Kitchen cooling loads- induction hobs, oven etc
I would like to check some figures I have been given for cooling loads.
I can see the loads from external sources but was wonder if 2kW of additional cooling is necessary for the electric oven, induction hob and toaster. Obviously they all produce heat but they are not on all the time, possibly as little as 15mins/ day except when we do a roast..
Around half of the total load is for appliances- does that seem reasonable? Does anyone have typical sensible and latent figures for these units?
In a load calc I believe it adds 500 btu/hr for each appliance. It shouldn't be half the load unless its a commercial kitchen, that's a whole other ball game. Large kitchen hoods need make up air. 2kw would be ~7k btus/hr. equipment btu=total equipment watts x 3.4
thank you, that is 500 byt/hr sensible. 150W per appliance gives a much lower number.. Curiously that is what I was estimating for a PC with monitor.
In residential settings, you factor them in somewhat, but there are 2 things to consider. Useage is usually short in duration (a couple hours) so the internal mass of a home can absorb much of it, Most people don't cook a huge meal at design conditions, an electric range might have 10kw in total heating elements, but the actual continous heat loss is much lower since it's insulated. Also, unless you have a room by room zoned system, the kithcen temeprature will increase, therefore the heat gain from the outside will be reduced at the same time.
Manual J doesn't consider thermal mass, but a range running in a 1200sqft house with carpeting will have a much larger impact than in a 3500sqft house with lots of tile and hardwood.
Finally, manual J alreayd has some margins for error built in that handle other scenrios. Do you really want ot oversize a AC unit by as much as 50%, to accomidate a infrequent load?
Now, if you cook daily for several hours, now you have a unique load, and probably need supplemental zoned cooling. If you cook all day long 4-7 days a week... its' now a commercial kitchen for all intents and purposes and should be designed accordingly including fresh air ventilation depending on what equipment. You also would need to contact your insurance company and consider adding the aprpopriate fire protection equipment if needed.
As mentioned, for larger range hoods. Those should have mechanical make-up aire units interlocked with them. They can make homes so negative that they can backdraft water heaters as well as creating big IAQ problems.