I recently serviced an apt.complex that is using a single pole LV T-stat for two 20a 220v wall mounted radiant heaters. This configuration leaves potential 120v to the unit until the t-stat closes. In my opinion this install would be more safe using a 2 pole t-stat that broke both legs to the units. What do I reccomend to the customer and is there any code issues that apply?
Line voltage T-stat
- Thread starter bnb
- Start date
- Status
bphgravity
Senior Member
- Location
- Florida
Re: Line voltage T-stat
If the thermostat does not directly interrupt all the ungrounded conductors it just cannot be used as a disconnecting means.
Why do you think a 2-pole t-stat would be safer?
If the thermostat does not directly interrupt all the ungrounded conductors it just cannot be used as a disconnecting means.
Why do you think a 2-pole t-stat would be safer?
- Location
- Windsor, CO NEC: 2017
- Occupation
- Service Manager
Re: Line voltage T-stat
Expanding on Bryan's statement, there's usually no way to lock a thermostat. There are means to lock out breakers however, and a two-pole breaker can be locked out. That would be the acceptable means of disconnect. From there, if you want to use a single pole thermostat, knock yourself out.
See 424.20(B).
Expanding on Bryan's statement, there's usually no way to lock a thermostat. There are means to lock out breakers however, and a two-pole breaker can be locked out. That would be the acceptable means of disconnect. From there, if you want to use a single pole thermostat, knock yourself out.
See 424.20(B).
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: Line voltage T-stat
I agree with what Bryan and George have said. But are you really talking about using the thermostat as a disconnecting means for the heaters? Is your question more along the lines of blocking both sides of the thermostat?s connections, rather than just one side, without regard to the status of the breaker that provides 220 volt power to the heaters? Is this a maintenance issue or some other safety issue that concerns you? Like Bryan said, why do you think a 2-pole would be safer?
I agree with what Bryan and George have said. But are you really talking about using the thermostat as a disconnecting means for the heaters? Is your question more along the lines of blocking both sides of the thermostat?s connections, rather than just one side, without regard to the status of the breaker that provides 220 volt power to the heaters? Is this a maintenance issue or some other safety issue that concerns you? Like Bryan said, why do you think a 2-pole would be safer?
Re: Line voltage T-stat
My thought would be. if a maintenence personel (who does not have as much knowledge about electric as a journeyman electrician) goes to service the unit and turns the t-stat off thinking this kills the power to the unit. He or she could potentialy get hit servicing that unit.
My thought would be. if a maintenence personel (who does not have as much knowledge about electric as a journeyman electrician) goes to service the unit and turns the t-stat off thinking this kills the power to the unit. He or she could potentialy get hit servicing that unit.
charlie
Senior Member
- Location
- Indianapolis
Re: Line voltage T-stat
In my opinion, that would not be a qualified person.
In my opinion, that would not be a qualified person.
- Location
- Lockport, IL
- Occupation
- Retired Electrical Engineer
Re: Line voltage T-stat
The problem is that, in that person's opinion, that person is qualified.
That is one reason for the code: to reduce the number of opportunities that the unskilled have to hurt themselves.
The problem is that, in that person's opinion, that person is qualified.
That is one reason for the code: to reduce the number of opportunities that the unskilled have to hurt themselves.
- Location
- Massachusetts
Re: Line voltage T-stat
bnb there is no excuse for working on electric equipment without a non contact voltage checker or at least a simple volt meter.
I look at like this, once a person pulls out a tool and deliberately opens electrical equipment they have to take responsibility for their own actions, they should not be relying on any code to protect them from themselves.
There is nothing to say that even if the thermostat broke both conductors that the unit is safe to work on.
The feed may run to the heater first then a switch leg out to the thermostat. Or if the heater is large enough the thermostat may only control a contactor in the unit.
bnb there is no excuse for working on electric equipment without a non contact voltage checker or at least a simple volt meter.
I look at like this, once a person pulls out a tool and deliberately opens electrical equipment they have to take responsibility for their own actions, they should not be relying on any code to protect them from themselves.
There is nothing to say that even if the thermostat broke both conductors that the unit is safe to work on.
The feed may run to the heater first then a switch leg out to the thermostat. Or if the heater is large enough the thermostat may only control a contactor in the unit.
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