HVAC Fuse Question


Old 01-13-07, 09:59 AM
Thread Starter
Join Date: Jan 2007
Location: Northridge, CA
Posts: 2
Unhappy HVAC Fuse Question

Hello friends,

I have a question concerning my rooftop Lennox HVAC unit. My heater stopped working recently. I went up to the roof to inspect the unit. When I pulled out the pull out fuse box, I was surprised to see that there were no fuses, rather a copper bar screwed in which connected the two leads.

Is this normal? My HVAC repair guy, says it's a "code thing." I'm not sure I trust him. What we are sure of is that I have a fried board now, which is going to cost $650 to repair. He reluctantly agrees with me, that if there had been fuses in the box, this wouldn't have happened. He's been my tech for years now, and has made countless repairs on the unit. He's now saying he will fix the box to accommodate fuses. (Only after I discussed this concern with him.) If it's a code thing, then why would he break code to satisfy me? Furthermore why would there be a code in CA that would force you NOT to use fuses? That seems backwards.

I hate to judge, but I can't help but think this may have been an unscrupulous act to create more work for this guys company.

I would appreciate a professionals feedback.

Thank you,

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Old 01-13-07, 11:20 AM
Join Date: Jan 2007
Posts: 22
There is NO code requiring local fuses. The only reason to use a fused disconnect would be to use a specific size fuse right at the unit.
A fuse would not have prevented your board from frying.
Old 01-13-07, 11:26 AM
hornetd's Avatar
Join Date: Aug 2001
Location: Maryland
Posts: 695
I fear you are jumping to conclusions. The code requires that there be a disconnecting means within sight of the equipment to insure the technicians safety by allowing him/her to have immediate control of the power to the unit at that location. The code also requires that the over current protective device specified by the manufacturer be used to protect the branch circuit serving that equipment. There should be a label on the unit that specifies the Over Current Protective Device (OCPD) to be used. Best practice is to house the OCPD indoors so that the occupants do not have to go outdoors to reset or renew the OCPD. I have been an electrician for forty years and have yet to meet a homeowner who is happy to face a multi hundred dollar expense but there is not always someone to blame for equipment failures. If the control board is fried it is likely that it is a victim of inadequate surge and spike protection which is provided as an optional extra by your electrician during the installation of your service equipment. There are protectors that can be installed at the unit but they are less effective because of the distance between the surge protective device and the Grounding Electrode System. Have an electrician check the impedance of the Grounding Electrode System. If it is higher then twenty five ohms have them propose a plan to reduce it to less then twenty five ohms with values of ten ohms or less being ideal for a home that contains modern electronic devices as part of it's electrical load. Have a hole hose surge protector installed at the service disconnecting means enclosure which is usually the main panel's cabinet. The best kind to have installed is one that protects all wired utilities that enter your home in the same unit. SquareD's offering can be seen at
Since the control boards on HVAC units only control the devices that switch the heavy currents used by these loads the most likely cause of the damage is surges and spikes that enter on your homes power utility wiring.
Old 01-13-07, 11:30 AM
Ed Imeduc's Avatar
Join Date: Aug 2002
Location: Mountain Williams Missouri
Posts: 18,389

Like said the fuse there didnt do your board in. You would still have the breakers in the electric panel for this unit. Years back yes they did have a fuse there by the units. They would like wear out . Not that there was anything wrong with the unitbut just blow now and then. So they got down to that code calls for just a disconnect by the units so a tech can pull it and work on them safe.

Old 01-13-07, 12:00 PM
Thread Starter
Join Date: Jan 2007
Location: Northridge, CA
Posts: 2
Smile Thank you

Thank you all for taking the time to help. This is good news. To a layman, seeing a fuse circuit defeated with a metal bar seems odd..I'm very glad to be wrong in this case.

Take care,


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