Zoning Application. Copyright 2011 Trane 2 Zoning Application Agenda Application Overview --Benefits...

Zoning ApplicationZoning Application

Copyright 2011 Trane2


Agenda

Application Overview --Benefits & Challenges with Zoning

HVAC System DesignsConventional Vs Zoning

Excess Air --Defining --Management Strategies



Why Zoning and how can a customer benefit from zoning?

Have you come across a zoning system that did not provide these benefits?

Zoning is the intentional restriction of capacity (air flow) into a specific zone.



Air Conditioning Contractors of America (ACCA) provides standards in designing HVAC system.

There are standards for conventional systems and standards for zoning systems.

Manual J8 is required for the proper application & design of zoning systems.

Which manuals are mandatory?

The lower green line shows the average sensible heat gain. This is used to size the HVAC system

The red line represents the actual hourly heat gain.

The yellow line represents a 30% buffer zone. Room temperature swings may be extreme if hourly load conditions exceed this buffer limit.

Zone Heat Gain Sensible Heat Gain Graph of Manual J8

Software will show “Powered by Manual J”BTU’s

Time

Some applications will have extreme excursions. This is especially true for homes with large glass loads or condominiums (small interior loads with only one external wall).

If zoning is applied, the duct size must be sized upon the red line peak excursion.

Zone Heat Gain BTU’s

Time



The fundamentals remain the same:An accurate heat load calculation & proper duct design is critical.

Zoning should never be applied to oversized systems or undersized ducting.

The HVAC system is sized on _________________________

The duct system is sized on _________________________


Zoning ApplicationThe BasicsZoning ApplicationThe Basics

Always start with a “common sense” approach when applying zoning. There are several tools out there to assist with calculations, but always stay focus on the obvious:

•Rooms that are open to each other should be in the same zone.

•With multiple story homes, each floor should be a zone.

•Unique rooms (detached rooms or rooms with large glass loads) should be individually zoned.


Zoning ApplicationThe BasicsZoning ApplicationThe Basics

•Each zone must have a dedicated return path.

•Each sensor must be in the air path of the zone it controls.

•Never apply more zones than the equipment can handle. What happens with only the smallest zone calling.


Zoning Application Daily Solar Load ShiftsZoning Application Daily Solar Load Shifts

Room grouping from ACCA Manual RSDaily solar shifts

Living Room

Kitchen

Guest Room 1

Master Bed

Add 1

Ad 2 Add 3

Office

Dining

Guest Room 2

EW

S

N


Zoning ApplicationSeasonal Load ShiftsZoning ApplicationSeasonal Load Shifts

Room grouping from ACCA Manual RSSeasonal load shifts and the 15% rule.

Living room

Kitchen

Guest room

Master Bed

Add 1

Ad 2 Add 3

OfficeDining

Guest room

61% C/HRatio

73% C/HRatio

63% C/HRatio

109% C/HRatio


Zoning ApplicationExcess AirZoning ApplicationExcess Air

What happens to a system when air flow is restricted?

How can this reduction in air flow be managed?


Zoning ApplicationExcess Air Management StrategiesZoning ApplicationExcess Air Management Strategies

Bypass

Dump

Variable Speed Air Flow Reduction

Multi Capacity Systems

Relief

Over Blow

Excess air must be managed based on worst case conditions!


Zoning ApplicationDST Thermal LimitsZoning ApplicationDST Thermal Limits


Which is the smallest zone in cooling?

How much excess air must be managed?

Which is the smallest zone in heating?

How much excess air must be managed?


Zoning ApplicationUnderstanding BypassZoning ApplicationUnderstanding Bypass

Manual D informs us how to size the ducting to each zone.

Return AirMixed Air

Supply Air

But how do I size a bypass duct?


Zoning ApplicationCalculating BypassZoning ApplicationCalculating Bypass

Return AirMixed Air

Supply Air

Bypass Air Reading

Return Air Reading

Mixed Air Reading

Turn on the system with the smallest zone calling and the bypass damper wide open.

