As always, a compromise is warranted.

For retrofits, you get a lot for the first $2000-3000 in energy improvements, after that it gets quite expensive to do more upgrades and usually not that economically feasible. Given the reduced operational costs of geo, more extensive (and expensive ) improvements might not pay off. But you want to make the improvements before you size the geosystem, otherwise you are only sized as a single stage system, decreasing comfort.

Different ball game with new homes, where it usually is cheaper to go an extra mile with better insulation.

I'm open to ideas, but the options you mention aren't feasible in my AO / demographic:

1) dehus, whether central or portable, increase, rather than decrease, load on a central AC. They add too much sensible load in return for reducing latent load. I've come in behind some competitors who incorrectly used dehus as an excuse to downsize the main system, with miserable results.

Dehus make perfect sense for northern basements and cellars - turn cold and wet to warm and dry - what's not to like? We simply don't have spaces that are cold and wet.

I have a couple portable ACs, including a ducted unit, that I lend out in no cool situations so that folks can get a good night's sleep while we hash out options, but they are to "kludgy" for clients to consider as a contiuing situation.

But now that you mention it I can envision a situation where we shave the tonnage of a geo system owing to high installed cost per ton, and backstop it with a minisplit in a large central room.

I had a retrofit client with a dead minisplit in a "Florida room" that had a door to the master bedroom. I first fixed the minisplit ($12 worth of R410a) which gave them a place of refuge while I worked through a reduct, SEER 19 retrofit, and addition of zoning. Their son basically lived in the Florida room anyway (PC, TV, and gaming gear there) and the door to master suite kept it reasonably comfortable at night.

That way I was able to work my crew on a normal schedule rather than super long day basis driven by client discomfort.

I think it's worth pondering, the picture in my minds eye has something dumping into the duct system. That also gives you a counter part to our "emergency heat"

I think, going forward, that true varable capacity systems will meet this need by having an extra 20% or so in reserve. I've skimmed the WF series 7 literature and I believe something like that is present, usable only a few hours at a time. They'll be awfully spendy until they become mainstream.

Minisplits sometimes have a "super powerful" mode that delivers a bit of extra capacity. They warn against sizing for the super mode, but it is present for extremes.

I like the idea of something extra dumping into the duct system, just not sure how to make it happen without a whole extra system.

If you rigged a central dehu with a refrigerant / water coax on the hot side that was only active during extremely high outdoor temps you could have a central dehu add an exta ton of cooling

Posted By engineer on 04 Sep 2012 09:57 PM
As of March we can no longer skip all the ACCA alphabet soup. Changeouts must be certified to Man J and S to meet code.

...

I know what would happen in the Dallas area if this same expectation became required: 9 out of 10 installers would simply take the tonnage that the customer has been happy with (before the changeout), or will use some kind of 600 SF / ton rule of thumb, and then make the Man J and S match up to it.  No way are most Dallas area installers going to spend any time at all doing real Man J and S calculations.  For every customer an HVAC professional decides to not bid on, there's 5 more professionals ready to 'swoop in.'

The Christmas period is about to end for Dallas area professionals - our first near 60 degree night is about to occur.  Soon the "gotta keep our crews working - we'll give to you free your A/C unit with just labor charges" advertisements will be underway.

Best regards,

Bill

A compressors with this "bonus capacity" not slightly oversized? Couldn't that be designed in as a 3rd stage and then a 4th added?
Justing thinking out load.
I like the WTA central dehumi.
Imagine a central deumi in an attached garage or with the heated discharge ducted outdoors.....

When true variable capacity systems and controls kick in we will no longer think in terms of "stages" but rather in terms of a continuously variable capacity ranging from 25-150% of nominal rating.

Enforcement of tight Man J calcs will be at the discretion of building permit departments. They can choose to stamp and approve whatever the applicant puts forth or do a little crosschecking against property appraiser and other databases to determine whether the load calc is reasonable or completely gundecked to justify whatever preconceived solution they put forth.

I recently lost a 5 ton changeout project to a competitor able to respond faster than I. That's all well and good, except that they went in for a like-for-like 5 ton system on a fairly new (2004) 2300 SF house with limited glass and pretty good screen porches and overhangs. My suspicion was that 5T was way overkill; that it would load out to 3T or so, which I proved over Labor day weekend. Meanwhile, I didn't know that they had selected "Quickie HVAC" (QH) for a same-same changeout.

As of March this year, HVAC changeout permits in Florida require a Man J.

QH has been in biz for 20 years, but a county record check a week later shows no permit pulled. I wrote the client, expressing regret that I wasn't able to timely meet their needs but strongly suggesting QH be required to pull a permit for ten good, homewoner-protecting reasons. (didn't mention load calc) Client wrote back, thanking me and assuring me they would have QH pull a permit.

