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Energy efficency and high cfm/ton.

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Garibaldibill

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Discussion starter · #1 ·
I am choosing a new heat pump for my house. It currently does not have central air/heat.

When looking at the AHRI ratings, the tax-credit-qualifying systems have a higher cfm/ton than traditional guidelines. A two stage, 2 ton system has a variable speed blower that has a minimum setting of 1000 cfm. That means that for most of the year, here in Oregon, it will be operating at 750 cfm/ton. We don’t have to worry about humidity here, but the system is for the whole country. And I do know what humidity can be like in the South as my wife is from Mississippi and I have been there in August!

I am assuming that the larger speed and larger coil uses less energy to transfer heat. So, can I just disregard those traditional figures (350-450 cfm/ton)? The high HSPF is what the Oregon Department of Energy wants me to choose.
 
#2 ·
Conventional wisdom should not be ignored off-hand

Garibaldibill said:
A two stage, 2 ton system has a variable speed blower that has a minimum setting of 1000 cfm. That means that for most of the year, here in Oregon, it will be operating at 750 cfm/ton.

So, can I just disregard those traditional figures (350-450 cfm/ton)?

The high HSPF is what the Oregon Department of Energy wants me to choose.
Click to expand...
What is the model number and manufacturer?
I am sure others here would know the recommended setting and unique features.
The numbers mentioned mean that the coil face area has nearly doubled.

What part of Oregon? You must be in a rain shadow( < 20 inches rain/ year).

Those numbers you mention must be MAXIMUM.

Most of us here would not see more than 450 CFM/ton in a manufacturers recommended set-point and only for the driest climates.
 
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Discussion starter · #4 ·
Beenthere: Yes, it is a Goodman: DSZ160241A, CAPF3642C6C, MBE1600AA. (AHRI #3372191)

The Oregon Dept of Energy has equally over sized units, though with a more adjustable blower than that Goodman. Here is a Carrier two stage, two ton: 3261437 25HNA924A31 FE5ANB004+UI (http://www.energy.state.or.us/res/tax/HeatPumps/HP.htm)

That blower unit can be adjusted down to 350/ton.

These are two stage units I am looking at. My calculated cooling load jumps from 1 1/2 T to 2 T if I stop shading (outside) my west windows in August. As I age, I find myself wanting to do less and less effort to maintain our house temperature. Currently I vent the house overnight, monitoring the inside upstairs temperature, the outside shaded temperature, and closing the windows when they are equal. It is like making your own bread: work.

dan sw fl: I do live in a rain shadow, but not the one you are talking about (The Cascade Mountains). Mine is a local 1600 ft mountain (Bald Peak). My calculated cooling load is: 23,500 sensible, 1400 latent. The load is reduced by 10,000 if I shade all the east, south, west windows.

When I talked to an employee at the ODOE about the tax credits and different models, she immediately dismissed any of my focus on SEER with: we don't worry about cooling loads here in Oregon. She did mean, I am sure, west of the Cascades where the majority of us live. A lot of us just left town last summer during our week of 100 degree temps last summer and went to the Coast where the temperature was 65 and foggy.

That MBE1600 Goodman blower has settings from 1000-1600. Since it has the variable speed blower, my understanding is that it will maintain that cfm regardless of static pressures (up to .9, anyway). I was just baffled why AHRI rated it with a 1 1/2-2 ton outdoor unit.
 
Discussion starter · #6 ·
Beenthere:

On page four of the product specifications for that Goodman blower unit (http://www.goodmanmfg.com/Portals/0/pdf/SS-2/SS-GMBR.pdf), I see the trim functions and the statement that Fan-only operations are 30%. I don't understand how the blower can operate at 350 cfm/ton while the outdoor unit is running in its first stage (1 1/2 ton), and increase when the second stage kicks in. It would have to function like the Carrier Infinity, wouldn't it!

I admit I want Cadillac quality at a Chevy price. However I currently drive an Oldsmobile 98 Elite, which you could take to mean I buy in the middle. But I "stole" it on the used market as the elderly wanted new cars, and younger than that only a foreign job would do (at least here in Oregon).

While I currently do not have the ability to circulate indoor air, I am looking forward to recirculating the indoor air and cleaning it regardless of heating or cooling needs. I was pleased to see that I can have a low cfm for that function.

When I replaced my 1940's era refrigerator with a modern one with fan, I noticed the formerly silent appliance started making noise while operating. After that experience, I am focusing on reduced cfm of the AHU assuming I would have less blower noise coming from the registers. One of the planned registers is very near the Lazyboy where I spend most of my "indoor sit-down time" (reading--no chattering TV to distract me).
 
