Inside Unit Not Working - Please Help!

[ThatDudeMike]

Hello,

A few weeks ago, during a cold snap, our heater stopped working. I tried the thermostat on A/C as well, and it was not working either. After some research and troubleshooting, I finally realized that the inside unit has it's own breaker in the attic - near the inside unit. I flipped the breaker on and off, and it started working again.

Since then, the inside unit has stopped working 3 or 4 times, and I have had to throw the breaker each time, thus making the unit work again. Today, it stopped working again, however when I throw the breaker today, nothing happens...

We have a American Standard split unit, Electric. Outside unit is American Standard Allegiance 14 (model# 2a7a4030b1000aa). Inside unit is American Standard Trane (model# TWE031E13FB1). Thermostat is a Ritetemp (model# 8050 0 84615 00020 4). There are a total of 4 breakers for the system: 2 at main breaker box - labeled 'Heat' and 'A/C'. 1 at the outside Unit, and 1 in the attic at the inside unit.

I am a true novice, so I am really not sure where else to look. Any thoughts or advice to troubleshoot the system? It's now cold again here, and my fiance and pets are shivering all night and day.. Please help!

Thanks,
Michael

[HayZee518]

4 breakers essentially taking care of air handling unit, compressor, condenser and aux electric heat. inside the main unit should be a control transformer, its secondary protected by a fuse or small circuit breaker. control circuit would ne 24 volt. all operating coils of all contactors look to be 24 volt. a contactor controls a higher voltage with higher operating currents, utilizing a low control voltage with low currents. so, basically you could have a contactor controlling 480 volts at 100 amps off a control circuit that operates at 24 volts with an inrush current of a quarter amp [example only] your heat operates off the thermostat and stepper relays and a heat sequencer. one side of the line connects to one side of alll heater elements, the other side to a different phase through a stepping relay. one per stage, as in three stage heating. its odd that all would cease to function but if one sequencer is bad an auxilarry contact wouldn't make up rendering the next contactor inoperable - check that out.

[ThatDudeMike]

Thanks for the reply. And I hate to sound like an idiot, but based on your response, I'm still not sure where to start. I am new to HVAC, and to testing AC with a DMM, so I'm just trying to understand.

Do I need open the inside unit and check for a secondary fuse/circuit breaker?

How would I check for 24 volts on the control circuit and operating coils/contactors? Is this inside the unit?

Someone also mentioned for me to test the breaker box connection with a DMM, however I am not sure how to do that either.. I have a DMM with scales: Vac (600 & 200), AAC (200m & 10A), Adc (200m & 10A), as well as Vdc, Ohms, and Bat.

[HayZee518]

The inputs to your DMM are VAC, VDC, Amps AC, amps DC, resistance. The range switch is what it will test for. 600VAC is 600 volts or less AC, 200 is a little more refined to test for 200 volts AC or less. DC will be the same range but at a DC connection.
Set your meter for 600VAC and place the probes - one on one hot breaker screw and the other on the other breaker screw and read the digits. - you are reading the line voltage coming out the breaker. For measuring 120 volts AC switch the range to 200VAC. Place one probe on the neutral strip [the thing with all the screws on it] and the other probe on one breaker screw and read the digits. if you screw up the meter should be protected with a fuse inside the unit. With the range switch on VDC and you place the probes on an AC line nothing will probably happen or you'll get some odd readout. DC is straight DC voltage, while AC is changing polarity 120 times a second. OK - open up the control panel on the AC. Look for a transformer - one side should be marked either 120VAC or 240VAC the other side should be marked 24VAC. There may or may not be a fuse on the transformer. The wire size on the secondary will probably be a smaller gauge then the line wires. One side of the transformer will be a common, the other side will be the hot. The common will connect to all contactor coils on one side. The hot wire will go through devices like a thermostat or control relay contacts back to its respective coil to make it work. If you have any knowledge of reading a schematic or ladder diagram it will help. One side marked L2 is common for the 24 volt, the other L1 is the hot from the transformer and goes through a device or devices. control relays are marked CR1 or K1, K2, CR2 etc. Motors are MOT or T1, T2. Fuses are FU1, Fu2. control breakers are CB1, CB2 etc.
ALWAYS test a circuit for the highest voltage range available THEN switch lower if you need more accuracy.

[ThatDudeMike]

Okay, I opened up the breaker and tested the input side (tested @ 245 on Vac-600, and @ 122 on Vac-200). The output did not read anything on Vac-600, but it did read @ 122 on Vac-200. Does this mean that I have a problem with the breaker?

I opened the panel of the unit, and I see the small fuse is still intact. Just wanted to relay the test on the breaker, because it seemed odd, but I don't know.. I'll go back up and test inside the unit.

[HayZee518]

ok, I will assume that the unit is operating at 240 volts AC single phase. A two pole breaker in your service panel will confirm this. Most residential units are not three phase. Your voltage readings are kinda screwy but let's continue. a two pole breaker should put out + - 240 vac. the control is 24 vac

[HayZee518]

A DMM is good for exact measurements of an AC or DC circuit. In this day and age, raw measurements are better than exact. A "wiggy" is better for close measurements but I'm not going to ask you to get a "wiggy." An analog meter, one that has a scale is easier to read than a DVM and offers much more flexibility than a DVM.
I have a tripplet v-o-m and a DVM and i trust my analog more then I do the DVM.

[ThatDudeMike]

Problem solved! Based on a series of tests to the breaker itself, I determined that this is where the problem resided. No power was coming out from the breaker. I replaced the breaker and now I'm up and running! Thanks for your help!!!

[HayZee518]

"That's great to hear!" AND you got a free lesson in operating your test equipment. Knowing how to use your equipment is half the battle. There's other specialized equipments to use for special problems, but the dmm and vom are the basics. Resistance measurements on heating elements can be mis-leading - a bad element will show you a resistance to each other and ground. In this case a meter designed to measure amps is better than a dmm or v-o-m. Get a clamp around ammeter. It'll save you a bunch of problems. It'll measure actual operating amperes of a circuit. Greenlee makes one that has ranges up to 1200 amperes with a current lock feature. Anyway and again, I'm glad you found your problem! - HayZee..................