Zoning Application

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Zoning Application
Zoning Application
Agenda
Application Overview
--Benefits & Challenges with Zoning
HVAC System Designs
Conventional Vs Zoning
Excess Air
--Defining
--Management Strategies
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Copyright 2011 Trane
Zoning Application
Zoning is the intentional restriction of capacity
(air flow) into a specific zone.
Why Zoning and how
can a customer
benefit from zoning?
Have you come
across a zoning
system that did not
provide these
benefits?
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Copyright 2011 Trane
Zoning Application
Air Conditioning Contractors of
America (ACCA) provides
standards in designing HVAC
system.
There are standards for
conventional systems and
standards for zoning systems.
Which manuals are mandatory?
Manual J8 is required for the
proper application & design of
zoning systems.
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Copyright 2011 Trane
Zone Heat
Gain
Sensible Heat Gain Graph of Manual J8
BTU’s
Software will show “Powered by Manual J”
The yellow line
represents a 30%
buffer zone. Room
temperature swings
may be extreme if
hourly load conditions
exceed this buffer limit.
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.
Time
Zone Heat
Gain
BTU’s
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.
Time
Zoning Application
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 _________
________________
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Copyright 2011 Trane
Zoning Application
The 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.
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Copyright 2011 Trane
Zoning Application
The 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.
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Copyright 2011 Trane
Zoning Application
Daily Solar Load Shifts
Room grouping from ACCA Manual RS
Daily solar shifts
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Copyright 2011 Trane
Living Room
W
N
Guest
Room 1
E
Add 1
Ad 2
Add 3
Office
Dining
Guest
Room 2
Kitchen
S
Master
Bed
Zoning Application
Seasonal Load Shifts
Room grouping from ACCA Manual RS
Seasonal load shifts and the 15% rule.
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Copyright 2011 Trane
Living room
Guest room
Guest room
73% C/H
Ratio
63% C/H
Ratio
Add 1
Ad 2
109% C/H
Ratio
Dining
Kitchen
Add 3
Office
61% C/H
Ratio
Master
Bed
Zoning Application
Excess Air
What happens to a system when air flow is
restricted?
How can this reduction in air flow be
managed?
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Copyright 2011 Trane
Zoning Application
Excess 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!
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Copyright 2011 Trane
Zoning Application
DST Thermal Limits
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Copyright 2011 Trane
Which is the smallest
zone in heating?
How much excess air
must be managed?
Which is the smallest
zone in cooling?
How much excess air
must be managed?
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Copyright 2011 Trane
Zoning Application
Understanding Bypass
Supply Air
Manual D informs us how to size the ducting to
each zone.
But how do I size a bypass duct?
Mixed Air
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Copyright 2011 Trane
Return Air
Zoning Application
Calculating Bypass
Supply Air
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.
Bypass Air
Reading
Mixed Air
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Mixed
Air
Copyright 2011 Trane
Reading
Return Air
Return Air
Reading
Temp split from return & mixed air.
Zoning Application
Understanding Bypass
Taken from the install guide of a popular zoning system.
Take a look at
what happens
with this much
bypass.
Mixed Air
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Copyright 2011 Trane
Return Air
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.
Temp Rise 30⁰ - 60⁰
43% bypass
on 80K 4ton drive
furnace
18% bypass
on 80K 4ton drive
furnace
Zoning Application
What are the main advantages of Bypass?
What are the main disadvantages of Bypass?
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Copyright 2011 Trane
Zoning Application
$$$ Savings on Energy Bills?
Will zoning deliver energy savings?
“The benefit of a set-up / setback schedule depends on
the cycle time. Long periods
(days or weeks) of set-up /
setback save energy. Short
set-up / set-back periods (less
than a day, maybe less than
16 hours) saves less energy,
or may increase energy use.”
ACCA Preliminary Manual Zr
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Copyright 2011 Trane
Zoning Application
$$$ Savings on Energy Bills?
4-ton AC
system
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10.6Copyright
EER2011 Trane
9.7 EER
8.5 EER
Zoning Application
Variable 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.
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Copyright 2011 Trane
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.
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Copyright 2011 Trane
Zoning Application
Multi Capacity Systems
Can multi capacity systems assist with zoning?
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Copyright 2011 Trane
Zoning Application
Over blow
Over blow makes the assumption that air will be
redirected through the ducting as dampers close.
