Misleading of furnace ad.?


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Old 03-07-10, 08:01 PM
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Misleading of furnace ad.?

I collected from Internet sth customer may be aware of:
1. Goodman GMH95 two stage can only be used with one stage thermostat. It is always started at low stage - its induce motor is single speed, then have a profile or manual set delay before switch to hi stage.
Compared with Carrier, which has matched inducer speeds, and thermostat can control two stages.
2. Goodman GMV95 "variable speed" is not like Carrier variable speed that change blower speed from 300RPM+. GMV is in fact multi-speed or each mode like lo/hi heat and lo/hi cooling has preset fixed speed.
3. Carrier 58MVC is not modulated furnace but 3-stage furnace. Modulated furnace can change BTUH from 40%~100% in 5% or finer, 58MVC adds 3rd valve after 2-stage gas valve to reduce gas to 40%. So you have 30stage:40%,67%,100%. Trane XC95M is very similar.
4.Rheem (needs its thermostat) and Lennox modulated furnace are real one. I can't find other brands spec. to verify. Anybody can give me a link?
I welcome any correction/comment.
 

Last edited by chinomango; 03-07-10 at 10:28 PM.
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Old 03-07-10, 10:06 PM
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It is surprising that a 2 stage furnace would not have a W2 terminal.





 
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Old 03-07-10, 10:27 PM
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Originally Posted by Houston204
It is surprising that a 2 stage furnace would not have a W2 terminal. ...
It may be because it uses single speed inducer.

Thanks for post spec. GMV95 uses profile or time delay to change CFM from low to high. 1st 30sec low CFM, next 7.5min mid CFM can be optionally inserted. This is quite different from Carrier variable speed where it provides near constant CFM regardless static pressure.
 
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Old 03-09-10, 05:14 PM
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Carrier uses this X13 ECM motor in their PHA furnace. It has an improved CFM output with a high static over a PSC motor.
It also has a lower wattage.

http://www.docs.hvacpartners.com/idc...58pha-03si.pdf
 
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Old 03-12-10, 10:59 AM
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the GMH uses a 2 stage gas valve and standard blower the second stage is controlled by the board and should be set in the AUTO mode. this way it collects data from the last few times it fired and switches to high fire based on that data. not not to be confused with a variable speed which has the variable blower in addition to the 2 stage gas valve.
 
 

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