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AC ambient air temp


kurt
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Good question. Obviously there are maximum ambient temperatures however I don't think I've ever seen this published from the manufactures (that's not to say manufactures never publish this information). The one picture you posted of the apartment building with all the condensing units is a good example of exceeding design conditions.

After a short Google ride I found this:

Trane Co. equipment data indicates proper unit operation up to a maximum ambient

temperature of 115°F (46°C). Problems should be expected only at temperatures above 115°F

(46°C). This is a typical limitation for an air-cooled DX packaged unit. Over-sizing the unit

cannot be an answer to the problem. The only solution to the problem is reducing the

condenser intake air temperatures by means of pre-cooling. This effectively will increase the

condenser capacity. Installation of a pre-cooling system for the condenser intake air will have

an additional benefit of reducing the power consumption by the refrigeration compressors.

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Originally posted by Terence McCann

Good question. Obviously there are maximum ambient temperatures however I don't think I've ever seen this published from the manufactures (that's not to say manufactures never publish this information). The one picture you posted of the apartment building with all the condensing units is a good example of exceeding design conditions.

After a short Google ride I found this:

Trane Co. equipment data indicates proper unit operation up to a maximum ambient

temperature of 115°F (46°C). Problems should be expected only at temperatures above 115°F

(46°C). This is a typical limitation for an air-cooled DX packaged unit. Over-sizing the unit

cannot be an answer to the problem. The only solution to the problem is reducing the

condenser intake air temperatures by means of pre-cooling. This effectively will increase the

condenser capacity. Installation of a pre-cooling system for the condenser intake air will have

an additional benefit of reducing the power consumption by the refrigeration compressors.

Yep, that's the one. One of the condo owner's asked if there was a maximum ambient air temp. I've never seen one, couldn't find one, so I came to the brothers & sisters to see if anyone here knew.

Terry, you da man. I was all over the Trane site, and never found what you're describing. Got a link or path to the info?

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The link to the text in my first post is here http://www.microcool.com/cooling/brochu ... ooling.pdf

Here is a link to an actual Carrier spec sheet however it is from a rooftop package unit. In this spec they say 125º -

2.1.8.3 Operating Characteristics

A. Unit shall be capable of starting and running at 125°F ambient outdoor temperature per maximum load criteria of ARI Standard 360.

B. Unit with standard controls will operate in cooling down to an outdoor ambient temperature of 0°F (-17.8°C).

C. Unit shall be provided with fan time delay to prevent cold air delivery.

D. Size 15, 18, and 20-ton units shall have 3 fully independent refrigerant circuits to allow for 33% loading.

Here's a link to HVAC Partners

I've got a call in to my contact at our local Trane dealer for a link to actual Trane literature. You need to be a Trane employee to access some of this information (why it's under lock and key I'll never know). I called my friend with Carrier and he said 115-125 is the rule of thumb.

We use to figure 30º over ambient for reading head pressure (I think that has dropped with higher efficiency units) so as an example:

R-22 at 125º ambient with 30º over gives you a head pressure of 405# - yikes! That's the pressure where most fusible plugs let go.

You have a hornets nest with that project. They ever look into the possibility of two fans, one to push and one to pull air through that space? It would be noisy as hell with all the condensing units singing and two good sized fans moving air but from the looks of it your options are limited.

One trick we use when a condenser fan would die is to run a lawn sprinkler over the condensing unit however this is very short term due to the fact that constant city water on the fins eats them alive.

I have to go now, I've given myself a headache. Good luck!

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Kurt, a few questions.

Is the installation new/newer? The installing contractor still in business? What have they said about the project? Is it plan & spec or design build? Plan & spec would put the onus on the design engineer, design build would put the onus on the mechanical contractor.

I lived for these types of problems when I was in the contracting business. There was nothing that compared to being challenged with a very nasty problem and finding a solution (as long as it wasn't your company that caused the problem). It was my drug of choice.

You're a lucky dog.

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Also very helpful. Thanks so much, you guys.

Terry, this isn't going to be my "solution"; I'm just trying to help a HOA figure out their problems.

This particular issue resulted from the builder making some offhand comment about ambient temps being just fine; we were looking for something to let the air out of the guy.

These #'s are what I was looking for.

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Kurt - I uploaded a pdf for a Trane 2 1/2 Ton Split System Cooling — 1 Phase 2TTX5030A condensing unit. It should be in the files section for download.

From the PDF file:

General

The 2TTX5 shall be fully charged from

the factory for matched indoor section

and up to 15 feet of piping. This unit is

designed to operate at outdoor ambient

temperatures as high as 115°F. Cooling

capacities are matched with a wide

selection of air handlers and furnace

coils that are ARI certified. The unit is UL

listed. Exterior is designed for outdoor application.

Hope this helps.

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