Daikin Zoning Kit

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March 31, 2024

How do you serve several small zones with one Variable Refrigerant Volume (VRV) split system without adding additional indoor fan coils, and still provide individual temperature control? Currently to achieve individual temperature control you might need separate fan coils for each room with the ability to control air flow. This is where the Daikin Zoning kit can help.

Would if the building has a bunch of small spaces too small for the smallest VRV indoor fan coil unit? Then the use of air volume dampers to divide up the capacity into smaller zones works best in these scenarios. With the use of the Daikin Zoning kit, the ability to serve small areas is better achieved. This is because zone dampers divide up the air from a single indoor fan coil to serve each space. Daikin’s Zoning Kit eliminates the need for multiple indoor fan coil units to create individual zones. This should save money.

This allows smaller spaces to be served and individually controlled. The smallest available indoor fan coil is currently 7,500 Btu/h. If your space required less than 7,500 Btu/h, then you would have a couple of options.

The smallest Fan Coil for this model of Indoor Unit is 7,500 Btu/h. Too large for these small spaces.

One would be to install an oversized indoor fan coil unit for the space or share the air with a fan coil that serves multiple rooms, leaving the room with a lack of individual control. There is the option to have up to 6 separate zone dampers supplying variable air flow to each zone based on the demand.

Table of Contents

Daikin Zone Damper Box Construction

The zone kit is basically a sheet metal plenum with zone dampers attached at one end, while the other is attached to the indoor fan coil. The individual zone dampers respond to the demand from the corresponding controller in each space.

Controls and Thermostats

Each individual zone damper has a zone thermostat that controls the air flow to the room. The thermostat allows for on/off function, schedule control, temperature set point, touchscreen interface and sleep function. The zone thermostats use 915 MHZ wireless communication and 2 AAA batteries.

All thermostats can be hardwired or just one. They could all be wireless except one needs to be hardwired.

There is also a Main Thermostat with a wired color touch display that is used to configure the zone damper kit and can be used as a room controller. An add on BACnet gateway module allows the control of individual rooms using BACnet/IP compatible building management system. The main thermostat uses AWG 20 – 4 wire (shielded) communication cable supplied with 12 VDC from the main control box. This main controller can control all the zones, eliminating controllers in each zone, while still allowing each zone to have individual set point capabilities.

Hardwired Thermostats

There must be at least one hard wired controller to the control box mounted on the Daikin Zone Kit. The other controllers will communicate wirelessly to the control box which can be up to 164 feet line of site distance from the wireless controllers. There is the option to also hardwire all zone controllers if preferred or if wireless communication is troublesome. In this case, the total wiring allowable for each terminal is 130 feet.

Electrical Power

The DZK control box will need 120/240 VAC power. The control box has an alarm input that allows for an alarm to be used to shut down the fan coil and close all zone dampers. Each of the zone dampers are powered by 12 VDC from the control box.

An interface board provides communication between the zoning control board and the indoor fan coil via the NAV controller.

Lastly, there is the ability for their intelligent Touch Manager (iTM) using the BACnet Client option to provide individual room control.

You can use the DZK with a VRV Heat Pump or Heat Recovery system. See our video on the differences between a VRF Heat Pump and VRF Heat Recovery system.

Compatible Indoor Units and their BTUH, CFM and Static Pressure Chart

Compatible Indoor Fan Coils and Capacities

The Daikin zoning kit can be attached to a compatible ducted indoor fan coil unit that ranges in capacity from approximately 15,000 Btuh to 54,000 Btuh and contains anywhere from 2 to 6 zones. So, depending on the capacity of your indoor fan coil, Daikin provides up to 6 zones with their zoning kit. With the largest indoor unit of 54,000 Btuh this allows the option between 2 to 6 zones, depending on the size of each zone.

There are 4 different zone damper configurations to choose from, and 7 compatible indoor fan coils. The zone damper kits come in 4, 5 and 6 damper configurations. This allows anywhere from 2 to 6 zones to be configured. This allows more than one damper to feed larger zones by combining dampers or allows one damper to serve multiple air distribution outlets.

Air Balancing

The air entering the fan coil is offset from the center of the zone box. This causes some of the zone dampers to receive less air than others. This is particularly relevant with the smaller DZK030E4 & E5 models. This causes a non-uniform air velocity, and the center dampers receive more air, while the outside dampers receive less. If all zone dampers are not required, then they can be blanked off. There must be a minimum of two zone dampers used.