Obtain two dry bulb temperature readings:

Temp split from return & bypass air.

Temp split from return & mixed air.



Return AirMixed Air

Take a look at what happens with this much bypass.

Taken from the install guide of a popular zoning system.

This is 75% bypass

Temp splits with 36%

bypass on a 4-ton cooling

system.

Temp splits with 64%

bypass on a 4-ton cooling

system.

43% bypass on 80K 4-ton drive furnace

Temp Rise 30⁰ - 60⁰

18% bypass on 80K 4-ton drive furnace



What are the main advantages of Bypass?

What are the main disadvantages of Bypass?


Zoning Application$$$ Savings on Energy Bills?Zoning Application$$$ Savings on Energy Bills?

Will zoning deliver energy savings?

“The benefit of a set-up / set-back schedule depends on

the cycle time. Long periods (days or weeks) of set-up /

setback save energy. Short set-up / set-back periods (less than a day, maybe less than 16 hours) saves less energy, or may increase energy use.”

ACCA Preliminary Manual Zr


Zoning Application$$$ Savings on Energy Bills?Zoning Application$$$ Savings on Energy Bills?

10.6 EER 9.7 EER 8.5 EER

4-ton AC system


Zoning ApplicationVariable Speed Air Flow ReductionZoning ApplicationVariable Speed Air Flow Reduction

A variable speed indoor unit can reduce air flow up to 30% in compressor only operation.

This creates similar results as bypass but with some energy savings.

Air flow reduction is the preferred method over bypass, but is not incorporated with gas furnaces or when resistant heat is in use.

Air flow reduction and bypass may not be utilized at the same time.


1985 CFM at 0.7 static consumes 824 watts.

A 30% air flow reduction will deliver1389 CFM.

1383 CFM = 396 Watts at 0.7 static.

Even if static remains constant as dampers close, blower reduction assists with energy savings.


Zoning ApplicationMulti Capacity SystemsZoning ApplicationMulti Capacity Systems

Can multi capacity systems assist with zoning?


Zoning ApplicationOver blowZoning ApplicationOver blow

Over blow makes the assumption that air will be redirected through the ducting as dampers close.


Zoning ApplicationOver blowZoning ApplicationOver blow

This duct system is moving 600 FPM. How much air flow will this 8 inch duct deliver__________?

Static pressure & velocity rates will increase as dampers close. How much air will this 8 inch duct deliver at 900 FPM?

Can you count on over blow with a high static duct system?


Zoning ApplicationSetting Duct Size -- WeightZoning ApplicationSetting Duct Size -- Weight

What are some advantages of an oversized duct system with zoning?

What are some disadvantages of an oversized duct system?

Should the zone control system know the duct size to each zone? Why?

Auto Zone Weighting or Manual Set up


A main duct is defined as any damper that controls more than one supply terminal.

Zoning ApplicationSetting Duct Size -- WeightZoning ApplicationSetting Duct Size -- Weight


Zoning ApplicationTime to add it all upZoning ApplicationTime to add it all up

Time to calculate a basic two zone single stage system with psc motor. But first, how will I obtain the following information.

•The required air for each zone

•The amount of excess air that must be managed

•The maximum allowable bypass

•The amount of over blow (if any)

•The remaining amount of excess air

12”14”

700 CFM @ 900 feet per minute1000 CFM @ 900 feet per minute

12”

700 CFM @ 900 feet per minute

Cooling Mode

Blower set to deliver 1600 CFM.

The bedroom is the only zone calling and requires 36% of this air flow. The bedroom requires ________ CFM.

Due to the limitations of the furnace, the maximum bypass is 18% which is ________ CFM.

I need to find a home for the remaining ________ CFM.

Factor in over blow. The 12 inch duct can handle 700 CFM at 900 FPM (700 – ______required by bedroom = ______ CFM of over blow).

1600 CFM – 700 into the zone – ______bypass = _______CFM (_____%) of excess air.

How can we manage this excess air?

1600 CFM – 1000 into the zone ______bypass = _______CFM (_____%) of excess air.



The living room zone is the only zone calling and requires 64% of this air flow. The living room requires ________ CFM.



