As Happy As I Can Be....(Almost)

[MrDodge]

Hey Guys,
I happened by this site about 2 wks. after a new install in my home. After reading this site for the past 2 months I feel my guy did me right. It appears properly sized for 1250 sq. ft. Goodman 2.5 Ton GSH130301 & ARUF303016 AH with HKR-15C Strips. (I know, a dinosaur by your standards, but a quantum leap from 15 yrs. of ceiling cable.) This unit has lowered my winter energy costs by at least 35-40% Woo-Hoo. I couldn't believe it. The reason I'm posting is about fan speed, Based on summer cooling (400 cfm per ton) I feel the ARUF3030 needs to run medium speed 1330/1239/980 @ .3 Static, but the specs. clearly states it must be on high with 15k strips. I have around a 60 degree Temp Rise on Emerg. Heat. I was curious if running on Med. speed if there was a danger with overheating, SA would probably 140+ in Aux. With that said smaller Air Handlers ARUF182416 have the same strips pulling the same amps with 1025/790/570 cfm. I know the strips aren't needed during cooling but I'd like to just leave it on Medium Speed year round cause you can't even hear it run. If it matters I have an 8"x14" trunk running left, right & up to 2nd Story Master Bdrm/Bath with a total of 10 6" supplies. Any Response Welcomed

[Pascone10]

Hey Guys,
I happened by this site about 2 wks. after a new install in my home. After reading this site for the past 2 months I feel my guy did me right. It appears properly sized for 1250 sq. ft. Goodman 2.5 Ton GSH130301 & ARUF303016 AH with HKR-15C Strips. (I know, a dinosaur by your standards, but a quantum leap from 15 yrs. of ceiling cable.) This unit has lowered my winter energy costs by at least 35-40% Woo-Hoo. I couldn't believe it. The reason I'm posting is about fan speed, Based on summer cooling (400 cfm per ton) I feel the ARUF3030 needs to run medium speed 1330/1239/980 @ .3 Static, but the specs. clearly states it must be on high with 15k strips. I have around a 60 degree Temp Rise on Emerg. Heat. I was curious if running on Med. speed if there was a danger with overheating, SA would probably 140+ in Aux. With that said smaller Air Handlers ARUF182416 have the same strips pulling the same amps with 1025/790/570 cfm. I know the strips aren't needed during cooling but I'd like to just leave it on Medium Speed year round cause you can't even hear it run. If it matters I have an 8"x14" trunk running left, right & up to 2nd Story Master Bdrm/Bath with a total of 10 6" supplies. Any Response Welcomed

it all depends on your static in YOUR system.. that needs to be calculated by the professional that installed the system. Also when your system runs it does not have to be at the same speed for both.. Thats all the info i can give w/o over stepping my boundaries. Call your contractor that you are happy with and let him tell you how its running and if it needs changes or what it needs... What sparked this interest? Why do you think it wrong?

[beenthere]

If you have a 60°F temp rise on 15KW of strip heat.
Your only moving 790CFM.

How did you figure you were at a .3" static(ESP).

[BaldLoonie]

Ya gots a typo there been, had me cornfused. That's 60° rise!!!

And that is a pretty healthy rise! Many brands don't allow 15kw in a 2 ton because running only 800 CFM is too little. Goodman didn't used to on the ARUF24 but I see it does now on the 1824.

But if you are getting 60° rise and 790 CFM as been has calculated, you must have considerably higher static and risk cycling on limit. Having the pump on and 3 elements will make it worse. 15kw for 1250 sq ft seems high unless you are in a very cold area. How about turning off the smaller breaker and trying only 10kw?

You have 1 14x8 supply? Or 3? Are the 10 6" supplies metal or flex?

[beenthere]

Ya gots a typo there been, had me cornfused. That's 60° rise!!!

LOL... Fixed it.

[MrDodge]

Guys Thanx 4 Your Replies,
Pas,
I'm not sure it is wrong, I've probably just been doin to much reading & it isn't even AC weather yet. By other posts Ive read 1350 cfm may be to much flow for 2.5 ton thats the main thing that sparked my interest.
BT,
thats the stats for airflow posted by the mfg.
BL,
I have three, each are about 12' in length running left,right, & up from supply plenum with 8- 6" & 2-7" Flex Ducts. Turning off the 2nd 30 AMP Circuit seems to be a viable option. I was uncertain if that was possible.
4 All Who Replied,
I spoke with my installer & he said just leave it on high I shouldn't have any problem which may be true. I was just thinking ahead to Mid August with short cycles, and 70% RH. I'm a worry-wart right?

[I_bend_metal]

If you have a 60°F temp rise on 15KW of strip heat.
Your only moving 790CFM.

This could be the dumbest question ever.....but what is the formula for figuring that?? Not busting balls at all, just extremely curious!!

[beenthere]

In order to use the mfg fan data. You must measure the actual static(TESP) that the blower is working against.

Then you would go to that static pessure column, and read how many CFM its moving, for the fan speed you have it running at, while your getting that reading.

Your not moving any of the CFM's you posted.

If after you turn off the 30 amp breaker, you get around a 40°F rise, your moving roughly 790CFM, at what ever speed the blower is currently running at.

[beenthere]

This could be the dumbest question ever.....but what is the formula for figuring that?? Not busting balls at all, just extremely curious!!

BTU output/(temp rise*1.08)=CFM
51195/(60*1.08=64.8)=790

34130/(40*1.08)=790

[hvaclover]

This could be the dumbest question ever.....but what is the formula for figuring that?? Not busting balls at all, just extremely curious!!

Fiddle with the equation to calculate CFM on an electric furnace and i think you'll get it.

[beenthere]

This could be the dumbest question ever.....but what is the formula for figuring that??

You got mail.

[MrDodge]

Thanx Everyone,
I've taken your advice & am running on 10k strips (turned off 30 amp Br.) & have opened all registers ( Mrs. had 2 bdrms. closed ) from original post. I have a 34-35 deg. temp rise in emerg. heat at supply plenum which is in line with the documentation I have. I was curious about capacity, with 26,800 btu cap. in heating would that mean approx. 26 deg. rise in a perfect world? I checked today & I have a 29 degree rise in heat mode @ 56 deg. ambient. Does this seem in the realm of ok?

[motoguy128]

I checked today & I have a 29 degree rise in heat mode @ 56 deg. ambient. Does this seem in the realm of ok?

If your flowing 1000 CFM, (400 CFM/ ton) you would be producing 31,300 BTU's. So if you think your capacity actually is 26,800 at 56F (is that from the product data sheets?) then you're flowing about 850 CFM or clsoe to 350CFM/ton which is nice for comfort, and will give good latent capacity in summer without freezing the coil.

However, if this was measured with a clean air filter, keep in mind that if the filter gets dirty, you may have issues. I'm not sure I'd cut it that close with a PSC motor without a air flow switch.