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Community and Q&A

HVAC fire safety: heat kit and plenum clearance

ChrisInIllinois | Posted in GBA Pro Help on
Trying to do away with  baseboard heaters  with minimal cost. To get me by until I finish a remodel and install a HRV and a mini split. This is a ways off. I currently need to replace 2 baseboards and thermostats. Cost vs heat kit not much more.

I have a Goodman ARUF30C14BA.

It was installed in a downflow application,with a gsx13 ac only. It’s a radial duct design. The unit sits on top of a square sheet metal plenum.
Building codes and permits are not enforced around here unfortunately, requiring me to oversee installations of any construction, just for safety.
When I was looking into this system. To see if it was matched and upgrades paths for heating, I ended up reading through documents older documents  found online for the unit. document supplied with the unit and documents Goodman support sent me because I had issues locating this exact model and revision. Aruf30 is 2.5 ton fyi.
The documents that came with it state if using a heat kit in a downflow application it needs to be installed on an L plenum with no outlets underneath it.

A newer revision of the document  (sent by support) omitted this clause.

A older one I found online and can’t find again stated a specific clearance from the heating element to the bottom of the plenum that need to be meet before duck branches or outlets could be installed.

After contacting a few HVAC installers explaining the situation they said they would just slap the heat kit in and it should be fine.
Please advise. Thank you.

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  1. Expert Member
    BILL WICHERS | | #1

    I really think you want to contact someone at Goodman for this. The manufacturer is the only one that can really tell you if it’s ok to use their product in any particular application like this. See if you can talk to someone in their engineering department. If they can’t or won’t do that, I’d try to find a Goodman dealer and see if they could help you get the info you need. I wouldn’t try to use a heating unit outside of the manufacturer’s guidelines.


  2. ChrisInIllinois | | #2

    I sent them a message about it before posting here.
    I don't expect to much from them. I sent them another email contact before and was told to contact a HVAC installer. My question to them was simple at the time and involved a licenced HVAC install of there equipment. My experience is they don't like dealing with diy/home owner/ non HVAC tradesman.

    This seems to be a nice solution, but not if I can't get it installed safely. I know sheet metal but not the specs I need. I'm thinking a simple cleat and drive add-on would suffice, but not without correct measurements.

  3. ChrisInIllinois | | #3

    Got a reply back. Do note, I told them basically the same thing posted up there.

    For the information that you have requested, you will need to contact a licensed HVAC contractor. If the contractor needs assistance, they may contact us to speak with our technical division that is available to the HVAC licensed contractors.

    How is this helpful, when the 3 contractor said they would just install it in existing equipment with the existing ductwork and it should be okay.

    I clearly read the paper work, my plenum does not meet Goodmans install requirements. I'm willing to fix it or pay the contractors to. It seem they just want easy money. So frustrating.

    1. Expert Member
      BILL WICHERS | | #4

      They probably don’t want to directly advise a homeowner for fear of liability. A licensed contractor will have an insurance policy so they’d be on the hook instead of the manufacturer for anything installation related.

      I would still advise you to not attempt to do this work yourself if anything is not clear from an operational safety standpoint. You don’t want to risk a fire by saving some money on a contractor.


  4. walta100 | | #5

    My guess is that it would not be a safety issue having a duct directly below the coil as long is the duct work is steel. It could be a comfort issue where a duct directly below the coils could get warmer air stream than the ones off the side. The coils will glow red and the radiant energy could affect plastic flex ducts.

    Lets a local pro or two have a look gets an estimate and follow their advice they have years of experience and a fat insurance policy to back them up. Of course on the phone they will say no problem we will make it work.

    Do not expect any useful help from the equipment manufacture. They do not see you as their customer, they sell equipment to HVAC contractors. If they gave you any advise and anything bad happens somebody would sue them.


  5. ChrisInIllinois | | #6

    I don't want to talk about the amount of time it took to get someone competent out to the house. The short of it is I had 6 different Techs out with full disclosure that I was getting multiply quotes and gave my understandings and expectations.

    Only 1 out of 6 seemed competent, cared about load calculations, static pressure, and CFM of amount of air. He was not local but a friend of a friend cost me some gas money and a lunch.

    The outcome and answers:

    radial duct design is okay for heat kits, his opinion was that the duct from the plenum should be metal for the first few feet at a minimum, even if other ducts products would work.

    the takeoffs should be 6" from the top at a minimum to allow for air mixing.

    I talked with him about my over sized system and my concerns:
    The CFM my air handler puts out vs the amount need for my home.
    The CFM need for a heat kit vs amout need for my home.
    The out come was I need more ducts to lower static pressure, It would help with the loud sound of rushing air to some degree.

    we could have addressed this, but I only have 4, Thats right 4 ducts pushing 1100-1300 CFM in a 950 SQ house.

    I would be freeing up wall space but giving up comfort.

    He said he could work with goodman and maybe able to come up with some type of solution.

    after talking with him about my plans, cost wise it just made more sense to put $250 in to baseboards and thermostats and deal with it for another year or two until I get to getting a correct heat pump.

    There it is. There are good people in the HVAC industry, you just need to find one that cares or that is knowledgeable. Its just a same the industry is the way it is atm aka lack of manual J, over sized installs, and quick money.

    Thanks for all the help and following along, I just thought I would come back to give the rest of the story.

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