Posted By Volleyball on 01 Jul 2010 06:18 PM
... I am thinking of insisting on lots of guages so I can monitor and record the different parameters. That way if something is off, I have some data to help expedite resolution.
Wonder if there are any electronic data recorders out there. I could build my own I guess

I'm another of the WEL (Web Energy Logger) systems available to look at.  Mine's at http://welserver.com/WEL0043/ , and illustrates a well performing 2 WaterFurnace unit system connected to a single closed loop with a vertical borehole field.

Best regards,

Bill

Posted By engineer on 04 Jul 2010 09:14 AM
If 3T meets 90% of calculated heating load, that is almost certainly the right way to go. 100% of load occurs only 1-2.5% of the time. Meeting 10% of your load with aux strips on only the few coldest nights is a trivial cost compared with the much higher installed cost and likely lower overall efficiency of an oversized system

If you look at the COP for 2 stage systems, you see a higher number for part load operation. It drops when the second stage kicks in. So I could see the argument. Don't know if it holds true or not. That is why I am asking.  If I spent an extra grand or so up front, but got better efficiencies would I come out ahead? For a single stage pump, the answer seems best go smaller. Being in  a predominant heat zone, it is a bigger concern.

As far as the trenches, if it doesn't freeze but the ground gets say upper 30's, would that not ruin your numbers?

Posted By Volleyball on 04 Jul 2010 07:36 PM


As far as the trenches, if it doesn't freeze but the ground gets say upper 30's, would that not ruin your numbers?

It all depends on the design and install.  I have seen trenches that don't drop below 42° F and I have seen vertical loops that drop below 20°F.

You are kidding yourself if you think that vertical is always better than horizontal.

Vertical heat exchangers of equal size perform better than horizontal once since the ground temp is much more stable further down, however you compensate with a lager heat exchange surface (e.g. more pipe) , so the overall performance is very similar. For example, in our part of the country (Western New York) we see that 300 ft of vertical pipe works as well as 600 ft of horizontal pipe, or 800 ft of horizontal slinky.
However 800 ft of slinky is the cheapest since you only need 100 ft of trench to dig.

The difference between a pipe buried at 8 ft and at 6 ft is 3.5 degrees F in the winter. Another example, you need about 50% more pipe if you go to 4 ft depth instead of 6 ft. So you loose performance almost exponentially. You can compensate for almost everything, but if it gets too large you might get into more head loss and increased pumping power.

The difference is more of a practical issue.

It take so much longer to dig the last 2 ft betwen 6 ft and 8 ft, plus as mentioned above, it becomes a safety issue.

It is faster and safer to stay at 6 ft and add 15% more pipe than you would do at 8 ft.

If you can't resist scratching the itch to oversize, oversize the loopfield, not the unit. A right-sized unit with an oversized loopfield will operate a bit more efficiently and have slightly more capacity.

I understand the attraction of oversizing the unit so as to stay in apparently-more-efficient part load / low stage mode more often, but know that published efficiencies are valid only for continuous operation, which happens in labs but not in homes. Every on and off cycle includes periods of inefficiency and low capacity, lasting for several minutes as the compressor works to build differential refrigerant pressures and heat exchangers reach steady-state operating temperatures. An oversized system will short-cycle more often, magnifying cycling losses. It will cost more up front, demand much larger ductwork, and likely operate more noisily.

I made a call to a manufacturer to see what they say as far as efficiencies. Waiting for their reply. I have no urge to oversize the unit. Only an urge to get the most bang for my buck. What truly gives me the lowest costs. And that includes installation. Maybe no aux heat unit or the cost of wiring it. For me it means a sub panel and expensive breakers.
I have the land but for lots of reasons, a trench is not reality. Both well drillers said that the eastern part of NY with it hilly terrain behaved differently than even 50 miles west where it levels out.
I am looking at more well as an oversize. I don't want to have to have the drilling truck back after restoring the damaged area from the first time. $500 up front would be cheap insurance.

Posted By Volleyball on 05 Jul 2010 09:40 AM
$500 up front would be cheap insurance.

Thank you.  I have made the point of slightly oversizing loop and unit elsewhere and used your insurance comparison as well.  There are advantages (recovery from set backs, handling outdoor temperature extremes, etc.), and disadvantages (including higher installation costs), and the homeowner needs to weigh them carefully and decide what is best for their situation.  Stick to your guns on this.  According to some installers posts, it is fine for installers to oversize slightly if in doubt or if the unit doesn't come in the exact tonnage that is needed for the load, but it is heracy for a homeowner with personal experience to suggest the same. 

