Sub Panel For HVAC Components?

Found this the other day and wasn’t sure about what was correct and not correct. Sub Panel was located in the attic and had a 40 amp breaker going to an air handler located in the attic and a 60 amp breaker going to another 60 amp breaker (disconnect means) out by the condensing unit. First of all, is it ok to have a sub panel mounted this way from the rafters. Secondly can you have the air handler and condensing coil both being fed by a subpanel which is only being fed by one circuit back at the Main Service Panel?

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It is fine to feed a sub-panel to support the HVAC system in the attic as we do this all the time. However, you need to make sure the feeder is properly sized for the application…this is important.

In regards to the mounting it would not be a huge concern if the unit is mounted securly to the web of that truss system…if the top of that panel is the only supporting location then you have to inform them it needs to be supported from the bottom as well…IMO it is not secure if only one screw is being used.

Now…the other issues is supporting the wires as they leave the enclosure…if they turn and go to the web of the truss and are supported with staples and so on then that is fine.

Make sure it is being fed with (4) wire…obviously, and that it is grounded and bonded correctly as usual…and if it is fed with SE…and done prior to lets say 1996…you can inform them that (4) wire is used today to feed sub panels but in fact they do not have to replace it…as it was code at the time of inspection…but I find it important to make them aware of the change to (4) wire because it was proven to be safer in reducing objectionable current on the neutral and so on…

Other than that…I would not get too pushy on this…many electricians install a SUB-Panel in the attic to feed the air handler if it is a larger one that required a 60A and 30A…just make sure they sized the feeder correctly.

UPDATE- Greg makes a GREAT point however…may not have any 120V needs at this location…clearance and location is key…and how it is labeled.

Just want to make sure we are on the same page, I’m used to seeing separate breakers at the Main, one for the Heater and one for the Air conditioner. This sub panel was fed by one breaker at the Main Panel and then it in turn fed both the Heating and Air conditioning units. Max circuit breaker size listed on the Air Conditioning was 30 amp but sub panel had a 60 amp breaker!

This gets tossed around a lot in inspector meetings. I have a question for you Paul.
I know you are careful to provide working space for the disconnect out there next to the condenser, how do you get 36d x 30w x 81h up in that attic?

Why pull a neutral if the system is pure 240v?

Well it depends on the attic space Greg…Also if the panel is being considered as the disconnect…usually it is also protected back at the main panel so the panel in our area is considered a service disconnect for the HVAC units.

IN fact it really also depends on the AHJ…here is an example…their was a space in an attic location for a high volume AC system…and it was up 3 stories…so even the AHJ suggested a 4 CKT panel be located in that location and let it serve as the disconnect…this is the local AHJ mind you…

Their was certainly 30" min space width in this location but did not have the required headroom…yet he classified it as a disconnect and not a service panel and allowed the installation…in actualness…it was the only way to really get the job done…

Most attics will still give you the 36d x 30w…now this height is not obtainable…but again depends on the classification of the panel…it is written on it as a disconnect and has no space for expansion…the AHJ ruled it was considered as a disconnect and allowed…

Just so happens most of the situations will depend on the situation but if you can get the AHJ to re-classify the equipment then their ruling will stand.

As for the 240V…take the unit I was speaking off…it had (2) heat strips each were 120V…not 240V…all depends on the installation.


Also remember that the clearance ruling applies to panelboards, switchboards and so on…by re-classifying the 4CK panel as a disconnect combined unit and relabeling as such…and clearly marking it as such and being it is less than 200A…the height room is also allowed to be less than 6 1/2 feet…per Art 110.26 (H) Exception…

Now…pulling straws here but in THIS case the unit is considered a disconnect…and COULD be 3 wire per say…but when you do not know the use perimeters we run (4) wire…because of potential 120V requirements…you just never know.

Now…for home inspectors the application of the wire is fine…which is why I said I would not flag it…but should be labeled as such if it is truly a disconnection assembly.

Now…some AHJ’s say that 110.26(F)(1)(A) suppasses this when it says 6 feet…yet again most AHJ’s will refer back to 110.26(H) and allow it…again if reclassified as a disconnect…

Just ends up being a local AHJ’s call…

Maybe Joe T can chime in on this one as well…again half the FUN is seeing the many ways the NEC is directed.

I have heard both sides. :wink:
What rule applies to the disconnect by the condenser that doesn’t apply here?

The Single Most Important Piece Of This Discussion, For All Inspectors Watching The Exchange Between Sparkys, Is That There May Be No Absolure In Any Electrical Situation. Items Are Open To Discussion With The AHJ, Depending On The Specific Situation. Knowledgable AHJs Will Often Work With The Electrical Contractor To Come Up With Work-arounds For Most Situations.

This Is The Most Valuable Lesson Here, And I’d Like To Thank Paul And Greg For Providing It To Us.

lol…Thanks Joe…I think…thehehe

Actually greg and I are having a great conversation…I am not sure if greg is debating with me per say…I think we both know that learning never stops and the moment you STOP thinking you are learning it is time to give up and move on…I learn something everyday and it is what keeps me going on.

Many times the AHJ’s do not even know the specifics of things because they just do not come up that often…so I find it fun to look at different aspects.