I will be quite interested to see how QH inc works through the load calc requirement to back-justify the 5T changeout. Either they will catch hell from the county and be required to downsize, or, (more likely) they'll find a way to get it rubber stamped.

At that point I will be quite tempted to gig the county folks over the quality of their review of changeout Man J's.

Posted By engineer on 09 Sep 2012 09:50 PM
... they went in for a like-for-like 5 ton system on a fairly new (2004) 2300 SF house with limited glass and pretty good screen porches and overhangs. My suspicion was that 5T was way overkill; that it would load out to 3T or so

... they had selected "Quickie HVAC" (QH) for a same-same changeout.

... no permit pulled.
 
... QH ... they'll find a way to get it rubber stamped.

At that point I will be quite tempted to gig the county folks over the quality of their review of changeout Man J's.

This sounds like how many jobs get done in the Dallas market.  There are soooo many HVAC professionals all competing for changeouts.  Getting a fast agreement to do a changeout is fundamental to getting the business.  There's no time to do Manual Js, etc. - if 5 tons was good, just use it again and get the customer signature.

Permits cost money.  If the changeout HVAC companies can avoid them, they not only avoid the permit cost, they also avoid the cost of doing the installation per code.  My municipality actually has code inspectors that roam the city, looking for these situations.  Unfortunately, Dallas, being so big, and with so many budget challenges, can't come close to do this, let alone have enough code inspectors to do simply what's scheduled for them.  It's a pretty sad situation for Dallas.

As I said before, 9 of 10 installers will simply figure out how to make the Man J fit the job.  Few will have the expertise to actually understand what to actually do with a Man J.  They'd just see it as an impediment to getting the changeout jobs.

As soon as you start complaining, you'll increase the difficulty of cultivating relationships with the people you need relationships with.  My recommendation is to simply move on.

Best regards,

Bill

Part of the purpose of this excercise is to divine whether I am spending too much time doing reasonably accurate Man Js. I could knock them out more quickly using property appraiser building sketches and Bing Bird's Eye View to SWAG the windows and doors.

In a time / cost competitive situation I lose work via "paralysis by analysis"

Curt. Part of your education in the which hill to die on is- "no ego in sales". Simultaneously add counter points to your arsenal.
When I was told a company could do it within the customers 2 week deadline, my introductory meetings pre-empted that advantage with the point that my loop excavator has been an excavator for thirty years, as has my electrician. I have no 19 year old staff wannabe's that will run over next week when I snap my fingers (to learn on their project). I will however ensure the most qualified person for every stage of the project.

My first meet literature includes the point that 2 or 3 permits are required for a geo and with 5 figures at stake don't you wanna make sure it's right?

It also includes R/Air and manual J load requirements. One recent customer (a lovely young lady attorney) looked up and verified the 6 sq"/ton requirement for geo and discounted others who suggested larger systems and said existing ducts were ok.

As an inspector, I promise you- you care more about code than your inspectors or customers.
As a salesman I promise you- people want it done yesterday so you have to be very compelling if you want them to wait.
As a friend (and inspector) I suggest to you, don't worry about whether the other guy pulled a permit- you already lost the sale. There may be days you don't wish to follow the rules- whether you are slappin' in a new boiler for ma in a state you're not licensed in or the neighbors slam-bang change -out 2 days before Christmas.....don't poke a hornets nest unless you like being stung; you will compete with these people again (and BTW 20 yrs is compelling if you read our shopper's check list).

there is a dance I do for my doityourself customers when they employ me to do the sheet metal. I am a licensed contractor/inspector on the project. It is easily reconciled in my mind as the sheet metal is a small fraction of the work and all my paper work outlines permit requirements. OTC equipment, combined with OTC custom sheet metal and hourly installation labor do not make me "the contractor". I am simply the company that sold them product (vs completely installed project). As a student of the code I can tell you that language does permit the GC to sub out phases of the project.

All good points.

This was a straight air source changeout.

Man Js just started being required on changeouts this past spring. I routinely do careful Man Js on deep energy retrofits, an integral part of which is "how low can I go" (tonnage reduction). following a good foam job and / or other measures such as window film or zoning.

Straight changeouts are a very price competitive biz, so it probably doesn't make sense to refine the Man J to the second decimal point if the county is just going to rubber stamp it regardless of what it actually says.

ahhh but taking the time to do a manual J seperates one from the pack. even on changeouts......

On the other hand:

Installer #1: I'll put in 3 tons because there is real data that that worked well for you
Installer #2: I'll put in 3 tons because I spent hours on a Man J and came up with 2.89234 tons

Posted By engineer on 08 Sep 2012 08:41 PM
I think, going forward, that true varable capacity systems will meet this need by having an extra 20% or so in reserve. I've skimmed the WF series 7 literature and I believe something like that is present, usable only a few hours at a time. They'll be awfully spendy until they become mainstream.

