How To Add Makeup Air System To An Existing Commercial Kitchen Hood?

x.three Commercial Kitchens

10.3.1  Overview

There are 4 energy saving measures associated with commercial kitchen ventilation.

These four prescriptive measures address:

• Direct Replacement of Exhaust Air Limitations

• Type I Frazzle Hood Airflow Limitations

• Makeup and Transfer Air Requirements

• Commercial Kitchen Organisation Efficiency Options

10.3.2  Mandatory Measures

In that location are no mandatory measures specific to commercial kitchens. Installed appliances and equipment must meet the mandatory requirements of §110.one and §110.2 respectively.

10.iii.3  Prescriptive Measures

10.3.3.1   Kitchen Exhaust Systems

This section addresses kitchen exhaust systems.  There are two requirements for kitchen exhaust:

• A limitation on use of short-circuit hoods §140.9(b)1A

• Maximum exhaust ratings for Type I kitchen hoods §140.ix(b)1B

A.   Limitation of Short-Excursion Hoods

Brusk-circuit hoods are limited to ≤ten% replacement air as a percentage of hood exhaust airflow charge per unit. The reasons for this include the following:

Studies by Pacific Gas & Electrical (PG&E), American Gas Association (AGA) and the Energy Commission have shown that in short-circuit hoods, direct supply greater than 10% of hood frazzle significantly reduces capture and containment. This reduces the extraction of cooking heat and smoke from the kitchen, forcing facilities to increment the hood exhaust rate. This results in higher consumption of energy and conditioned makeup air.

Figure 10-2: Curt-Circuit Hood

B.   Maximum Frazzle Ratings for Blazon I Kitchen Hoods

The Energy Standards too limit the amount of exhaust for Blazon I kitchen hoods based on Table 140.9-A. (Table 10-1 below), when the total exhaust airflow for Type I and 2 hoods are greater than five,000 cfm.  Similar to the description regarding brusk-circuit hoods, excessive exhaust rates for Type I kitchen hoods increases free energy consumption and increases energy use for conditioning of the makeup air.

In that location are two exceptions for this requirement:

• Exception 1 to §140.9(b)1B: where ≥75% of the full Type I and II exhaust makeup air is transfer air that would otherwise have been exhausted. This exception could exist used when you have a big dining area adjacent to the kitchen, which would be exhausting air for ventilation purposes even if the hoods were non running. The exception is satisfied if: the air that would otherwise take been exhausted from the dining area (to meet ventilation requirements); is greater than 75 percent of the hood frazzle charge per unit; and is transferred to the kitchen for use equally hood makeup air.

• Exception ii to §140.9(b)1B: for existing hoods that are not being replaced as function of an improver or alteration.

The values in Table 140.nine-A are based on the blazon of hood (left cavalcade) and the rating of the equipment that information technology serves (columns 2 through 5). The values in this tabular array are typically less than the minimum airflow rates for unlisted hoods. These values are supported by ASHRAE research for use with listed hoods (RP-12002). To comply with this requirement, the facility will likely have to employ listed hoods. The threshold of five,000 cfm of total exhaust was included in the Energy Standards to exempt small-scale restaurants.

The definitions for the types of hoods and the duty of cooking equipment are provided in ASHRAE Standard 154-2011.

Table 10-1: Maximum Internet Exhaust Flow Charge per unit, cfm per Linear Foot of Hood Length

Type of Hood	Calorie-free Duty Equipment	Medium Duty Equipment	Heavy Duty Equipment	Actress Heavy Duty Equipment
Wall-mounted Canopy	140	210	280	385
Single Isle	280	350	420	490
Double Isle	175	210	280	385
Eyebrow	175	175	Not Allowed	Non Immune
Backshelf/Pass-over	210	210	280	Not Immune

Energy Standards Table 140.9-A

10.3.3.2   Kitchen Ventilation

This department covers two requirements:

• Limitations to the corporeality of mechanically heated or cooled airflow for kitchen hood makeup air §140.ix(b)2A.

• Additional Efficiency Measures for Large Kitchens §140.nine(b)2B.

