Correct wire size?

I just had a new oven installed that required a new 240-volt, 40-amp circuit. The installer used 6-gauge wire for the two hots, but smaller 12-gauge wire for the neutral and ground. Is the use of the smaller wire okay?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
In article <XjSxb.125114$Ec1.5271126@bgtnsc05-

--
Mark

The truth as I perceive it to be.
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

No. Refer to NEC, Article 250-95. The equipment ground must be #10 minimum.
He's probably OK on the neutral, though -- very doubtful that the 120V load (clock, timer, lights, etc) is anywhere near 20A.
-- Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Elros wrote:

40 Amp ckt requires #10 for the equipment grounding conductor. Built-in oven may or may not require a Neutral connection, check the nameplate or install instructions. If it requires a Neutral, I would have gone full size (#8).
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Yes.

No need. The heating elements would be 240V and thus not use a neutral. Other features such as lights, timer, clock, etc. are likely only 120V and thus do need the neutral, but certainly not a #8.
-- Doug Miller (alphageek at milmac dot com)
How come we choose from just two people to run for president and 50 for Miss America?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.