I had a guy I work with tell me that 12,000 British thermal units (1 ton of cooling) equals 7 amps of alternating current. Is this accurate or is this just hearsay? I was taught to always refer to the manufacturers specs per article 110.3 (B) and will continue to do it that way but I'm interested in finding out if there is any truth to this.
Sounds like 12 apples = 7 oranges to me. I spose you could work backwards using your efficiency to find the power required and calculate the voltage where 7 amps would be the required current. Easier to just say it's apples to oranges as stated. Joe
#69763 - 09/18/0606:40 PMRe: Does 1 ton of cooling equal 7 amps?
I think he is actually exactly right, the only variable he left out is the voltage I'm sure one ton is equal to 7 amps at some voltage. Back in the olden days we used 1.25kw per ton when SWAGing a computer room HVAC calc but we really wanted the numbers from the manufacturer. I think that 1.25kw assumed some duty cycle adjustment.
#69764 - 09/18/0607:01 PMRe: Does 1 ton of cooling equal 7 amps?
this may be related to the idea that 1HP = 1 ton- which is not necessarily true, but 1 HP = 760 watts = ~7 amps @ 115v? But 1 HP does not correlate to 1 ton of refrigeration, sometimes it takes a 2 HP motor to drive a 1 ton load.
#69765 - 09/18/0607:55 PMRe: Does 1 ton of cooling equal 7 amps?
I should have mentioned that the application here are split-system central A/C's rated at 240 volts. All I have to hear is "this is what the old-timers used to do" and that's good enough for me. It's not until you start listening to the old-timers (and I mean that respectively) that the serious learning can begin.
#69767 - 09/18/0609:34 PMRe: Does 1 ton of cooling equal 7 amps?
I looked up how they compute SEER which would affect the current and I am even more confused. Wikpedia makes it sound like a 10 SEER machine would give you 12000 BTU/hs with 1200w but that doesn't sound right (5a per ton at 240v) but it is close to the old number we used (1250w). I do think SEER is an average too. I tried looking up some installation info from Trane but my eyes started glazing over before I found any real specs.
#69768 - 09/18/0610:42 PMRe: Does 1 ton of cooling equal 7 amps?