Did anyone else find it ironic that we recently had some conversation about over sizing loops for better efficiency and then criticized oversized flowcenters due to an extra consumption of (with our electric rates from DTE) $20 a year?
Any contractor that has ever built a system based on a mechanical print has shaken their head over by the book designs. My most recent one is an assembly area where the caterer's sterno, the DJ's equipment, a capacity crowd, dancing and blind faith in load sharing and load calcs, had the bride ready to shuck more than her garter.
End consumers by and large are more happy if they are comfortable when it's colder or hotter than the book says you should get. Indeed the geo reputation of not being warm enough is in part due to over tight designs. If you make your living selling equipment lord help you if you tell a customer...."That's as warm as it gets, it's not supposed to get that cold here."
Some also find comfort in redundency (as one of our friends mentioned on the flow center thread) or allowance for contingency. Who wants a system that's at it's worst when you need it most?
I have customers that are monitoring their usage and ask about tweeking different things and they have my blessing. In this predominately retrofit market, however, many folks just want to set it and forget it.
Tight sized is as unfortunate as oversized. Ask the owners of an assembly hall that have a reputation of not being able to keep cool when it's hot out.
Joe

Totally agree. Once you dig a hole, put in the man hours, backfill, etc.... The cost of the PE pipe is nothing compared to excavation or drilling. I've even installed them at our expense in the past. I don't ever want to be associated with an undersized loop. Can't handle loosing sleep over it either. We did a horizontal bore recently. I pulled 2 loops into each of the last two holes just because. I don't know how much I'll gain from it, but it's gotta help simply by adding volume to the loopfield. I don't think we're going overboard however. I wouldn't want to install so many loops that we have to bump up a pump size.

I was out on the first loop we ever installed last week. Now that one is definately over-sized due to the fear factor back then. It's running at 44 degrees first of Feb.

A flowcenter is where all the loops connect together right? Would it be possible to have a shut off in the overflow center, so if unless the EWT drops to a certain temperature, one of the loops would be shut off? This way, the pump will not have to work harder to move the water thru the extra pipe unless it's needed. This would maximize effiecency while still giving the extra capacity if it's required.

Just my informal thinking on the subject, but considering it might be an extra $20 a year to run the pump, I don't think the kind of hook ups you'd need would make it worth it to have it. I seem to recall Joe's philosophy was to put the head in the ground, which means you'd need some part of the cut off to run from there to inside where you could access it. Especially if you got into any kind of circuitry that would deal with doing it in response to temperatures. Also not sure if there's a practical disadvantage to having a loop set to "ideal", and not circulating water. Probably next to none. Also, the cut off becomes another fail point. Saving $20 year really isn't worth it if you ever have to have that loop fixed because the extra point of failure means you have to dig it up and re-fill the loop and re-seal the cut off.

A flow center is the pump(s), housing and 3 way valve(s) TG. What you are referring too is a multistaged field there are also multi speed pumps that are spoken of in another thread. Making your loop system as short as possible would be the opposite of our conversations about extra loop for better performance.
The thing is that there are those here working very hard to eek the last few KW's savings out of their system and that's great. I appreciate their efforts and observations. The practical matter for the contractor though is that most consumers want comfort when they want it and end up with extra something to compensate for unrealistic usage desires.
That's not a criticism of anyone, just a fact of the contractor world that it is easier to explain away a few extra bucks on the electric bill than to explain less heat than desired when it's cold out.
J

Just to clarify the $20 reference was regarding extra kilowatt usage by "oversized" pumps, not loops.
(Obviously one more of Joe's poor self expression moments:)

This topic is much of the "pain" that we went through during our retrofit from air-source/dual fuel-oil to geothermal. The vendor/installer tended to be far closer to the "tight-size" thinking that they were going to save us on ROI and initial cost. However, our house was "hot" in the winter and cold in the summer. We never thought about tight-sizing impacting our comfort, until I started questioning every single thing. We ended up slightly oversizing loops and probably oversizing one or two of the units (we have three separate systems - gshp). (I can tell this from the recent cold spell where our systems still cycle with very cold temps for our area, and loop temps that are still above 40F.)

Had we needed AUX or have ended up spending a fortune on monthly Electric to stay at sub-70 internal temps, we would have really freaked-out, especially when the old system would take the house to 80 if needed!

So, my point. As a consumer, It is great to have a vendor think about cost, but I need to be able to make the call. Larger loops (and associated costs) are absolutely OK if it means that my comfort does not change. ROI is important, but not nearly as important as feeling good all winter/summer!

This was a hot-topic with our vendor, and I took a lot of crap on forums when asking for information that all really centered around "my comfort" and doing the right thing up-front...

So vendors/installers: Please remember comfort and let people know the "truth" about what to expect and why.......

Joe, you make a lot of good points. I tend to approach things from the point of view of an obsessive engineer - if I was installing systems for other people every day I'd approach things a lot differently. As you said, the difference between an efficient pump and what I consider an energy hog might be on the order of $20-30 per year in electricity. Generally not enough to warrant incurring added risk for the installer.

I do think that it is advantageous if you can recognize the few customers that do want the ultimately efficient system even at the expense of added risk or cost. For me it has occasionally been frustrating when I'm trying to figure out something like why my COP is 15% below spec for a given temperature and flow. A lot of people don't understand why I'm even worried about it when I'm saving $3-4k per year.

cny, I appreciate you for accepting this thread at face value.
It certainly has been a new challange to have such a large influx of retrofit customers who have very-VERY different levels of geo savvy and expectations. 10 years ago most geo inquiries were from folks who grasped the systems before we met. How geo works is the more common topic these days.
The Mechanic v Engineer quarrel is an old one. Our relationship is more of a synergistic one than most of us admit.
I don't emphasize often enough how much I appreciate everyone's shared experience here.
Most of us who install systems, do so in a manner that we know keeps us out of trouble with our customers.
Those of you unfettered by customer relationships (oops ;) are responsible for most of the amazing leaps of technology we've seen in the last 20 years after almost 40 years of hvac business as usual.
It's actually an unfortunate situation for mechanical engineers in general that none of us want our customers to be the first to try something new. That's probably quite a buzz kill for the guy with the better mouse trap schematic on his desk.
It is all a matter of perspective as well. Ask Tuffluck how much time he spends worrying about flowcenter kw usage. We also have huge leaps with ASHP's that are not to be ignored. I'm very interested in their lower ambient operating capabilities and hope to find a good solution to help folks that don't have 15 or 20 grand to invest.
Daniel makes a good point about the confusion of some of the new researchers we see. It's probably a good reminder that comfort is okay to factor in to our discussions between kw's and ewt's.
J