you removed previous cooling kw's from your baseline electric use then that is a problem.

I'm having trouble reconciling your oil/kw use. 18,000 kws is around 62m btu right? So if your fuel oil burner was only 50% efficient thats still at least 67.5M. So that would be less btu's in a colder winter and free cooling. If your oil burner was 80% efficient and your fuel oil was worth 145,000 btu's then the numbers are really off (116M). Is my math right?

It's possible that not sucking air from your home for combustion has really brought the infiltration (thus the btus) down, but I'm having a difficult time making sense of the data before us.

Spray foam in the attic may be a very good idea.

joe.ami:  The fuel oil burner also took care of the hot water, so that would have accounted for some of the oil used. My guess is the oil burner was around 70%-80% efficient (I'm pretty sure I would have remembered seeing a number in the 60s). The Manual J calculations showed a 55k Btu/hr, 78.4MMBtu heating load, and 30.2MBtu cooling load, and 18.2MMBtu DHW load.

eric anderson: The electric usage (18,000kwh) includes heating, cooling, and hot water.

I'm thinking I will likely pay to have someone come out and take a thorough look at the system. I'm starting to think there may be a number of issues (efficiency and otherwise). For example, looking at the manual for the heat pump, I see it saying that some piping should be insulated that is not, some piping it says must be copper but doesn't appear to be, no P/T ports where they are shown in the diagrams, the loop was likely filled with tap water with a guestimate of antifreeze tossed in (they came back at one point to put more antifreeze in). Having a fresh pair of eyes look at the system seems like a good idea at this point.
                                 -Scott

Scott, If your loop is protected with Propylene Glyco,l Enertech Mfg. calls for a minimum 25% mix in order to prevent bacterial growth in the loop field. P/T ports are required at three points in the system. The Source side (Loop Field), the Load Side (Buffer Tank) and at the air handlers. The 5 ton Geo requires 15 GPM on BOTH the source and load side. Flow through the air handlers depends on entering water temp and temp diff. Without T/P ports there is no way of knowing if the flow rates are properly set, while using the least amount of pumping power.

Bergy

Sorry for the bad information, going a bit too fast with the calculator earlier today. Thanks Jon for catching my math error.
1 kwh= 3412 btus, 18000 kwh = 61 million btus of electrical energy input . Multiply that by a year round average cop of 3 gives you 183 Million btus (you can debate what the true cop is)
The calcs given to you indicate expected usage of 78.4+30+ 18 = 126 million btu’s so that is a big difference between calculated and actual.
As far as what is the true efficiency of an oil boiler- that depends on a lot of factors. The combustion efficiency is likely to be somewhere between 78 and 82%. But that does not take into account any standby losses, which depend on whether the unit was located in conditioned or unconditioned space. Usually if the boiler has to stay hot, just to provide hot water, the summertime efficiency is very low. The waste heat may or may not be going into the house, making the electrical usage for ac worse. If your max heat loss is55 kbtu’s, your previous boiler was likely at least 95 kbtu net so it was almost 2x oversized which also decreases efficiency.

On the other hand if heat and hot water with oil net use was 90 million btu’s, the calcs indicating you would use 78+ 18 mbtus for heat and hot water are in the right ballpark- 90 vs 96. In other words their manual J calcs matched previous oil usage reasonably well.
So the big question is why are you using 18000 kwh of electrical energy. That is too big a number to be accounted for by last years increased heating degree days.
Going after reducing shell heat loss might make sense, but your troubles seem to be hvac related, not shell.

Cheers,
Eric

The numbers initially quoted indicated 126 mbtu total yearly energy needed for heat, cooling and hot water, and that that would require 10,364 kwh of electricity .

10,364kwh*3412= 35mbtu of source electrical energy 126 mbtu /35 = 3.6 expected average COP for heating, cooling and hot water production

18000kwh*3412 =61 mbtu of actual source electrical energy 126 mbtu /61 = 2.1 actual COP for heating, cooling and hot water production.
 
The above average heating degree days  last year will skew this somewhat but this is still a huge difference and indicates a system problem of some kind.

rscott, did your "baseline" electric use included cooling in previous years.

"Your usage is above the estimate and above what 1000 gallons of oil suggests."

