carrier two ton package unit

[spiderslayer]

At our shop,whenever you turn the power on to the unit,it feels like the heat strips are energized.I mean you can feel heat coming out of vents.Tried disconnecting red wire on thermostat but to no avail.Did some work as a ac tech in Texas a few years ago but this has me stumped.Thank you!Also when the heat is called for it seems like the blower is hardly moving the air.

[Pegi]

Do you know if the heat strips are coming on?  Or is this a heat pump also with emergency heat strips.. Now these units will use low fan speeds for heat so the unit will not move too much air that cannot pick up the heat so the air will not be too cool coming out of the vents....I might start by seeing if the heat strips might be grounded letting them come on when power is supplied...also check the thermostat to be sure it is not wired wrong or has welded contacts.

[spiderslayer]

It is not a heat pump,I noticed that heat was still coming out even with the red thermostat wire disconnected.It does not seem that the strips are grounded,everything looks okay in the unit.Thank you!

[Pegi]

Then looks like you are about down to see what is feeding the heat when it is set for cooling, thermostat, control board if it has one?   Still need to be sure the element is not grounded or something is not across it touching the element and some metal in the unit...

 

[spiderslayer]

I don't know if there is something wired wrong in the unit or not.This is about a 92 year model so it's fairly simple inside.When you energize the unit the fan starts to rotate and quits,but the strips are still energized,even with the red wire disconnected from the thermostat.I may get on the net and try to track down a decent wiring diagram.Thank you for the input!!!P.S. When ac is called it works,but the strips are still energized.

[Pegi]

You have something shorted out somewhere, t-stat. perhaps, bare wire touching, element grounded, might check that capacitor for the fan motor problem..

[dkpd1581]

At the unit disconnect your 18/8 control wire to the low voltage terminal board and jump the unit out in each mode.  This will halve your problem.  If everything functions while jumping the unit at the controls section then the T-stat/contorl wiring is suspect.  If the unit is operating the heat without the control wiring attached, then the problem is most definitely at your unit.

With the 18/8 disconnected, check to see if the heat is energized.  If so, you probably have a grounded heat element or a defective switch (contactor, sequencer, relay)

If it is a 3 phase unit, 1 line usually is energized.  If you feel heat with the unit disconnected from the 18/8 control wire you may have an element grounded or in contact with another element. 

Use your clamp on meter to verify that current is flowing and from which line.  A visual inspection inside the heat section will show evidence of burned or burning/melting wires, connectors, etc..

As to your indoor motor, chances are it was damaged as a result of the heat strips being energized and the motor deenergized.  Even low KW elements produce enough heat below a motor to destroy the bearings, seals, and integrity of the winding insulation.

I have had several Trane and Carrier RTUs exhibiting the exact same symtoms and all have been defective elements.  Pay close attention to the strip heat contactors and make sure that one or more poles are not welded closed.  Running the indoor motor after experieincing heat trauma like that produced catastrophic results. 

Write back and let us know

[spiderslayer]

Thanx for your reply,I realize now I need to take it loose at the unit.I ohmed the red and white at the unit and there was no short.High speed for ac works fine on indoor fan,tried switching from low to medium on other terminal but had same result in heat mode.If I disconnect one lead and check to ground will that work on the heat strips?When I ohmed the two control terminals on the heat strip contactor it was not a short.Voltage also showed on one terminal only(low side terminals).When called for heat nothing changes in the symptoms.I will test some more Monday.Owe you one,too,I did a few years in Texas attics and know Hotlanta isn't far off!!Domo to both y'all!!

[Pegi]

Texas attics in the summer, gotta be worse than Death Valley at high-noon...:burning: