AC 101

[mgbinspect]

Here is a label on a Janatrol Condensing unit. When I see two possible multiples of six or twelve, I'm never certain which is the actual BTU info. Is there a rule as to how the numbers are ordered? Is this 2.5 tons or 3 tons? I always assume the first multiple is probably right, so I would guess 2.5 tons. But, if there's a sure-fire trick to this that I've never been taught, I'd sure love to hear of it.

So, once again I tee up a question to learn from the brain trust.

School me!

Thanks in advance.

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[Terence McCann]

Forgot the picture of the label Mike.

024 means 2 ton, 036 means 3 ton etc. Remember that 12,000 BTUS = 1 ton of cooling. Then again there are times where the model/serial numbers are totally unintelligible (manufactures do have a sense of humor).

[mgbinspect]

Yeah, I know that Terry. It's when you have two possible right answers like this one, that throws me. Is it 2.5 tons or 3 tons? It seems, of late, I've had a run of these where you look at it and think, "Well darn! Which is it?" is there some nifty little rule to deciphering one like this?

[Marc]

It's a 36,000 btu/hr, 3 ton. The btu/hr is expressed in units of thousands of btu/hr. There is usually a zero to the left of this two digit specification, which is generally in the middle of the model number. In my experience, there is only one brand of condenser unit in which the tonnage cannot be read from the model number: Carrier.

If I see 3036 on a Goodman air handler, I'll take that as meaning that the coil can be fitted with either a 2 1/2 ton or 3 ton piston. But on a condenser unit, if I see 3036, I recognize the 036 as the correct spec of the tonnage.

Do keep in mind that you might see something like 037 (37,000 btu/hr) or 041 (41,000 btu/hr). The 37k is marketed as a 3 ton and the 41K as a 3 1/2 ton. As for Carrier, call their service center.

Marc

[mgbinspect]

Yup, I know that Marc, Here's my source of confusion: I'm under the impression that 18,000 BTU/hr is 1.5 tons; 30,000BTU/hrs is 2.5 tons; 42,000 BTU/hrs is 3.5 tons.

Just before the "036" is a "30". That's where I get stuck, so if the BTU rating ALWAYS has a "0" before it, I suppose I have my answer.

Is that how to know which multiple to choose - a "0" before?

This was on a 2900 SF home.

[Marc]

That's what I do. I never call the manufacturer about it because the dang phone never works, but I've bought hundreds of condenser units and when I look at the model number, that two digit # with the zero before it was the actual tonnage that I specified to the dealer.

Marc

[mgbinspect]

Cool! That's what I needed to dismiss the "30". That's the nifty trick I needed. Thanks Marc! [^]

(The really scary part is maybe I knew that once and am going senile...) [:-weepn]

Brace yourself, Chad, memory starts going bit by bit down hill soon after 50... it's a bit freaky...

[Bain]

The number you aren't considering is the "1." Lately, Janitrol and Goodman are putting the SEER rating in the model number. What you're looking at is a 13 SEER, 3 ton unit.

[mgbinspect]

Bain! EXCELLENT! Now that's gold! I had no idea. Sweet! I'm pretty good with HVAC (maybe a C+ or a B-), but difinitely no Einstein. I've actually toyed with the idea of going to night school and taking the courses necessary to become a tech, just for the brainfood, not the trade.

Thanks Bain and Marc. Good stuff...

[Bain]

Bain! EXCELLENT! Now that's gold! I had no idea. Sweet! I'm pretty good with HVAC (maybe a C+ or a B-), but difinitely no Einstein. I've actually toyed with the idea of going to night school and taking the courses necessary to become a tech, just for the brainfood, not the trade.

Thanks Bain and Marc. Good stuff...

High praise. Thank you.

Lots of manufacturers have the model codes listed on their web sites. You can typically go to SPECIFICATIONS, then NOMENCLATURE and see what every number or letter means. Click the link below to check out a similar label to the one in your original post.

http://www.goodmanmfg.com/Portals/0/pdf/SS/SS-GSC13.pdf

[Neal Lewis]

Well, looking at the minimum circuit amps of only 16.8 and a 20 amp max breaker, I would think it's a 2 1/2 ton unit. Those numbers seem awfully small for a 13 SEER, 3 ton unit.

[Bain]

Well, looking at the minimum circuit amps of only 16.8 and a 20 amp max breaker, I would think it's a 2 1/2 ton unit. Those numbers seem awfully small for a 13 SEER, 3 ton unit.

You're mistaken. Check out the link.

[Neal Lewis]

Interesting, the electrical specs in the linked brochure don't match what's printed on the tag.

[Chad Fabry]

One must consider that as efficiencies creep up, btu's per amp creep creep up as well. The old rules of thumb no longer apply. Neal, I know you know that but it's food for thought for those folks who may have just passed (double entendre' intended) through a HI school. Sometimes the curriculums can be a tad out of date.

[Neal Lewis]

Well, my own 3 ton 14 SEER unit is rated for a 30 amp max breaker and about a 25 amp minimum ciruit. That Goodman 3 ton 13 SEER is rated for 20 amps. Go figure, I guess mine's not as good as that Goodman.