Comments on: The Energy Vanguard Blog’s 14 Most Controversial Articles of 2011

By: Danny Gough

Danny Gough — Wed, 28 Dec 2011 18:48:19 +0000

David,

David,
I didn't intend to imply Carrier's GreenSpeed was "the answer". Although the 3 and 5 ton models will drop to 40% of rated capacity, I still don't believe there is a market for these units - Especially with ground source tax credits.

I do think inverters have a future. We just need to learn more from the Japanese.

I just installed my first ECM circulators on a radiant heating system. They run all the time and modulate flow based on pressure differential. In the future, I think we will see compressors do the same thing. Moreover, someone will figure out we can manipulate evaporator temps to increase humidity removal. Wait till Bubba and Earl get a hold of one of those units.

By: pj

pj — Wed, 28 Dec 2011 18:22:22 +0000
On old homes you have no clue
On old homes you have no clue as to the inputs , the GIGO factor is so large as to make “calculations” silly, a joke. But hey, since no one knows the inputs, everyone can be right. They all get to be scientists. Even if you believe the GIGO factor can be narrowed on some new homes to where a single data point might be estimated to within “reasonable tolerances”, why put the focus on one point that happens for only seconds?

Have we not moved beyond Cave fires “sized” to cook, away from medieval homes built around a single hearth, past smoky fireplaces in every room, and evolved to modulating furnaces, first described in Nicolas Gauger’s Mechanics of Fire published in1713? All this “science” only to install an on/off furnace “sized” to the CFM requirement of the AC unit, sounds like we are back in the cave. But hey, the cave was over 2000 sq ft/ton!

I do understand the marketing requirement to pretend this is science. Plus it makes us feel smart.

By: David Butler

David Butler — Wed, 28 Dec 2011 13:16:36 +0000
Danny, I also can't predict
Danny, I also can't predict the future, but the inverter-based systems available today have fairly limited dynamic range, and from what I understand, there are significant engineering trade-offs with extending that range. In other words, proper sizing is still important.

Here's the problem: You mentioned Carrier's new variable system, the Infinity 25VNA. The minimum capacity of the 2-ton model at 75F is 67% of full capacity at 95F. The larger models have a bit more range, but even a system that can operate at 50% of capacity needs to be sized reasonably close to the design load or else it will end up operating at minimum speed during full load conditions. Moreover, in my experience, variable capacity (and multi-stage) equipment is nearly always oversized to the load, often grossly so.

By: Danny Gough

Danny Gough — Wed, 28 Dec 2011 09:52:38 +0000
I can't predict the future
I can't predict the future but there may be a time when one or two sizes fits all. Inverter compressors are comin' to America. Nordyne and Carrier are now on board, with Lennox and Trane right behind them. Just a matter of time before ground source mfrs join the fray. Of course this technology will foster a lot more opportunities to do it wrong, particularly with duct design and zoning.

By: Geoff Hartman

Geoff Hartman — Wed, 28 Dec 2011 00:02:30 +0000
to Pj - I respectfully
to Pj - I respectfully disagree.

I will grant you that the results are never “Precise” to the nth degree, but if we accept a level of accuracy sufficient to hit the target 10 out of 10 times, while maybe never hitting the dead-on bullseye, I think +/- better than 10% is very realistic.

IF 10 people complete the Manual J correctly and use proper measurements with verified information . . . Sound like a HERS Rating? - They will surely get similar answers. - Always. Let’s add documentation and accountability (Maybe use the ENERGY STAR V3 improved checklists?) then the reliability improves significantly. Finally, add oversight and QA – maybe the RESNET Providers to check and validate their Rater’s work? - - It’s not a perfect system, but it’s improving.

Yes GIGO holds true. - Always.

