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BoilerHorn · Jun 26, 2005, 12:46 PM

A neighbor of mine commented that the fan for his AC/heater unit is wired in a somewhat unorthodox (or is it?) fashion. On the 220 line, he has 2 parallel 40 amp breakers feeding 2 sets of wires whose load is the fan. Essentially, it looks like the electricians that did the work (before he owned the house) determined that 2 parallel 40amp circuits - and associated less expensive, smaller wire, in parallel - would be sufficient. According to my basic circuit training from decades ago, this seems like a reasonable solution.

Has anyone experienced this before? Thanks!

Comments are welcomed!

labman · Jun 26, 2005, 02:01 PM

Sounds Mickey Mouse to me. 80 amps to run the fan in a residence? Are you sure one circuit isn't for the heaters? In heavy industrial loads it is common to use multiple conductors, but they are still fed off the same breaker or fuse.

BoilerHorn · Jun 26, 2005, 02:14 PM

labman -- thanks for your quick response...

Perhaps it is for the heater. The problem is that the A/C guys won't look at it because they claim there is an electrical issue. The electrician that they hired was w/o a clue apparently. All of this is complicated by the fact that these neighbors have a home warranty and are at the mercy of the folks the warranty company sends.

So, in reading your reply, the dual 40-amp breakers is an uncommon (wrong?) way to feed it. Multiple conductors from an 80-amp fuse might be more appropriate?

Sorry for my ignorance and thanks so much for your reply!

labman · Jun 26, 2005, 04:36 PM

What is the problem? Is the unit not working? Warranty or no warranty, major systems such as the HVAC must be working at the time of sale, or the seller is responsible to make it work. They are also responsible to make it meet code, or at least the code when it was built. If they can't get somebody out soon to get it working, your neighbor should check with the lawyer he had a closing.

BoilerHorn · Jun 26, 2005, 05:48 PM

labman -- thanks again for the response.

I will get more details and post tomorrow. Based on our discussions, it appears that the AC is not cooling in 1/2 of the house. He called the AC guys out, who pointed at an electrical issue. The electrician disabled the breaker to the unit and found that it still had power. The electrician was confused and left. The owner then debugged the circuit, discovering the 2-parallel 40-amp circuits w/ parallel wire driving the 1 heater/ac unit. My main question was whether this was common or not. Essentially, he cannot get the AC guys or the electrician to look at it, as they are each pointing fingers at the other.

I know that the previous owners performed several repairs on their own before reselling. Whether they performed electrical work is unknown.

Thanks.

tkrussell · Jun 26, 2005, 07:16 PM

While this arrangement may seem uncommon, it is popular for heating systems of your type. I suspect the heat is electric. Code allows for a maximum circuit of 60 amp rated, or 42 amps of load, for electric heat systems. It is typical for two smaller circuits to be run, thus comply with code and not running an 80 amp circuit, which is not allowed.

However, each circuit must be treated as a separate circuit, and cannot be tied together as parallel. If the two circuits are connected together at the unit, then here is where the installers went wrong.

Is there any documentation or instructions with the unit? Here is where you will find how the unit is to be wired, and along with having a qualified electrican that understands the code, the problem should be resolved.

Try the manufacturers website for complete wiring instructions.

So if the wires are separate treated as two circuits, this is fine, if they are connected together at the unit, they must be separated to handle their own load, which may be the ac compressor and some heat on one, and the fan and some heat on the other.

Hope this helps.