Program Help with XL20i

[Mike8189]

I am looking for some insight. I recently replaced my 12 year old builders Goodman 5 ton unit with a Trane xl20i with a TEE4c variable handler. I live in a 2600 square story home in South Florida. I am not used to this AC unit as of yet it seems to run alot more often then my old unit. I find that it takes longer to recover to a lower setpoint. I had the installer out once again to check the setup and the charge assist. He made no changes and said everyhting was fine. My handler is in a closet up stairs and the thermostat is there as well. I feel that it when it ramps down once it is close to the setpoint it stays there for along time and never turns off. Is this normal or more efficient? I worried about even higher bill due to it never turning off. The T900 control says i have 50% humidity.With it running slower it does keep it more constant temp but> just not sure i am comfortable with it running at super low speed die to cost of Elec. I did just the unit to be set for more agressive cooling. Should i keep this setting..I know my duct work in attic is in good shape no leaks... as for the first floor no telling no access to it... I just need some peace of mind that if the consistant low ramp is correct.

Thoughts anyone...

[jimj]

Your's is a common concern when first getting use to a multi stage unit, don't worry. Enjoy the comfort now and the low utility bills to come.:)

[mark beiser]

Well, if your new system when running in 2nd stage, uses half as much electricity as the old system did, and 1st stage on the new system uses half as much electricity as 2nd stage, the system can run twice as long in 1st stage as the old system used to, and still only cost you half as much to cool the house.

Make sense?:D

[snacktray]

I have the same system. Mine runs most of the day in 1st stage and so far I have noticed my utility bill cut down at least 1/3rd of what it was before. And I've only had it since June..

[dan sw fl]

Well, if your new system when running in 2nd stage, uses half as much electricity as the old system did,

and 1st stage on the new system uses half as much electricity as 2nd stage,

the system can run twice as long in 1st stage as the old system used to, and still only cost you half as much to cool the house.


Make sense?:D

Thanks, Mark


Spending 1/2 on electricity for more comfort is quite simple to understand.

What are your Written guarantees, if any, on energy cost reduction from existing SEER 10 to highest efficiency equipment ?

_ Just Do It _ on your next A/C replacement !


How about heating energy cost for heat pump?

[Mike8189]

Thanks for the input but the more i hear this system ramped up the emptier i am feeling my wallet get....I am only going for 76... There has got to bea point when this unit should kick off..?? what is the swing on this thermostat... is it just trying to keep close all the time... My AC contractor is no nelp..

[catmanacman]

wait till you get a couple of bills then see if you like it

[motoguy128]

Thanks for the input but the more i hear this system ramped up the emptier i am feeling my wallet get....I am only going for 76... There has got to bea point when this unit should kick off..?? what is the swing on this thermostat... is it just trying to keep close all the time... My AC contractor is no nelp..


Maybe this will make sense if it's put in more detail. If the sytm had 55% capacity on 1st stage...so lets say 32,000BTU's. On 2nd stage it's 60,000BTU's. I=f your system is sized correctly, and your design temp is 97F (temperature where the system will run constantly) wit ha indoor degin tmp of 75F (typical), then if it's 90F outside and you're trying to maintain 76F indoors, the system will be at 67% capacity. So 1st stage can be expected to run constantly in those conditions, and should go to 2nd stage about 30% of the time (if I did my math right).

Also keep in mind that in 1st stage, the unit is mor eefficient than 2nd stage. And, the XL20i, typically "underperforms" a little in terms of capacity. The 5 ton sytem probably only produces about 58,000 BTU's.


Does any of that make sense???

When it's over about 85F outside, you can expect the system to run in 1st stage almost continuously.





How about a Florida metaphor.... 6 halves of oranges make the same amount of juice as 3 whole oranges. SO a unit running at 1/2 capacity uses the same electricity as a unit at full capacity running 1/2 of the time.


A 100 Watt light bulb running for 30 minutes uses THE SAME electricity as a 50 Watt light bulb running for 1 hour... but produces /2 hte light the entire time.

[mark beiser]

Thanks for the input but the more i hear this system ramped up the emptier i am feeling my wallet get....I am only going for 76... There has got to bea point when this unit should kick off..?? what is the swing on this thermostat... is it just trying to keep close all the time... My AC contractor is no nelp..

If the outdoor temperature is high enough that the house gains more heat per hour than 1st stage of the system removes, the system will run pretty much continuously in 1st stage.
Under those conditions, the thermostat will cycle 2nd stage on as needed to maintain the temperature, but will switch back to 1st stage rather than ending the call for cooling.

There isn't really a swing with the newer Honeywell thermostats, which includes the Trane XL900 thermostat. There is a control logic Honeywell calls P+I control, you can find a description of it near the back of the installers guide for the thermostat.
Essentially the thermostat is watching how fast the home is cooling off, or warming up, and cycles stages of cooling to maintain the set temperature. Keep in mind the thermostat is actually measuring the temperature to the tenth or hundredth of a degree, so you may not actually see any change in the display temperature.
The thermostat actually "learns" over time, and gets better at maintaining the set temperature.

[Mike8189]

Thats all good info. I do understand alot of it.
.. Just now last month i spent 2768kw on the bill and with 6 days to go I am at 3300kw.. So I did find the installer did not size the wires he 10ga going to condensor when it calls for 6ga. will this spend more elec.? I am hurting here as well as having the new ac we are not putting it lower than 76 at night...

[mark beiser]

How is the duct system?