So maybe I measure 2,500 sf floor, and you get 2,550 or I calculate 18% framing in the walls, and you use the default 23%. The answers will be very close. The largest variables, things like design temperatures, infiltration rates, ventilation, and solar loads are all well defined, and as a Rater, we actually verify and measure these values. So how could the calculated loads be significantly different? The significant differences come when users start inserting their own "adjustments" and creating their own building science. That is Garbage.

In any case, if you, or anyone else, has a better method or procedure, please enlighten us and let’s get this better science into the knowledgebase.

By: David Butler

David Butler — Tue, 27 Dec 2011 23:09:48 +0000
PJ: No one
PJ: No one ever claimed that a MJ load represents anything other than the 1% condition. After all, it's only a sizing procedure. What sizing procedure to you advocate? Please tell us.

> ...you will get 10 answers...

Yes, but those who understand the procedure will get results that are reasonably close to one another. No one really cares if a system is 15% too big (or even 25%, in my opinion). But what we can avoid by doing a proper J (and S) is a system that's twice as large as the design load. Egregious oversizing is the issue, especially as homes become more and more efficient.

By: Pj

Pj — Tue, 27 Dec 2011 22:14:14 +0000
Look,

Look,
If it makes us feel better to call this science, great.

In science, results are reproduced. Give 10 contractors the same old house (or prints) you will get 10 answers, and each will all goto their grave telling you they were right!

How is this science?
I do understand the need to pretend there is value to this .I just don't see how lying to ourselves helps.
Happy new year!!

Pj

By: Allison Bailes

Allison Bailes — Tue, 27 Dec 2011 21:56:39 +0000
Pj: I
Pj: I appreciate your persistence on this topic, but I respectfully disagree with your position. Manual J is more than a SWAG. I think GIGO (Gargage In ==> Garbage Out) is a more appropriate acrynym.

By: Geoff Hartman

Geoff Hartman — Tue, 27 Dec 2011 21:49:13 +0000
Thanks for the collection.
Thanks for the collection.

I must have missed the #10 article on AC benchmark. You were right on there. In fact, we saw literally millions of homes built between about 1975 and 2000 that used that very standard as the MAXIMUM. I think we can agree that as a rule, even the best home built in 1980 was nowhere near as efficient as even an ENERGY STAR V-2.0 home, and I am not aware of even one of those million-plus homes that did not perform due to AC sizing. We still had insulation and HVAC/duct inSTALLation issues. So we learned to be diligent about quality control (read multiple inspections! and documentation!) to avoid those problems.

ENERGY STAR V3 and some equally rigorous standards are finally getting the baseline process right. The 1 ton per 2,000 square foot home is now easily reachable.

Oh & I would argue that Manual J IS Science, we just have imprecise inputs. QC, inspections, and verification standards increase accuracy and improve performance. So, if we could make 1 ton per 1,000 sf work in 1980, with less precision than we can easily achieve today, AND MJ-8 improvements, I think it will still work VERY well today.

By: pj

pj — Tue, 27 Dec 2011 20:59:51 +0000
10.How is Manual J science?.
10.How is Manual J science?.

On old houses you have no clue.On new houses you rely on prints that never match real world conditions. On production houses you assume worst case orientation regardless because you don't know what direction a house will be built.

Best Case, You "calculate" one number, at one condition, that occurs less than 1% of the time.

You can only accurately state, "Your cooling load will be "X" at some point during the year, most of the time there will be no cooling load, sometimes your load will be more than "X", and your will be something other than" X" 99.99% of the time."

Science? Come on.

Also,
"Large errors are possible if there is uncertainty about insulation levels, fenestration performance, envelope tightness or the efficiency of the duct runs installed in the unconditioned space.” ACCA

Since on old houses we don't know any of the numbers with any level of confidence your load calculation becomes Performance Art, nothing more. A sales gimmick.

I will give you any loads you want on any house, that is the way it works.

See: http://www.nrel.gov/docs/fy11osti/51603.pdf

Let's not insult real scientists by pretending we are doing anything closer to science than SWAG.

Thanks,
Pj