Yes the WaterFurnace 7 Series has whats known as superboost mode. The compressor essentially has 12 stages with as little as 20% of capacity(stage 1) up to 100% of capacity for heating(stage 12) and then it has staged backup heat strips for auxiliary heating. Unlike most geo, in my area a 4 ton geothermal will only get about 40-42K BTU of actual capacity at 40 EWT numbers where as this unit gets 50-52K BTU's at 40 degree EWT

For cooling it has stage 1 which is still 20% of capacity but now stage 9 for cooling is 100% of capacity. Stages 10, 11 and 12 are known as "SuperBoost" mode and provide up to 130% of cooling load for up to 24 hours if needed. Conventional two stage will provide 50K BTU's at 70 EWT while the variable capacity will get 50K BTU's(if its cooling and not dehumidifying) at 70 EWT but has the ability to jump up with a 30% higher capacity or getting 65K BTU's of cooling at 70 EWT.

Meaning if the cooling load is only stage 8 of 12 even though superboost is on it will still only stay at the stage needed. WaterFurnace mentioned this is for when the temp is 100% or above of design load or if you have a wedding at the house and have a one day very high load from the people and cooking and doors constantly opening and closing. After 24 hours superboost mode turns off and the system returns to normal operation. You can view my install of the system on my YouTube channel listed below. It is as of now the ONLY video of a variable capacity residential geothermal install that I can find on youtube. Cost for the system is about $2,500 to $3,500 higher than a two stage variable speed system but keep in mind this also includes a variable speed flow center pump, an energy monitor, a refrigerant monitor, performance monitor and a thermostat that can display the energy usage in realtime and it allows up to 6 zones with no bypass.
Rated efficiencies are up to 5.3 COP at 50% capacity and 41 EER in closed loop configuration, compared to most other systems are 4.8 COP and 30 EER at part load.

Here is a video of the system that we installed in SuperBoost mode.
WaterFurnace 7 Series Variable Capacity Geothermal Installed By Sky Heating in Portland Oregon

Posted By jonr on 19 Sep 2012 08:50 AM
On the other hand:

Installer #1: I'll put in 3 tons because there is real data that that worked well for you
Installer #2: I'll put in 3 tons because I spent hours on a Man J and came up with 2.89234 tons

so you would consider them equally concerned with your results? I think not.

Installer #1: I'll put in 3 tons because there is real data that that worked well for you
Installer #2: I'll put in 3 tons because I spent hours on a Man J and came up with 2.89234 tons
so you would consider them equally concerned with your results? I think not.

Given the inaccuracies we have seen with Man Js, approach #1 is the most likely to yield correct results and shows a concern for not wasting time/the customer's money on theoretical results when real data is available. Now if there were changes made or adding insulation is an option, then that's a different story.

We'll certainly accept that advice instead of following sound industry practices and Florida building code! Thank you for the special dispensation, Oh Ominous Dominus.

The best answer may per to perform a Man J accurate to within a quarter ton or so and then use that to think about what low hanging envelope fruit may exist so as to bring the unit size down a half or whole ton.

Posted By jonr on 20 Sep 2012 08:00 PM

Installer #1: I'll put in 3 tons because there is real data that that worked well for you
Installer #2: I'll put in 3 tons because I spent hours on a Man J and came up with 2.89234 tons
so you would consider them equally concerned with your results? I think not.

Given the inaccuracies we have seen with Man Js, approach #1 is the most likely to yield correct results and shows a concern for not wasting time/the customer's money on theoretical results when real data is available. Now if there were changes made or adding insulation is an option, then that's a different story.

Given that historically contractors have oversized equipment significantly, I think the individual doing the math is more reliable. If following code and searching for a customers best options are "wasting time" then I misunderstand my job.

Real data is a 750 sf house I saw recently with a 115,000 btu furnace in Ann Arbor, has always had enough heat. Why change it? By your criteria "it worked well" for them, no reason for change.

You are trying to find an excuse to criticize good practice.

You are creating a straw man from a strange definition of "works well". Obviously, if the customer says that their previous unit short cycled, then it didn't "work well" and should not be duplicated. And if they aren't sure, then you don't have data.

Name calling and the straw man of "you are suggesting I violate code (where required)" are also cute. But go ahead, show potential customers what you are like.

So with record high temps this summer I had several phone calls where homeowners wanted their AC checked because it was running all the time. with several days of 100+* weather and a design temp of 93* for Detroit/Ann Arbor they were convinced their equipment didn't work well.
So by the definition of "works well" you offer jonr, they must have undersized equipment if it ran most of the time at 110% design load.
I suppose I should race to these homes and charge folks for a visit.
You are the one with the strawmans position if you continue to suggest that doing the math or following code are extraneous if the customer thinks it works well.
Lots of folks with oversized equipment thinks it works well so why should I bother?
You criticize folks for not doing the math, now you suggest it's extraneous. You may not have it both ways.