I have a 20 X 30 foot trailer. And my ac unit id dying its over 10 years old too. I'm having problems finding what ton my ac is or the sheer for a new one, but its design pressure is 450 high 150 Lcw and the compressor amps are 17.0 and LRA is10.5 It's made by Nortek Company and Model # S3QA-042k and the Serial # is S3QA-042K. I'm needing to find some prices on new units so when I bye one we are getting what we pay for you know I think our ac guy is marking it up bad he wants $2300.00 too undo the old one hook up the new ac and cost of it I just have feeling he isn't being strait forward with his services, thanks I hope some one can help me I'm in dire need.

for 20 x 30 foot you only need a 1-1/2 ton but you will have to change the indoor and outdoor to 13 seer 410A units.