Wednesday, April 2, 2014

Using a Multi Meter to Locate Reverse Polarity on a Circuit

Do you know how to Use a Multi Meter to Locate a Fire Alarm Device or Appliance that has been connected with reverse polarity?

If not this article will explain how to set the multi meter up as well as how to properly break down fire alarm circuits to locate an initiating device and or notification appliance that has been connected with reverse polarity.

Real quick we will start with the basics.  "What is polarity?"  Polarity in electrical circuits is known as "Positive" and "Negative".  In DC (Direct Current) circuits one pole is always positive (typically marked with a + or red) and the other is always negative (typically marked with - or black).  Note that electrons within a DC circuit only flow in one direction.

This is where a lot of people become confused.  There are two common notations of flow for DC circuits. See below:

#1 is the Conventional Flow Notation.  This notation is based on Benjamin Franklin's conjecture regarding the flow direction of charge.  This notation shows charge flow moving from the Positive Pole of a DC circuit to the Negative Pole.  This is the notation that is most commonly used my engineers and is technically incorrect.

#2 is the Electron Flow Notation.  This is the true notation of charge flow as it shows the actual motion of the electrons in a DC circuit.  Note that this notation shows the charge flow moving from the Negative Pole to the Positive Pole. 

Now that we have covered how a charge or current flows through a circuit, it is important to understand how a diode works and how it can allow or block this flow from occurring.

Definition of a DIODE: A semiconductor device with two terminals, typically allowing the flow of current in one direction only.  This direction of current flow moves from the ANODE side through the CATHODE side of the DIODE.  An easy way to remember this is a DIODE allows current to flow in the direction of the arrow within the symbol.

Here is the electrical symbol for a DIODE:

DIODE showing the Anode and Cathode Orientation


Below are two diagrams that depict the same image however they show the current flowing in opposite directions (conventional vs. electron flow notation).  Notice that even though they both have a diode facing in the same direction the lamp is still illuminated.  "Why is this?"  I thought that a diode only allows current to flow in one direction and that a DC circuit only flows in one direction.  "This would make it impossible to illuminate the lamp in both scenarios, right?"

Conventional Flow Notation with Diode and Lamp
Conventional Flow Notation with DIODE
Electron Flow Notation with Diode and Lamp
Electron Flow Notation with DIODE
           
This is correct.  However the symbol for a DIODE has never been updated to match the Electron Flow Notation.  Therefor the DIODE is always shown with the "Line" or Cathode side pointing towards the positive flow based on the Conventional Flow Notation.  Note that if we were to update the DIODE symbol and show the arrow facing the opposite direction, the diagram based on the Electron Flow Notation would make more sense.

Now on to the point of this article.  "How do I use this information regarding current flow and diodes to locate a fire alarm device or notification appliance that has been connected with reverse polarity?"

A fire alarm initiating device or notification appliance that is polarity sensitive meaning it must be connected with the correct input (positive/negative) will have an internal DIODE to restrict the current flow in one direction as stated above.  We can use the diode setting on our Multi Meter to locate any section of a fire alarm circuit that has been connected backwards or with Reverse Polarity.

How it works:  When you select the DIODE setting your Multi Meter will force a small amount of current through the DIODE and measures the voltage drop across your Multi meter test leads.



Forward Bias Diodes:  If you have the Positive test lead connected to the Anode side and the Negative test lead connected to the Cathode side of the DIODE, your Multi Meter should display something close to 0.548 Volts.

Reverse Bias Diodes:  If you have the Positive test lead connected to the Cathode side and the Negative test lead connected to the Anode side of the DIODE, your Multi Meter should display OL (Open Line).

Multi Meter DIODE Test for Reverse PolarityI suggest testing a single device/appliance on a specific circuit prior to searching for reverse polarity on a fire alarm run. This can be accomplished by using a spare or by taking down a device on a circuit you need to test.  Once you have the fire alarm device or notification appliance removed, place your positive (red) multi meter test lead on the positive terminal of the equipment and the negative (black) multi meter test lead on the negative terminal of the equipment.  If your multi meter displays 0.548 Volts then you have a circuit with Forward Bias Diodes.  If your multi meter displays OL then your circuits has Reverse Bias Diodes.

Here is the key to the puzzle.  If you test the wire in your circuit and your meter displays a dead short (0.000 and typically sounds a steady beep) then your circuit has one or more devices wired backwards.  This is known since diodes in Forward and Reverse bias positions would allow the current in your circuit to travel in both directions ultimately resulting in a dead short.