Excessive amounts of refrigerant piping can be reduced by using a Daikin Zoning Kit. Image of a six zone VRF system — Excessive amounts of refrigerant piping can be reduced by using a Daikin Zoning Kit

Key Benefits of using the Daikin Zoning Kit

Avoid adding indoor fan coils to achieve individual zone control.
The ability to serve an area that is smaller than the smallest VRV indoor unit.
Increased comfort with individual control.
Increase in the VRV systems ability to meet the demand of smaller spaces.
A reduction in the amount of refrigerant required.

How a Buffer Tank Works

By

MEP Academy Instructor

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March 20, 2024

0

A buffer tank acts as a thermal energy battery for heating hot water or chilled water systems that lack enough water volume during low load conditions to avoid short cycling. They can be used with geothermal heat pumps, chilled water systems, low-mass boilers, and low mass radiation systems. We’ll show you how they work and a couple examples of how to size them for a heating hot water and chilled water system. See Calculations below.

If you prefer to watch the video of this presentation, then scroll to the bottom.

A buffer tank serves several important functions.

Preventing Short Cycling

Buffer tanks prevent short cycling of boilers, heat sources and chilled water systems. Short cycling occurs when the heating or cooling system turns on and off rapidly due to small fluctuations in demand. This can be inefficient and cause wear and tear on the heating and cooling equipment and is one of the top causes of failure in a heating system.

The buffer tank provides a reservoir of heated water, allowing the system to operate more steadily. A buffer tank can help prevent a compressor from short cycling during low load in a Geo-thermal or chilled water system.

Here is what happens during low load conditions. The boiler or compressor turns on and quickly satisfies demand, shutting off just as quickly because of low load condition. This short cycling of on and off continues under low load conditions creating additional wear on the boiler or compressor. So, by adding additional load and water volume with a buffer tank, this short cycling period is reduced or eliminated during low load periods.

A buffer tank is basically an insulated storage tank that adds additional mass to absorb or reject heat during low load conditions to prevent short cycling of the equipment, and to prevent accelerated equipment wear.

Table of Contents

Sizing Buffer Tanks

Here are two different formulas, one for a geothermal heat pump system, and another for a chilled water system.

chilled water buffer tank diagram — Chilled water buffer tank diagram

Chilled Water Buffer Tank Sizing

The following formula is offered by one manufacturer, and any calculations you make should be confirmed by a Mechanical Engineer or the manufacturer.

chilled water chiller buffer tank calculation formula. How to size a chilled water buffer tank — Chilled Water Buffer Tank Calculation Formula

Volume of Buffer Tank = (C x V_R) – V_A

C = Total Chiller Capacity in Tons

V_A = Actual Chilled Water Volume in Gallons

V_R = Recommended System Volume per Ton as Recommended by Chiller Manufacturer

We’ll need to make up some values for this example. Let’s say we have a small chiller of 100 Tons, and the manufacturer requires 6 gallons per ton minimum volume. If we use this information, we can derive a value at which anything below that value would require a buffer tank.

100 tons x 6 Gals. /Ton = 600 Gallons minimum system volume.

If the actual system volume is less than 600 gallons, then a buffer tank becomes required. Let’s say our system volume is 480 gallons.

Chilled Water Buffer Tank Calculation

Chiller Buffer Tank Volume = (100 Tons x 6 Gals. / Ton) – 480 Gallons = 120 Gallons

From the calculation, we can see that for every gallon the existing system total is under 600 gallons, another gallon is added to the tank capacity to provide the minimum required of 600 gallons of system volume.

Water Source Heat Pump Buffer Tank Sizing

The following formula is offered by one manufacturer, and any calculations you make should be confirmed by a Mechanical Engineer or the manufacturer. The calculation is meant to allow for the Boiler or Source of Heat to run for a minimum amount of time before cycling off.

Buffer Tank Calculation Formula

Heating Hot Water Buffer Tank Sizing Calculation Formula

V = M x (Q_H – Q_M) / T x 500

V = Buffer Tank Volume (Gallons)
M = Desired Heat Source Minimum Run Time or “On Cycle” Time (Min.)
Q_H = Heat Source Output Minimum (BTU/Hr.)
Q_M = Heat Output for Minimum System Load (BTU/Hr.)
T = Tank Temperature Rise, Delta between supply and return. (Deg. F)
500 = 8.33 Lbs./Gallon (weight of water) x 60 Minutes/Hr.