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Copyright 2011 Trane
Zoning Application
Over 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?
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Copyright 2011 Trane
Zoning Application
Setting 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
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Copyright 2011 Trane
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Copyright 2011 Trane
Zoning Application
Setting Duct Size -- Weight
A main duct is defined as any damper that
controls more than one supply terminal.
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Copyright 2011 Trane
Zoning Application
Time 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
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Copyright 2011 Trane
14”
1000 CFM @ 900 feet per minute
12”
700 CFM @ 900 feet per minute
Blower set to deliver 1600 CFM.
The bedroom is the only zone calling
and requires 36% of this air flow. The
bedroom requires ________ CFM.
Cooling Mode
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?
12”
700 CFM @ 900 feet per minute
Blower set to deliver 1600 CFM.
Cooling Mode
The living room zone is the only zone
calling and requires 64% of this air
flow. The living room 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 14 inch duct
can handle 1000 CFM at 900 FPM
(1000 – ______required by living
room = ______ CFM of over blow).
14”
1000 CFM @ 900 feet per minute
1600 CFM – 1000 into the zone
______bypass = _______CFM
(_____%) of excess air.
How can we manage this excess air?
Blower set to deliver 1275 CFM.
The bedroom is the only zone calling
and requires 43% of this air flow. The
bedroom requires ________ CFM.
Heating Mode
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).
1275 CFM – 700 into the zone –
______bypass = _______CFM
(_____%) of excess air.
How can we manage this excess air?
12”
700 CFM @ 900 feet per minute
Blower set to deliver 1275 CFM.
Heating Mode
The living room zone is the only zone
calling and requires 57% of this air
flow. The living room 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 14 inch duct
can handle 1000 CFM at 900 FPM
(1000 – ______required by living
room = ______ CFM of over blow).
14”
1000 CFM @ 900 feet per minute
1275 CFM – 1000 into the zone –
______bypass = _______CFM
(_____%) of excess air.
How can we manage this excess air?
Cooling mode bedroom calling.
Cooling mode bedroom calling.
Living room damper stop must
be set to manage 612 CFM.
38% relief.
576 CFM is required based on
conventional system design .
412 CFM is managed through
over blow & bypass.
Cooling mode living room calling.
Cooling mode living room calling.
1024 CFM is required based on
conventional system design.
288 CFM is managed by bypass.
Bedroom damper stop must be
set to manage 312 CFM.
20% relief.
14”
1000 CFM @ 900 feet per minute
12”
700 CFM @ 900 feet per minute
Heating mode bedroom calling.
Heating mode bedroom calling.
Living room damper stop must
be set to manage 345 CFM.
27% relief.
548 CFM is required based on
conventional system design .
382 CFM is managed through
over blow & bypass.
Heating mode living room calling.
Heating mode living room calling.
727 CFM is required based on
conventional system design.
503 CFM is managed by over blow
& bypass.
Bedroom damper stop must be set
to manage 45 CFM.
4% relief.
14”
1000 CFM @ 900 feet per minute
12”
700 CFM @ 900 feet per minute
Living Room Damper
Bedroom Damper
Damper relief must be set for
worst case conditions which is
38% for the cooling mode (only
27% required in heating mode).
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 11% more
air than is required during the
heating mode.
The zone will receive 16%
more air than is required
during the heating mode.
Would a variable speed motor help? Why?
Would multi capacity systems help? Why
14”
1000 CFM @ 900 feet per minute
12”
700CFM @ 900 feet per minute
Would oversizing the duct system help?
Moving from a 14 to a 16 inch
duct allows for an additional 500
CFM of over blow.
Moving from a 12 to a 14 inch
duct allows for an additional 300
CFM of over blow.
This reduces the bedroom
cooling damper stop from 20%
to 0%.
This reduces the living room
cooling damper stop from 38% to
20%.
It reduces the bedroom heating
damper stop from 4% to 0%.
It reduces the living room heating
damper stop from 27% to 4%.
What are the risks of oversizing ducting?
16”
1500 CFM @ 900 feet per minute
14”
1000 CFM @ 900 feet per minute
What happens as the number of zones increases?
8”
250 CFM @ 900 feet per minute
10”
410 CFM @ 900 feet per minute
How well will a single stage system work on 4 zone application?
12”
700 CFM @ 900 feet per minute
8”
250 CFM @ 900 feet per minute
What happens in a home with different zones at different temperatures?
