Correct Hookup? Trane XV95 & xl16i (4 ton)

Hi -
Getting pretty frustrated, "new system" installed 12/08 - heat works great but we haven't been happy with the A/C side of things. Whenever it is hot, unit runs all the time while the temp slowly increases. The unit doesn't freeze up, I've got a good temp differential, 21 degrees the last time I checked, but just doesn't seem to blow enough. The original installer company is out of business, won't return calls, I had another company out yesterday - they found a leak and recharged the system. Before I had a chance to ask him to confirm the hookup, he was off to the next job :-( Unit worked a little better, but still just not able to cool quickly, even in the evening when the temperatures are down. Seems to remove humidity quite well, just won't cool down. Sometimes internal temp is as high as 80.

Assuming unit is fully charged and operating, could it be the wiring? Maybe the blower not engaging properly to high speed on cool mode? Here are the details:

XL16i - 4TTX6048B1000BA
XV95 - TUH2COOA9V4VAA
Coil - 4TXCC049BC3HCAA
Stat - TCONT802A

DIP SWITCH SETTINGS:
SW1
1 - OFF
2 - OFF

SW2
1-0N
2-ON

SW3/4
1-OFF
2-OFF
3-OFF
4-OFF
5-ON
6-ON
7-OFF
8-ON

WIRES:

STAT=FUR=A/C
Y2=Y=Red lead to Yellow w/ red stripe (Y2?)
W2=W2=n/a
R=R=n/a (RC/R JUMPED ON STAT)
W1=W1=n/a
Y=YLO=Y
G=G=n/a
B=B=B

Could someone point me in the right direction on how to confirm this setup?

Thanks in Advance!
Brandon

 

You are right the blower is running to slowly (but in low speed).
You are not wired correctly.

 

Thanks - could you help point out the correction necessary? I really appreciate it!

In looking over my setting - I overlooked the jumper on the thermastat - RC-R is in place right now.

Brandon

 

You now have this...




You need to move the Y1 and Y2 wires and remove the jumper between R and BK.
Place a jumper between R and O.



Color codes vary...

 

Looks like your SW switches are setup for four tons at the furnace if the missing digit in your model number is a 1 (as in 100,000 btu)


http://www.trane.com/webcache/un/fur...7_05012011.pdf

 

Yes - it is a 4 ton unit, 4TTX6048B1000BA

I've made the wiring adjustments - see if that makes a difference.

 

thermostat option 170 = 8 - 2 heat/2 cool

 

Thanks - how do I check the thermostat option? I can't seem to find that on the menus anywhere -thermostat option 170 = 8 - 2 heat/2 cool

Sorry for all the questions - I really appreciate the help!

Brandon

 

The TCON802 is really a Honeywell TH8320.
Page 6 explains how to enter configuation mode...


http://customer.honeywell.com/techli...it/69-2693.pdf

 

Thanks for all the help. I've verified the stat settings, they were ok... I've changed the wiring.... I flipped the switches to adjust to 450cfm rather than 400 thinking this might help...

Based on the wiring, was the original config, running my first stage too low, ie 50%, rather than 80%?

I think the unit did a bit better today - outside got as high as 105, not really humid though, and house stayed at 74! We were in and out late in the afternoon and it jumped up to 76, but held there the rest of the evening.

I checked the coil a bit earlier and noticed a small amount of ice on the ubends in the coil, nothing on the fins - should I be concerned about that?

Is there any way to confirm the blower is on high? I thought that might be something with the green flashes, I count 21 between red on front of furnace.

Thanks again!
Brandon

 

Yes you were running 50% on low cool. The 2 compressor 19 seer unit uses that setting.

74 to 76 degrees is good for 105 degree outdoor temp.

No ice should be present on the ubends as this would indicate lack of airflow or lack of refrigerant (including possible TXV restriction).

Note 6 of page 22 in the manual that I posted states that the green LED flashes once per 100 cfm so we are running 2100 cfm. (5 tons)

I prefer 1600 cfm for a 4 ton unit to get good humidity removal.

You might remove the furnace blower door and verify that the furnace insulation has not come loose and blocked one side of the blower. This would fool the blower into thinking that it is moving more air then it actually is. (back emf reading would be thrown off)

 

I am not an expert but having just rewired my own Trane XV90 to work properly (and doing a lot of reading into how the variable speed functions work) I need to disagree with Houston. If I am missing something, I will by all means bow to a pro, but this just doesn't seem right based on what I've read.

The 802 series doesn't have the dehumidification control (and the 803 just does overcooling, doesn't have a dehum output), so I believe he was wired correctly on the cooling side with Y = YLo = Y1 and Y2 = Y = Y2.

The R-BK jumper is a wire loop on the circuit board, not a wire between the terminal screws. So unless Witteb physically cut that loop basically all the new wiring did was make the furnace run in full-speed single stage mode while the compressor was running in its low stage.

Also, the jumper to O (enables Comfort-R profile) should be from YLo, not R per the furnace wiring instructions. Due to the built in heat warm-up delay there is little or no advantage to Comfort-R in heat mode.

