Theoretically, it should help. Practically, it will malfunction sooner or later

Does it make sense to use it at all? In particular, I'm thinking about the local (Arizona) climate - it might make a lot of sense because the temperature range gets close to 40F, or there are other considerations I'm not aware of?
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--vt

Arizona is actually a good climate for an econimizer due to the low enthalpy. The only consideration is the type of e-mizer to use. Some don't have a good reputation as being dependable. Ask other contractors which ones they recommend.

It's all aboaut free air conditioning when the temperture and enthalpahy is correct as menioned already.

We just finished installing a 30ton LGA series Lennox with dual enthalaphy sensors with their system and gravity dampers with power exhaust.... That will save them big $$$$$ on thier cooling requirements...

Mel

AllTemp Heating & Cooling
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AllTemp Heating & Cooling

Newer ones that use electronic controls are much more reliable than the electro-mechanical ones. I rarely find them broken nowadays.

David

I think you need to do some serious calculating to justify an economizer in a house. The costs for the controls,dampers,motors and extra duct can add up real quick.I doubt if it would make sense in any house under 2500 sq ft. The money would probably be better spent on upgraded windows and insulation.Having said that, IF I ever upgrade my own place I'll probably put it in.(I'll do it myself )
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I love my job, but paydays Thursday

Rich Pickering:

The reason I started thinking about the economizer is the Trane manuals I was looking at - it seems to me that the economizer, as they made it, is an add-on to the heat pump, which I need to replace anyway, so there's no extra ductwork (granted, there are dampers, motor and control system details of which I don't know yet, *that* bothers me).

As for windows and insulation, I'm afraid I'm gonna do it anyway along with the heat pump
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--vt

VT,

In Arizona, with a rooftop package unit such as yours, I would definitely consider an economizer. Granted, there are good ones and bad ones, but like osneone else mentioned, they are very reliable now days. The Belimo actuators are powerful and sturdily built, and the enthalpy controls (especially the Honeywell and CPC ones I have tested) are really rugged.

Now, when accessing the need/worth of the economizer, here is an important consideration; how often do you perceive you will need cooling while it is actually cool outside? I'm not really knowledgable about Arizona's climate, but if the temperature drops off quickly in the summer, so that you are still warm in the house while it is 50� outdoors, you can get free cooling. But, the economiser is going to try and maintain a 55� discharge air temperature, (combination of outdoor air and air from the house) meaning if you have 70� air in the house, the outdoor temp would have to be below 50� to provide that 55� mixed air temp.

If you can't easily perceive a situation like this, you are not likely to ever recoup the investment.

Commercial units have economizers because the internal building load is usually high enough they need cooling year round. Lights, people, and mechanical loads inside the building keep the interior warm year round. But residential homes usually trade enough air with the outdoors, and have such a relatively low internal load, the economizer is not justified.

Hope I have not clouded the issue too much.
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There are no stupid questions. . .just a lot of inquisitive idiots.

Bama Don't you ever sleep anymore?

Not nearly enough. My shoulder is killing me, my wife is snoring, and I ate too many barbecue ribs last night for dinner.

What's your excuse?
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There are no stupid questions. . .just a lot of inquisitive idiots.

My shoulder is killing me also. Did a service change-out Wednesday and po'd an old injury while setting the panel.
Back on the anti-inflam meds again.

I know your gonna give me grief, but what is the p.f. thing at the beginning of your posts about?

http://hvac-talk.com/vbb/showthread.php?threadid=11015&pagenumber=2

Federally mandated reader protection.
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There are no stupid questions. . .just a lot of inquisitive idiots.

I used to have great results from taking Naprosin, but my doctor has put me on Celebrex. The Celebrex has done wonders for my arthritis pain, but nothing for my shoulder.
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There are no stupid questions. . .just a lot of inquisitive idiots.

I missed that charming bit of dialog.
I am familiar with P.F. as "pucker factor". Used as it applies to those jobs that make the sphincter contract.

I hear you. Feldene, prescription Naprosyn,Celebrex.
Still gets po'd and I have to favor it until it settles down.
The pain killers for the migraines worked wonders on the other aches, but it is hard to work it in a drug fog all the time.

Been there done that!


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There are no stupid questions. . .just a lot of inquisitive idiots.

Wolfdog, I have a similar problem I use catmaflam works great. http://www.healthsqr.com/newrx/vol1486.htm

Thanks, Tried that one too. I'm afraid we're talking about the knife eventually.

and help this guy with his econo problem. We are all getting old. Econos help up here to cool when the outside temp is low and the system isn't designed for winter run. Usually an econo will do the job unless it's a computer room or something. I must agree, they are made to break and have a high failure rate. I bet many of them right now are not operating correctly and seen lots of them with the little bypass plug installed instead of the wiring harness from the cheapy economizer.
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Hey cockroach, don't bug me!

Whining is God's way of letting you know that I'm still alive. :dice

I grew up in Phoenix before Uncle Sam relocated me to NC. If it's a house you are trying to cool, try a whole house fan which brings in air from open windows and pushes it through the attic. We had one in our 2200 sq ft house. After the sun went down, the fan went on, and boy did it do the trick. That's one of the perks of the desert climate-high relief.

quote:

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Originally posted by wolfdog
I missed that charming bit of dialog.
I am familiar with P.F. as "pucker factor". Used as it applies to those jobs that make the sphincter contract.

