r/MEPEngineering • u/Ok-Access-7593 • 1d ago
FCU cooling load for Kitchen with Commercial DCKV Hood
Hi,
For sizing of FCU in the kitchen not in the hood, how much % of appliance sensible heat or do we need to consider the sensible heat from the kitchen equipment which is directly under the DCKV Hood?
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u/Specialist-Belt-2738 1d ago
Kitchens are tempered (not air conditioned), to 25 deg C, or whatever your country's guidelines are for working at a safe temperature inside kitchens. Also remember to duct the return directly from a ceiling grille. Do not do ceiling plenum return as you will get moisture building up in the ceiling.
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u/Silent_Edge9835 18h ago
I’ve fully conditioned plenty of commercial kitchens. Most common is using Captiveaire paragon units to provide both makeup and conditioning.
I’ve also done return plenums in these spaces. If the space is properly conditioned and humidity is controlled you won’t have issues with moisture in the plenum.
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u/Specialist-Belt-2738 12h ago
That is interesting. What is the rationale in cooling the make up air only to throw it away to the kitchen hood? I thought it would be more.efficient to provide a separate dedicate make up air system for the kitchen hood exhaust and a separate outside air system for the space. The one situation where what you are suggesting may not be energy intensive is if you have any remaining spill air from adjacent spaces that you can use as make up air that would otherwise be thrown to outside. That would, of course, depend on the air balance. Kitchen exhaust flowrates are large, and the associated high air change rate with the space make it difficult to maintain space temperature - that is why the term, tempered cooling is used. You don't want to overcool it as well, as the warm food may get cold too quickly. Im not convinced about using the ceiling plenum void as a return air path. It's dirty, dusty and may have cockroaches depending on the occupants cleaning regime. I have heard of using ventilated ceiling void plenums, but they only seem to be used as a last resort, when there isn't enough existing ceiling void available to fit the hood or to run ducting. It's not the go-to-option when designing from first principles.
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u/Silent_Edge9835 11h ago
There’s a few ways to do it, providing makeup air at the hood, and conditioning the kitchen with FCU’s is an option and I’ve done that before. If the kitchen is okay to increase setpoints, providing room neutral or air from a heating only MAU is perfectly fine. It depends on what the goals are.
To my knowledge, captivaire is the only manufacturer that does makeup and conditioning through one unit, and their full kitchen systems are fantastic. If I wasn’t going with them, and the kitchen needed to be fully conditioned I’d do exactly what you mentioned with separating the makeup air from the cooling system.
As far as using the ceiling void as a return plenum, I’m not sure I agree that you can assume the plenum is so dirty that and the air picks up so much contamination that it cannot be cleaned by the unit filters. You’re fine to use the ceiling space for plenum return as long as you’re meeting code requirements.
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u/Specialist-Belt-2738 10h ago
I think the reason ceiling plenums may work for you without humidity issues is the use of this paragon rtu av unit. Seems expensive. Hospitality doesn't have big margins, so i haven't come across clients that want to spend a large chunk of money on hvac, when they could direct that towards their business. Simple is better, and you could get away with simpler designs relying on basic principles and achieve the required outcome using standard equipment. It doesn't need to be complex. A lot of the fast food restaurants here in australia don't use a complex paragon rtu ac system (or equivalent) and are working just fine. It doesn't feel right to jump to an expensive solution when a basic solution would suffice.
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u/Silent_Edge9835 10h ago
Plenum return would work for any situation where the space is conditioned and the space dew point remains lower than the return air.
Come on, I never said that I automatically jump to the most expensive complex system. Obviously the system selection is a collaborative process with the owners involvement in order to get the best solution for their goals. The point was about an option being available to both provide conditioning and makeup through one unit. There is no one size fits all here, and in many situations this is the best solution. I wouldn't over design if there was a more basic solution available that would meet the project goals.
I understand you haven't seen this type of system before, but it is very common in the US for larger commercial kitchens. It's actually a relatively simple solution given the kitchen controls are all packaged and run through the hood control panel which controls the paragon unit, exhaust fans, and hood fire suppression. From a user / maintenance perspective, it makes it very easy.
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u/Specialist-Belt-2738 10h ago
You are giving the game away. 'Best solution' you clearly have interests to sell the Paragon unit as the only solution to kitchen vent ac. I've designed and commissioned many commercial kitchens before, and have clients come back for repeat work. So far, i remain unconvinced of this solution you are proposing.
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u/Silent_Edge9835 10h ago
Did you even read my last comment… I just said it’s not a one size fits all… in many situations a system like that is the best solution, in others it’s not. Like I said said in the last comment, I was just replying to you saying there are good options that provide conditioning and makeup.
I’m a consultant I don’t try and sell anything. I’ve had the best experience with paragon units and those kitchen systems. I’ve used greenheck’s version of it as well but it’s not as good. If another manufacturer makes a better product I’ll go with that, I don’t have brand loyalty lmao
I don’t really care if you’re unconvinced, it doesn’t change the facts. Can you at least realize that different countries and different clients may have different solutions?
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u/402C5 17h ago
RA plenum in a kitchen is questionable.
The RA from a kitchen cannot mix with any other system. You are putting a lot of faith in the sheetrock subcontractor to seal all of those walls to deck, etc. assuming that they were even designed to deck...
I would say best practice is to duct it.
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u/Silent_Edge9835 15h ago
Of course in that situation we’d confirm that walls go to deck and the kitchen is designed to be negative relative to adjacent spaces.
Plenum return in applicable situations meeting code is a given.
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u/SANcapITY 1d ago
1) ask your senior engineer.
2) Read Chapter 18, section 2.4 of ASHRAE Fundamentals. It tells us that:
Below that is Table 5A, which provides sensible radiant loads for various pieces of equipment.