So basically if you set it up per that diagram (including cutting the jumper on the circuit board) what happens is:

> Stat calls for stage 1 cool (Y)
> Stage 1 compressor kicks on. Fan turns on to 10% for one minute
> Fan then ramps up to 50% for 7.5 minutes
> Fan ramps up to 80% for remainder of stage 1 call
> If stat calls for stage 2 cool (Y2), it kicks on stage 2 compressor and ramps fan up to 100%.
> If stage 1 cooling call ends without going to stage 2, blower will shut off immediately.*
> If stat shuts down while in stage 2 (such as if a programmed setpoint changes), the blower will run on for 90 seconds at 50% to extract more cool air from the coil.*

* This is not the way this function was designed to work. It was designed to work in conjunction with a humidistat across the R-BK terminals. If the humidistat is still above the setpoint at the end of a cooling call, the blower is shut down immediately to prevent moisture from re-evaporating off the coil. Otherwise the blower is allowed to run on in order to suck a little extra 'free cooling' from the coil.

Ideally you would either put in a thermostat with a built-in humidistat and humidify/dehumidify terminals, or you would install a separate humidistat (if you have a central humidifier that is controlled by a humidistat somewhere in the house or in the return plenum, you can use that too). This will allow greater control over the fan speed based on the humidity in the house. Lower fan speeds = greater dehumidification. If dehumidification is not needed, the fan is ramped up to full (65% stage 1, 100% stage 2) immediately when a cooling call begins.

Here's where the jumper is located - just snip it and separate the halves. Please note I have only one cooling stage now, but YLo has a wire there. It does nothing for now. That's why my O terminal is jumpered to Y.

Also notice on the right side, under the fan connector there is another green LED. THAT is the one that tells you the current fan speed - 1 blink per 100CFM. However, the geniuses at Emerson Control didn't locate it in a place you can see when the door is closed. The only way to watch it is to thumb the safety switch. The ones toward the top of the board that you can actually see through the peephole in the door do not tell you the CFM. The red one flashes a code if there is a fault (one blink every 20 seconds = OK), and the green one flashes twice per second during a heat call and once per second any other time. It's not indicating 2100CFM.

Houston I have to also disagree that there is no sensor that detects the airflow - based on my recent experience with the motor thermistor burning out. The board did not indicate any fault as my evaporator froze solid. The CFM light simply flashes whatever CFM that the controller is commanding the motor to deliver. The motor is programmed to know what RPM correlates to a given CFM.

 

Matt you obviously are not a pro and have never read the installation instructions when an Variable speed furnace is used with an XL16i. Houston is 100% CORRECT. Houston posted a picture directly from the thermostat manual for setup when using VS furnace/AHU and a 16 seer a/c.

Again, you are wrong about how the VS motor works. The control board tells the module what CFM it should be running at. The module then adjusts the output to control the motor speed based on the signal and the module has a sensor to know what the cfm output is. The point of a VS motor is that it will adjust the rpm of the motor to match the correct cfm output as called for and that the VS motor can overcome some ductwork and other types of restrictions. The Control board flashes what CFM signal it is sending to the module.

 

Thanks for all of the assistance, it is really appreciated. Can someone confirm the Red/Black jumper which needs to be cut/removed - is this the JUMPER labeled on the circuit board? I did not have a a wire jumping R-BK but the wire on the circuit board labeled JUMPER IS in place. Per Houston's instructions I placed a jumper from R - O.

Thanks again -
Brandon

 

What red/black jumper are you talking about? Yes, the BK jumper on the control board needs cut.

 

It was a good picture. Strange color code.
Cut the BK jumper and separate the the wires.
A jumper between R and Y2 might have caused ice.

 

Thanks - I've cut the wire jumper on the board as shown in the photo and separated - maybe that will do the trick!

Should I drop fan back to 400CFM (OFF/OFF/OFF/OFF SW3) rather than 450 (OFF/OFF/ON/OFF SW3)? In the manual 400 was described as "Normal" and 450 as "High" in the manual.

Thanks -
Brandon

 

I would use 400 cfm per ton unless you are in a dry climate. (not the case in my area)

 

Ok, I will admit that I did not read the install instructions specific to the XL16i. I did not realize that Trane engineers would be so stupid as to design a two stage condensing unit that is incompatible with the feature set built into their high end furnaces. My bad. I guess that means I won't be buying an XL16i.

BUT, the GE programmable motors DO NOT have an airflow sensor. That one I DID look up. They simply correlate CFM with RPM, and can adjust for restriction based on how increased static pressure or intake restriction will cause the blower to slow down, and it increases its torque to maintain the desired RPM.

The CFM light only signals what command the furnace controller is sending to the motor controller. There is seemingly no feedback that the motorcontroller sends back to the furnace controller board - if there were, the furnace would be able to shut down and give an error when the thermistor burns out at its predetermined just-out-of-warranty time, rather than allowing the compressor to keep running and freeze up.

 

That's the color code originally used by whoever installed the system originally. The blue and tan wires were back-wrapped at both ends, so I assigned them to BK and YLO for later use. What I found odd is that the cable used for the connections to the current return plenum humidistat, humidifier valve, and outdoor unit has red and black conductors, not red and white. The red wire on O goes to the outdoor unit - simply so there aren't three wires under one screw at Y.

 

The ECM 2.3 is an impressive motor. It can use back EMF to calculate cfm output fairly accurately. The limitation is in that furnace board.

Carrier uses this information to display RPM, CFM and static pressure at the stat...






Trane is a great product. They also offer a communicating system.

 

That's a nice display. So basically what it's doing is comparing the current that it's drawing in order to maintain a specific RPM to a preprogrammed table of current draw at specific CFM/SP levels to determine those values. It's not sensing the actual airflow..

 

It's much more accurate than that. Research Back EMF.

 

Very interesting. Never heard of that.

 

Houston204 - thanks for your help and patience, the system ran real well today! Thanks again!

Brandon