Greg…I guess I would have to ask you to provide in your opinion the ART. that sets the specifics on height and so on regarding a disconnect for a Air-Conditioning and Heating units so that I can then point to the article that opposes what I think is what the local AHJ’s are using…

Actually greg in many cases the Art.90 section will give the AHJ levy to allow something…I am not saying height requirements should not apply as listed in Art 110 but I just happen to be a realist and the debate has run wild on many forums regarding this…

Personally I appeal to the AHJ’s knowledge of the situation and in my opinion it depends on the attic space…30 x 36 is not hard to achieve…the height can be an issue but in many it is not…boils down to the local AHJ making the call…

A quote from a VERY knowledgable AHJ inspector- “The purpose of the local disconnect is to provide a means to isolate the equipment in the field. When you remove the requirement for this disconnect to be readily accessible, I’m not sure that you don’t also remove the 110.26 work space rules. Many of these disconnects are installed where the 110.26 space is not and cannot be provided. An example would be the local disconnect for a piece of equipment that is installed above a drop ceiling. There is no way to provide a 30” wide by 36" deep work space above the lay in grid. The grid itself interferes with the workspace that is required by 110.26, yet this is a very common commercial installation."

I agree having the disconnect is more important than the working space. I was just pointing out some of the issues that fly around inspector meetings.
For the HI it is probably more important to simply point out this equipment us up there in the attic so they will be able to find it.
For a while a large part of Florida made it unattractive to put air handlers in the attic because it had to be in environmentally controlled space but that rule did not make it into the unified FBC. Personally I thought that was a good rule. In 98% humidity these things will sweat like a pig and quickly rust out, as does the drain pan. When my wife was selling HVAC she refused to sell one unless they bought an auxillary drain pan. It was just part of the price. Perhaps that is something the HI should put on their check list.

I agree Greg…you and me BOTH know that getting around the NEC for someone who knows the NEC is not too difficult but in the end it also helps to know your local AHJ and his past experience.

On the HVAC units in the attic…I would have to agree in that even in OUR area the temps change from down in 20’s one day to in 70’s the same day…causing condensation and moisture and well…rusty pans and units are a big issued everywhere.

I think the main reason the allowance on clearance takes place is because of the direct use…with it comes to disconnects the specs are not clean cut in many cases…so adaption is applicable.

I also agree, and a simple safety improvement would be to add a breaker lock at the service panel for that main feeder so that the sub-panel/disconnect can be examined/repaired without it being energized … which if energized kicks in the 110.26.A clearance requirements for working on energized components.

Perhaps because there needs to be a 125V receptacle close to (within 25’) of the air handler (NEC 210.63) which are typically 240V equipment.

Something does seem wrong. Having a 60A main panel/sub-panel breaker seems about right, but the sub-panel or the disconnect outside by the condenser should have a 30A breaker for the condenser per the nameplate. If it’s a 60A circuit/breakers and the condenser nameplate has 30A max then it is a defect that should be corrected.

Why would you clutter up your HVAC panel with the service outlet circuit (additional load calc etc) and if you did, wouldn’t it be off when you did the LOTO at the service panel you spoke of. Not very handy if you are turning off your service outlet to work on the AC. That is the reason they require a separate service outlet in the first place.
It is a lot easier to keep the HVAC circuit clean and tag a general lighting circuit for your service outlet.
At my house I tagged the <otherwise> dedicated circuit for my computer room on the other side of the wall from the condenser. I did pull the conductors through the same raceway tho.

I also think in doing that it would make the panel that is re-classified as a disconnect to the HVAC unit as now a panel itself and thus causing the fight for clearance to be MORE of an issue.

AS well as all the things Greg has mentioned…

Remember in many cases when dealing with local AHJ’s the labeling and listing comes into play…when relabeling and dedicating this lets say 4CKT panel as a disconnect and labeling as such…leaving it as service disconnection means to the HVAC system is what I would intend it to do…making the argument for it not being a panel per say even more valid in some AHJ’s authoritive eyes

Greg … I was looking at the disconnect clearance and 3-wire 240V/120V feeder to the air handler as two separate issues. I agree that adding a breaker lock to a feeder that includes the 120V service receptacle doesn’t work well.

Normally I see a separate 2W+G 240V circuit to the AC condenser outside, and a separate circuit to the air handler … which is sometimes a 3W+G 240V/120V circuit to a 1900 box at the unit, which has both a 120V service receptacle (always hot) and a snap switch used as the air handler disconnect (typically 240V … at least for newer air handlers). The air handlers typically do not draw much.

JMO & 2-nickels … :wink:

Perhaps that is the difference. An air handler here will have 10 to 15 KVA of toaster wire heater. We don’t have furnaces. Since that is electrically interlocked with the compressor, the circuit going outside is just tapped off this. They deal with the smaller OCD requirement in the condenser disconnect. There is no neutral load.

Here in the NE that would spin the elec meter in the very cold winters … :smiley:

Normally there would be an inline gas furnace or inline hot water heating coil off a boiler zone for forced air systems. There are a few heat pump systems with supplementary 10kW-15kW heat strips, but they are not very common due to the high operating costs.