Ona
Basic Member
Posts:189
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| 22 Jan 2009 09:33 AM |
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There have been several discussions regarding concern over run times as well as whether a system is undersized. I wanted to share my experience as a homeowner. Before my installation, my chosen installer went over the numbers with me. I live in a heat centric area (upstate NY).
My installer chose to undersize the system for heating and explained his logic to us and we bought it (still do). He also gave us the attached geolink report... it is a canned program from WaterFurnace. It helped us to understand how the unit would run based on the selected geo unit size (3 tons). Page 5 of the 7 pages on the attached document prepared me that when outside air temps got around freezing that my geo system would be running 100% of the time.
As you can see, the way our system is designed, we are using a fairly significant amount of aux (according to the attached doc). This is mostly because our installer typically undersizes, but also because we discussed future projects like insulating our attic space and the areas above the foundation in our basement as well as new garage door (which opens to the basement). So far we insulated the attic space and we are using less aux because of this.
At this point I am very happy with my installers guidance and the way in which my geo system operates and keeps my home consistently warm. The reason that I am attaching this document is to show what one contractor specified in a heat centric location and his customer is happy with it because she was well informed before installation. Furthermore, I know some people were a little nervous about 24/7 operation, and as far as I can tell, it is OK and works well in my application.
p.s. I did get my installers permission to post this.
if you go to the link below you can download the pdf file that I refer to above. It was too large to post in this email. Also, give it a minute, it may take a moment to load onto your computer.
http://www.geochoices.com/pre-installation_info.html |
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joe.ami
Veteran Member
Posts:4377
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| 22 Jan 2009 10:20 AM |
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Ona,
We've recently talked about use and expectation being some of the problems we're seeing. I can't look at what your installer provided but we try to get our % of heating around 95 and consider that right sized not undersized. A recent comparison I did for a home owner that's having trouble showed us that while a 4 ton might use the aux. coil to the tune of $150/yr and the 5 ton only $27, the operating cost difference between the 2 units was <$70/yr due to higer cost of running a 5 ton compressor. Installation cost difference however would be more than $2,000 (assumming adequate duct work) which was obviously not worth it.
So we commonly design in aux. (not emergency heat) and our systems would perform poorly without them (particullarly in recent cold snap).
That's why I had my melt down recently:)-
You've explained it much better than I.
Thanks for the feed back on your system.
J |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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conniepangan
Basic Member
Posts:112
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| 22 Jan 2009 10:28 AM |
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Hello Ona, thanks for your input. I know that we have similar condition to tonnage size and weather condition. It has been in the teens and 20's lately. It is good to know about the auxilliary heat being on all the time because the extreme cold weather we have here in northeast. I wonder if the auxilliary heat is on, does it help the heating pump produce the heat? or is it electric heat that stands on its own when the heat pump can't produce enough heat because of the cold weather?
I see the aux heat coming on every 5 to 10 minutes, then come off. I know I will be expecting a very high bill this coming February.
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joe.ami
Veteran Member
Posts:4377
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| 22 Jan 2009 10:36 AM |
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A typicl installation would have your auxiliary coil supplementing the heat pump out put. It could also run alone in the absence of heat pump operation (for whatever reason).
A system in MI currently would show brief aux operation during many cycles for short periods of time.
A new owner who has been logging his energy use found that even with second stage of aux. coil kicking in his extreme cold day operating cost was about $14. Sounds like a lot, but his fuel oil system would have cost $35.
J |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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conniepangan
Basic Member
Posts:112
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| 22 Jan 2009 10:41 AM |
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Joe, if the auxilliary comes on all the time during this extreme cold season and it comes on every now and then like in my case,how much KWH does it approximately consume? |
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joe.ami
Veteran Member
Posts:4377
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| 22 Jan 2009 10:48 AM |
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Some coils are multi stage, but the simple answer is a 10K coil usually uses 10kw. Find out the size (or model number of your coil) and you'll have your answer.
J |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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conniepangan
Basic Member
Posts:112
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| 22 Jan 2009 10:53 AM |
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Ok, I'll check that out. Joe, we have 2 thermostat, one located at Ground floor but heats up the small basement as well and that's the thermostat that I noticed the auxilliary heat come on. While 2nd Floor thermostat doesn't come on at all. We have single stage compressor on both which one is split package.
So 10 KWH is per day as an assumption?
thanks again. |
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cnygeo
Basic Member
Posts:170
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| 22 Jan 2009 10:54 AM |
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Wow, I'd consider that considerably undersized for our climate (I'm in the fingerlakes region) but the main point is that you were aware of the cost/benefit tradeoffs during the design and quoting process and were able to make an informed decision. In my opinion a report like this outlining projected costs is an absolute must-have. Since I've been internet-armchair engineering I've seen way too many cases where customers were shocked at the electric use of their new system, especially in heating-dominated climates. Much of the marketing for GHPs is focused on the middle part of the country where heating bills might only be a couple of hundred dollars a year. When someone in the Northeast with double the electric cost and 4 times the heating load spends $1k or more on heating it shouldn't be a surprise - compared to oil or propane it may be pretty good.
Posted By Ona on 01/22/2009 9:33 AM
There have been several discussions regarding concern over run times as well as whether a system is undersized. I wanted to share my experience as a homeowner. Before my installation, my chosen installer went over the numbers with me. I live in a heat centric area (upstate NY).
My installer chose to undersize the system for heating and explained his logic to us and we bought it (still do). He also gave us the attached geolink report... it is a canned program from WaterFurnace. It helped us to understand how the unit would run based on the selected geo unit size (3 tons). Page 5 of the 7 pages on the attached document prepared me that when outside air temps got around freezing that my geo system would be running 100% of the time.
