cooling a high heat load space
cooling a high heat load space
(OP)
I'm faced with somewhat of a unique situation. I trying to determine the best configuration to cool a small (~75 SF) space that houses ice cream machine condensers. There are (5) machines each rejecting about 13MBH each (65 MBH total). The is an interior space and the owner wants a ductless split only as a last resort (as it will have to be a large system - $$$). The remainder of the property is served by a 5-ton DX unit, so not enough to supplement this condenser room. The space is interior but it is adjacent to an under-floor crawl space. The crawl space temperature remains in the 50F - 80F range year round. A transfer duct isn't an option due to the high heat load and limited primary AHU capacity.
I'm trying to size an exhaust system to cool the space, but I think this will result in the need for an enormous system. I'm looking to maintain 95F in the space with an estimated peak ambient of 80F in the crawl space (where the air will be exhausted). Based on these parameters, I think I would need a fan in the 4,000 CFM range (please correct me if I'm doing this wrong). In addition, I would need a make-up air system pulling and filtering OA from the crawl space. Fortunately I shouldn't need to temper the crawl space inlet air.
I have limited experience with this type of setup, so I would appreciate any input: Alternatives, critiques, corrections, etc.
Thanks
I'm trying to size an exhaust system to cool the space, but I think this will result in the need for an enormous system. I'm looking to maintain 95F in the space with an estimated peak ambient of 80F in the crawl space (where the air will be exhausted). Based on these parameters, I think I would need a fan in the 4,000 CFM range (please correct me if I'm doing this wrong). In addition, I would need a make-up air system pulling and filtering OA from the crawl space. Fortunately I shouldn't need to temper the crawl space inlet air.
I have limited experience with this type of setup, so I would appreciate any input: Alternatives, critiques, corrections, etc.
Thanks





RE: cooling a high heat load space
I don't see a real alternative to exhausting into the crawl space and taking makeup from there too, unless you add a cooling coil. It's possible that you can get by with a smaller split system and reduce the air flow. You basically need just over 5 tons of sensible-only cooling. You could get the whole 5 tons with ventilation (4000 CFM) or you can get the whole 5 tons with a split system (maybe 2000 CFM). Or, you could design something in between. Couple tons of split system, couple tons of ventilation. Lots of choices.
Best to you,
Goober Dave
Haven't see the forum policies? Do so now: Forum Policies
RE: cooling a high heat load space
couldn't you just equip those ice machines with remote condensers that you put outside, like any grocery cooling system?
I realize someone else may have set this up originally, but locating the condensers inside this space was a dumb idea (sorry). I'm sure those machines are offered with remote condenser for that exact reason.
RE: cooling a high heat load space
The crawlspace ventilation is a major concern of mine. It is not actively ventilated, but it is equipped with (2) louvers that allow some passive or natural ventilation. Seeing that I am considering a make-up air system, I didn't think pressure (+ or -) in the crawl space would be an issue. Temperature, however, worries me a bit. The crawl space is about 1,500 SF with a slab-on-grade and above-grade CMU walls.
RE: cooling a high heat load space
You will very possibly create a happy place for some form of biology. Mold, bacteria, mice, bugs, lions and tigers and bears.... Ice cream is food. Food and critters should be kept well separated.
Run ducts for supply and exhaust to and from the condenser room.
Can you go up, through the roof?
RE: cooling a high heat load space
RE: cooling a high heat load space
If not, does he have the owner's permission to use the crawlspace for any purpose at all?
RE: cooling a high heat load space
RE: cooling a high heat load space
Is the 13 MBH rejection based on nameplate info or based on real heat rejection? Real might be on the order of a fifth of nameplate. A very important consideration.
RE: cooling a high heat load space
You bring up a great point about the heat rejection rating. 13 MBH is the rated heat rejection, so I'll dig into the equipment specs to see what I can find. I'd imagine you're correct in that the actual output is considerably less.
RE: cooling a high heat load space
RE: cooling a high heat load space
an interior space contain ice cream machines, rejecting 65000 BTU/hr.
this space is adjacent to under floor crawl space, how come?
is this interior space under floor too or above the crawl space,
crawl space usually is less than 8 feet in height( is it a crawl space or basement).
you want to keep the space with 95F (why),and the crawl space at 80F,
if you exhaust 95F, 4000 cfm to the crawl space then how the crawl space will reject this amount and heat to outside
RE: cooling a high heat load space
RE: cooling a high heat load space
To follow up on other design comments: I ran a quick simulation of the crawl space in order to determine a design temperature. A typical CDD isn't applicable here since the space is partially sealed from the outside and it is on=grade. The simulation showed a peak annual temperature of around 77F. I used 80F to be conservative. 95F was recommended by the owner. I'm working on contacting the ice cream machine manufacturer to check temperature ranges.
RE: cooling a high heat load space
RE: cooling a high heat load space
RE: cooling a high heat load space
I'm leaning towards using a hybrid system with a small ductless split and an exhaust fan system. This will allow for a significantly reduced fan size and allow for a reduced cost since a smaller system will be used.
Thank everyone for all of your help.
RE: cooling a high heat load space
RE: cooling a high heat load space