As always, gets lots of quotes and check all references.  With our temperature extremes this past winter and so far this summer, no one will convince me that I shouldn't have oversized a little.

"heresy" , not "heracy"

If you must condemn installers, at least do so with proper spelling!

Thanks Curt. Not a condemnation at all. Just an observation of a double standard that has been presented occasionally regarding slight over-sizing. No offense was intended. :-)

I have met some great dealers. They make it tough to make a decision. I am not afraid of getting what I want. If I said put in a 2ton, they would object but would. But I cannot hold them responsible if there is a problem. But either way, it is my problem if something isn't working right. Only I will be too cold or too hot or paying too much. I live in a kinda custom home. Not that it the only one of its kind, just that there are none near me. That and what I have done to it makes it unique. I cannot ask neighbors with the same track home what they have, what they miss or what is over done.
From listening, asking questions, and calculating, I think a 3T would easily cover me 80% of the time. Can it cover me 90 or 95% of the time, maybe. Will running it full out 10 or 15% of the time make it costly to operate? MY truck doesn't have the biggest engine. It gets me around fine. When I tow/haul heavy loads the gas expense goes way up. Depending on how much I haul, there is a point where a bigger engine would be cheaper to operate. I drive enough with a small or no load that my decision was right. I am running as cheaply as I can.
Having most initial uncalculated experts say 4T and then with further inspection say 3 may be enough explains my current issue.
I mentioned before that I had repaired a trane XE? furnace for someone , It was about 40K btu and it took a day or so to bring the place up to temp but it does keep the place warm all but some extreme days and even then not too bad. Do I want a similar setup? Do I need to consider future needs? I have a full finish basement. It is storage and not likely to be living space but maybe part of it will. I also have a 3 season room going up and what if I enclose it? These are very unlikely, and even if I did, I could treat them separately but they do weigh in.
Back to the truck, for years I got by with my sedan and trailer. Much more efficient than those who commute with a big truck all the time and may need the bed a few days a year. As my car aged and my needs grew, the truck was the answer. I size accordingly.

Truck engine size scenario doesn't equate here. More accurately you could say I do most of my driving in 1st and second gear but some times the load requires even more Ummph. That third gear would be the auxiliary heater. With that mindset, the choice is clear.
Joe

Actually a vehicle would be more efficient in the inverse, 3rd would be more efficient over 1st or 2nd.
I thought engine size,(tonnage or btu) would directly equate. Beat gas mileage for the driving you do most. A turbo 4 can put out the power of a v6 and if you rarely use the turbo, you'll get better mileage. Kick in the turbo too many times and not only will you pay in fuel cost, it won't last as long.
Are all heat pumps designed for cooling primarily?

Posted By Volleyball on 02 Jul 2010 03:26 PM
I would think once you disturbed the ground the values would not be very useful. From what I've been told, even though the frostline is 42", the ground temp does drop significantly. Could be because the snow does not remain to insulate. So 8' deep horizontal loops perform poorly in winter. And how would you insert in in frozen ground? leave in since fall? If you drilled down, you would not get good contact .

I intended to address this as well.
DJ and Dewayne have both commented, but I'd like to add some real world numbers. In mid MI where heating is dominate and a .075 kw charge going rate for electric with one utility, we design at Climatemaster's default of 30* for the minimum loop temperature.
Volleyball, somehow you have become convinced that even in the high 30's efficiency suffers and vertical is the solution.
Check this:
In a 5 ton I was designing today....
at 30* EWT design minimum:
Horizontal loops at 6' deep are .02 less on average annual COP and $2 more expensive to operate/ heating year.
Raising your minimum EWT to 35* requires 40% more pipe and bore for vertical and more than double the pipe for horizontal. Your largest savings for heating is $19/yr. Your additional install cost is many thousands of dollars.

Given that in this case it takes two extra wells on a 5 ton (40%) at a cost of ~$5,500 (in my area) to save you $19/year, "a little extra loop" will have no discernable impact on op cost.

The only time we install "extra loop" in my area is when we find the soil is very dry. In this case, it is not "extra" it is compensation for job conditions.

Vertical loops cost about $1,200 more/ton (here). So if you buy a 3 ton and your electricity costs 3 times than ours does, your ROI on additional investment is only 600 years (before tax credit).

IMHO I'd much rather you worry about duct design and heat pump size and let your contractors design and size the loops (and own the results).

