What is diff between 38TKB and 38TRa?

[stevenm]

Hello All - replacing my outdoor compressor and indoor coil, gonna stick with Carrier.

I have two quotes, one for a 38TKB024 and one 38TRA024

I am not in the business so I don't know how to evaluate these. My web searching so far only shows that the TRA is less noisy. What accounts for the difference in cost?

We live in a small townhouse and the top floor is always too hot in the summer - so I was thinking about going for a 2-1/2 ton unit instead of the 2 ton, but there again, the difference in the cost of going up 1/2 ton is markedly different.

How should I evaluate these two different units?

Thanks

[BaldLoonie]

TKB is 10 SEER recip compressor, TRA is 12 SEER with Copeland scroll under blanket with special sound deadening top. World of difference. If mild summer and/or low electric rates don't justify 12 SEER, then what you are paying for is the better compressor and sound suppression methods.

Bigger doesn't mean better cooling. Oversized unit runs less which can mean higher humidity. Longer run cycles suck more moisture out. Also, long run cycles help spread the temp out between floors. Bigger unit comes on, satisfies the stat quicker leaving upstairs warmer.

[stevenm]

OK thanks

I have a wireless t-stat that I will keep upstairs during the summer, I dunno if that changes anything

One more question - do you know anything about Carrier's humidity control technology that purportedly controls humidity *between* cooling times of the unit? sounds too good to be true ...

[BaldLoonie]

Only thing I've heard of is overcooling to lower humidity. If the unit hasn't run for a few hours because the temp set is close to room temp, some stats will turn the cooling on a bit to mix up the air and remove a little moisture.

Wireless stat upstairs will overcool the downstairs. Balancing dampers to throttle down (not too much) the 1st floor could help in the summer.

[stevenm]

Yes I use the dampers to send most of the air upstairs

the downstair stays cool no matter what's going on upstairs!

So you sound like you are definitely endorsing the TRA over TKB? Our cooling bills are not killing me, but they are not trivial either. I'm all for efficiency ... mostly I just want to be comfortable (i.e. low humidity in the upstairs) when I go to bed at night ...

TRA it is then?

[BaldLoonie]

Where are you? What's your electric rate per kwh?

[stevenm]

Virginia - 4.28 cents kwh

[BaldLoonie]

Unscientifically, with a small unit in a mild climate and a very low electric rate, what you would be paying for in the TRA is the better compressor and the quiet. Odds are what little you save over the 10 SEER wouldn't pay back in any reasonable timeframe unless electric bills drastically changed. We have the same situation here. Our rates are similar. Our utility says savings is about $4 per ton per SEER point. So savings of 12 over 10 in a 2 ton would be maybe $16 per year.