For our example let’s assume that we have a heat pump that outputs a minimum of 60,000 BTU/Hr., and that the manufacturer recommends a minimum cycle time of 10 minutes, and that the smallest zone is 9,000 BTU/Hr., and the radiant heating zones allowable temperature differential is from 90 to 100 (F). If zones 1 through 3 were off, and only zone 4 was running at 9,000 BTU/Hr. our calculation would look like this.

Hot Water Buffer Tank Calculation

V = 10 minutes x (60,000 – 9,000) / (100 – 90) x 500 = 102 Gallons

For more information see our article on our website which goes into greater detail about the benefits of using buffer tanks.

Other Benefits of a Buffer Tank

Temperature Regulation

The tank helps maintain consistent water temperature in the system by absorbing excess heat or releasing stored heat as needed.

Increasing System Efficiency

By reducing the frequency of the boiler or compressor cycling, buffer tanks can improve overall system efficiency. They allow boilers and chillers to operate at their most efficient levels for longer periods, reducing energy consumption.

Accommodating Variable Demand

In systems with fluctuating demand for hot water, such as those serving large buildings or facilities, buffer tanks provide a buffer of stored hot water that can be drawn upon during peak demand periods. This helps ensure a consistent supply of hot water without putting excessive strain on the heating equipment.

Protection Against Stratification

Buffer tanks help prevent stratification of water temperature within the heating system. This occurs when hot water rises to the top of the system while cooler water sinks to the bottom, resulting in uneven temperatures and reduced system efficiency. The tank allows for mixing of water to maintain more uniform temperatures throughout the system.

Overall, buffer tanks play a crucial role in optimizing the performance, efficiency, and reliability of heating hot water systems in various applications, including commercial buildings, hospitals, and other facilities.

How Buffer Tanks work and to Size a Chilled Water and Heating Hot Water Buffer Tank

Heat Transfer thru Walls and Windows

By

MEP Academy Instructor

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March 8, 2024

0

How does the “R” value of a material affect the cooling or heating load of a building? What is the basic equation for the conduction of heat through building construction such as walls and windows? What happens to the total heat when the temperature difference between the outdoors and indoors increases, or the “R” value is doubled?

If you prefer to watch the Video of this presentation, then scroll to the bottom.

We’re often asked to add air conditioning to a space that has never had air conditioning before. One of the factors that needs to be considered is the components of the building shell that will contain the conditioned air. This would be the walls, windows, roof and floors over unconditioned spaces,.

Here is the equation for the transmission of heat through building components by conductance. This doesn’t consider other heat gain or loss methods, such as infiltration, ventilation, lights, people, plug, or solar loads. This also just looks at single components and not the full wall assembly including interior and exterior air films.

Q = A x U x Delta-T

Where:

Q = Total Btu/Hr.

A = Area (Ft2) of wall or window

U = Building assemblies overall heat transfer coefficient (Btu/hr.ft2.°F)

Delta-T = Difference in outside and inside design temperatures. (°F)

Heat Transfer Examples

Here are a couple of examples of how different construction materials stand up against preventing heat transfer by conductance. This could either be heat coming into the building, or heat going out of the building.

We’ll start with a wall that has 1,000 square feet, and a design indoor temperature of 75 F and an outside design temperature of 90 F. This equates to a 15-degree F delta-T.

So far, we have the area of the wall and the delta T, the missing factor is the “U” value which is determined by adding up all the resistance of the components of the wall and taking the inverse value.

Typical Construction Materials and their "R" values (Resistance), and "U" Coefficients — Typical Construction Materials and their “R” values (Resistance), and “U” Coefficients

Here are four different building construction components and their “R” values.

1/8” Clear Glass R=0.76

1/2” Plywood (Douglas Fir) R=0.79

8” Light Weight Concrete Block “R” value = 2.33

3-1/2 R-11 Insulation “R” value =11

We performed the heat transfer equation on each of these building components. Starting with the 1/8” clear glass and an “U” value of 1.32, we get the following.

