Wire Identification

[Drifter582]

I am looking for a visual aid to distribute to my HVAC service technicians and salesmen that has pictures and identifies the various household wire types (NM-B, THHN, THWN, etc.). When the salesman gives the estimate for a new air conditioner it is important to determine the correct wire size and type is used and to arrange for an electrician to perform the electrical upgrade on the same day as we install the equipment.. Since our techs are not electricians, many times a wiring deficiency is not discovered until the installation process has begun which forces a frantic call to the electrician who, of course, is busy and can not respond to the call that day forcing the homeowner to be inconvenienced by having to stay home another day for an electrician to arrive.
Any help locating such a chart will be greatly appreciated as it will reduce unnecessary return trips and red tags.

 

[Dennis Alwon]

Unfortunately it is not as simple as a chart. Table 310.15(B)(16) is as close to a chart as you will get but there are many tricks and exceptions.

As an electrician I am often able to tell the wire size by the feel of it-at least with the smaller sizes. However, nm cable should be marked as to what size the cable is.

This is not exactly what you want but it may help

http://www.mikeholt.com/files/PDF/Wire_Raceway_Chart.pdf

 

[Drifter582]

Thanks for the response. I have furnished them with a chart that details to amp ratings for the various wire sizes and types. The issue I am having is the techs are having difficulty identifying the wires in the disconnect as many times the marking on the insulation proves difficult to read especially in the out door disconnects.
I was thinking of going to home depot and buying a foot of each type of wire to create my own picture chart. One of the biggest issues we run into is an existing disconnect out doors is supplied by romex and inspectors are siting this as a "wet location" forcing the entire circuit to be replaced from the panel to the disconnect.

 

[augie47]

I think I would politely challenge an inspection that required an interior run of NM cable to be replaced due its supplying an exterior disconnect. 300.9 makes it clear the interior of raceway installed in a wet location is also considered a wet location but to include the supply run to the disconnect if its simply fed thru the wall is indeed a stretch.
Often times due to poor factory marking and/or the limited length of conductor outside the raceway, we all have difficulty determining the exact conductor type.
IN the case of a supply to an outside HVAC unit I often do some assuming.

 

[gadfly56]

Thanks for the response. I have furnished them with a chart that details to amp ratings for the various wire sizes and types. The issue I am having is the techs are having difficulty identifying the wires in the disconnect as many times the marking on the insulation proves difficult to read especially in the out door disconnects.
I was thinking of going to home depot and buying a foot of each type of wire to create my own picture chart. One of the biggest issues we run into is an existing disconnect out doors is supplied by romex and inspectors are siting this as a "wet location" forcing the entire circuit to be replaced from the panel to the disconnect.

That's a tough one. It's certainly not your fault and the guilty party is long gone, but you're going to take the "heat" for it.

One thing you might do is have your salesmen and techs confirm the size of the existing breaker feeding the existing HVAC unit. Generally, if the breaker size required by the new equipment is the same or smaller you should be good to go. Of course, if the last guys didn't feed the circuit with the proper sized conductors, you're back where you started.

 

[Drifter582]

That's a tough one. It's certainly not your fault and the guilty party is long gone, but you're going to take the "heat" for it.

One thing you might do is have your salesmen and techs confirm the size of the existing breaker feeding the existing HVAC unit. Generally, if the breaker size required by the new equipment is the same or smaller you should be good to go. Of course, if the last guys didn't feed the circuit with the proper sized conductors, you're back where you started.

That's usually the case.

 

[gadfly56]

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That's usually the case.

Well dang. You've got limited choices.

1. Live with it.
2. Exclude the extra in your quote, and hope the client doesn't think you're trying to sandbag him when a wire/breaker change is needed.
3. Make a deal with a local electrician to check on locations where you have a firm sale to make sure it's OK to go.

 

[texie]

I am looking for a visual aid to distribute to my HVAC service technicians and salesmen that has pictures and identifies the various household wire types (NM-B, THHN, THWN, etc.). When the salesman gives the estimate for a new air conditioner it is important to determine the correct wire size and type is used and to arrange for an electrician to perform the electrical upgrade on the same day as we install the equipment.. Since our techs are not electricians, many times a wiring deficiency is not discovered until the installation process has begun which forces a frantic call to the electrician who, of course, is busy and can not respond to the call that day forcing the homeowner to be inconvenienced by having to stay home another day for an electrician to arrive.
Any help locating such a chart will be greatly appreciated as it will reduce unnecessary return trips and red tags.

Assuming that you can teach them to identify the type and size of the existing circuit, as others have pointed out there are other complex requirements for determining cable or conductor sizes for an AC condensing unit. If they are like many who do not thoroughly understand sizing conductors for an application such as this they will likely get the wrong answer. My experience tells me that usually they end up with conductors that are larger than required.
As an example, what size NM cable would be required for a small unit with a nameplate of, say, 18 MCA and a max OCPD of 25? Can they answer this?