Wiring practices

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don_resqcapt19

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Staff member
Location
Illinois
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retired electrician
Exactly. There's no excuse for full-voltage control circuits in residential applications anymore. Thermostats, appliance controls, et al have cheap enough control alternatives. ...
I see no good reason to add a control power transformer and a contactor to control electric baseboard heat. The line voltage thermostat works just fine and if you buy the correct one it provides the required means of disconnect.
 

kwired

Electron manager
Location
NE Nebraska
I see no good reason to add a control power transformer and a contactor to control electric baseboard heat. The line voltage thermostat works just fine and if you buy the correct one it provides the required means of disconnect.
I agree.

I have no problem with full voltage control for a single motor controller with control switches mounted in same enclosure as the controller. Why do we need a control transformer just to run a simple start - stop that does not leave the enclosure? Remote control switches I can understand wanting low voltage controls to a certain degree.
 

sbrehler

Member
We were that close to having a house fire.

Fortunately, my wife discovered it before going to bed that evening or she and our daughters could very easily have been trapped in a house on fire because that thermostat is located on the same wall as the stairway to the 2nd story.


~While eveyone's technical replies are of great importance, greater still should be that you have operating smoke detectors and alternative escape routes figured out (ladder from second story).

Please forgive my reply format...it's my first one and I'm not sure how to include only a section of quote in the grey box like I always see...any help would be appreciated.
 

kwired

Electron manager
Location
NE Nebraska
We were that close to having a house fire.

Fortunately, my wife discovered it before going to bed that evening or she and our daughters could very easily have been trapped in a house on fire because that thermostat is located on the same wall as the stairway to the 2nd story.


~While eveyone's technical replies are of great importance, greater still should be that you have operating smoke detectors and alternative escape routes figured out (ladder from second story).

Please forgive my reply format...it's my first one and I'm not sure how to include only a section of quote in the grey box like I always see...any help would be appreciated.
Easiest thing to do is click the "reply with quote" button after the post you wish to quote. You can quote multiple posts by clicking the button to the right of that on each post you wish to quote. If you want to only quote part of a post just delete the parts you don't want before hitting the "submit reply button"

There are more complex things you can do (and I'm not really that knowledgeable what is all possible or how to do some things) but give that a try first.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
Easiest thing to do is click the "reply with quote" button after the post you wish to quote. You can quote multiple posts by clicking the button to the right of that on each post you wish to quote. If you want to only quote part of a post just delete the parts you don't want before hitting the "submit reply button"

There are more complex things you can do (and I'm not really that knowledgeable what is all possible or how to do some things) but give that a try first.
We were that close to having a house fire.

Fortunately, my wife discovered it before going to bed that evening or she and our daughters could very easily have been trapped in a house on fire because that thermostat is located on the same wall as the stairway to the 2nd story.


~While eveyone's technical replies are of great importance, greater still should be that you have operating smoke detectors and alternative escape routes figured out (ladder from second story).

Please forgive my reply format...it's my first one and I'm not sure how to include only a section of quote in the grey box like I always see...any help would be appreciated.
(

Danged if that doesn't work! Well I'll be. Wondered how that was done.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
Easiest thing to do is click the "reply with quote" button after the post you wish to quote. You can quote multiple posts by clicking the button to the right of that on each post you wish to quote. If you want to only quote part of a post just delete the parts you don't want before hitting the "submit reply button"

There are more complex things you can do (and I'm not really that knowledgeable what is all possible or how to do some things) but give that a try first.
Danged if that doesn't work! Well I'll be. Wondered how that was done.
With a little practice you can do this. Hit the "reply with quote button" to see how it is formatted.
 

ActionDave

Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
wire pulling grunt
And I did want to learn how that is done.

It did not show the format - just showed your reply only:(
Your right. It must only show the formatting when I check my own posts.


Cut and past the first quote box [.Quote=blahh blahh] from the second quote to the top of the reply so that it is in front of the first quote box of the first quote.
 

hurk27

Senior Member
Back on topic:

Don is right on that the problem in the OP was most likely cause by a loose connection with a glowing arc or close to one.

