Trane XB14 and XR80
I just had a brand new 3.5 ton Trane put in our Townhouse, XB14 and XR80. It replaced a 4.0 Carrier. My concern is this, as old and beat as the Carrier was, if I set it to 73 degrees regardless of the outside temp, it went to 73 degrees. This new unit runs all day and never get to 73 degrees only 75 degrees. Did I buy too small of tonage? is there something wrong with the balance of gas? Something the contractor may not be telling me? The A/C company owner said it is operating correctly, and that it is just too hot outside. Seem incorrect to me...Please help your input is much appreciated.
Steve - Tampa, Florida
What is the outlet temperature of the air in the ducts? The only way to tell if things are working properly are to check the operating pressures, temperatures, and air flow. If you didn't have a manual-J heat loss analysis done, the size may not be proper. This one is 25% less powerfull, and that may be the difference. The bigger question is how is overall comfort? If the air ends up drier because it runs longer cycles, you may end up more comfortable that a bigger unit that turns on and off. Continuous running removes more moisture, and that is often a big issue. If the air is drier, you can often feel the same at a higher temperature. the last thing, did they change the thermostat as well? The readouts on some never were calibrated really well.
At night, when it cools done some, can it ever get to the set point? If not, something is wrong.
Thanks Jim - The A/C put a gauge on the system, said it was balanced freon wise. Since he left the inside temp has gone up 2 degrees to 77 and the humidity is 51%. Seems to be getting worst. I may have picked the wrong contractor...I pray not.
They said they would put in a 4 ton...we'll see
Any idea what the cfpm setting on the fan is? Is the air flow stronger/weaker/non-existent? Is the evaporator coil clear or is it iced up? Is the air filter clogged?
Jim - I am not sophisticated enough to know these answer. I could ask the contractor in the morning but may insult his integrity. Will see
The furnace air flow (in cfpm or cf/m) is adjustable to accommodate different a/c units. If the fan speed is not set to the proper value, it won't move the heat efficiently which can lead to the coil becoming too cold and freezing the condensed moisture, or too fast, and creating excess backpressure and reducing the air temperature of the outlet. If it is faster than desireable, it should still probably cool things off, but may need to run longer. But, if it is too slow, and things freeze up, there won't be enough air moving to properly cool.
Ideally a 4 ton unit produces a nominal 1600 CFM (cubic feet/minute) where a 3.5 ton unit would be a nominal 1400 CFM. Since you are stuck with this unit you should have your contractor verify the fan speed is on the high setting (if equipped). Theoretically at higher fan speeds (greater CFM) you would be doing more sensible cooling and less latent cooling (moisture removal). Since the summer outdoor design temperature for your area is probably around 94 dbt or so, your system will function at reduced capacity when the outdoor temperature is greater than the outdoor design temperature. Above it was mentioned to do a Manual J calculation which would give you an indication if your 3.5 ton unit is large enough. But again it maybe due to the unusually hot outdoor temperatures (like here in Alabama lately).
Trane XR80 appears to be a gas furnace (not having all the numbers and letters, exp; TUD100***, I am not sure what size it your furnace is). Was your old Carrier unit a gas furnace also? Gas furnaces usually have to be selected based on the CFM required vs. static pressure capability, in most cases a gas furnace size selected on CFM required vs. static capability, especially in your area, will be large enough to handle the cold weather (probably heating will be oversized but still needs to be verified) Straight cool AHUs typically do not have this problem since the internal static losses are less then that of a furnace unit therefore the remaining external static for an AHU is large enough to handle the duct pressure drop. For a furnace, the remaining external static has to be great enough to handle the cooling coil and duct pressure drop, if not, you will operate at a reduced CFM. Bottom line is that you furnace may not have enough external static capability to produce the desired nominal CFM.
For me I do not care if the unit cycles because it is a little larger therefore doing less moisture removal...When I come in from working outside, I want it to cool down when it is hot. Energy wise over sizing is not the proper approach but comfort wise this suits me.
I am surprised you are not having uneven cooling with one unit serving a two story townhouse.
Wow! This is all so complex to me, but know (and Thank you) for the time and effort. The A/C company replaced the 3.5 ton unit with the same Trane but 4.0 ton. It hits 73% and sustains it without run continual. I raise the temp to 74, and 75 as the humidity go down and the feel is very good. I'll write back when I get the numbers you asked for Gator, but my hope is that the man that I am (have) dealing with is honest and very competent in his field. At least ~~~~ I hope and pray. We'll see over the next few days, and certainly over the winter. I wish there were some simply test a lug like me could perform to test the performance. Thanks again, Steve in Tampa (98 degrees today). Wonder what Al gore has his thermostat set at?
On a unit like a TDU..., there is a number at the end of the complete number indicating relative blower size. A 3, or 3F, or 32 would be 3 ton drive. A 4 or 42.....4 ton drive.
Don't let the word Commercial on these Trane web pdf sites bother you. You will probably find you unit on the second web page listed below. If not try the third web page for a starting point.
Thanks everyone who has helped me...you all are great!
The A/C seems to be working correctly now that we have a 4 ton but may I ask a couple more question: Gator do you have the same information for the XB14 A/C and is there another number for the coil? Is there a way a layman can check to verify proper air flow CFM? and lastly since this place is three levels can I adjust the supply vents to get better temp. balance from floor to floor.
Thanks, Steve ( Should have been an A/C!)
One more thing folks ~
Here are the numbers that I was given -
Install New Trane straight cool, condenser with Gas Furnance -
16 Seer - MD# 4TTB4042E1000A ( this may have changed since my man put in a 4.0 ton after this bill)
Furnance - MD# TUD1C080A9H41B
Case Coil - MD# 4TXCD050BCHCA
IS this a good set up, good match? My A/C man seems to be a really qualified person, but what the heck do I know - just trust God and my Gut@!
Your componets look like a match. Only thing left is air flow/cfm set up. One question.....you want 73.....what temp do you ask for on the T stat? If you set it to say 70, will it bring the temp down more?
http://www.trane.com/COMMERCIAL/DNA/View.aspx?i=1113 for cooling coils
Cooling Trane Furnance - MD# TUD1C080A9H41B are the digits "9H41B" in the model # correct? or should they something like 9601A it could be a 1B for a series change.
Could not locate the xb14
The 3.5 ton never would go below 75, but this 4 ton seems to go as low as I set the stat...73 = 73, never tried to go to 70, but can do.