[Burghangler]

Hello, I was trying to upgrade my thermostat for my fuel oil, water-baseboard heating system. I fried two programmable Honeywell’s. (I’m not an hvac tech, but can handle most minor projects I’m the house) It’s a two zone system, downstairs went fine, and works perfectly, upstairs has two larger black and white wires, and if I’m using my cheapo volt meter correctly, I’m getting 123 volts. I ordered a line voltage thermostat, hooked it up, digital read out worked for about 5 minutes, and nothing, think I fried it to. Any idea what to do next? Thanks in advance.

 

[roughneck]

What thermostat was used originally?

 

[Burghangler]

It was really old, not sure. I tested the new honeywell (RTH2300B) heat turned on when I turn it up, so I thought is was working and threw out the old one. The new digital programmable one would run, but the heat would stay on all the time while in on position regardless of temperature.

 

[Nealtw]

It was really old, not sure. I tested the new honeywell (RTH2300B) heat turned on when I turn it up, so I thought is was working and threw out the old one. The new digital programmable one would run, but the heat would stay on all the time while in on position regardless of temperature.

Does it say it is good for 120 volts? Like this one does.

https://www.homedepot.com/p/Cadet-1...able-Wall-Thermostat-in-White-TH106/202247918

 

[Burghangler]

It says 120v/240v

Copied what eBay ad said


Cadet by Honeywell TH401 Line Voltage Electric Heat Thermostat
Single-Pole 10.4 Amp 120/240-Volt Digital Electronic Non-Programmable Wall Thermostat in White
Brand New Item, box has been opened.

 

[Nealtw]

It says 120v/240v

Copied what eBay ad said


Cadet by Honeywell TH401 Line Voltage Electric Heat Thermostat
Single-Pole 10.4 Amp 120/240-Volt Digital Electronic Non-Programmable Wall Thermostat in White
Brand New Item, box has been opened.

But you said new honeywell (RTH2300B)

 

[Burghangler]

That was the first ones I fried, after doing a voltage test, I tried the line voltage one, it’s junk now too

Sorry, I should be using quotes, I’m a noob

 

[Nealtw]

Have you read the instruction, I haven't played with that one but some when you have a pre set temp, you can over ride that to keep the heat on. Check it out before you give up. You can call them for help too.

they have a live chat here.
https://cadetheat.com/customer-service

 

[Burghangler]

Have you read the instruction, I haven't played with that one but some when you have a pre set temp, you can over ride that to keep the heat on. Check it out before you give up. You can call them for help too.

they have a live chat here.
https://cadetheat.com/customer-service

I’ll try the chat. I wired it up, showed the display, heat came on for a second, then display went blank. I was skeptical that it would work, bc everything thing I read says line voltage thermostats were for electric baseboard heaters, but being such high voltage, I tried it. The RTH2300s are only rated for like 20-30 volts

Thanks

 

[surferdude2]

There may be problem with what the thermostat is controlling. Is it only hooked to a zone valve? Was that zone valve working alright before you changed thermostats. Is it a line voltage zone valve.

It sounds like you are over loading the thermostats rated 10.4 amps. It's a solid state Triac so it would tolerate an overload for a while but finally go bad from overheating.

Check whatever it's supplying power to and see if it's rated for line voltage and less than 10.4 amps.

Can you post a schematic of the electrical system for this stat?

 

[Burghangler]

There may be problem with what the thermostat is controlling. Is it only hooked to a zone valve? Was that zone valve working alright before you changed thermostats. Is it a line voltage zone valve.

It sounds like you are over loading the thermostats rated 10.4 amps. It's a solid state Triac so it would tolerate an overload for a while but finally go bad from overheating.

Check whatever it's supplying power to and see if it's rated for line voltage and less than 10.4 amps.

Can you post a schematic of the electrical system for this stat?

As a said, I’m not an hvac guy at all. I googled zone valve, is it possible my system doesn’t use them?, can’t find anything that looks like one. Could a bad circulation valve be causing this? A while back, the zone with the problems pump started screaming, I shut that zone off with thermostat, ordered a new pump, but noise never happened again, so I still have a new one. The main power comes into a electrical box, one wire goes to the “brain” of boiler, one goes directly to the circulation pump. Also it’s looks as though both zones thermostat wires come out of electrical box main powers comes to.

 

[surferdude2]

I'd be very suspicious of that pump. Since you have a new one, I'd install it. That pump may well have been locked and that would explain why the thermostat was fried.

 

[beenthere]

Some pics of the wiring in the box might help us help you.