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post #1 of 13 Old 08-20-2013, 11:26 AM - Thread Starter
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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. eek.gif

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 and I only need 0.75 tons to cool the equipment and people.

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 (just in case).

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

I cannot replace the system due to shortage of funds so I am looking for a cost effective fix.

Any advice/help please.
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post #2 of 13 Old 08-20-2013, 12:38 PM
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Quote:
Originally Posted by Digione View Post

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. eek.gif

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 and I only need 0.75 tons to cool the equipment and people.

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 (just in case).

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

I cannot replace the system due to shortage of funds so I am looking for a cost effective fix.

Any advice/help please.

All those solutions would seem to cost more than simply replacing the condenser. The main problem with excess capacity is your locality. In NJ, you get high humidity and an over sized unit will only dehumidify when running.

Generally you can use a larger coil with a smaller condenser so the air handler could be left alone.

The re-heater approach is often used in technical facilities where precise temperature control is needed. But it's a huge energy waster.

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post #3 of 13 Old 08-20-2013, 12:57 PM
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If you've already reduced the fan speed as much as you can without the coil icing over, that's about all you can do. I agree with Glimmie that adding the heater is a colossal waste of energy dollars.

The cheapest fix is blankets biggrin.gif , but aside from that what do you think about installing a set of dampers on your supplies and a pressure balancing bypass damper on the main unit itself? This would allow for the extra air pressure from having the theater dampers partially closed to be bled off directly into the return duct and recycled. Just an untested thought...
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post #4 of 13 Old 08-20-2013, 02:59 PM
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Is there some area in the house you could cycle some of the excess capacity?
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post #5 of 13 Old 08-20-2013, 03:28 PM
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I've never seen a split system less than 1.5 ton, which is probably why you were given that. Did you call your hvac guy and see if there was any way to reduce the cooling capacity? I'm not aware of any, but an hvac tech has probably had this problem more than once.

You could try connecting a return to another part of the house and diverting some of the air as Big stated. Perhaps to your equipment room? Or another part of the home that isn't air conditioned?

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post #6 of 13 Old 08-20-2013, 05:50 PM - Thread Starter
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Glimmie, TMcG, BIGmouthin DC & Mr. Tim,

Thank you all for your suggestions. I will be contacting a large HVAC company tomorrow to see if they can come up with a vilable solution short of replacing the whole system. For $55 I can get the electrical heater but I would still need a controller for it as I do not want it to just switch on and off. I realize that it is a terrible waste of power but I only need to run it at an average of 1.5KW for fairly short bursts.

Emerson who make the Copeland Scroll compressor were not too helpful as I was not a distributor but end user, and just referred me to one of their local distributors, who were also less than helpful.

I will report back after chatting with a local HVAC company tomorrow, unless somebody comes up with something "revolutionary". smile.gif
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post #7 of 13 Old 08-20-2013, 06:11 PM
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Quote:
Originally Posted by Digione View Post

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

Is there any area outside the theater where the ducting running to the theater can be accessed, or is the whole ducting system inaccessible? A bypass damper on the main unit can dump the excess supply back into the return.

I don't know how realistic (or practical or code-compliant) this is, but when looking at homes a number of years ago I recall one HVAC system where they installed a takeoff immediately above the a-frame coil on the main system take-off. Depending on the size of the take off, you could substantially reduce the amount of air supply to the theater by dumping it immediately outside the HVAC unit - which you do have access to modifying. Adjusting a manual damper on this takeoff would allow you to throttle the amount of supply to the theater room.

I'll be interested to hear what your HVAC company says.
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post #8 of 13 Old 08-21-2013, 08:40 AM - Thread Starter
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Quote:
Originally Posted by TMcG View Post

Is there any area outside the theater where the ducting running to the theater can be accessed, or is the whole ducting system inaccessible? A bypass damper on the main unit can dump the excess supply back into the return.

I don't know how realistic (or practical or code-compliant) this is, but when looking at homes a number of years ago I recall one HVAC system where they installed a takeoff immediately above the a-frame coil on the main system take-off. Depending on the size of the take off, you could substantially reduce the amount of air supply to the theater by dumping it immediately outside the HVAC unit - which you do have access to modifying. Adjusting a manual damper on this takeoff would allow you to throttle the amount of supply to the theater room.

I'll be interested to hear what your HVAC company says.

Yes I can do what you are suggesting. The air handler and all the ducting is in a 4 foot high crawl space immediately below the room and access is easy to add the bypass and freezstat. Hopefully I will be talking with an HVAC "expert" today to see what he recommends. I am not worried about code at this stage.wink.gif
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post #9 of 13 Old 08-21-2013, 03:15 PM
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I think they make a split air system that is smaller than 1.5 ton. The only viable option is to push another run into another part of the house. If you have a basement room or something that you can add a duct line to that will reduce the air capacity.
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post #10 of 13 Old 08-21-2013, 06:22 PM
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I know Mitsubishi makes a 12000 BTU/hr (1 ton) ducted (or ductless) mini-split.
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post #11 of 13 Old 08-21-2013, 06:36 PM - Thread Starter
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Unfortunately I have no way of "dumping" the excess air/cooling capacity, and replacing the whole system with a ducted split system is above my current budget. Also I cannot speed control my Copeland Scroll compressor either.

So, according to the experts, it looks like I am going to first try a send/return bypass with a damper and freezstat. This may then need to be supported with a heater in the air handler if absolutely necessary.

I have met with two HVAC companies and both selected the above option as the easiest way of dumping both extra air and cooling capacity.

I will get the quotes next week. Shouldn't be too much for 8 feet of 8" duct, a damper, freezstat and a few hours of installation. Here's hoping.
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post #12 of 13 Old 08-21-2013, 07:24 PM
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Good. That seems like the most logical first step. I'd clarify with them if they plan just to install a bypass damper or an automatic static pressure balancing bypass damper, which is essentially a damper with an adjustable counterweight which can modulate the pressure, especially for a variable speed blower system. It's also handy if they put in-line mechanical dampers to your theater's supply to further control the amount of supply.
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post #13 of 13 Old 08-22-2013, 12:16 PM - Thread Starter
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Quote:
Originally Posted by TMcG View Post

Good. That seems like the most logical first step. I'd clarify with them if they plan just to install a bypass damper or an automatic static pressure balancing bypass damper, which is essentially a damper with an adjustable counterweight which can modulate the pressure, especially for a variable speed blower system. It's also handy if they put in-line mechanical dampers to your theater's supply to further control the amount of supply.

Thanks for the advice, will do.
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