While we all know an AFCI will not detect a glowing or series arc and would not be of any value in such cases I believe a thermal fuse or even a bi-metal contact that is electrically and thermally connected to each and every point of termination would, it wouldn't be hard or costly to manufacture devices such as receptacles and switches or other types of devices with a small thermally sensitive contact that would open if any heat above a certain temperature was to occur at a termination, a simple bi-metal strip between the plate with the side screws and the contacts inside of a receptacle that would just pull up and disconnect the receptacle and the load connected to it would stop it from getting any hotter and it could be designed that it would it would require intervention (reset that required the removal of the receptacle) and the re tightening of the screws before allowing to work again, while not many fires are cause by this some are.

I was thinking about asking a friend at UL about this if something like this would fly?

Of course a differant aproach would have to be developed for wire nuts but then again if they are installed correctly to begin with we wouldn't be seeing burnt up wire nuts.
 
Last edited:

kwired

Electron manager
Location
NE Nebraska
Back on topic:

Don is right on that the problem in the OP was most likely cause by a loose connection with a glowing arc or close to one.

While we all know an AFCI will not detect a glowing or series arc and would not be of any value in such cases I believe a thermal fuse or even a bi-metal contact that is electrically and thermally connected to each and every point of termination would, it wouldn't be hard or costly to manufacture devices such as receptacles and switches or other types of devices with a small thermally sensitive contact that would open if any heat above a certain temperature was to occur at a termination, a simple bi-metal strip between the plate with the side screws and the contacts inside of a receptacle that would just pull up and disconnect the receptacle and the load connected to it would stop it from getting any hotter and it could be designed that it would it would require intervention (reset that required the removal of the receptacle) and the re tightening of the screws before allowing to work again, while not many fires are cause by this some are.

I was thinking about asking a friend at UL about this if something like this would fly?

Of course a differant aproach would have to be developed for wire nuts but then again if they are installed correctly to begin with we wouldn't be seeing burnt up wire nuts.
If everything else is done properly though, it should only effect first inch or two of conductor, it should all be in an outlet box with no unused openings, and box should be flush with combustible wall finish or no more than 1/4 set back in non combustible wall finish. The risk of starting a fire should be pretty minimal. Note that I said should.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
...
While we all know an AFCI will not detect a glowing or series arc and would not be of any value in such cases I believe a thermal fuse or even a bi-metal contact that is electrically and thermally connected to each and every point of termination would, it wouldn't be hard or costly to manufacture devices such as receptacles and switches or other types of devices with a small thermally sensitive contact that would open if any heat above a certain temperature was to occur at a termination, a simple bi-metal strip between the plate with the side screws and the contacts inside of a receptacle that would just pull up and disconnect the receptacle and the load connected to it would stop it from getting any hotter and it could be designed that it would it would require intervention (reset that required the removal of the receptacle) and the re tightening of the screws before allowing to work again, while not many fires are cause by this some are.

I was thinking about asking a friend at UL about this if something like this would fly?

Of course a differant aproach would have to be developed for wire nuts but then again if they are installed correctly to begin with we wouldn't be seeing burnt up wire nuts.
That is what these guys are working on. I just don't see the need for AFCIs or this type of device. When you start studding the dwelling unit fire cause and origin stats, the one thing that jumps out is that over 80% of these fires are in dwelling units built over 20 years ago, and that the fires that are said to be of electrical origin are less than 10% of the dwelling unit fires.
 

ptonsparky

Senior Member
Location
NE (9.06 miles @5.9 Degrees from Winged Horses)
Occupation
Electrical Contractor
If everything else is done properly though, it should only effect first inch or two of conductor, it should all be in an outlet box with no unused openings, and box should be flush with combustible wall finish or no more than 1/4 set back in non combustible wall finish. The risk of starting a fire should be pretty minimal. Note that I said should.
With exception of once, the most severe damage I have seen with arcing connetions has been limited to the space within the box aslong asthe box was covered.
 

kwired

Electron manager
Location
NE Nebraska
With exception of once, the most severe damage I have seen with arcing connetions has been limited to the space within the box aslong asthe box was covered.
Same here as long as there were no other code violations or misapplied products.