1,000 Ft2 of Glass x 1.32 “U” Factor x 15 F Delta-T = 19,800 Btu/Hr, or 1.65 Tons of cooling required for the heat gain through conductance. Obviously there glass windows with much better “U” values, but our purpose is to show you how the “R” value and inversely the “U” value effects heat transfer.

"R" Values and the Inverse "U" coefficient. — “R” Values and the Inverse “U” coefficient.

As, you can see if we built the wall with just plywood, we would do a little better with a heat gain of 18,975 Btu/Hr, or 1.58 tons. Using 8” Light Weight Concrete blocks helps considerably by reducing our total heat load in thirds. The greatest effect comes when we add R-11 Insulation to the wall, which in this case looks like this.

1,000 Ft2 of R-11 Insulated wall x 0.09 “U” Factor x 15 F Delta-T = 1,350 Btu/Hr, or 0.11 Tons of cooling. This is a huge reduction in the amount of heat that can transfer from outdoors to indoors. This shows the importance of properly insulating the shell of a building.

This chart shows that the greater the “R” value or resistance of the construction component, the smaller the “U” value will be. The smaller the “U” value, the smaller the heat transfer rate. This is why energy codes mandate a certain “R” value for insulation in walls and roofs.

If the outdoor temperature increased to 105 F, this would double the Delta-T in our equation, which would double the heat gain through our building components. This is one of the reasons why the temperature outdoors makes a difference in the energy consumption of the building for comfort cooling or heating.

A doubling of the Delta-T, causes a doubling of the Heat Load

Most energy codes have standard requirements for the total allowable transmission factor that can be used to construct a wall or roof for a space that is air conditioned. It wouldn’t make sense to allow the heating or cooling of a space built with paper walls, as heat would easily enter or escape the space, requiring enormous amounts of energy to condition.

A high quality wall, floor, window or roof assembly is essential to prevent heat gain or loss in buildings, ensuring energy efficiency and maintaining a comfortable indoor environment by effectively insulating against external temperature fluctuations.

1/8” Clear Glass R=0.76

Solve for U Value. U = 1/R

U = 1/0.76 = 1.32
Q = A x U x Delta-T
Q = 1,000 ft2 x 1.32 x 25 Delta-T
Q = 33,000 Btu/hr.

1/2” Plywood (Douglas Fir) R=0.79

Solve for U Value. U = 1/R

U = 1/0.79 = 1.265
Q = A x U x Delta-T
Q = 1,000 ft2 x 1.265 x 25 Delta-T
Q = 31,625 Btu/hr.

8” Light Weight Concrete Block R=2.33

Solve for U Value. U = 1/R

U = 1/2.33 = 0.429
Q = A x U x Delta-T
Q = 1,000 ft2 x 0.429 x 25 Delta-T
Q = 10,725 Btu/hr.

3-1/2 R-11 Insulation R=11

Solve for U Value. U = 1/R

U = 1/11 = 0.09
Q = A x U x Delta-T
Q = 1,000 ft2 x 0.09 x 25 Delta-T
Q = 2,250 Btu/hr.

How conductance heat gain works through walls and windows

Closed and Open Loop Controls

By

MEP Academy Instructor

-

February 28, 2024

0

heating hot water temperature reset schedule diagram

In this article we’ll give you an example of a closed and open loop DDC control system. The use of open and closed loops is found throughout sequences of operation for most building DDC control strategies.

If you prefer to watch the Video of this presentation, then scroll to the bottom.

Table of Contents

Closed Loop Control of AHU Discharge Air Temperature

In HVAC systems, a closed-loop control system using a discharge air temperature sensor and a control valve controlling the flow of hot or chilled water is employed to maintain a consistent supply air temperature from a coil. Here’s how it generally works:

A discharge air temperature sensor is placed in the air stream after the heating or cooling coil. Its purpose is to measure the temperature of the air leaving the coil, which is known as the discharge air temperature.

Supply Discharge Air Temperature Sensor in a DDC Closed Loop

The discharge air temperature is sent to a controller in the form of an analog input. The controller compares the actual discharge air temperature to the desired set point temperature.

The controller sends an output signal to the coil control valve, which is responsible for regulating the flow of heating hot water or chilled water through the coil. The control valve is positioned by the controller based on the comparison between the actual and desired discharge air temperatures.

