Lennox SLP98v and Honeywell FocusPro 6000

ghostdog1108July 27, 2011

Recommended by my installer.

Is this a good fit in that we would only be adjusting temps at night?

Would it hinder the operation of the SLP98v in any way?

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What would I gain other than bells and whistles if I purchase the iComfort thermostat?
I do not desire many options as far as automatic temp
changes as I will soon be retired.

    Bookmark   July 28, 2011 at 8:45PM
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SLP98 has variable speed fan and variable output burner. Theoretically behaves as a furnace sized for the load at that moment. On a colder day behaves like a bigger furnace and on a warmer day behaves like a very small furnace. This needs a thermostat that can control the variable output feature. Unfortunately, there is no standard for this. If you buy a variable output furnace, you must buy the corresponding thermostat from the same manufacturer to use the variable output feature. Otherwise, the furnace will behave as a single or two stage furnace depending on what the thermostat can handle.

If you look at the furnace manual regarding DIP switch settings on installation, it basically asks you to select single stage, dual stage or variable output thermostat where only the Lennox icomfort can run as variable output. In addition, while this is not made clear in the literature, the discharge air sensor helps this furnace. If it is not in place, fan speed and burner output level move together as a best guess. If the discharge air sensor is used, the two are delinked with the burner running to maintain a target output temperature. This is particularly useful if there is excess airflow resistance or zoning since under those conditions, the relationship between ideal fan speed and ideal burner output level is not constant.

    Bookmark   July 31, 2011 at 5:01PM
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Thanks for the excellent explanation zver11.
That is also my understanding however my installer who has been in the community for decades and has a great reputation felt the Honeywell would be fine to maximize the abilities of the SLP98v.
I am obviously no expert but I totally agree with you.
Should be an interesting conversation tomorrow. :-)

    Bookmark   August 1, 2011 at 12:23AM
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zver11 is incorrect. I have this furnace. It can be used with any two-stage thermostat. The FocusPro 6000 will be just fine and will allow the SLP98V to work in variable capacity mode, just make sure the dip switches on the furnace board are set correctly to variable mode - and both heat connections (Y1 and Y2) are connected.

    Bookmark   November 26, 2011 at 12:41AM
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Does the iComfort really control the modulation or does it do it's thing the same way it does with a 2 stage? Still can't fathom wanting a modulating furnace that can't modulate down when less heat is needed.

    Bookmark   December 3, 2011 at 5:15PM
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