68⁰
8”
250 CFM @ 900 feet per minute
75⁰
12”
700 CFM @ 900 feet per minute
77⁰
10”
410 CFM @ 900 feet per minute
84⁰
8”
250 CFM @ 900 feet per minute
Zoning Application
What are the chances any dealer / designer is
going to go through all these steps?
How many zoning
systems are working
properly?
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Copyright 2011 Trane
Zoning Application
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.
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Copyright 2011 Trane
Zoning Application
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
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Heating Mode
Relief
Relief
Temperature /
Pressure Bypass
Temperature /
Pressure Bypass
Copyright 2011 Trane
Zoning Application
Relief
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.
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Copyright 2011 Trane
Zoning Application
Relief
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.
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Copyright 2011 Trane
Zoning Application
Temperature / Pressure Control
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Copyright 2011 Trane
Zoning Application
Temperature / 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.
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Copyright 2011 Trane
Zoning Application
Temperature / Pressure Control
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.
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Copyright 2011 Trane
Zoning Application
Understanding Bypass
Four zone single
stage cooling system
with PSC air handler.
Supply Air
Discharge
Temperature
Sensor
All zones are set in
cooling mode.
Discharge temp
sensor cut out is set
at 42 degrees.
Return Air
Mixed Air
Cooling
Zone LV
Damper Position
Bypass enabling
static pressure set
point is 0.7 inches of
water.
Static
Pressure
Transducer
Zone 1
Zone 2
Zone 3
Zone 4
0
0
0
0
0%
0%
0%
0%
Zoning Application
Understanding Bypass
The thermostat came out of
program mode. All zones have
a load value of 100.
Supply Air
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
Cooling
Zone LV
Damper Position
Zone 1
Zone 2
Zone 3
Zone 4
100
100
100
100
100%
100%
100%
100%
Zoning Application
Understanding Bypass
The house is cooling off and the
dampers start to close.
Supply Air
External static pressure
increases to 0.7 and discharge
air temperature is 56 degrees.
What is the bypass damper
doing ____________?
What method of relief is being
used _______________?
Return Air
Mixed Air
Cooling
Zone LV
Damper Position
Zone 1
Zone 2
Zone 3
Zone 4
75
60
80
100
75%
60%
80%
100%
Zoning Application
Understanding Bypass
The house continues to cool and
dampers continue to close.
Supply Air
External static pressure reaches
0.8 and discharge air
temperature is 52 degrees.
What is the bypass damper
doing ____________?
What method of relief is being
used _______________?
Return Air
Mixed Air
Cooling
Zone LV
Damper Position
Zone 1
Zone 2
Zone 3
Zone 4
60
40
60
100
60%
40%
60%
100%
Zoning Application
Understanding Bypass
The house continues to cool and
two dampers close.
Supply Air
External static pressure
stabilized at 0.85 and discharge
air temperature dropped to 45
degrees.
What is happening with the
bypass damper ____________?
What method of relief is being
used _______________?
Return Air
Mixed Air
Cooling
Zone LV
Damper Position
Zone 1
Zone 2
Zone 3
Zone 4
0
0
50
100
0%
0%
50%
100%
Zoning Application
Understanding Bypass
The relief strategy is
implemented.
Supply Air
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
Cooling
Zone LV
Damper Position
Zone 1
Zone 2
Zone 3
Zone 4
0
0
50
100
0%
0%
100%
100%
Zoning Application
Understanding Bypass
The relief strategy is exited.
Supply Air
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__________________?
Return Air
Mixed Air
Cooling
Zone LV
Damper Position
Zone 1
Zone 2
Zone 3
Zone 4
0
25
50
100
0%
25%
50%
100%
Zoning Application
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?
‹#›
Copyright 2011 Trane
Zoning Application
Summary:
What steps must be taken when designing a zone
system?
1) Consult with the homeowner and obtain
their comfort desires.
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.
3) ACCA Manual RS. Follow the
guidelines when joining multiple
rooms into zones.
Never lose focus on the common
sense approach.
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Copyright 2011 Trane
Zoning Application
4) What is the smallest zone and can the system
manage the excess air.
5) Have the steps been taken to manage excess air (i.e. have
you installed a Comfortlink II / AccuLink zoning system)?
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)?
7) Follow through with the
homeowner about system
limitations and relief strategies.
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Copyright 2011 Trane
Questions?
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Copyright 2011 Trane
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