For these requirements information technology is important to empathize the definition of mechanical cooling and mechanical heating, which the Free energy Standards ascertain as:

• Mechanical cooling is lowering the temperature within a infinite using refrigerant compressors or absorbers, desiccant dehumidifiers, or other systems that require energy from depletable sources to directly condition the space. In nonresidential, high-ascent residential, and hotel/motel buildings, cooling of a space past direct or indirect evaporation of water solitary is not considered mechanical cooling.

• Mechanical heating is raising the temperature within a space using electric resistance heaters, fossil fuel burners, heat pumps, or other systems that require energy from depletable sources to directly condition the space.

It is important to note that straight and indirect evaporation of h2o alone is not considered mechanical cooling. Therefore, air cooled past the evaporation of h2o tin can be used every bit kitchen hood makeup air with no restrictions.

A.   Limitations to the Corporeality of Mechanically Heated or Cooled Airflow for Kitchens

This section limits the corporeality of mechanically cooled or heated airflow to any space with a kitchen hood.  The corporeality of mechanically cooled or heated airflow must not exceed either:

• The supply flow required to meet the space heating or cooling load.

• The hood frazzle minus the available transfer air from next spaces.

The supply menstruum required to meet the space heating or cooling loads can be directly documented past providing the load calculations.

To summate the available transfer air:

ane.  Calculate the minimum outside air (OA) needed for the spaces that are side by side to the kitchen.

ii.  From the corporeality calculated in i, decrease the amount of air used by frazzle fans in the side by side spaces. These include toilet exhaust and any hood exhaust in adjacent spaces.

iii.  From the amount calculated in two, decrease the corporeality of air needed for space pressurization. The remaining air is available for transfer to the hoods.

An exception is provided for existing kitchen makeup air units (MAU) that are non existence replaced as part of an addition or alternation.

While the requirement to utilize available transfer air only refers to "adjacent spaces", bachelor transfer air can come up from any space in the same edifice equally the kitchen.  A kitchen on the ground floor of a large office building, for example, can describe transfer air from the return plenum and the return shaft. The entire minimum OA needed for the building, minus the other exhaust and pressurization needs, is available transfer air. If the render air path connecting the kitchen to the residue of the edifice is constricted, resulting in high transfer air velocities, so it may be necessary to install a transfer fan to assist the transfer air in making its way to the kitchen. The free energy apply of a transfer fan is small compared to the extra mechanical heating and cooling free energy of an equivalent amount of OA.

Example 10-1

Question

What is the available transfer air for the kitchen make up in the scenario shown in the following effigy?

Answer

5,000 cfm calculated every bit follows.

The OA supplied to the dining room is 5,500 cfm.  From this we subtract 500 cfm for the toilet exhaust and 0 cfm for building pressurization.

v,500 cfm – 500 cfm – 0 cfm = v,000 cfm

The remaining 5,000 cfm of air is available transfer air.

Example 10-2

Question

Assuming that this kitchen needs ii,000 cfm of supply air to cool the kitchen with a pattern supply air temperature of 55°F, would the post-obit pattern airflow run across the requirements of §140.nine(b)2A?

Answer

Yes. This case meets the first provision of §140.9(b)2A.  The supply menses required to run across the cooling load is 2,000 cfm.  Thus up to two,000 cfm of mechanically conditioned brand up air tin be provided to the kitchen. Annotation that the supply from the MAU, 2,000 cfm, is non as large equally the hood exhaust, v,000 cfm. This ways that the remainder of the MAU, 3,000 cfm, must be transferred from the dining room space.

Although this is allowed under §140.9(b)2Ai, this is not the near efficient manner to status this kitchen every bit demonstrated in the next case.

Case x-3

Question

Continuing with the same layout equally the previous case, would the following blueprint airflow meet the requirements of §140.ix(b)2A?

Answer

Yes. In this example, 100% of the makeup air, 5,000 cfm, is provided past transfer air from the adjacent dining room. Note that the OSA on the unit serving the dining room has been increased to 6,000 cfm to serve the ventilation for both the dining room and kitchen.  Since the dining room has no sources of undesirable contaminants we tin ventilate the kitchen with the transfer air.