Now that you know which orientation your circuit's diodes face, you can start breaking down the circuit in halves.  Each time you cut the circuit in half, read the wires in both directions paying attention to multi meter's display looking for either 0.548 V, OL or a dead short.

This easy to use Multi Meter trick will help you eliminate very time consuming labor when troubleshooting fire alarm circuits.

Tuesday, April 1, 2014

How to Use a Multi Meter to Measure for AC/DC Current on a Fire Alarm Circuit

As you may know, fire alarm control equipment has current ratings and limitations.  For example, an addressable relay module from Notifier (FRM-1) has the following current limitations:

3 Amps @ 30 VDC Resistive Non-Coded
2 Amps @ 30 VDC Resistive Coded
.9 Amps @ 125 VAC Resistive Non Coded

This is letting us know that if we need to switch a 30 volt DC (Direct Current) circuit through this relay, we must be below 3 amps (for Non-Coded) and 2 amps for (Coded).

There are two ways to find out if we are below this number.

#1) Read the data sheets and instruction manuals of the equipment that is being powered by this circuit.  These informational sheets should have the current load numbers for your use.  Add this number up by the quantity of equipment to be powered and you should have a number close to reality.  I do not recommend this as you may end up calculating a number lower than actuality therefor jeopardizing the fire alarm relay.

#2) With the proper use of a Multi Meter we can get an exact current reading from any circuit (as long as it is energized).  Now keep in mind that Multi Meters have limitations on the current that can read as well.  For example the Multi Meter we are using for this example has a 10 A fused limit for reading AC/DC current. Read below to find out how to set your Multi Meter up for reading current.

Before we continue please know the difference between a series circuit and a parallel circuit.  In order to measure the load or current of a fire alarm circuit, we must place the Multi Meter test leads in SERIES with the circuit to be read.  This is very important as it is impossible to do otherwise.  Also note that you will need to move the positive test lead to the Amp test lead port as shown in the pictures below:

FLUKE Voltmeter or Multi Meter Test Lead Terminals
FLUKE Voltmeter or Multi Meter Test Leads for Current


This picture shows the Fluke 117 Multi Meter with the test leads in the normal position to meter for voltage, resistance, capacitance, etc.







This pictures shows the Fluke 117 Multi Meter with the positive test lead moved over to the Amp port.  This is mandatory when checking a fire alarm circuit for current.





Now as we stated above you need to place the Multi Meter test leads in series with the circuit being read. For example:  If you have a relay with one leg landed on the C (Common) terminal and the other leg landed on the NC (Normally Closed) terminal your circuit is complete and the equipment being controlled should be functional.  If you pull the wire leg off of the Common terminal, the equipment should stop.

Before we connect the Multi Meter to the circuit we need to insure we have the meter on the correct setting. Be aware if you are reading an AC or DC circuit and select the appropriate setting as noted in our previous article discussing Multi Meter basics.

Now with the wire disconnected from the Common terminal, land your negative (black) test lead on the Multi Meter to that same terminal on the relay.  Now we need to complete the circuit to get an accurate current reading.  Land the positive (red) test lead on the multi meter to the wire leg you disconnected from the Common terminal.  If done correctly the equipment should power back up and your Multi Meter will display the total current of that circuit.

Below are a couple of pictures showing how the Multi Meter test leads should be connected to the circuit to properly read for current.  Please note that the circuit used in these pictures is an SLC connected to a Notifier NFS2-3030 branching off to five FCM-1 addressable control modules.

Fire Alarm SLC Data Circuit Connection
Fire Alarm SLC Circuit Connection

Fire Alarm SLC Connection for Current Reading
Fire Alarm SLC Circuit with One Leg Disconnected for Current Reading


Reading Fire Alarm Circuit for DC Current with FLUKE 115
Fire Alarm SLC Circuit with FLUKE 115 Multi Meter in Series for Current Reading

If this is not something you feel comfortable with, then Fluke has you covered.  Below is a picture of a current reading clamp that they make for their Multi Meters.  All you need to do is plug it into your Fluke Multi Meter and clamp the spring loaded clamp around one leg of the circuit.  This way you do not need to disconnect any live circuits.
Fluke Amp Clamp Attachment for Multi Meters

Also note that relays are not the only application where you might need to take a current reading on fire alarm circuits.  Other example applications may include NAC (Notification Appliance Circuits), Door Holder circuits, Magnetic Door Locks, etc.  Always remember that you need to verify that you are not over-loading the circuit based on the limitation set forth in the data sheets and instructions manuals.