I'm thinking poor design, lack of efficient pump strategy, poor control strategy all are tanking this to about a 2 COP as Eric suggested. Then the numbers jive.....except if the predicted load came from manual J, then there should be a 20%ish fudge factor. This seems closer to dead on so I still have a lot of questions. Almost need to start design from ground up.

I'd still like to know if cooling was included in previous baseline usage.

Posted By joe.ami on 21 Dec 2014 09:07 AM
"Your usage is above the estimate and above what 1000 gallons of oil suggests."

I'm thinking poor design, lack of efficient pump strategy, poor control strategy all are tanking this to about a 2 COP as Eric suggested. Then the numbers jive.....except if the predicted load came from manual J, then there should be a 20%ish fudge factor. This seems closer to dead on so I still have a lot of questions. Almost need to start design from ground up.

I'd still like to know if cooling was included in previous baseline usage.

Hi,

The previous baseline electric usage does include cooling, although the cooling was fairly limited (a window AC in just one of the four bedrooms, and one window AC for the downstairs).

I'm starting to think that the installer (who just does geothermal) knows basic HVAC stuff reasonably well, but just has no clue about electric efficiency (making decisions based on cost, comfort, etc.). I think he would see the total annual kWh generated in the reports, see that geothermal was saving customers money, and figured that was all there was to worry about regarding efficiency.
                     -Scott

Ok. Not good. You would still be enjoying savings if your cost kwh wasn't so high. Your installer might be a good WTA guy but dabbling in WTW. Let's start with the basics in case he is not even that. Call your electric provider and see if they have an electric heating discount. Start dialing down your buffer tank temp and notice out side temp. Also try to notice down time on the heat pump. If you wanted to get a monitoring system this might be easier. over the next few weeks see if you can get a feel for what you need when and then you can manually replace outdoor reset for now.
Are your load side and line side pumps running all the time or only on demand?

The equipment startup form here should be useful.

Yes, COP between 2 and 2.4 is what I would have guessed. The system is inherently in efficiency due to the air handlers needs for hot water.

Outdoor resent will help, so would re-piping and using more efficient (and lesser) pumps. But to get rid of the air handlers for heating would be a tough effort..

I agree with better insulating and air sealing the attic air handler. That's probably a source of energy loss that you didn't have before.

joe.ami: I have been thinking of a monitoring system, which I think could help identify some issues. From what I have seen, the load/line side pumps are powered on whenever the compressor is powered on, and powered off whenver the compressor is powered off (based on the controller).

jonr: That startup form is very handy to have! And thinking about it, I believe the attic air handler doesn't have any insulation (aside from whatever it may have come with on the inside), whereas most of the the ductwork and pipes are insulated. So insulating and air sealing the air handler would likely provide a much better value than sealing the whole attic.

docjenser: The air handlers may make the system less efficient, but the estimated annual kWh was based on using air handlers. So if I were to switch to something more efficient than the air handlers, it would (in theory, of course!) end up using less kWh than originally estimated.

What operating cost model was used? I'm not aware of one that factors in hydronic air handlers.

Posted By joe.ami on 25 Dec 2014 08:44 AM
What operating cost model was used? I'm not aware of one that factors in hydronic air handlers.

The installer gave me a GeoAnalyst Geothermal System Report. In the fine print, it states that operating costs are based upon IGSHPA and ASHRAE algorithms, and that all calculations are based upon GeoComfort equipment. The report does not specify the air handlers, but does specify the GWT060, which is water-to-water.
                              -Scott

I don't believe that accounts for loss between the heat pump and the air handlers. What temp does it show the water at? Did your installer put antifreeze in the air handler side (load side) of the system?

Posted By joe.ami on 27 Dec 2014 07:05 AM
I don't believe that accounts for loss between the heat pump and the air handlers. What temp does it show the water at? Did your installer put antifreeze in the air handler side (load side) of the system?

It should account for loss between the heat pump and air handlers -- you can't come up with annual kWh usage without including everything in the system.

It shows a load temp (entering) of 85F (heating) and 45F (cooling).  It also shows a loop temp of 30F to 85F, with average heating loop temp of 47.6F and average cooling loop temp of 69.3F. Deep earth temp of 52F and annual temperature swing of 21F.