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BamaCracker:

I have an impression that I will be able to use it quite often. Take look at http://freehold.crocodile.org:8080/image_archive around October/November, you will see that the cooling is on only when the ambient is higher than indoors ('cause it drops really fast), however, I was really budget concerned and kept the house at 82F. Since the fan, especially the variable speed, is going to take a fraction of a cost, I wouldn't mind dropping the indoors to 75F, and the ambient sometimes drops below 68F in early September. The heating season, on the other hand, started on November 23 last year. Three monts in one half of the year is something to consider seriously.

Another thing, I see a need to further investigate the way the economizer is controlled - if it depends on "smart thermostat", then I've got it covered. Common sense tells me that this is probably the case. However, if I'm wrong and the economizer is a self-contained unit, I'll either don't install it at all, or install it and rip the guts out , or just put it together myself (well, good mechanics might pose a problem, but it's not entirely impossible). Dry bulb solution is going to cost me $3 per sensor, humidity is going to be more problematic because a) I didn't touch that part yet b) the sensors are pricey (last time I checked it was like $50) and they tend to be heavily backordered.

One more thing, the Trane manual I was looking at mentions that their economizer can work in two modes: if the air is sufficiently cool, it will just exhaust the indoor air and take the outside air in (I wonder how do they plan to filter it?), if it is not, but it's lower than the indoors, it's going to put the outside air through the indoor coil to just cool it further (filtering again?).

Diceman:

quote:

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Usually an econo will do the job unless it's a computer room or something

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This one I don't get. Computer room is way hotter than the rest of the house (4 to 8F is a norm), and will benefit from the colder outdoor air sooner than the rest of the house (actually, I was thinking about separating the A/C for the computer room from the house altogether, but it's noisy enough already). Can you please explain why do you think it's not going to help?

And to finish it on a light note, here's one:

"If you are over 30, you wake up in the morning and nothing hurts, you are probably dead".

I though it was a joke. Now I'm over 30
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--vt

quote:

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Originally posted by vt
I wouldn't mind dropping the indoors to 75F, and the ambient sometimes drops below 68F in early September. The heating season, on the other hand, started on November 23 last year. Three monts in one half of the year is something to consider seriously.

I may not be tracking very well with your thought processes on this one, but here's how the economizer works, if you use it as the factory built it:

If there is a call for cooling, and the outdoor temperature is less than 50� drybulb (on single enthalpy models) the econmizer will open just enough to send 55� air back into the living space. If the economizer is full open, but the air returning to the space is still above 55�, then mechanical cooling will run (compressor). On dual enthalpy models (the only way to go in my opinion), the total energy in the air is measured (sensible and latent) in both indoor and outdoor air. This allows the air to be mixed to a more exact match for what the air would be like if the compressor were running.

As you may notice, the ambient temp will need to be below 50� before the economizer will function, and I don't know how often you will need cooling when the ambient is below 50�.

Now, I assume that all economizers work like that, since we buy economizers from Johnson, Honeywell, and Rooftop Systems, all of them behave identically to what I have described here.

Another thing, I see a need to further investigate the way the economizer is controlled - if it depends on "smart thermostat", then I've got it covered. Common sense tells me that this is probably the case. However, if I'm wrong and the economizer is a self-contained unit

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Every economizer I have ever seen was completely self contained. The only requirement from the thermostat is an additional stage of cooling. Because first stage cooling now powers the economizer. The economizer control determines if free cooling is available, opens the dampers, measures the mixed air, and modulates the mixed air temperature.

I have access to a couple of enthaply sensors I will give you, and maybe even a control board you can use to figure out what you need.
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There are no stupid questions. . .just a lot of inquisitive idiots.

Attic fans are great, have one, but when you use them they bring in all of the outside dust, dirt, humidity and oh yes smog. The also cost as much as a furnace blower to run. The old kind are also a great source of air leaks.

I still like idea just need a better way to get the job done. I don't know if something like a economizer would do much in my area Southern California. We don't get the extream temp drop in the summer when the sun goes down like other areas.

The biggest thing I see is getting the hot air out of the house quickly. I have been thinking about a way to use the HVAC to do that job. I was thinking about opening a large outside air damper to the return if the outside temp is lower than the inside temp along with another damper, maybe barometric, that vents house air into the attic. II just don't know if it worth the effort.

quote:

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Originally posted by duckman373
I grew up in Phoenix before Uncle Sam relocated me to NC. If it's a house you are trying to cool, try a whole house fan which brings in air from open windows and pushes it through the attic. We had one in our 2200 sq ft house. After the sun went down, the fan went on, and boy did it do the trick. That's one of the perks of the desert climate-high relief.

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BamaCracker:

OK, I see the disconnect now. I presumed that the economizer kicks in as soon as the outdoor air temperature (heat) becomes reasonably lower than the indoors.

Of course it doesn't make sense for me to use the economizer if it just kicks in at about 50� - here, that happens long after the heating mode is engaged. But then again, it will make a perfect sense to hack one to make it utilize outdoor temperatures as high as 70�.

I agree that dual enthalpy is the way to go.

It'll be a while before I can find time to fiddle with this - the parts that were on backorder are coming this week, so I'll get back to this as soon as I'm finished with the controller installation and tuneup.

One thing is not yet clear to me: how is the filtering problem usually solved? The usual location of the filter is on the return intake, that makes sense. The air inside the house is recirculated, thus making the filter's job easier. However, if the economizer is installed, then

- the indoors filter filters the air to be discarded immediately, very smart - and there's no realistic place to move it to
- if there's a filter on the economizer intake, it's gotta get pretty dirty pretty fast
- and it's going to be a royal pain in the {censored} to replace/clean it once a week

In this climate, the dust is a major problem, especially when the wind season starts.
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--vt