AC wont turn off at set point without having to turn to "off" mode

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  #1  
Old 05-17-14, 09:53 PM
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AC wont turn off at set point without having to turn to "off" mode

Ok so I picked up a new thermostat recently so I could set a programmed schedule and installed it earlier today. All seemed good, Markings on old Totaline P474-0100 matched up well to the new Venstar t5800. Followed instructions in manual to a "T"

Everything appears to be working correctly other than the ac doesn't shut off once it reaches the set point temperature. It will shutoff (inside and out) if I set the mode to "off". Thermostat is set to 76F and shows that the temperature has reached below the set point, ie 73F, correctly but the outside unit is still running and there is cold air blowing out the vents inside. I have used in all modes and does the same thing, cool or auto or the schedule I setup.

At first I was wondering if maybe I have the dip switches set wrong on the new stat but after much research I believe everything is all setup correctly and I may have some kind of coincidental issue going on. But please correct me if you see anything as I don't do hvac for living but I do have a technical job so I don't consider myself completely helpless with stuff like this.


I have the following equipment:

Outside Unit: Bryant 662cj030-c
Inside Unit: Bryant/Radco FA4ANF030



Dip switch settings on the Venstart t5800:

HP
O
ELEC

Wires Using the following from manual page 51:

6 Wire, 1 Stage Cooling, 2 Stage Heat
R 24VAC Power
C 24VAC Common
W1/O/B Reversing Valve
Y1 1st Stage Compressor(Cool or Heat)
W2 Aux Heat
G Fan

After second guessing myself on connections I hooked back up the old t-stat and tested = same thing. Will not shut off after setpoint unless I move to the off mode. While connected I reviewed the settings in the "advanced" mode to verify: Heat pump and "O" settings which are what I used on the venstar.

Im lost, can someone throw me a bone as to what might be happening? Im kinda tight right now due to medical expenses and not sure how I can get repair tech fit in the budget. My only guess from much research is wires? I don't quite understand what tests to perform at this point.

Thanks for any help!
 
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Old 05-17-14, 11:12 PM
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Im lost, can someone throw me a bone as to what might be happening?
I could see you having problems with a new thermostst but for the old one.... that was working fine... to be doing the same thing defies logic.
 
  #3  
Old 05-17-14, 11:18 PM
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I don't know much about your new T-stat or old T-stat, but I suggest you bypass the T-stat and see if you still have the same problem. Here is what you do: Open the T-stat cover, twist 3 wires together (R,Y,and G), system should start, then un-twist those 3 wires, if system stops, then the problem may be T-stat, or at least related to T-stat..
 
  #4  
Old 05-17-14, 11:37 PM
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LoL! Don't tell me that! I don't like the sound of defies logic....crap!

Ok if that is so, then the tech in me tells me I had to screw something up when wiring the new one and I repeated the same mistake on the old one when I rewired it up? Logical troubleshooting? Or something broke somewhere.

Im 99.99% sure the wires are correctly terminated in the tstat as I have pics of old one before I changed and all the same labels\colors on the new one.

That's kinda why I think something just happen to break or give out at same time I was switching, bad luck. But I don't know where to start.


.
 
  #5  
Old 05-17-14, 11:48 PM
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Ok so I did twist the 3 wires RGY together for about a minute and system turned on and shutoff about a minute after I let them go. Normal op im guessing?

BTW, thanks for replying guys, I appreciate it.
 
  #6  
Old 05-18-14, 12:53 AM
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Is this unit a 2 stage heat? That was the one thing I was unsure of as I don't know how to tell and couldn't readily find on the net. It has 6 wires hooked up to old tstat, one to w1ob (orange wire) and one to w2 (white)
 
  #7  
Old 05-18-14, 03:56 AM
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Did you say the old tstat will no longer work correctly ?

I will try to find a pdf , on the internet for your new electronic tstat .

God bless
Wyr
 

Last edited by WyrTwister; 05-18-14 at 04:29 AM.
  #8  
Old 05-18-14, 04:58 AM
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I d/l'ed a pdf on this tstat . Wow ! Way to complicated for me !

The thought occurred to me . Disconnect all the wires to the new tstat , except the red ( 24 VAC " hot " ) , green ( fan ) and 24 VAC Common .

The tstat should remain " awake " . Set to cool . Set the cool temp low enough to force the tstat to " call " for cool . The indoor fan should come on .

Use your volt meter , with one lead / probe on the common . Use the other lead / probe to measure for voltage on the other terminals on the tstat .

Manipulate the cool set point to cause the tstat to no longer " call " for cool . Give it enough time for any time delays to be satisfied . Then measure for voltage as before .

Please post the results of this test . Also any photos you have of the old tstat / wiring .

I am trying to determine if the tstat is not " turning off " the 24 VAC going to the condenser unit ? Or if , some how , 24 VAC is finding its way there , due to a " short " in the wiring . Some where between the tstat & the condenser unit ?