The installer put antifreeze in the loop side, but I'm not aware of him putting antifreeze in the air handler side (although he may have and just didn't mention it).
                               -Scott

You cannot feed air handlers efficiently with 85F entering, which means around 95F leaving. In reality, you need at least 115F feeding an air handler. That means your leaving load temp is at least 125F, yours being more likely around 130F. Which means that your heatpump is 35F higher on the load side. A good rule of thumb is 1.5% less efficiency per degree of higher temp so 35F degree higher temp also means over 50% lesser efficiency. Add the inefficient pumping to it, and you found your reason why your system is 75% less efficient as estimated.
47.6F on the loop side for average EWT is also unrealistic.

Your installer set unrealistic operating condition for the report, either on purpose to suggest higher savings to you (unfortunately a sales spiel), or he did not know better.

There are always 2 parts to the equation The first is to get your btu’s as cheaply and efficiently as possible (system efficiency). The second part is to need less btu’s in the first place (shell efficiency)

Ok so the geo guys have basically laid out why the system is not performing that efficiently. The second part of the puzzle is to insure the duct system and shell are as good as can reasonably be. At this point, my guess is that your geo system can be improved a bit, but is going to have some limitations. Docjenser and others have you covered on that.

When the system was installed, did they measure airflow in cfm for the air handler in the attic?. How about for the one in the basement? What about system duct leakage? Was it measured? That is critical to insure the system is performing correctly. Did they reuse old ductwork, or is it all new? Flex duct or rigid? Is it insulated? If it is flex duct, one quick sign is to look at where the flex duct connects to the boot. If they used Mastic (it looks like a white or grey hardened paste between the inner liner and the boot) it is probably sealed well.

After dark, turn all the lights in the house on. Go up in the attic and shut the hatch or door. Turn off all the attic lights and look for light shining through at the ceiling. If you see lots of light pinholes near the duct boots, (or elsewhere)you have some sealing to do.
 Next question, what is the air filter size and what type of filter are you using?

Last questions, How many SF is the house, and have you ever had a blower door test performed on the house? What is your current attic insulation level?

Cheers,
Eric Anderson

"It should account for loss between the heat pump and air handlers -- you can't come up with annual kWh usage without including everything in the system."
Design software is inexpensive or free and generic. I'm not aware of any that have a hydronic air handler selection.
As Doc said 85F is going to show the lowest op cost, but not be consistent with the requirements of your system. Your installer appears to be unevolved. Things have changed a great deal in our industry in the last few years. Hard to keep up without a lot of time invested......

Posted By Eric Anderson on 27 Dec 2014 10:29 PM
There are always 2 parts to the equation The first is to get your btu’s as cheaply and efficiently as possible (system efficiency). The second part is to need less btu’s in the first place (shell efficiency)

Ok so the geo guys have basically laid out why the system is not performing that efficiently. The second part of the puzzle is to insure the duct system and shell are as good as can reasonably be. At this point, my guess is that your geo system can be improved a bit, but is going to have some limitations. Docjenser and others have you covered on that.

When the system was installed, did they measure airflow in cfm for the air handler in the attic?. How about for the one in the basement? What about system duct leakage? Was it measured? That is critical to insure the system is performing correctly. Did they reuse old ductwork, or is it all new? Flex duct or rigid? Is it insulated? If it is flex duct, one quick sign is to look at where the flex duct connects to the boot. If they used Mastic (it looks like a white or grey hardened paste between the inner liner and the boot) it is probably sealed well.

After dark, turn all the lights in the house on. Go up in the attic and shut the hatch or door. Turn off all the attic lights and look for light shining through at the ceiling. If you see lots of light pinholes near the duct boots, (or elsewhere)you have some sealing to do.
 Next question, what is the air filter size and what type of filter are you using?

Last questions, How many SF is the house, and have you ever had a blower door test performed on the house? What is your current attic insulation level?

Cheers,
Eric Anderson

Thank you for your help. The ductwork is all new, and insulated (not sure of the R value offhand). It is rigid. A third party came to test the ductwork (e.g. sealing the returns), and said that it was sealed well.

I had air sealing done in the attic before the geothermal system was installed.

The air filters I am using are 20x20x1 (MERV 8). The house is 3,200SF. I did have a blower door test done (shortly before the air sealing). The attic has about 6"-8" of blown in insulation.
                             -Scott