Posted By tinoue on 18 Jun 2010 06:44 AM

Furthermore, for the house in question, you're looking multiple zones and a heat load of what, 200+ kbtuh, so if you're shooting for 20%, and you're rounding up, you could be quoting the homeowner 3-4 tons of extra capacity.

I don't "shoot for 20%", heat pumps are in 5 sizes period. If a home is getting oversized by me it is because there aren't 1/2 sizes available in the 2 stage equipment everyone has to have.
 
You obviously have chuckleheads in your area that have a problem following instructions i.e. man j. I don't.

You seem to feel that calculating down to the last btu is critical, yet heat pumps are produced in ~12,000 btu increments. Why would I need to know if the load is 49 or 57kbtu either way the heat pump will be the same size (likely a 3 ton in MI).

In sum if you were to find me a ton oversized it would be because 2 zones called for 1/2 ton increases and I'd have to go up a full ton on each. Because we don't try to cover 100% of the load with geo (we use electric auxiliary) oversizing is virtually non existant.

You can perform 8 hour load calcs if you like, I don't have time and estimates are free. If someone would like to pay me 8 hours to conduct that kind of load calc I'd take their money (though I'd advise against it). 

J

Again, all I'm endorsing is that people DO follow the directions and enter high quality data. Manual J, especially the latest update, is very specific on not up-estimating or adding pad factors. You, Joe, seem to be a real pro, and I wish there were more out there like you. The problem is that you are in the minority, especially as an increasing number of hacks get into this business.

I am in the business of ensuring that my clients make the best choices for their unique needs. They gladly pay me $500 to help them sort through the variety of quotes they get and help them make the best choice when they're plunking down the types of dollars these systems cost.

In the original poster's notes, he indicated that he was quoted an AC only system with some ridiculous amount of capacity for an incredibly high cost. It doesn't take a Manual J to figure that even a black cardboard box wouldn't have the kind of cooling load that that "chucklehead" was proposing. And you're right, we have a lot of them out here!

Again, I'm supporting the professional work that you, and many others on this group, are promoting. I'm just adding that consumers must be vigilant, and contractors need to be sure that they're putting in real numbers wherever possible.

So if they follow your advice and are hot in the summer or cold in the winter what do you do about it?
Anyone who has bid commercial knows the worst case scenario is a job designed by someone other than the builder. We are told to "bid the print" even when we know it won't pass inspection and expensive extras ensue.
j

That's a valid concern. What do you do if that happens?

I have an unfair advantage in my climate. We've got about double the heating requirements compared to cooling/dehumidification, so a heat pump or GSHP will almost always have too much air conditioning capacity. In the winter, the systems will have backup heat to pick up the slack. The detail I worry about is sizing large enough to minimize backup heat requirement but not so large that it's useless for AC or drives the install cost up too much.

We are doing a similar house right now, using w-w units for the radiators and using additional w-w units for the unico systems. The provide chilled water in the summer, and provide a boost in the winter if needed. 30 ton system, 12000 sqf, including DHW....

Posted By tinoue on 18 Jun 2010 09:01 PM
That's a valid concern. What do you do if that happens?

I have an unfair advantage in my climate. We've got about double the heating requirements compared to cooling/dehumidification, so a heat pump or GSHP will almost always have too much air conditioning capacity. In the winter, the systems will have backup heat to pick up the slack. The detail I worry about is sizing large enough to minimize backup heat requirement but not so large that it's useless for AC or drives the install cost up too much.

What we do is a man. J load and a "geo  design". Systems perform as anticipated. If not we figure out why and make adjustments. If it is our (including sub contractors) fault we would fix it. Only thing remotely close to not performing as advertised is hot water costs that soared in a home where I didn't install a buffer (won't drink that kool aide again). A buffer tank was installed at our expense.

So what would you do? Pay for corrections out of your pocket? Or is there language in your pocket absolving you of performance liability?
Not trying to pick on you. I seldom encourage 3rd parties in a design as it lends to finger pointing if something goes wrong.
I'd like folks to employ you for advice on the envelope not design of the geo system.

I'm in MI; a heating dominated climate as well. Biggest oversizing problem I see is 100% loaders. It's not people who don't understand load, it's people who don't understand geo. I've spent hours here suggesting auxiliary heat is a good thing vs 1 more ton that saves $50/yr in operating cost. So I worry about comments like "minimize back-up heat requirement" too many people (some contractors included) see auxiliary heat as the anti-christ.
j
 

These are all valuable discussions - I don't feel picked on.

I'm doing analysis and making suggestions, but the size of system ultimately is the installing contractor's responsibility. I work hand-in-hand with the HVAC guys, so we'll go back and forth until we're both comfortable with the numbers. So it's a collaboration rather than a real outsider design. This also helps prevent wasting time of the contractors dealing with minutia. I can sanity check things on behalf of the client, suggest tweaks and do whatever analysis the client wants, all with feedback/interaction with the guys who actually have to make it happen. Sometimes I learn something. Sometimes they do. It's a great interaction.

In fact, more than once, I've gone to bat for the contractor who was recommending something that the client didn't understand. Since I'm an independent, the client trusts that I am making recommendations that are in their best interest (which of course they are).