God bless
Wyr
 
  #9  
Old 05-18-14, 08:14 AM
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-So you trist RGY, it starts, you un-twist RGY, it stops. everything OK, but both T-stats can start, not stop, ....does not make sense no matter which way you look at it. I hate to say this and I know you won't believe me, but if you ask me, the only explanation I have now is "'the room temperature was never reach the set point'". (the other possibility is both T-stats were damaged when you hooked it up, this is a long shoot, but can you come up another reason?)
 

Last edited by clocert; 05-18-14 at 08:30 AM.
  #10  
Old 05-18-14, 08:27 AM
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I have seen occasions in which the wires behind the tstat " back plate " had bare spots on the insulation & might be touching . Or the copper broke inside the insulation ( does not sound like that is the problem in this instance ) .

If bare wires , tape them up . Or better yet , go down to Harbor Freight and pick up the assortment of heat shrink . Side the appropriate diameter of heat shrink over bare spots . If you use a long enough piece , it will hold itself in place , well enough . If you decide not to shrink it . Remember to preserve the correct color coding of the wires , with colored tape or written labels .

Bad wiring could also be the case at the furnace , if not at the tstat . But I would check the tstat location , first .

If you are getting hot and need cooling , now , hang the old tstat with just R , G & Y Connected . Or hang a cheap , temporary stat . Until you get the bugs worked out .

And , yes , compare the temperature indicated on the tstat with a known good thermometer .

God bless
Wyr
 
  #11  
Old 05-18-14, 08:55 AM
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Got a good amount of sleep and getting ready to give it another whack as soon as I eat some breakfast.

I know it sounds like a weird issue. Im at a complete loss.

WyrTwister: "If you are getting hot and need cooling , now , hang the old tstat with just R , G & Y Connected . Or hang a cheap , temporary stat . Until you get the bugs worked out . "

It will turn off when I turn the mode button to "off" so that's what I have done last night, turn it on for awhile then just turn to off when its cooled. Wouldn't the wiring have to be ok if it able to turn on the ac fine and just wont shut off until I turn the mode to off? Just trying to think things out.

I will need to pickup a volt meter as I don't have any here at the house.

I do have pics pre-install, I will upload one here shortly.


clocert: Id be really mad if somehow both stats were damaged somehow and would have to believe I have another issue that would cause the damage. I was pretty careful about doing it and shut the breakers off to both the furnace and outside unit before making any changes.

Yes it is cooling down the room and will just keep on cooling, both thermostats will show this on display and my body tells me the same.....cold...brrrr.
 
  #12  
Old 05-18-14, 09:04 AM
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Wow the manufacturer emailed me back on sunday!!! Does this below make any sense to you guys to my situation?

This is what they said (although I didn't know about the old tstat having issues when I emailed):

thanks for giving us the wiring and DIP switch settings. That’s unusual and very helpful. That said … you have it set / wired correctly. I assume that the home screen on the thermostat shows “EQUIPMENT IDLE” when this runaway cooling is occurring? If so, the issue might be a compatibility mismatch between our thermostat and your unit. That is very rare, is fixable but involves adding a small pilot duty relay to the Y1 output of the thermostat. If you are interested, I’ll happily provide you that relay and wiring details. If not and the stat indeed shows IDLE, you should probably disconnect the thermostat, get a refund and install prior thermostat for now.
 
  #13  
Old 05-18-14, 11:14 AM
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Wow I guess im really screwed now.

Hooked everything backup today and all I get is hot air.

My old thermostat also now makes a buzzing noise.

Gonna be a hot one today boys.
 
  #14  
Old 05-18-14, 11:33 AM
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Try just connecting the R , G , C & Y1 ? To the old Tstat ? If that does not work , & maybe the Orange ?

God bless
Wyr
 
  #15  
Old 05-18-14, 01:16 PM
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I tried connecting the R , G , C & Y1 to the old Tstat and I get hot air. I then tried connecting the Orange as well and same thing. Its like it turns the heater on now. With just the fan setting on I get normal room air thru, not hot.

I guess at least its a little cooler here today, only about 85 and not the normal 90-95.

I think I figured out in the air handler where the thermostat wires come to (what a rats nest of wires, jeesh), if I want to test for wiring shorts im guessing I could hook the thermostat up directly there to bypass the wires in the wall, correct?

I don't have any spare wire laying around and would require a trip to store.
 
  #16  
Old 05-18-14, 04:56 PM
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Yesterday you twisted RGY and it worked. Can you do that again ? do not connect C.
 
  #17  
Old 05-19-14, 09:23 AM
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Figured I would at least update the thread with the final results after getting it fixed.

It was the wiring between the thermostat and the airhandler, at a minimum the orange wire was bad maybe another one (at least one of the unused wires was bad when we tried to switch to it).

Just replaced the entire group of wires and all is good now.

Lucked out and setup a barter with a independent ac guy I have used in the past. He needed some computer work done so all worked out.

Thanks to everyone who tried to help!
 
  #18  
Old 05-20-14, 02:43 AM
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You replaced the wire from the tstat to the AHU / fan coil unit ? Good job , that makes sense .

From what I read on the internet , if you have the wi-fi doggel , you can access the tstat from a desktop or smart phone ?

God bless
Wyr
 
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