20 Most Recent Honeywell TH4210D1005 Heater - Page 8 Questions & Answers

Actually the 24 hour time makes it easier to correctly set the thermostat for when you want it to change setting.

No battery backup in this thermostat.

You need to remove the thermostat from the wall plate to change the battery. Look on the bottom of the thermostat for a locking screw. Loosen this screw with an appropriate screw driver. Then pull the bottom of the thermostat away from the wall plate and then lift up from the bottom. When you put the thermostat back on, line up the brackets at the top of the thermostat with the slots on the wall plate. Then push the thermostat against the wall plate and tighten the locking screw. The documentation for the Honeywell RTH2300B1012/U is available on the product page: https://www.honeywellstore.com/store/products/5-2-day-programmable-thermostat-honeywell-rth2300b.htm . Click on the Manuals tab. See page 4 (page 6 of the PDF) for removing the thermostat from the wall plate. See page 9 (11 of the PDF) for replacing the batteries and putting the thermostat back on the wall plate. The current link to the manual is https://www.honeywellstore.com/store/images/pdf/rth2300b1012-u-5-2-day-programmable-thermostat.pdf . I hope this helps. Cindy Wells

A manual is what you need to unlock and reprogram the schedule. Keep off the set up steps for the thermostat, only the scheduling and security steps. https://www.manualslib.com/manual/1189747/Honeywell-T6-Pro.html?page=8#manual

Terminal X is also common.

Remove the faceplate of the tstat. If fan still continues to run you likely have a stuck fan relay in the unit.

Expose the wires and carefully put the yellow wire in with the red. See if outdoor unit kicks on.

try this web site for your manual. I think this is what you are looking for. https://customer.honeywell.com/resources/Techlit/TechLitDocuments/68-0000s/68-0280.pdf

Without seeing the wiring diagram, I can only say that the MV/PV terminal in many cases is used as the common from the thermostat/transformer. Usually, the 24 volts is supplied to the thermostat from a step down transformer and the thermostat sends voltage to the controller. I would hesitate to "guess" at this without a complete understanding of the wiring requirements. Any HVAC tech should be able to help you.

It has been my experience that the screen is damaged. You will most likely have to replace the thermostat. I have seen where heavy scratches will cause this condition.

So if the temp changes what are you wanting to change? I'm confused.

Typically the box will say "C wire required " Any 24v tstat will work, just make sure it doesn't say c required.

What's the model of your outdoor unit.

Hello Ed, Here are some links that are going to help you solve your problem. Good luck, JP

Hey Chris, Call Honeywell,see if they can help with that. 1800-468-1502 https://www.honeywellhome.com/en/faqs/thermostat

When you turn power on/off your resetting the entire system. The problem is your air handling unit or outdoor unit. Something is locking out the system. Would need model number outdoor unit/indoor unit. What breaker are you resetting? For what unit.

Help how do I unlock this?