What is a "ton" as it relates to HVAC/heat pump units?

Factual Questions
1

Inquiring minds want to know.

2

12,000 btu/hour. No idea how the convention came about, though.

3

A ton is 12,000 BTUH of cooling capacity. In other words, a unit with 1 ton of capacity can remove 12,000 Btu’s of heat from a room every hour. A 5 ton unit can remove 60,000 Btu’s per hour and so on.

It’s not always that easy when buying equipment, however. There is nominal capacity, and actual capacity. Nominal capacity is what the unit can do at some specified standard conditions and actual capacity is what the unit will do at your conditions. For instance, the nominal rating could be for operating with an outside air temperature of 85 degrees at sea level. If you used the same unit at an outside air temperature of 100 degrees at 4,000 feet elevation, you would not get the same amount of cooling. There are quite a few variables, but you should always look at actual cooling capacity of a unit if possible.l

4

I’m not exactly sure, but I think it is related to the cooling you would get from a ton of ice.

5

You would think that I would know this, since I work at an HVAC company - but nope. If I remember, I’ll ask around tomorrow. Someone there should know.

6

I didn’t know, I googled.

Apparently early ice plants were described/rated as the number of tons of ice production per day. This was before home or commercial refrigeration without the ice. The 12,000 btu/ton idea stuck as a measure of cooling when home/office units replaced the ice as the cooling method.

7

That’s correct. Starting with 2000 lb. of water at 32[sup]o[/sup]F you need to remove 288000 Btu in a day to freeze 2000 lb of ice in one day. Dividing by 24 gives 12000 Btu/hr.

8

Bingo
More accurately the amount of cooling to make a ton of ice. See Post #7.

9

Yes, this is 100% correct. It is not the weight of the unit…as one may first think. Also, I think it should be mentioned, you may see the unit of BTUH = Btu/hr. And, when devices claim how many Btus they put out (if heating) or reject (if cooling), they really mean Btus/hr = BTUH

It’s amazing it works out to such a nice, round number!

  • Jinx