Factor in over blow. The 14 inch duct can handle 1000 CFM at 900 FPM (1000 – ______required by living room = ______ CFM of over blow).

14”


Cooling Mode


The bedroom is the only zone calling and requires 43% of this air flow. The bedroom requires ________ CFM.



Factor in over blow. The 12 inch duct can handle 700 CFM at 900 FPM (700 – ______required by bedroom = ______ CFM of over blow).



12”


Heating Mode


The living room zone is the only zone calling and requires 57% of this air flow. The living room requires ________ CFM.



Factor in over blow. The 14 inch duct can handle 1000 CFM at 900 FPM (1000 – ______required by living room = ______ CFM of over blow).



14”


Heating Mode

12”


Cooling mode bedroom calling.

576 CFM is required based on conventional system design .412 CFM is managed through over blow & bypass.

Cooling mode living room calling.

Bedroom damper stop must be set to manage 312 CFM. 20% relief.

14”


Cooling mode living room calling.

1024 CFM is required based on conventional system design.288 CFM is managed by bypass.

Cooling mode bedroom calling.

Living room damper stop must be set to manage 612 CFM. 38% relief.

12”14”

700 CFM @ 900 feet per minute1000 CFM @ 900 feet per minute

Heating mode bedroom calling.

548 CFM is required based on conventional system design .382 CFM is managed through over blow & bypass.

Heating mode living room calling.

727 CFM is required based on conventional system design.503 CFM is managed by over blow & bypass.

Heating mode bedroom calling.

Living room damper stop must be set to manage 345 CFM. 27% relief.

Heating mode living room calling.

Bedroom damper stop must be set to manage 45 CFM. 4% relief.

14” 12”

1000 CFM @ 900 feet per minute 700CFM @ 900 feet per minute

Damper relief must be set for worst case conditions which is 20% for the cooling mode (only 4% required in heating mode).

The zone will receive 16% more air than is required during the heating mode.

Damper relief must be set for worst case conditions which is 38% for the cooling mode (only 27% required in heating mode).

The zone will receive 11% more air than is required during the heating mode.

Would a variable speed motor help? Why?

Would multi capacity systems help? Why

Living Room Damper Bedroom Damper

16” 14”

1500 CFM @ 900 feet per minute 1000 CFM @ 900 feet per minute

Would oversizing the duct system help?

Moving from a 12 to a 14 inch duct allows for an additional 300 CFM of over blow.

This reduces the living room cooling damper stop from 38% to 20%.

It reduces the living room heating damper stop from 27% to 4%.

Moving from a 14 to a 16 inch duct allows for an additional 500 CFM of over blow.

This reduces the bedroom cooling damper stop from 20% to 0%.

It reduces the bedroom heating damper stop from 4% to 0%.

What are the risks of oversizing ducting?

12” 8”



8” 10”

What happens as the number of zones increases?

How well will a single stage system work on 4 zone application?

12” 8”



8” 10”

What happens in a home with different zones at different temperatures?

Cooling

Heating

68⁰ 77⁰

84⁰75⁰

Cooling

Cooling



What are the chances any dealer / designer is going to go through all these steps?

How many zoning systems are working properly?



Bypass is a way to manage excess air.

The downfall is it’s extremely difficult to configure and impossible to maintain consistency.

The Comfortlink II / AccuLink zone system has the ability to manage excess air based on static pressure and discharge air temperature.

•System configuration is simplified.•System performance is improved.•Homeowner comfort is maximized.



The Comfortlink II / AccuLink zone system has two strategies for managing excess air:

Stand Alone Relief or Temperature / Pressure Bypass.

You can set these independently for heating & cooling modes.

Cooling Mode

Relief

Temperature / Pressure Bypass

Heating Mode

Relief

Temperature / Pressure Bypass


Zoning ApplicationReliefZoning ApplicationRelief

Based on the installation set up (manual or auto zone weighting), the zone control knows:

•The size (weight) of each zone•The position of each damper•The blower speed (total air delivery)

The zone control knows how much air is being delivered into each zone and how much excess air must be managed.


