2nd floor Ceiling Heating 220V tapped from existing 110 junction

[AylorJ]

I have an older 4-Plex with ceiling heating. It looks like they have created the 220v needed for the thermostat from an existing 110 junction. What are some of the problems that this could cause?
There is no crawl space or attic access here, but I do not want to leave it a dangerous situation if it is.The Circuit breaker is a single 20A.

 

[jumper]

Welcome to the forum.

A little clarity please.

How are you getting 240V from a box that has 120V fed from a single pole breaker?

A few details seem to be missing.

 

[infinity]

If the heater is just a purely resistive load then nothing will happen if you connect the 240 volt heater to a 120 volt source other than you get get only 1/4 of the rated output.

 

[jaggedben]

I have an older 4-Plex with ceiling heating. It looks like they have created the 220v needed for the thermostat from an existing 110 junction. What are some of the problems that this could cause?
There is no crawl space or attic access here, but I do not want to leave it a dangerous situation if it is.The Circuit breaker is a single 20A.

"looks like"? Did you measure the voltage? Or just look at the color of the wires?

One would have to draw from two 120V outlets on separate legs in order to have 240V.

Problems could include violating 300.3 and 300.20 and getting inductive heating on ferrous conduit. Not likely to be a real-world issue if it's really just the thermostat, but if it's the heater... :happyno: