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Vowder
September 30th, 2004, 10:44 AM
I am planning on running wire to four plugs (recepticals) that will be used to plug the block heaters my cars in.

I am wondering what the demands of a block heater are? Do I need 1, 2, or 4 circuts?

The wire will be about 125 ft in lenght. Can I still use 14 guauge wire or should I use a 12 or even 10?

Thanks for all your help.

Vowder

joed
September 30th, 2004, 11:22 AM
How many watts are the block heaters, if you know? You don't more than 1500 watts on a 15 amp circuit.

Unregistered
October 1st, 2004, 08:10 AM
The run is a little long for #14--you should go to 12 to make up for line loss. How many receptacles are you running? They really should be 1 receptacle for each circuit. They also should be GFI protected. The cheapest way to do this is to buy the receptacle as a GFI--as the breakers are expensive.

Vowder
October 1st, 2004, 08:33 AM
I need four plugs. That means four circuits. I am okay with that. I guess I will use 2 12/3 runs. Can you two circuits to a GFI receptical?

Vowder
October 1st, 2004, 08:35 AM
I have just learned that a block heater requires 1200 watts. That makes it clear. What is the line loss for a 14 guage wire over that distance. I may be able to live with it?

Unregistered
October 1st, 2004, 10:49 AM
Here is a table Vowder. It shows the load and distances allowed. I would go with 12 at least and run a separate circuit for each plug. Using a 3 wire---I am not too sure on that but I have done it by using a 2 gang box and making a tail for the neutral. I suspect in this case it may overload it?

Unregistered
October 1st, 2004, 10:49 AM
http://www.nwes.com/Wire%20Loss%20Tables.htm#120%20Volt%20Wire%20Loss% 20Table

Vowder
October 1st, 2004, 12:17 PM
30 degree C ambient? Not in this country very often :).

The blockers heaters will be on when it is -15 C or lower.

I will dedicate the circuits to the plugs and use 12/3 wire on a 15 amp circut. I have lots of space in my panel box. It means purchasing 4 breakers.

Thanks for all your help.

Vowder

Homer
October 1st, 2004, 03:04 PM
A 1200W, 120V block heater will draw 10A. Each heater will need its own 120V circuit.

Using adjustments for ambient temperature on conductor resistance and resulting voltage drop (NEC, Chapter 9, Table 8, Note 2), we can state the following.

If you use #14 wire for a distance of 125 feet at an ambient temperature of -15C, then the voltage drop is 5.4V or 4.5%.

If you do use multiwire circuits and both legs will be drawing current at the same time, you will save big on voltage drop. Since the neutral currents will cancel out, a 14/3 multiwire circuit will only have half of the voltage drop. You will have a 2.7V or 2.2% voltage drop on each leg of the circuit (117.3V at both loads).

In order to GFCI protect these multiwire circuits, you will need to have a GFCI receptacle at each outlet. You will bring the 3 wires into the first box and pigtail the neutral. A white pigtail and black supply conductor will go to the line terminals of the first GFCI. A 2-wire cable will go to the second receptacle. The white will connect to both the white pigtail and white supply conductor while the black will connect to the red supply conductor. In this way the neutral is no longer shared and the two GFCIs will work. Connect the black and white to the line terminals of the second GFCI.

For the second multiwire circuit you will just repeat the same steps.

Remember that you could also use expensive 2-pole GFCI breakers instead of using a GFCI receptacle at both outlets.

Also, you must use either UF (Canadian NMWU) cable or run in conduit to these receptacles. Don't even think about jury rigging extension cords!

Also, I am assuming that your 4 cars are NOT in a detached structure (garage) and are parked along your driveway. If it is a detached garage, you can't run 2 multiwire circuits. You would need to put a sub-panel in the garage and power it with a feeder.

Homer

Unregistered
October 10th, 2004, 11:13 AM
I am planning an outlet for a block heater as well . I put a GFCI inside the house wired with 12 gauge wire to a 20 amp breaker. A GFCI will flow through 20 amps according to the instructions. I have a 20 amp rated switch and a 20 amp rated plug outside. Any problems with this ?

Homer
October 10th, 2004, 11:41 AM
I am planning an outlet for a block heater as well . I put a GFCI inside the house wired with 12 gauge wire to a 20 amp breaker. A GFCI will flow through 20 amps according to the instructions. I have a 20 amp rated switch and a 20 amp rated plug outside. Any problems with this ?If you were under the jurisdiction of the NEC then I would say that you are OK.

However, under Canadian code you have just described two code violations.

1) You cannot share outlets inside the dwelling with outlets outside the dwelling.

2) A 15A GFCI receptacle with 20A 'flow through' cannot be placed on a 20A circuit in Canada. You must use a T-slot, 20A GFCI receptacle.

So, in order to comply with 1) and 2), you will need to;

1) Use a 20A GFCI breaker in your panel and remove the indoor receptacle from the circuit.

OR

2) Replace that 15A GFCI receptacle (with 20A 'flow through') with a 'blank face' GFCI receptacle rated at 20A.

http://www.levitonhelpdesk.com/catalog/productimages/device8590.jpg Blank Face GFCI Receptacle

OR

3) Remove that 15A GFCI receptacle from the circuit and place a T-slot, 20A GFCI receptacle outside.

Homer

Unregistered
October 10th, 2004, 04:14 PM
Homer,

Well your advice certainly don't make me happy . The outlet in question can be changed as you have recommended. But I have another outdoor plug .shared with an indoor plug . What's the deal with that ?
I also have a whirlpool bath supplied with 20 amp wire ( heater wire actually ) and it has a 15 amp GFCI wired under tub with the flow through protection. A local electrician only recommended that the GFCI be moved beside the breaker panel as it should be accessible once a month for testing and I would be skirting in the one under the tub .
What should be the protection on an outdoor septic pump with 20 amp power requirement ?

Unregistered
October 10th, 2004, 04:53 PM
Homer,
Another quick quesstion : can two outdoor plugs be connected together ?

Homer
October 10th, 2004, 06:49 PM
I have another outdoor plug shared with an indoor plug . What's the deal with that ? ...Another quick question : Can two outdoor plugs be connected together ?Circuits for outdoor receptacles are supposed to be used for outdoor receptacles only but you can place more than one receptacle on an outdoor receptacle circuit.

I also have a whirlpool bath supplied with 20 amp wire and it has a 15 amp GFCI wired under tub with the flow through protection...What should be the protection on an outdoor septic pump with 20 amp power requirement ?Once again, under Canadian code you can't use a 15A GFCI receptacle on a 20A circuit. To be correct code wise, you could use the blank face 20A GFCI receptacle so that you're not sharing an indoor receptacle with the septic pump.

Well your advice certainly doesn't make me happy.I can only say that if something is permitted by the NEC but not the CEC, then it is not a question of safety but a difference of opinion on how best to provide for electrical demand in the dwelling. I am only telling you how to guarantee a pass for an inspection of new work.

Also, the sharing of indoor and outdoor receptacles is not allowed now but may have been OK in past years. I would not go out of my way to address this if you have existing outdoor receptacles.

Homer

Unregistered
October 11th, 2004, 10:04 AM
Homer ,
Well this is a new construction and still not final inspected.
It was supposed have been wired by an electrician but I suspect my builder did some of it like the GFCI for the whirlpool tub . However the electrician didn't think it was a problem when he saw it last week.
Will keep your advice in mind and try to implement it .
Thanks !

Homer
October 11th, 2004, 02:47 PM
Homer ,
Well this is a new construction and still not final inspected.
It was supposed have been wired by an electrician but I suspect my builder did some of it like the GFCI for the whirlpool tub . However the electrician didn't think it was a problem when he saw it last week.
Will keep your advice in mind and try to implement it .
Thanks !If your septic pump has a rated load of 50% of the circuit ampacity, then you can't have any receptacles on that circuit. It has to be a dedicated circuit. This is true under both the CEC and NEC. So using a GFCI receptacle to protect the pump will work, but it provides another outlet on what's supposed to be a dedicated circuit. That's why the 'blank face' GFCI can be used instead. If the pump load is less than 10A on that 20A circuit, then it's OK to share it with receptacles.

These details may seem to be nitpicky, but if you have a 'by the book' inspector you want to be able to pass inspection.

Homer