Zoning ApplicationReliefZoning ApplicationRelief

Once the zone control calculates the amount of excess air, it will distribute this air based on the following hierarchy:

•Open dampers in all calling zones--up to 100% if necessary.

•Open dampers (25% minimum) in the same mode zones that are not actively calling—up to 100% if necessary (an off zone is the same mode zone).

•Open dampers (25% minimum) in opposing mode zones.


Zoning ApplicationTemperature / Pressure ControlZoning ApplicationTemperature / Pressure Control



The installation technician must pick a design static pressure when setting up the zone panel (from 0.4 to 1.0 inch of water column.

The zone panel evaluates the system static pressure and discharge air temperature.

Static pressure will increase as supply dampers close, and the zone panel will begin to open the bypass damper when the static reaches its configured target.



The ∆T from the return to the supply duct will increase as the bypass damper opens.

The zone control will freeze the bypass damper and initiate the relief strategy when the supply temperature is within 4 degrees from the trip limit setting.


Return Air

Mixed Air

Supply Air

Static Pressure Transducer

Discharge Temperature Sensor

Four zone single stage cooling system with PSC air handler.

All zones are set in cooling mode.

Discharge temp sensor cut out is set at 42 degrees.

Bypass enabling static pressure set point is 0.7 inches of water.

Cooling Zone 1 Zone 2 Zone 3 Zone 4

Zone LV 0 0 0 0

Damper Position 0% 0% 0% 0%


Return Air

Mixed Air

Supply Air


Zone LV 100 100 100 100


The thermostat came out of program mode. All zones have a load value of 100.

External static pressure is 0.5 and discharge air temperature is 60 degrees.

What is the bypass damper doing ____________?

What method of relief is being used _______________?


Return Air

Mixed Air

Supply Air


Zone LV 75 60 80 100


The house is cooling off and the dampers start to close.

External static pressure increases to 0.7 and discharge air temperature is 56 degrees.




Return Air

Mixed Air

Supply Air


Zone LV 60 40 60 100


The house continues to cool and dampers continue to close.

External static pressure reaches 0.8 and discharge air temperature is 52 degrees.




Return Air

Mixed Air

Supply Air


Zone LV 0 0 50 100


The house continues to cool and two dampers close.

External static pressure stabilized at 0.85 and discharge air temperature dropped to 45 degrees.

What is happening with the bypass damper ____________?



Return Air

Mixed Air

Supply Air


Zone LV 0 0 50 100


The relief strategy is implemented.

External static pressure stabilized at 0.7 stabilizes at 48 degrees.

What is happening with the bypass damper__________?

How will the dampers react to relief__________________?


Return Air

Mixed Air

Supply Air


Zone LV 0 25 50 100


The relief strategy is exited.

External static pressure stabilized at 0.6 stabilizes at 52 degrees.

What is happening with the bypass damper__________?

How will the dampers react to relief__________________?



Time for a vote:

Who wants to manually set up a zoning system?

How will auto zone weighting make this easier?

What are the benefits of intelligent relief?

What are the benefits of T/P bypass?



Summary:What steps must be taken when designing a zone system?

3) ACCA Manual RS. Follow the guidelines when joining multiple rooms into zones. Never lose focus on the common sense approach.

2) ACCA Manual J8, S & D. Size the system based on average block load design. Size the ducting on peak demands. Do not oversize equipment.

1) Consult with the homeowner and obtain their comfort desires.



4) What is the smallest zone and can the system manage the excess air.

6) Since the ducting is sized based on peak load conditions. Are the registers placed in a manner to mix air through the room at different velocity rates (ACCA Manual T)?

5) Have the steps been taken to manage excess air (i.e. have you installed a Comfortlink II / AccuLink zoning system)?

7) Follow through with the homeowner about system limitations and relief strategies.


Questions?Questions?

Zoning Application. Copyright 2011 Trane 2 Zoning Application Agenda Application Overview --Benefits...

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