It's a Maytag 2 stage 80% eff, variable speed, 100btu, new furnace. I
posted previously with some related Qs, but this 2-stage stuff is
bugging me.

The "timer" (relay, delay, whatever) does this: The igniter starts,
gas is delivered to 3 of the 5 burners. After the time set on the
"timer" (1 to 10 minutes), if the stat is still wanting heat, the
other 2 burners will start.

Near as I can tell my "fan-only" blower speed remains the same during
"fan only" and low heat. The speed increases with high heat.

Without sitting around all day and watching and listening to this
think I cannot measure how ofter the low heat get the job done before
the high heat kicks in.

I guess waiting up to 10 minutes before the high heat kicks in is not
all that bad, although this seems pretty rudimentary, but I'm not sure
how a 2-stage stat could really be all that more intelligent. It
would come down to the stat having some kind of knowledge systems that
would tell it when to kick into high asap vs wait 5 or wait 10, etc.
It seems like the characteristics of the furnace, the current inside
temp, the outside temp, the desired temp, and the efficiency of the
furnace/ducting would all have to be constantly analyzed to sort out
the best approach. Seems like too much to ask of a $100-$200 piece of
electronics.

On a somewhat related note, how can I tell what fan speed my blower
should be set at? I guess there are like 10 low/high settings. I'm
currently 2 down from the highest output.

On Fri, 14 Jan 2005 03:16:22 GMT, Bubba
wrote:

On Thu, 13 Jan 2005 16:28:50 -0600, (Hello
Friend) wrote:

'I have a normal programmable thermostat. On the furnace they installed
a "timer".

I think by 'timer' , you mean an automatic Time Delay Relay (perhaps ?)
whereby the signal to the 2nd stage is delayed for 10 minutes.

'After the thermostate turns the furnace on, it will run at low heat (3
burners) for 1 to 10 minutes (depending on the manual setting of the
timer). After that time it will kick into high heat (2 more burners). '

From this description, it would only be possible if you had a split
manifold in your furnace with one gas valve controlling 3 burners, and
another gas valve controlling the remaining 2 burners. I doubt this is
what you have very seriously. Typically on a 2 stage gas furnace, you
would have ONE gas valve that works in 2 incremental stages : the first
stage produces a smaller flame thru ALL burners...then, when second
stage is demanded, the same gas valve would let more gas into the ALL
the burners thus increasing the flame (and hence , heat output) until
the thermostat is satisfied then all gas is shut off to the burners. A
2 stage setup is advantageous , especially in areas where there is a
significant milder winter period . Personally, a 10 minute time delay
before 2nd stage is engergized..is too short of a duration ; 15-20
minutes would be better to give low stage a chance to satisfy the
thermostat.

Not at 6am on a butt-ass cold morning after you've programmed the
thermostat to go back to 62 or 64 degrees at night. In the morning,
you want that stat to kick in high immediately and stay there till its
warm. THUS, the need for a 2 STAGE STAT! If you dont have a 2 stage
stat you dont need a 2 stage furnace.
Bubba