As you can see, the way our system is designed, we are using a fairly significant amount of aux (according to the attached doc). This is mostly because our installer typically undersizes, but also because we discussed future projects like insulating our attic space and the areas above the foundation in our basement as well as new garage door (which opens to the basement). So far we insulated the attic space and we are using less aux because of this.
At this point I am very happy with my installers guidance and the way in which my geo system operates and keeps my home consistently warm. The reason that I am attaching this document is to show what one contractor specified in a heat centric location and his customer is happy with it because she was well informed before installation. Furthermore, I know some people were a little nervous about 24/7 operation, and as far as I can tell, it is OK and works well in my application.
p.s. I did get my installers permission to post this.
if you go to the link below you can download the pdf file that I refer to above. It was too large to post in this email. Also, give it a minute, it may take a moment to load onto your computer.
http://www.geochoices.com/pre-installation_info.html |
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joe.ami
Veteran Member
Posts:4377
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| 22 Jan 2009 11:01 AM |
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Exactly right. We are competeing against 2-5K annual heating bills, so $800-$1,200 might sound like a lot in Tennesee, but it's great around here.
I'm a big fan of my operating cost calculators for this very reason, it gives the user an expectation that helps avoid excitement when a high electric bill comes. It also can signal trouble if it is higher than expected.
J |
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Joe Hardin
www.amicontracting.com
We Dig Comfort!
www.doityourselfgeothermal.com
Dig Your Own Comfort! |
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Ona
Basic Member
Posts:189
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| 22 Jan 2009 11:04 AM |
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Conniepangan ~ I understand about the electric bill. Since I have submeters, I'm well aware that this next electric bill is going to be much higher. My total KWhs for my first month on geo was ~1550 (11/15 - 12/15), my second month was ~ 1100 (12/15 - 1/15) - this represents my whole house demand, not just geothermal. We'll see what my third month is... ugh! Attached you can see my electric usage and my aux electric use spiking up during this last cold patch. Again, it's a pdf, but much smaller than the last one I posted so it shouldn't take too long to open: http://www.geochoices.com/results.html |
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conniepangan
Basic Member
Posts:112
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| 22 Jan 2009 11:17 AM |
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I'm sure we have similar consumption. Our total consumption between Nov.-Dec. was 1600KWH (including other electric appliances) then Dec-Jan was 1500KWH after thermostat adjustment. I'm pretty sure, it spiked this month too. Ona, thank you so much on your input. |
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Jan 2009 01:18 PM |
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Posted By conniepangan on 01/22/2009 10:53 AM
So 10 KWH is per day as an assumption?
This is 10 KW per hour of run time on aux heat.. So if your aux heat runs for 2.5 hours in a day, then you have 2.5 KWH for the day.
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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conniepangan
Basic Member
Posts:112
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| 22 Jan 2009 02:02 PM |
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Thank you Dean! How do I calculate if the aux. heat comes on every 10 to 12 min. and it runs around 2 to 3 minutes at a time? Given a 24 hour/day on a very cold day?
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Ona
Basic Member
Posts:189
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| 22 Jan 2009 02:16 PM |
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Wouldn't a 10 KW strip running for 2.5 hours in one day mean that you used 25 KWhrs?
conniepangan ~ if we assume your aux runs 3 minutes out of every 15, then we can also assume that it runs 12 minutes an hour. So in a 24 hour period you run 12 minutes x 24 hours = 288 minutes per 24 hrs. 288 minutes divided by 60 minutes per hour gives you 4.8 hours of operation per day.
The way I see it, if you run a 10KW strip for 4.8 hours that gives you 48 KWhrs per day usage for aux (which is much lower that what I used during the cold snap). |
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conniepangan
Basic Member
Posts:112
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| 22 Jan 2009 02:24 PM |
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Ona, then that almost double up our usage per day? I was looking at our last electric bill, I was averaging almost 60KWH per day from Dec. to Jan. |
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Ona
Basic Member
Posts:189
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| 22 Jan 2009 02:30 PM |
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Maybe one of the professionals here can check my math before you take my word for it :o)
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heatoftheearth
Basic Member
Posts:113
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| 22 Jan 2009 04:01 PM |
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your #'s look right to me ona,geodean forgot to move a decimal point(i guess even the master can make a mistake) |
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Jan 2009 04:21 PM |
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Posted By Ona on 01/22/2009 2:16 PM
Wouldn't a 10 KW strip running for 2.5 hours in one day mean that you used 25 KWhrs?
Right you are !!! This what happens when you try typing and talking on the phone at the same time :)
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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Palace Geothermal
Veteran Member
Posts:1609
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| 22 Jan 2009 04:24 PM |
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Posted By conniepangan on 01/22/2009 2:02 PM
Thank you Dean! How do I calculate if the aux. heat comes on every 10 to 12 min. and it runs around 2 to 3 minutes at a time? Given a 24 hour/day on a very cold day?
As Ona said you can try and calculate. If you want to measure, one of these devices will do the job
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Dewayne Dean
<br>www.PalaceGeothermal.com<br>Why settle for 90% when you can have 400%<br>We heat and cool with dirt!<br>visit- http://welserver.com/WEL0114/- to see my system |
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cnygeo
Basic Member
Posts:170
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| 22 Jan 2009 04:33 PM |
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We can also try to predict the aux. use based on degree days and capacity. Connie, do you know at what temperature the heat pump is maxed out and the aux starts to come on? The geo unit should be running constantly at that point. |
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