If the actual discharge air temperature is higher than the setpoint, it indicates that more cooling is needed. The controller signals the control valve to open, allowing more chilled water to flow through the coil.

If the actual discharge air temperature is lower than the setpoint, it suggests that the space is adequately cooled. The controller instructs the chilled water control valve to close or reduce the flow, reducing the cooling effect. The heating hot water response in a similar manner.

This entire process forms a closed-loop system. The controller continuously receives feedback from the discharge air temperature sensor and adjusts the coil control valve to maintain the desired discharge air temperature.

Benefits

Energy Efficiency: By precisely controlling the coil operation, the system optimizes energy consumption.

Comfort: Consistent discharge air temperature ensures a comfortable environment for occupants.

In summary, a closed-loop system using a discharge air temperature sensor and a coil control valve allows for real-time adjustments to maintain a stable and desired supply air temperature from the cooling coil or heating coil in an HVAC system.

Open Loop System for Heating Hot Water Temperature Reset

In an open-loop control system using an outside air temperature sensor and a 3-way heating hot water control valve, the goal is to reset the hot water setpoint of a boiler based on the outside air temperature. Here’s a breakdown of how this system typically operates:

Boiler Controller - Heating Hot Water Temperature Reset Schedule — Boiler Controller – Heating Hot Water Temperature Reset Schedule

An outside air temperature sensor is located outdoors to measures the ambient temperature. The information gathered by the outside air temperature sensor is crucial for determining the heating requirements based on the actual outdoor temperature conditions.

The outside air temperature from this sensor is sent as an analog input to the boiler’s controller. The controller analyzes the outside air temperature and compares this to the Heating Hot Water Temperature Reset Schedule programmed into the controller before deciding on whether to adjust the set point temperature.

The controller lowers the hot water supply temperatures set point as the outside air temperature increases. When the outside air temperature gets colder, the boiler controller increases the heating hot water supply temperature set point.

Closed Loop using a Temp Sensor

Using a closed loop control sequence, the hot water temperature sensor sends an analog input signal to the boiler’s controller indicating the current temperature of the heating hot water. The boilers controller will compare the reset schedule with the current hot water temperature and send an analog output signal to adjust the 3-way valve to either increase or decrease the flow based on the current water temperature.

The 3-way control valve is responsible for controlling the flow of hot water in the heating system based on the analog output signal from the controller. It has three ports and can direct the flow in different ways based on the control signals it receives.

As the outside air temperature changes, the controller adjusts the set point temperature of the boiler and if required will send a signal to the 3-way hot water control valve to meet the current demand. This adjustment is based on the heating hot water reset schedule.

When the outside temperature is lower, indicating colder weather, the controller will adjust the boiler supply water temperature upwards. This is based on the HHW reset schedule. An analog output to the 3-way valve will more hot water to flow into the system. This will increase the temperature of the heating medium.

Conversely, in milder weather, the controller may adjust the 3-way valve to allow less hot water into the system. Thereby reducing the temperature of the heating medium.

Benefits

Energy Efficiency: By resetting the hot water setpoint based on outside conditions, the system optimizes energy usage by providing only the necessary amount of heat.

Weather Adaptation: The system can automatically respond to changes in external temperature, ensuring efficient heating in various weather conditions.

In summary, an open-loop system using an outside air temperature sensor and a 3-way hot water control valve allows for real-time adjustments of the hot water setpoint of a boiler based on external temperature conditions. This approach helps optimize energy consumption and provides effective heating in response to changing weather patterns.

DDC Control Loops Explained

Daikin Zone Damper Box Construction

Controls and Thermostats

Hardwired Thermostats

Electrical Power

Compatible Indoor Fan Coils and Capacities

Air Balancing

Key Benefits of using the Daikin Zoning Kit

Sizing Buffer Tanks

Chilled Water Buffer Tank Sizing

Chilled Water Buffer Tank Calculation

Water Source Heat Pump Buffer Tank Sizing

Buffer Tank Calculation Formula

Hot Water Buffer Tank Calculation

Other Benefits of a Buffer Tank

Temperature Regulation

Increasing System Efficiency

Accommodating Variable Demand

Protection Against Stratification

Heat Transfer Examples

Closed Loop Control of AHU Discharge Air Temperature

Benefits

Open Loop System for Heating Hot Water Temperature Reset

Closed Loop using a Temp Sensor

Benefits

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