# Thread: calculating tonnage through chilled coil

1. Professional Member
Join Date
Jan 2001
Posts
838
Post Likes

## calculating tonnage through chilled coil

is there a way with flow,splits to calclate tonnage of a chilled water coil

2. Yes, you will need entering water temp, leaving water temp and flow rate and you can do it.

3. You can calc cooling capacity either using the water or air side flow and temperatures. Water is method is the simplest:

GPM*500*H20 Delta T = BTU/H Note: The 500 constant assumes straight water (no glycol)

For air you'll need to measure airflow and take wet bulb and dry bulb temperature readings across the coil. Find the resulting entering and leaving enthalpy for each using the psychometric calculator located here http://www.trane.com/commercial/soft...eb_toolbox.asp

CFM*4.45*Delta enthalphy = BTU/h

There you have it....Git 'er dun!

4. Professional Member
Join Date
Jan 2001
Posts
838
Post Likes
there is glycol in the system. to get gpm divide pressure difference by design pressure difference. how do i get dsign pressure delta

5. The design gpm is usually documented on the equipment data page of the job drawing or you'll have to go back to the coil manufacture. If you figure out the specific gravity of your glycol mixture, there is another formula to correct the difference between water and glycol, using the previously listed formula. (Hope that makes sense) I can try and find that correction factor formula tomorrow, but the water formula gets you pretty close, even with a 33% prop. glycol mixture.

6. Regular Guest
Join Date
Mar 2009
Location
Illinois
Posts
8
Post Likes
Originally Posted by hvac17011
is there a way with flow,splits to calclate tonnage of a chilled water coil
This is a useful site. http://wea-inc.com/hvac_calc.htm it has helped me in the past.

7. Professional Member
Join Date
Nov 2008
Location
NE Texas & Houston
Posts
57
Post Likes
If you can get a curve for that coil from the manufacturer you can use the water pressure drop across the coil to determine GPM flow and read capacity.

When you have that, calculate 1 btu to lower the temp of one pound of water 1 degree. Convert pounds of water to gallons.

8. Regular Guest
Join Date
Mar 2009
Location
medellin colombia
Posts
6
Post Likes
ok, you do get GPM with the drop water in vs out pressure , delta p is view at chart of fan coil desing factory and view gpm and ok FLYFARN REASON

#### Posting Permissions

• You may not post new threads
• You may not post replies
• You may not post attachments
• You may not edit your posts
•

## Related Forums

The place where Electrical professionals meet.