I was doing a government funded housing rehabilitation once - (used to be lots of these projects a few years ago). I remember running new receptacle to near a window that had an air conditioner in it. On the floor was melted circular pattern in the carpet. Wonder what size extension cord was coiled up there when that happened? Just installing receptacle where it was needed was probably worth more than protecting it with an AFCI (which btw was not required at that time).
 

pfalcon

Senior Member
Location
Indiana
Exactly. There's no excuse for full-voltage control circuits in residential applications anymore. Thermostats, appliance controls, et al have cheap enough control alternatives.
I see no good reason to add a control power transformer and a contactor to control electric baseboard heat. The line voltage thermostat works just fine and if you buy the correct one it provides the required means of disconnect.
Then you should read to OP again. Nickel and dime parts would have contained the hazardous voltage and current within the baseboard heater and its supply while the thermostat wiring could have been run off less than 24V. Less than 5V actually with milliamp current and 32 gauge wire. The cheaper wire may actually pay for the control components to reduce the voltage for the thermostat. I think you've gotten comfortable with normal voltages. A low volt thermostat would have meant low volt wiring and not being "that close to having a house fire" in this case specifically.

... It wasn?t the thermostat that was the problem and I don?t know how this situation can possibly be avoided using current wiring practices and materials. When I installed that thermostat originally, the bare grounded wire had come into contact with the insulation on one of the ungrounded conductors and over the years somehow managed to wear through the insulation enough to begin arching. How can this be avoided when we're stuffing wires into a box? It wasn?t enough to trip the circuit breaker but enough that the insulation on that wire got charred and brittle. We were that close to having a house fire. ...
I think he was on target when he mentioned avoidance and current practice. I think its past time to rethink some of that "full voltage" stuff. Its convenient - yes. We're familiar with it - yes. But lowering control voltages in homes would have more impact for safety than either TR's or AFCI's.
 

kwired

Electron manager
Location
NE Nebraska
But lowering control voltages in homes would have more impact for safety than either TR's or AFCI's.
You have some points worth consideration. I would not have mentioned the TR's. The safey they provide is not in the same category as AFCI's, or even overcurrent devices in general. It is more along the lines of open bare vs insulated.

So what happens when we move the control device to the appliance? Yes we have a switch that has less energy potential to start a fire. We still have a contactor someplace that opens the full voltage and current to the load. What it is enclosed in and how it may stop the spread of fire when something goes wrong is what needs addressed regardless of whether it is part of the controlled appliance or not - JMO.
 

don_resqcapt19

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Staff member
Location
Illinois
Occupation
retired electrician
Then you should read to OP again. Nickel and dime parts would have contained the hazardous voltage and current within the baseboard heater and its supply while the thermostat wiring could have been run off less than 24V. Less than 5V actually with milliamp current and 32 gauge wire. The cheaper wire may actually pay for the control components to reduce the voltage for the thermostat. I think you've gotten comfortable with normal voltages. A low volt thermostat would have meant low volt wiring and not being "that close to having a house fire" in this case specifically. ...
Why would I expect the baseboard heater to contain the heat from a electrical fault any better than a switch box?
 

pfalcon

Senior Member
Location
Indiana
You have some points worth consideration. I would not have mentioned the TR's. The safey they provide is not in the same category as AFCI's, or even overcurrent devices in general. It is more along the lines of open bare vs insulated.
:) But worthy of a discussion in a different thread.

So what happens when we move the control device to the appliance? Yes we have a switch that has less energy potential to start a fire. We still have a contactor someplace that opens the full voltage and current to the load. What it is enclosed in and how it may stop the spread of fire when something goes wrong is what needs addressed regardless of whether it is part of the controlled appliance or not - JMO.
I mentioned this also in response to Don. The contactor should be located in a factory housing that is listed and tested. Heat issues during failure should be considered. I consider addressing the heat issue in the factory enclosure to be a better approach than trying to address the factory enclosure + wall wiring + switch box. It also provides that the most likely point of owner created damage and owner contact is at only 24V or less.

So like you, I believe the fire spread needs to be addressed no matter where it is. It's just my opinion that by limiting the higher voltages to the factory enclosure that the problem becomes simpler to address.
 

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
Because the heater should be tested and listed with factory connections and a heat resistent chamber where the switch box might be all DIY installed.
I have seen more connection failures with the factory heater connections than I have with the field installed connections.
 
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