Trane XV90 Dipswitch Settings. Right or Wrong??

[mcginkleschmidt]

From reading in this forum that sometimes the installing technicians are not always prone to perfection and after four seasons of cooling and heating, I decided last week to check my dipswitch setting for the first time on my Trane XV90 furnace/air handler. Based on the information in my Trane XV90 Installer’s Guide, page 12, Service Facts, the settings appear to be wrongly set and since I plan to call for my semi-annual maintenance check for the cooling season, I invite you pros to give me some input about my settings so the technician can address my dipswitch settings if indeed they need to be adjusted.

My system is used to cool/heat a 2350 sf single story house in Marietta, Georgia with horizontal furnace and ductwork in attic that consists of the following units:

Trane Gas Furnace XV90/Air Handler UY100R9V4 (100BTU)
Trane XL14i Compressor Model No. 4TTX4048A1000AA (4 ton)
Trane Evaporator Coil Model No. RXC054S3HPCO
Honeywell Thermostat VisionPro TH8320

Below is a visual of my current dipswitch settings and based on the information given in the Installer’s Guide, Service Facts, pg. 12, it appears to me that dipswitch numbers 1, 4, 7 & 8 are not correct. The current settings of switches 1, 2, 3 & 4 appear to be set for the “low” air flow setting for a 3.5 ton condenser (mine is 4 ton) and switches 7&8, for heating, appear to be set for “medium low” air flow setting and need to be set exactly opposite of how they are now set.

Last summer during the repair of a refrigerant leak situation, I recall the technician telling me that switches 5&6 were not correct for Comfort-R to work effectively and he changed them at the time and they appear to be set correctly. Also, I remember the same technician telling me the sub-cooling temperature should read between 9 & 13 degrees and he deemed my system ready for service at 11 degrees sub-cooling. One thing I wonder about is if dipswitches 1 through 4 are changed to the factory “medium” settings for 4 tons (all 4 dipswitches off) with increased airflow through the evaporator coil (457 CFM difference from the current setting at 0.1 external static pressure), how will this affect the sub-cooling degree readings? And, will this increased air volume change likely require any addition or removal of refrigerant as, from a homeowner’s understanding, the gas line temperature would be raised by the increased air volume over the coil and would change the sub-cooling temperature readings at the outside unit?

I recall reading a post by Baldloonie about setting the airflow setting to 350 CFM/TON to improve comfort in high humidity situations during the cooling season and maybe this is why some of my dip switch setting are set at other than medium/factory settings. The heat settings, I just don’t know?

Any thoughts, suggestions or comments are appreciated.
http://i105.photobucket.com/albums/m215/mcginkleschmidt/TraneXV90DipSwitchSettings.jpg
http://i105.photobucket.com/albums/m215/mcginkleschmidt/Page12InstallerGuideUY100R9V4W.jpg

[czkidd]

Don't use much gas furnaces in the south florida area but I do see that the dip switches for the available outdoor size is incorrect if what you are showing is accurate. Go with 400cfm per ton. Works well in south florida where humidity is high.

I would suggest going with a TRANE thermostat for control. A TCONT802 would be good. The thermostat must be programmed for your type of system and once the parameters are set it works quite well.

TRANE recommends a 10 degree sub cool for proper performance and efficiency of the cooling system.

Not sure what "Comfort R" is related to. Is the furnace equipped with a variable speed fan motor? Could this mean "Enhanced Mode"?

Always make sure that the thermostat, condenser wiring terminate on the terminal board of the Furnace/Air Handler.

[mcginkleschmidt]

Thanks czkidd for the reply. As a homeowner, I do know some things and Comfort-R settings and "Enhanced Mode" are the same thing.

I already have the Honeywell VisionPro TH8320 and the Trane TCONT802 thermostat is a re-branded VisionPro TH8320 with a Trane logo. so they are identical thermostats.

What effect of increasing the air flow volume to 400 cfm/ton from current flow volume will it have on the sub-cooling measurements? And will that likely require removal or addition of refrigerant, which in this case is R-410A?

[beenthere]

It might need a slight asjustment for the charge.
If your in a high humidity area, why do you want 400cfm per ton.

Bring up your concerns to the tech that performs your service check.

[mcginkleschmidt]

I don't know that I need 400 cfm as that's what I'm trying to find out. But I'm also concerned about the setting for heat, switches 7 & 8, that are set for "medium low" air flow setting. I read a post by someone on this forum that said warmer air from ceiling register (read: lower CFM) equates to shorter heat exchanger lifetime. So my purpose is to try to determine the correct switch settings for both heating and cooling.

