We bought a new home and it came with this state-of-art system. The model number is #48XT-A6011530TP. Haven't had much luck finding information about this model or type of unit online.

I've got a box inside by the thermostat, in a closet, behind the return air filters, and a box outside about 4-foot square. They tell me that is called a "split unit".


1) Where is the pilot light on my Carrier 48XT Hybrid Furnace/Air Conditioner unit?

2) Why is there almost no information on this type of unit available online. There are all kinds of videos on YouTube about how to turn on a pilot light on different models of heaters, but not this one.

3) Is this some magical type of unit that all-of-a-sudden doesn't have a pilot light? If so, when did they start doing that? Is it controlled by a computer, like automobiles are now?

If for some reason I have an outdated understanding of how things work, the main thing I want to know is How do I turn on my hybrid furnace?

Any help is appreciated.

  • There seems to be a lot of information about the 48XT system on the Carrier website (including the feature of electric ignition rather than a pilot light). Also, as a new house, the builder should be able to provide information on the unit. You should also call Carrier directly if the website does not have what you need.
    – Barry
    Oct 26, 2017 at 1:22

1 Answer 1


Pilot lights went out of style sometime in the 90s

Your furnace, being a modern-day unit, does not use a pilot for ignition. Instead, what you have is most likely what's called a direct spark ignition (DSI) system that has the furnace board trigger a spark at the appropriate time to light the gas -- it indeed is a computer control system!

As to how you turn this thing on -- you should be able to turn on the serviceman's switch/disconnect and the thing will be ready and waiting for a call for heat. Your system won't call all the time though, because it's a hybrid system with gas backing up a modulating heat pump -- this means that the gas will only kick in when the outdoor reset shuts down the heat pump (if it gets cold enough, the heat pump can't run), or the heat pump itself is inoperable.

  • I started in heating and air conditioning in 1987 and pilot lights were long gone before then. Although indirect ignition stuck around a lot longer where the pilot light was automatically lit with a spark igniter but using a match has been gone since the early 1980s.
    – user76730
    Nov 5, 2017 at 18:54
  • @user76730 -- yeah, when I refer to pilots being gone, I refer to completely pilotless systems (DSI/HSI). My understanding is that manual pilots were obsoleted by spark-to-pilot systems well before HSI/DSI came on the scene Nov 5, 2017 at 19:09

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