# Any Lennox Pro's can answer my iComfort Wi-Fi Modulating Question?

• 10-23-2012, 10:10 AM
tuffcalc
Any Lennox Pro's can answer my iComfort Wi-Fi Modulating Question?
(SLP98V only)

When an SLP98 Furnace is connected to an icomfort Wi−Fi thermostat, the thermostat takes complete charge of the variable capacity staging of the furnace. Load−tracking Variable Capacity is only available with icomfort Wi−Fi thermostats.

How is Load−tracking Variable Capacity different from Variable Capacity?
Load−tracking Variable Capacity will smoothly track the load (sensible temperature changes) up and down and adjust the furnace heating rate both ways. Variable capacity only tracks the load upward (rising temperature). Variable capacity uses the thermostats stage differentials but not stage timers. LVC disregards both stage differentials and stage timers.

What makes Load−tracking Variable Capacity work?
With icomfort Load−tracking Variable Capacity, the thermostat uses a Proportional Integral Algorithm (PIA) to control firing rates of the furnace. The algorithm in the Load−tracking Variable Capacity provides much more precise control over the furnace than the Variable Capacity algorithm.

Interesting points about the Proportional Integral Algorithm (PIA):
The further temperature is from the current set point, the higher PIA sets the heating rate.

The longer away from a programmed set point, the higher the heating rate.

If needed, PIA will turn heating on and off in short cycles when there is a heat demand that is lower than the lowest the furnace can provide.

If the heat demand is higher than the minimum the furnace can provide, the furnace will run without shutting off.

As the room temperature rises nearer the set point, the heating rate will decrease.

As the room temperature falls further away from the set point, the heating rate will increase.

The stage differentials have no effect when running the PIA.

The second stage timers have no effect when running the PIA.
• 10-23-2012, 10:06 PM
tuffcalc
My question was erased when revising the above... it is...

In the installer menu there are two options.

1. Modulating Gas Heat Step Change PI Gain; and
2. Modulating Gas Heat Steady State PI Gain.

The selections for both are "Less Aggressive, Standard and More Aggressive".

Can anyone explain how these settings will affect the furnace modulation?

Thanks
• 10-25-2012, 12:24 AM
pacnw
hate to say this, but I LOATHE the iComfort stats, new and old.

WAY, WAY, WAY, WAY too much control over the operation of the unit for 95%+ of the customers out there.
• 10-25-2012, 12:34 AM
tuffcalc
... and 95%+ of the "pros" that have no idea as well?