If 350 cfm is best for cooling, should the switches be changed each time between the heating and cooling season? And if the switches are set for Comfort-R (Enhanced Mode) should the dip switches also be set for 350 cfm at the same time? Would this be the enhanced, enhanced mode?

[lbf]

I would set the switches to medium to lower the temperature rise to 50 degrees if you have ceiling registers. This should help move the heat down from the ceiling ( both by adding throw and by destatification). Your cooling airflow, I would set at 400 cfm/ton, again to put a little more throw from the registers, and then install a humidity control to automatically slow the blower when the humidity in your home increases and then return to normal when the humidity is under control. I don't know if you've been told about that option or not.

[mcginkleschmidt]

I am familiar with slowing the blower to achieve enhanced humidty control and Comfort-R (Enhanced Mode) is currently in operation with dip switches 5 & 6 turned on in conjunction with the variable speed blower in the Trane XV90 furnace/air handler. I'm already set up with this operation. Some have recommended leaving the blower speed at 350 for enhanced humidity control but is it advisable with dip switches 5 & 6 set up for Comfort-R at the same time.

I recall last summer the tech telling me that with Comfort-R settings the blower doesn't run for the first minute allowing the coil to reach a near-freezing condition, then the next 7.5 minutes the blower runs at 80% and after 8.5 minutes, the blower advances to 100% speed, if required. At the end of the cooling cycle the compressor cuts off but the blower speed ramps down from 100% to 0% over a 3 minutes period to extract the last of the coldness from the evaporator coil before the air handler shuts down.

My concern is with a reduced blower speed through Comfort-R operation, is it also advisable to have an even further reduction of blower speed to 350 CFM through dipswitch settings?

Any advice on the furnace heat setting?

[BaldLoonie]

You are really hurting if you are at 350 cfm/ton, but for a 3.5 not the 4 you have AND have Comfort-R turned on. I'd try 400/ton for a 4 ton with Comfort R. If that makes it too humid, drop back to 350 but for a 4 ton.

The way it is set, you are at 1225 CFM for a 4 ton. Too low, especially since it takes 8.5 minutes to even get that.

[lbf]

The control I mentioned is designed to work in addition to the Comfort-R settings. The Comfort -R just tells the motor to go through the ramp stages by time. The actual cfm it moves is determined by the cfm settings(in this case for a 4 ton system) determined by the dip switch settings. I think everyone agrees that setting the cfm lower than 400/ton will give you better humidity removal, some are saying set it that way all the time and I was saying use this additional control to only do it when needed. (it gives you a 20% reduction when the control asks for it)

[mcginkleschmidt]

The control I mentioned is designed to work in addition to the Comfort-R settings. The Comfort -R just tells the motor to go through the ramp stages by time. The actual cfm it moves is determined by the cfm settings(in this case for a 4 ton system) determined by the dip switch settings. I think everyone agrees that setting the cfm lower than 400/ton will give you better humidity removal, some are saying set it that way all the time and I was saying use this additional control to only do it when needed. (it gives you a 20% reduction when the control asks for it)

Thanks lbf. Would this be accomplished by using the Honeywell IAQ thermostat? I've read about the IAQ thermostat and what you are proposing sounds very much like the IAQ. If not this, I don't what you are proposing. Could you please elaborate?

[lbf]

The control I was referring to is a BAYSTAT253. You could also use Honeywell's IAQ stat with a relay to do it also. Using a control allows your system to vary it's sensible heat ratio by the actual humidity load on the house.

[BaldLoonie]

The IAQ doesn't need a relay. Very simple to hook up. I shut off Comfort-R when I hooked mine up. I think it cools better in dry weather to have the thing come on full blow right away. I have mine set for 450/ton for dry and 350/ton when the IAQ sez humid.

[mcginkleschmidt]

Do you think the relay that lbf is talking about is the Equipment Interface Module (THM5421C1008) that interfaces with the thermostat?

[lbf]

No, it is just a small relay that any hvac service co would have. There would be a way to hook up the IAQ without one but if I were doing it, I would use the relay.

[mayguy]

I still don't understand why you would use a relay?? IAQ does not need one. Just wire it up to the furnace's board.

[kevinmac]

Mine is setup under Comfort R,ans works as you described whereas the VS AH will come on as soon as the condensor kicks on in a ramp up mode.
There is also a setup for a no blower start to allow the coil to become chilled before the blower kicks on and goes into Comfort R. I have two distinct settings. I do not have the Vision Pro since my Xl19i was installed before this thermo was on the market. But my Trane at that time was the top thermo, and it had Comfort R and enhanced delayed blower startup.
My switches are set to match the condensor size.