Blower speed question
#1
09-27-08, 10:03 AM
Blower speed question
As I posted in a different thread, I got a new Lennox system installed last week. (G60UHV furnace - dual stage, variable speed, XC14 A/C, Honeywell IAQ thermostat)
After the install I checked the dip switches on the Furnace board, and noticed some interesting settings that are different from the factory default. They have reduced the cooling mode blower speed from "High" to "Medium Low", and advanced the speed by +10%. Did they do this based on the size of the A/C unit? (although my tonnage has not changed - 2.5 ton) My old furnace was not variable speed, but I'm pretty sure it was wired for high speed blower speed for cooling. (cold air is heavier) Does this make any sense? Wouldn't increasing the blower speed be more efficient?
--Rob in VA
After the install I checked the dip switches on the Furnace board, and noticed some interesting settings that are different from the factory default. They have reduced the cooling mode blower speed from "High" to "Medium Low", and advanced the speed by +10%. Did they do this based on the size of the A/C unit? (although my tonnage has not changed - 2.5 ton) My old furnace was not variable speed, but I'm pretty sure it was wired for high speed blower speed for cooling. (cold air is heavier) Does this make any sense? Wouldn't increasing the blower speed be more efficient?
--Rob in VA
#3
09-27-08, 01:03 PM
Originally Posted by Jay11J
What's the full model # of your furnace?
They may of changed the settings to match to your system.
They may of changed the settings to match to your system.
--Rob in VA
#4
09-27-08, 04:51 PM
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Ok, the way the had it up was to move about 1,230 CFM of air.
Ideal set up is 400 cfm per ton, your system is 2.5, so should move about 1,000 cfm of air. So with those settings it's not too bad, but i'd rather back it down a bit, unless you can't get air at a distance vent. The setting below will move about 1,100 cfm.
So, here are the settings I'd set it to.
Dipswitch
1-off
2-on
3- not used (two stage jumper should be in place)
4-
5-off
6-on
7-off
8-off
9-off
10-off
11-off
12-on
11-12, I would do a temp rise to see where you are at.. Should be in the mid-range of the spec on the model plate in the furnace. If the temp rise is too high, then need to speed up the blower, if it's too low, then need to slow down the blower.
Ideal set up is 400 cfm per ton, your system is 2.5, so should move about 1,000 cfm of air. So with those settings it's not too bad, but i'd rather back it down a bit, unless you can't get air at a distance vent. The setting below will move about 1,100 cfm.
So, here are the settings I'd set it to.
Dipswitch
1-off
2-on
3- not used (two stage jumper should be in place)
4-
5-off
6-on
7-off
8-off
9-off
10-off
11-off
12-on
11-12, I would do a temp rise to see where you are at.. Should be in the mid-range of the spec on the model plate in the furnace. If the temp rise is too high, then need to speed up the blower, if it's too low, then need to slow down the blower.