Comparing this paradigm to the previous instance you will see that this pattern is  more than efficient for the following reasons.

one.    The total outside airflow to be conditioned has been reduced from 7,500 cfm in the previous example (2,000 cfm at the MUA unit and 5,500 cfm at the dining room unit) to 6,000 cfm; and,

2.    The dining room exhaust fan has dropped from 2,500 cfm to ane,000 cfm reducing both fan energy and first cost of the fan.

Note that an even more than efficient design would exist if the kitchen MAU had a modulating OA damper that allowed it to provide upward to v,000 cfm of outside air straight to the kitchen when OA temperature <kitchen space temperature.  When OA temperature > kitchen space temperature then the OA damper on the MAU is shut and replacement/ventilation air is transferred from the dining area.  This design requires a variable speed dining room frazzle fan controlled to maintain slight positive pressure level in the dining area.  This design is the baseline design modeled in the Alternative Calculation Methods (ACM) Reference Manual for performance compliance.  The baseline model assumes that transfer air is available from the unabridged building, not merely the side by side spaces.

Instance 10-4

Question

Continuing with the aforementioned layout as the previous examples, would the post-obit design airflow meet the requirements of §140.nine(b)2A?

Respond

Not if the kitchen unit is mechanically heated or cooled. Per §140.9(b)2A the maximum corporeality of air that can exist mechanically heated or cooled must be less than either: Per §140.9(b)2Ai: 2,000 cfm, the supply needed to cool the kitchen (from Example 10-2) Per §140.9(b)2Aii: 0 cfm, the amount of hood exhaust (5,000 cfm) minus the bachelor transfer air (too 5,000 cfm from Case 10-2).

B.   Additional Efficiency Measures for Big Kitchens

For kitchens or dining facilities that have more than 5,000 cfm of Type I or II hood exhaust, the mechanical system must encounter one of the following requirements:

one.    At least fifty% of all replacement air is transfer air that would have been exhausted.

2.    Demand ventilation control on at least 75% of the frazzle air.

3. ' Listed energy recovery devices with a sensible heat recovery effectiveness ≥twoscore% on ≥50% of the total exhaust flow.

4.    ≥75% of the makeup air volume that is:

a.    Unheated or heated to no more than 60°F.

b.    Uncooled or cooled without the use of mechanical cooling.

Transfer Air: There is an exception for existing hoods not beingness replaced as part of an addition or alteration.

The concept of transfer air was addressed in the word of §140.nine(b)2A above.

Demand Ventilation Command: Per §140.nine(b)2Bii demand ventilation controls must have all of the following characteristics:

• Include controls necessary to modulate airflow in response to appliance operation and to maintain full capture and containment of smoke, effluent and combustion products during cooking and idle.

• Include failsafe controls that result in total flow upon cooking sensor failure.

• Include an adaptable timed override to permit occupants the ability to temporarily override the arrangement to full menstruation.

• Be capable of reducing frazzle and replacement air organization airflow rates to the larger of:

o fifty% of the total design exhaust and replacement air system airflow rates; or

o The ventilation rate required per §120.one.

There are several off the shelf technologies that use fume detectors that can comply with all of these requirements.

Effigy x-iii: Need Control Ventilation Using a Axle Smoke Detector

Free energy Recovery: Energy recovery is provided using air to air heat exchangers between the unit providing makeup air and the hood exhaust.  This option is most effective for farthermost climates (either hot or cold).  Information technology is not commonly used in the mild climates of California.

Tempered Air with Evaporative Cooling: The final selection is to  control the heating (if there is heating) to a space by setting the temperature setpoint to 60°F and to use evaporative (non-compressor) cooling or no cooling at all for almost of the makeup air.

10.3.iii.iii   Kitchen Exhaust Credence

Credence tests for these measures are detailed in NA7.11.  Meet Chapter 13 this manual.

10.3.4  Additions and Alterations

The application of these measures to additions and alterations was presented in the text from the previous section.

Source: https://energycodeace.com/site/custom/public/reference-ace-2016/Documents/103commercialkitchens.htm

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