In general I have often commented that too much emphasis on EWT here has pointed folks down an unfortunate road. In this case, I'm not sure anyone here has suggested EWT's in the high 30's are bad (or necessary). Frankly I'm alarmed if that is the message we're conveying. 
Good Luck,
Joe

Posted By Volleyball on 06 Jul 2010 10:44 PM
Actually a vehicle would be more efficient in the inverse, 3rd would be more efficient over 1st or 2nd.
I thought engine size,(tonnage or btu) would directly equate. Beat gas mileage for the driving you do most. A turbo 4 can put out the power of a v6 and if you rarely use the turbo, you'll get better mileage. Kick in the turbo too many times and not only will you pay in fuel cost, it won't last as long.
Are all heat pumps designed for cooling primarily?

Caught me oversimplifying. Permit me to rephrase.....
If you only rarely tow a trailer, it is ridiculous to have an engine big enough for a trailer if occasional turbo contribution will handle your occasional needs.
An engine that eliminates need for turbo (even in extreme conditions) will guzzle more fuel.
It appears you got my point though disagree with my explanation.

RE your closing question, geos are predominantly better coolers than heaters. Some claim to be superior heaters or designed for heating dominated climates, but I am yet to be convinced. Both are refrigeration processes. 
If you look at it practically, a heavy cooling load (i.e. 40* delta T) from ambient (112* to 72*) is much less likely than
a heavy heating load (i.e. 70* from 0*). If the process is the same to satisfy the requirement, one is going to swing the ground temp way more and make the job harder.
j

I have no choice but go vertical so yes I am convinced. Both well drillers ( who do have their bias) and some HVAC people said that the slinky loops perform poorly. Not being a viable option, I've done no research. 20 miles away, different soil, different topography, maybe different results.
For vertical bore, 150' / ton seems to be everyones design standard. Cannot go down more than 500'. Say I go with 3T, instead of 450, I go 480, could I get a 1 degree up on my EWT?
While I sit here in upper 90's F, I am thinking that my goal to get cheaper heat my result in detriment to the summer and cooling. hot and humid summers mean a short cycling cooling won't be good.
I don't know about saying it is refrigeration so cooling is better. It is all about removing heat. I think the designers are more focused on the cooling virtue.

Posted By Volleyball on 07 Jul 2010 09:52 AM

I don't know about saying it is refrigeration so cooling is better.

Sounds rather silly, to me. You could argue that a heat pump works better
for heating because the kWh used to run the compressor and pumps are
working for you. In cooling mode, the 'waste heat' is working against you.

Or try saying it's a heat pump -- so obviously, it must be better at heating.

...of course, physics doesn't care what you say,

Looby

Posted By Volleyball on 07 Jul 2010 09:52 AM
I have no choice but go vertical so yes I am convinced. Both well drillers ( who do have their bias) and some HVAC people said that the slinky loops perform poorly. Not being a viable option, I've done no research. 20 miles away, different soil, different topography, maybe different results.

I don't know that anyone here said slinkies perform badly, we've said poor designs perform badly. BTW, slinkies are not the only kind of horizontal loop.

I don't know about saying it is refrigeration so cooling is better. It is all about removing heat. I think the designers are more focused on the cooling virtue.

Not sure I said that. I did mention that in our areas there is much disparity of load and that broader temp swings in EWT during during dominant task (lowering output). If you give a high enough EWT during heating season you would find a superior btu output to rated capacity. 

I've tried to offer perspective on loop design with real world numbers and you mention unsubstantiated comments about poor slinky performance. Yes verticals perform better than horizontal loops that is why drillers only put half the loop in the ground......twice the performance with 1/2 the pipe = same operating cost. For that anyone would be nuts to pay an extra $1,000/ton if job site didn't demand it.
I truly hope your system works very well for you.
J 

> 150' / ton seems to be everyones design standard

I'd be careful in using this figure - soil, grout and groundwater conditions can change it significantly.

> Say I go with 3T, instead of 450, I go 480, could I get a 1 degree up on my EWT?

That's in the ballpark, as is a COP increase from 3.35 to 3.37 and an operating expense decrease of $13/year - but use software to try various designs and see what is most cost effective.

I second Joe's comments, particularly in regard to getting the ductwork right. All the bickering about a couple degrees of EWT or hundreths (or even tenths) of COP pale in comparison to how poorly the system will run and how much it will cost to operate if the ductwork is screwed up. Getting the right CFM through the unit and to every room is key to successful operation but often overlooked.

I am paying attention to all details. I will be running the plenum up through a first floor closer and then boxing it in on the second floor hallway above it. I will run a trunk both ways to tap the flex lines from for the 6 rooms. Since it will be the second floor zone, do you think some insulation as it passes through the first floor would be warranted? I will insulate the attic portion, most likely closed cell foam. I am hearing R8 is optimum