House inspected yesterday had 2 Lennox condenser units:
#1
Model HS23-411-1P
Serial 5193M13649
Max breaker 35 amps
#2
Model HS29-311-3P
Serial 5897E 22695
Max breaker 25 amps
I’ve got the age figured out as 1993 and 1997 but I’m puzzled on the size of the units. There is no number divisible by 12 in the model numbers. Does the 411 and 311 part mean 4 tons and 3 tons?
According to the Technical Reference Guide the first two digits in the second group are Mbtu.
411 = 41,000 btu,
311 = 2 1/2 tons.
Serial 5193M13649 - Dec, 1993
Serial 5897E 22695 - May, 1997
Hi Ronald,
According to Prestons guide the first unit is a 36,200 BTU (3 ton) 10 seer unit, and the second is a 28,600 (2 1/2 ton ?) 9.3 seer unit.
Regards
Gerry
Thanks guys, that’s why I love this place. 
Ronald -
If I wanted to be 100% accurate and take more time, I would get out my Preston Guide or Carrier Bluebook and look up the answers. Or I would simply look at the numbers 311 & 411 and guestimate that with Lennox Units I had ABOUT a 2.5 Ton (+/-) Unit & a 3.5 Ton (+/-) Unit.
In 28 Yrs I’ve never had a complaint doing it the 2nd way.
Preston guide book any ideas where I could get a copy cheaper than $68 where my school had offered it? I’ll take 1 used.