York Meridian, Technical Manual

Page: 26 / 28

26 Meridian

Systems
Zoning Design Guide
036-21478-001 Rev. A (0802)
System Installation
Figure 1-16: Transformer And Wire Sizing Considerations
FILENAME
DATE: B. CREWS
DESCRIPTION:
PAGE
DRAWN BY:
Wire & Transformer Sizing
JOB NAME
11/30/99
MWIRSIZ1.CDR
Meridian
1
24VAC Power - Transformer & Wire Sizing Considerations
Component Power Requirements
120 / 24VAC
120 / 24VAC
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
ZONE
CONTROLLER
Distance A to B cannot exceed 46.30 Ft.
Distance from A to B cannot exceed 92.60 Ft.
Distance from A to C cannot exceed 92.60 Ft.
Distance from A to B cannot exceed 185.20 Ft.
Distance from A to C cannot exceed 185.20 Ft.
Distance from A to D cannot exceed 185.20 Ft.
Distance from A to E cannot exceed 185.20 Ft.
120 / 24VAC
Some installers like to use one large 24VAC transformer to power several controllers. This is allowable as long as polarity is maintained to each
controller on the transformer circuit.
Using
separate transformers also allows redundancy in case of a transformer failure. Instead of having 8 controllers inoperative because of a malfunctioning
transformer you have only 1 controller off line. If the installer does decide to use a large transformer to supply power to several controllers, the
following transformer and wire sizing information is presented to help the installer correctly supply 24VAC power to the controllers.
Following is a typical example to help the installer to correctly evaluate transformer and wiring designs.
Each Zone Controller with actuator requires 10 VA @ 24VAC power. In the examples below we have a total of 8 Zone Controllers.
8 Zone Controllers @ 10VA each................ 8 x 10VA = 80VA.
The above calculation determines that our transformer will need to be sized for a minimum of 80VA if we are to use one transformer to power all the
controllers.
Next we must determine the maximum length of run allowable for the wire gauge we wish to use in the installation. Each wire gauge below has a
voltage drop per foot value we use to calculate total voltage drop.
18ga wire.................................0.00054 = voltage drop per 1’ length of wire
16ga wire.................................0.00034 = voltage drop per 1’ length of wire
14ga wire.................................0.00021 = voltage drop per 1’ length of wire
For our example we will use 18 gauge wire. York recommends 18 gauge as a minimum wire size for all power wiring.
Next use the voltage drop per foot value for 18 gauge wire from the list above and multiply by the total VA load of the 8 controllers to be installed.
0.00054 (Voltage drop per foot for 18 gauge wire) x 80VA controller load = Volts/Ft.
Meridian controllers will operate efficiently with a voltage drop no greater than 2 Volts. Divide the total allowable voltage drop of 2 Volts by the number
you arrived at above and you have the maximum number of feet you can run the 18 gauge wire with an 80VA transformer with no more than a 2 Volt
drop at the farthest controller from the transformer..
2 (Volts total allowable voltage drop)
=
0.0432 (Voltage drop per 1 ft. @ 80VA load)
Parallel circuiting of the wiring instead of wiring all 8 controllers in series allows for longer wire runs to be used with the same size wire (as shown in
our examples below).
Warning:
If polarity is not maintained, severe damage to the controllers may result. York recommends
using a separate transformer for each controller in order to eliminate the potential for damaging controllers due to incorrect polarity.
0.0432
46.30 feet
It is often necessary for the installer to calculate and weigh the cost and installation advantages and disadvantages of wire size,
transformer size, multiple transformers, circuiting, etc., when laying out an installation. No matter what layout scheme is decided upon, it is mandatory
that the farthest controller on the circuit is supplied with a minimum of 22 Volts.
System Manager ......................25VA GPC Controller .........................20VA
Zone Manager ..........................25VA
Wetbulb Module .......................20VA
Zone Controller ........................10VA Lighting Panel Controller ..........25VA
CV Controller............................20VA
Zone Relay Expansion Board ...10VA
CV-C Controller ........................20VA Staging Expansion Board .........20VA
Optimal Start Scheduler ...........25VA
A
A
A
B C D E
B
B C