I totally agree with you on 100% load. I should have written "optimize back-up heat requirement" for exactly the reason you mention. In fact, I had this very discussion with a professional group I was teaching today.

Agreed, we are splitting hairs. As long as someone is accountable at the end of the day, it's all good.
J

joe and tinoue....good information provided here. ..thanks

Please keep in mind that for straight forward residential houses it is sufficient to calculate the thermal envelope, especially with a single heatpump. Also, when we do manual J for retrofitting, much is guesswork anyway. What is the exact R value for this 50 year old window, and how well is that wall insulated? Then I spend more time, look at previous heat bills to give me assurance. With big old mansions I spend up to 2 days coming up with a correct load. Multiple units would require zone calculations, so do more complex or older houses. Yes, if I am wrong I will fix it at my expenses. I give a performance guarantee for all of our systems. My key goal is to make the customer happy. That is why my previous customers are my best sales team! One problem is that you cannot follow a book which is written for the whole United States. Geo in Arizona or Florida is different from Geo in Canada (or close to it). We monitor all of our systems, and adopt when we find out that one thing works better than the other. Over the years we started to violate the IGSHPA recommendation to size the units for cooling, to better serve the needs of our customers in our heating dominated climate. What they want is to have their heating bill reduced, and do this in an environmentally friendly way. Humidity is not so much of an issue in western New york, and 90% of the run times is related to heating. Biggest leap was 2 stage design.

Posted By docjenser on 20 Jun 2010 02:59 PM
I give a performance guarantee for all of our systems.

Hi Doc, can you explain how your guarantee works?  From a homeowner's perspective, I like your philosophy.

We do a manual J, which we give to the customer, size the system and guarantee design temperatures, meaning the house will stay at 70 degrees when it is 0 degrees outside. If not, we will fix it at our own expenses, which luckily never happened.
Keep in mind that energy star qualifications for geothermal heatpumps require a 2 year performance guarantee for the loopfield anyway.

Thus a I do not think it is a big deal, but it means a lot for the homeowner. I had an older lady which had 3 estimates, one was 7 tons and 2 heatpumps, and we ended up installing a 4 ton system for about half as much. But she was very nervous since others had told her that she needed the capacity and that her house would not warm.

So I started to write it in the contracts. Why wouldn't you ?

doc,

I tip my hat to you. Way to go!!

Thanks for explaining Doc! Sounds great. Your guarantee is far superior to a performance guarantee that would only cover the difference in utility bills for a period of time.

Doc - wish your company were here in West Chester, PA!  Does anyone have a recommendation for likeminded Geothermal companies in this area?  (suburbs of Phila).

Posted By daveydogg on 21 Jun 2010 09:13 AM
Does anyone have a recommendation for likeminded Geothermal companies in this area?  (suburbs of Phila).

Yep. My geo installer provided the same guarantees, or maybe more.

Hint: Check IGSHPA's list of installers for Kennett Square, PA.

Looby

Our customers are walked through bin reports and know exactly when to expect auxiliary heat, full time geo operation etc.
Not the same as a performance warranty but they are told to let us know if their experience doesn't mostly jive with the predictions. I suppose a written performance warranty would be a lateral move from there...might be a good idea for the fuzzy feelings....
Unfortunately we still have old school 100% loaders and newbies who routinely oversize around here. So much so that I am often alone in my smaller tonnage suggestions. This might be a fair remedy.
j

ENERGY STAR® Program Requirements for Geothermal Heat Pumps Partner Commitments Commitment The following are the terms of the ENERGY STAR Partnership Agreement as it pertains to the manufacturing of ENERGY STAR qualified geothermal heat pumps. The ENERGY STAR Partner must adhere to the following program requirements: "Since the performance of the geothermal heat pump is significantly related to the design and installation of the ground heat exchanger, Partner will strive to ensure that the customer receives warranty protection for the integrity and performance of the ground heat exchanger for at least two years. Partner will inform all distributors and dealers of ENERGY STAR labeled geothermal heat pumps of the need for warranty protection for the customer. Partner will focus its ENERGY STAR marketing efforts in regions where contractors provide customer warranties" So this comes from the Energy Star label. By now, you should know on how to make a loop perform in your area, and the heatpump's performance is well characterized and guaranteed by the manufacturer. The rest is math and professionalism, why wouldn't you guarantee the performance of your work? I really think that is what the geo industry is missing. Me taking on this risk, which really is not any at all, differentiates me from guys running around in a rusty van with a cell phone with no insurance, who say they can do geo since they heard it from the local supplier at a 2 hour workshop. But I should be grateful, 30% of our business is addressing our competitors performance issues. That is when you can really shine, and built a reputation.

As I said, I didn't provide the written warranty as such, just told folks exactly what to expect and to call me if it wasn't happening. While I agree with you it is all math and low risk (not zero as some folks expect same performance regardless of weather) a written assurance sure has a fluffy bunny feel to it.
We will likely adopt such a warranty.
j

It is more cut and dry down here since there is no equivalent "auxiliary strip cooling" to bail us out if we undersize a system, OTOH relentless humidity militates against oversizing. We walk a fine line between guaranteeing reasonable comfort on the very hottest days while maintaining reasonable humidity on cloudy damp days