Discussion starter · #8 ·
beenthere:

An airflow performance table for a Trane air handler (4TEE3F37) with a variable speed blower, shows that as the external static pressure goes up, the cfm stays the same (isn't that the primary benefit of the vs blowers?). If that air handler is set at 700 cfm, it puts out 700 cfm as the external static pressure increases to .7 and then drops to 660 cfm at .9 where the table ends. At the 900 cfm setting, it stays at 900 cfm all the way to .9, impressive.

Are the specifications fudged? Does Goodman use a different motor or control board than other manufacturers? I don't know the answers to those questions. I can only go by what the manufacturers publish and (most importantly) what you all have to say about this issue.

I really was just baffled by AHRI rating the oversized AHU with a 1 1/2 ton(for most of the year) outdoor unit. In my research, over and over ("tigerdunes" is especially prone to quoting the ratings), the question is asked: "Does the combined AHU and outdoor unit have an AHRI rating?"

I actually started dreaming of swapping out the control board on that Goodman (MBE1600), as I liked the larger cabinet (to match with an air filter).
 
#9 ·
Not sure this will clear things up but the air handler CFM is set based on the 2nd stage cooling tonnage. If the unit is operating on first stage, the air handler will operate at 65% of the high stage cooling CFM setting.

-2-stage units require two wires. The t-stat decides when to switch from 1st to 2nd stage. The t-stat will power the 2nd stage wire telling both the heat pump and air handler to go to 2nd stage when necessary. It doesn't require Infinity type control.

-Variable speed blowers do maintain (not exactly, but very close) the same CFM regardless of static.

-Static will not affect your CFM with variable speed blowers but it does affect the heat transfer at the coil which does affect the system operation. Higher static requires less CFM to transfer the same amount of BTUs.

The Amana systems are the cadillacs at the price of a chevy. The goodmans are not. The goodman DSZ18 is a really efficient unit, though.
 
Discussion starter · #10 ·
badtlc:

Thanks for telling me that an airhandler has other settings besides the dipswitches. The product specifications for the Goodman (5 & 6 dipswitch settings) states that the minimum setting is 1000 cfm for "Cooling & Heat Pump CFM". At the lowest setting (1000 cfm) with a "CFM Trim Adjust" of -15% that translates to 566 cfm for the first stage, and 425 cfm for two stage operation. It was confusing to me reading page 4 of the product specifications as the "CFM Trim Adjust" table is under a heading of Thermostat "Fan Only" mode, leading me to think the adjustment only applies to that mode.

If Goodman was the only manufacturer with poor documentation on their internet site, I would wonder about their manufacturing QC. Panasonic has an especially poor site. I often get the information I seek from sellers or sites such as this wonderful one. It is possible to seek too much information, but usually the more the better. In the economic/political world it is called "transparency".

My understanding from other posts is that the Amana is identical to the Goodman. Same with Carrier/Bryant and Trane/American Standard. An image sticks in my mind of one poster quoting a friend who worked in a Carrier factory, that identical units coming down the line had Carrier/Bryant/Payne cabinets installed on them depending on the demand for each brand. I don't know if that is a true statement. Manufacturers can use different components for different brands, but often it is just marketing. "I, (sniff, sniff) can afford a Cadillac and you can't!"

I am what I like to call a value shopper: pay more/get more until pay more/quality stays the same. Harbor Freight is a good example of pay less/ get less. But more and more of their products are being made in Taiwan (higher quality) instead of "low bid" China.
 
#11 ·
Amana is under the Goodman name but they are not identical. Amana usually comes with the higher end components. The Goodman DSZ line is about the only thing close to the Amana line.
 
Discussion starter · #13 ·
beenthere:

I wasn't comparing the Trane air handler to the Goodman. I was quoting the Trane blower performance table, to illustrate that vs blowers maintain cfm as esp increases. That kind of information is missing from the Goodman specifications.

I also assumed modular blowers to be identical to the blowers encased in an air handler, in their function and performance.

I was joking about the control board. I was trying to make the point that if the Goodman control board of the ECM motor is different from the Trane (less options), perhaps I could get my Cadillac quality at a Chevy price.
 
#14 ·
Garibaldibill said:
I also assumed modular blowers to be identical to the blowers encased in an air handler, in their function and performance.
Click to expand...
An air handler already has a coil in it. And the coil resistance was included with the air test.
A blower, doesn't have the coil resistance included. Since they don't know what coil will be used.

Different brands, use different blower wheels.
So you can't compare one brand to the next.
 
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beenthere
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