# HVAC Advice



## Digione (May 8, 2006)

During the build of my dedicated HT room I requested a 1 ton, 300 CFM split ducted system to be installed. Unfortunately what got installed was a 1.5 ton 450CFM system (Goodman GSX 130181BA compressor with matching Goodman air handler). I was ill at the time and didn't discover what had happened until after the project was complete and both my contractor and HVAC company had gone bankrupt...I was their last job. 

The HVAC system is dedicated to the HT room and cannot be ducted to the main home due to isolation issues etc.

Has anybody got any ideas how I can effectively reduce its cooling capacity to 1 ton or less as the air entering the room is far too cool. I have reduced the air flow to about 350 CFM and the unit never ices as it is on for such a short time. The room is only 1900 cubic feet.

A few ideas that I had were:

1. Altering the speed of the compressor using an inverter. Not too sure if this is possible with the Copleand Scroll compressor.

2. Looping the air handlers send return and using a damper & freezstat

3. Adding a 1.5KW electrical heater to the air handler to come on with the compressor

Any advice/help please.


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## RBTO (Jan 27, 2010)

Hope you got a good deal on the extra large capacity system!

Couple of thoughts & a suggestion:

Can you install a bypass duct around the cooling coils with a damper or slide to control how much air bypasses the coils. You might run into an icing problem like you anticipated previously.

Another possibility is to tee the duct going to your room and bring in another duct with forced outside air and, again, a damper or slide to allow control over the mix (alternately, a speed controlled fan on the mix line). You would have to vent the room to the outside to equalize pressure so the outside mix could come in if you go this route.

Check with the manufacture and explain your problem. There might be a variable frequency drive available for the unit which would allow you to back off on the capacity.


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## Digione (May 8, 2006)

RBTO said:


> Hope you got a good deal on the extra large capacity system!
> 
> Couple of thoughts & a suggestion:
> 
> ...


I tried to contact Emerson who sell/manufacture the compressor but they referred me to a distributor who I will call tomorrow and then probably an established HVAC company.

Thank you for your suggestions. I looked at the bypass solution but have real concerns about freezing. I think that the lowest cost, and most inefficient solution, is to add an electrical 3KW heater ($55) as I have the breaker and cabling in place to support it. However, I need a suitable control system for it as I need to have control over its supply rather than just on or off. Again I will see what I can find out tomorrow.


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## ironglen (Mar 4, 2009)

Sorry to hear of your hvac issues.

I do hvac changeouts and new installs for a couple companies and I find fault with oversizing perhaps 7/10 times. It typically results in short-cycling (on/off/on), increased noise (duct undersized for the airflow), and uncomfortable temperature fluctuations. That 15x16x8 room could have used a 1/2 ton mini-split, perhaps 3/4 ton, at most.

I'm no expert :whistling: If the distributor's technical representative doesn't help you, shoot me a message and I'll check with mine, as he is pretty knowledgeable and helpful.

If it were me, I'd try placing the fan in the lowest setting along with installing a freezestat on the coil to cutout the compressor in the event the coil ices. Compressors are either two stage or dual compressors in variable speed systems, so slowing the compressor is probably not an option. 

While not inexpensive, you _might_ be able to changeout the condenser to a smaller capacity while retaining the indoor equipment while running the fan on slow, but that would be something a tech rep would have to verify. I'd be concerned that the total capacity would still be oversized for that rooms heat load. You might consider offsetting the cooling capacity with a tower of pro-amps to generate heat...:dontknow:


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## Digione (May 8, 2006)

ironglen said:


> Sorry to hear of your hvac issues.
> 
> I do hvac changeouts and new installs for a couple companies and I find fault with oversizing perhaps 7/10 times. It typically results in short-cycling (on/off/on), increased noise (duct undersized for the airflow), and uncomfortable temperature fluctuations. That 15x16x8 room could have used a 1/2 ton mini-split, perhaps 3/4 ton, at most.
> 
> ...


Thank you for your advice. I am hoping to talk with at least two HVAC "experts" today to see what their advice might be. The current air volume is manageable and the rooms NC rating is about 25 with the air running. If I reduced the air volume to half what I have now it would still be enough and it would probably drop the NC rating to maybe as low as 15/20 as all the noise is from the excessive duct velocity (mainly LF noise) as I only have three 1SQFT outlets feeding three separate plenum chambers within the room for distribution.

If I get nowhere I will PM you to see if any of your contacts can help out.

I could always turn the water heating on...no room for more amps.


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