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AssuredElectrical
AssuredElectrical, Master Electrician
Category: Electrical
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Experience:  Contractor-42+ Years in the ElectricalTrade
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I recently wired in 4 separate Honeywell 410b (4 wire)

Customer Question

I recently wired in 4 separate Honeywell 410b (4 wire) thermostats to replace old existing ones for a friends home. My initial wiring caused two pair of 2-pole, 15amp breakers to trip(circuits 3,5 & 7,9). Upon closer inspection of the wiring in each wall box, I noticed the hot legs were colored a black/red pair & confirmed with a meter (220 volts). Initially i had wired L1 to T1 with the black/red pair, respectively. There are two other 14/2s with each of the black legs spliced together with other black wires & a separate black pigtail from each 14/2 to land to T1 & T2. I proceeded to wire L1 & L2 to black & red "hot" legs respectively. Switched breakers on & no longer tripped circuit 7,9 2-pole breaker. However, no notable heating was noticed after turning the dials on. Circuit 3,5 2-pole breaker stuck in the ON position & not able to flip to OFF position. Any ideas on What am I doing wrong ?
Thanks,
Allan in SF
Submitted: 1 year ago.
Category: Electrical
Expert:  AssuredElectrical replied 1 year ago.

Welcome. My name is ***** ***** would be glad to assist.

Looks look over the situation once again Allan.

On the 2 pole thermostats, you are correct with the situation, power connects to the L1 and L2 terminals or wires.

The power out to he heaters connect on the T1 and T2 terminals or wires.

So, once installed, use your meter and test the L1 and L2 for 240 volts.

Then with the thermostat ON, test the T1 and T2 for 240 volts.

It may be the thermostat was damaged and is not switching the 240 volts, maybe only 120 is getting out, therefore no heat.

On the one breaker, if it will not turn off to reset it, you will have to replace it for operation.

You can try a quick remedy we use many times, take the handle of a screw driver and give the breaker a quick rap with the end of the handle, then try it again.

Many times, this opens the internal contacts freeing up the breaker to reset and work properly.

If it doesn't, the breaker has failed and needs replacing.

Keep me posted on anything further needed or difficulties, just reply and we can continue to get you operating.

Thanks

Diagram is below:

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