A bad duct system will cripple the performance of a 2 stage system.

[smittyii]

Thats all good info. I do understand alot of it.
.. Just now last month i spent 2768kw on the bill and with 6 days to go I am at 3300kw.. So I did find the installer did not size the wires he 10ga going to condensor when it calls for 6ga. will this spend more elec.? I am hurting here as well as having the new ac we are not putting it lower than 76 at night...

maybe i missed it , but you never did say what tstat was installed w xl20i.

[Mike8189]

Bad duct in what way? undersized over sized leaking? What Can i look at. I am a service manager of a large commercial company, Just great with Hvac. Elaborate please

[snacktray]

I keep mine set at 73 and it stays there just fine, even in 93° heat w/80% hum...still cut kW usage by 1/3.

sounds like an install issue

[venting]

I keep mine set at 73 and it stays there just fine, even in 93° heat w/80% hum...still cut kW usage by 1/3.

sounds like an install issue

What humidity percentage do you keep it at running to 73?

[snacktray]

What humidity percentage do you keep it at running to 73?

Its set to 45% but rarely gets there due to the humid climate I live in. It rains frequently as well. But it never gets above 53%..

[Mike8189]

I keep mine at 77.. with the humidity set at 60 i have tried at 55 and 50 just runs even more. As for the install the whole process was cut and dry swap out 5 ton for another 5 ton same lines all properly sized. I would be happy to share the stories like " i keept it at 73 when it is 93" but it doesnt happen.
I have contacted trane lets see if they respond.

[dan sw fl]

Thats all good info. I do understand alot of it.
.. Just now last month i spent 2768kw on the bill and with 6 days to go I am at 3300kw.. So I did find the installer did not size the wires he 10ga going to condensor when it calls for 6ga. will this spend more elec.? I am hurting here as well as having the new ac we are not putting it lower than 76 at night...

Call FPL for:

1. Wiring inspection
2. Energy audit with thermal imaging..

You have a Superior A/C system.
Now, you need to determine how to effectively reduce the cooling load.

For example, window and sliding glass door tinting
should provide S.H.G.C. of < 0.35

Based on the kW being used, it appears that the unit is running in high stage more than desirable.

[Mike8189]

Took some more readings tonight with my better thermometer that i had before my outlet temp in low speed on stage 1 (i assume) is 60 degress It is 85 outside and the inlet air is 76. I have the installer coming out again on friday. I am looking for a set of questions to find out. I know this is a superior system I belive that.... I just need it to prove it to me. How help is greatly appreciated.


Soon to be divorced if not fixed :)

[Mike8189]

So tonight i sat out side after it had cooled outside.it was 81 outside and the house temp was 76 at 52% humidity. I timed each cycle and watched the meter to see what stage it was in the unit would cycle between stages every 7 to 10 minutes with a 1 stage off time in between. This is Unaceptable!!! it never turns off and cycles back and forth.... What happen to the stage 2 only run when needed on hot days over 90.... B/S. What can cause this....

Please Help..

[wraujr]

First of all it sounds like you ran your test late in the day. Your attic is still radiating stored heat into house along with 4 degree temp difference that the unit will be running in first stage with occasional calls for second stage. My xL16i does this up until 8PM or so. For that matter, my 2nd stage doesn't start to kick in util around 4PM or so on these 90 deg days. Even when OD = ID temp in the PM my unit still runs in 1st removing the heat the house has gained during the day. Heat gain and loss and transfer are not instantaneous, so even though its 8 PM with the sun going down, try going up in your attic and measure the temp and get an appreciation for just how much heat is up there...

If you don't do a setback at night, how is the system cycling at 8AM or 10AM?? and what is OD temp??

Second thing, is how many return ducts do you have?? Where are you mesuring return air?? In my home with a 4 deg diff between floors my 1st floor return air measures 77* while my 2nd floor measures 81*, when mixed the temp is somewhere in between which is why for accuracy I measure at the return air filter....


Your attic reaches over 120 deg from solar gain and it holds that heat and radiates it into your house all evening. Even at 80 deg, with direct sun your attic can gain a large amount of heat.

[mark beiser]

Bad duct in what way? undersized over sized leaking? What Can i look at. I am a service manager of a large commercial company, Just great with Hvac. Elaborate please

Mainly leaking or poorly insulated ducts are a real issue with 2 stage equipment because the long run times in 1st stage multiply the effect of leakage and heat gain in the duct system.

I think heat gain in ductwork running in unconditioned areas doesn't get the attention it should when going to 2 stage cooling systems.
Single stage equipment is more tolerant of it because of the higher air velocities and shorter equipment run times, but it can cripple 2 stage equipment because the lower air velocities and longer run times allow much more heat gain in the ductwork.

Combine the heat gain in the ducts with a little leakage, and you end up with a "high efficiency" 2 stage system that costs more to operate than an old single stage system.

While it is not exactly the same thing, there was a study done in Florida a few years ago that is still relevant to what I'm talking about.
In the study they replaced the over sized systems in some houses with higher efficiency systems "correctly" sized per ACCA Manual J.
They did nothing with the duct systems, which were over sized for the new smaller systems, not well insulated by current standards, and had more leakage than is acceptable.
Predictably, the results were pretty bad. The occupants of the homes had comfort and humidity problems they did not have before, and did not realize the energy savings that were expected, or in some cases, any energy savings at all.


In my part of Texas, virtually all of the houses have the duct systems and air handling equipment in the attic, so duct heat gain and leakage is something I have to deal with all the time.