This concept is no different that your house.  If you plug too many electronics into electrical outlets on one 120 VAC circuit then you are going to pop the breaker.  These limitations are put in place for the protection of the equipment as well as your personal safety.

How to use a Multi Meter when Troubleshooting Fire Alarm Systems

One of the most important tools a fire alarm technician posses is the digital voltmeter or digital multi meter.  This article will explain the different settings and how they can help you track down important circuit information such as end of line resistance values, current draw, reverse polarity, dead shorts, ground faults, AC inductance and capacitance.

I cannot stress enough the importance of purchasing a quality voltmeter or multi meter.  For the purpose of the this article I will be utilizing a Fluke 117.  This is a high end meter that won't break the bank.  It has all of the key settings including a back-light for dark spaces as well as non-contact voltage detection.  In case you did not catch that last one, it will detect high and low AC voltage just by simply holding the meter close to the source.

FLUKE 117 Multi-Meter for Fire Alarm Troubleshooting
You can read more about this powerful true-rms multi meter here.

In this article we will show you how to properly tune the voltmeter or multi meter to the correct settings as well as when to move the test leads depending on what circuit information you are trying to obtain.

Now it is important to explain the different symbols and buttons so that you better understand how to navigate through this information.

Please note that although I am referencing the Fluke 117, these symbols should be close to the same on any multi meter you are using in the field.

Buttons:

"HOLD" This button will hold the display at the current view for documentation at a later time.  As you may know, the multi meter display may fluctuate from time to time so this button can prove to be useful if you want to lock it in at a particular time.

"MIN/MAX" As stated above the multi meter display will fluctuate between higher to lower readings.  This button can be pressed to either lock in the lowest/minimum or the highest/Maximum reading. Also note that on this meter, there is another selection with this button that will display the average between the minimum and maximum.

"RANGE" This multi meter has both manual and auto-ranging modes.  In auto-range mode the meter will automatically select the range with the best resolution.  In manual mode you must use this button to cycle through the different ranges whether it be for resistance, voltage, current capacitance, etc.

"YELLOW BUTTON" the yellow button on this meter is like a shift key.  It will allow you to select the yellow options located on the rotary wheel.

Below is a list of the most important multi meter modes and what they can be used to test for.  Feel free to click on the separate links to read further on these topics:  Please note the picture below is of a FLUKE 115 which is basically the same as the 117 minus the AUTO-V LoZ and Volt Alert settings.
FLUKE 115 Multi-Meter Settings and Uses

Selections via Rotary Wheel:

"AUTO-V LoZ" Automatically selects ac or dc volts based on the sensed input with a low impedance input.
AC voltage from 0.06 to 600 V.
DC voltage from .001 to 600 V.

AC voltage from 6.0 to 600 mV
DC voltage from 0.1 to 600 mV

Learn More About Reading for Voltage on Fire Alarm Circuits Here.

Ohms from 0.1 ohms to 40 milliohms
Continuity beeper turns on at less than 20 ohms and turns off at greater than 250 ohms.

Learn More About Reading for End of Line Resistance, Ground Faults, Shorts and Continuity on Fire Alarm Circuits Here.

Diode test.  Displays OL (Open Line) above 2.0 V.

Learn More About Reading for Reverse Polarity on Fire Alarm Circuits Here.

Farads from 1 nF to 9999 micro Farads

Learn More About Reading for Capacitance on Fire Alarm Circuits Here.

AC current from 0.1 A to 10 A.
DC current 0.1 A to 10 A.

Learn More About Reading Current on Fire Alarm and Control Circuits Here.

"Volt Alert" Non-contact sensing of ac voltage.

Friday, March 28, 2014

Low Frequency Sounder Requirements Based on NFPA 72 2013 Edition

System Sensor Low Frequency Sounder and Sounder StrobeIs your jurisdiction enforcing the new code mandated 520 Hz low frequency sounders for fire alarm audibility yet?  If so how are you tackling this new requirement?  And finally did you know that the smoke alarms within the sleeping rooms and guest units must also meet the 520 Hz requirement?

When did this start?

Not a lot of people are aware that this requirement was originally noted in the (2010) NFPA 72 National Fire Alarm Code section 18.4.5.3.  It states "Effective January 1, 2014, where audible appliances are provided to produce signals for sleeping areas, they shall produce a low frequency alarm signal that complies with the following:
(1) The alarm signal shall be square wave or provide equivalent awakening ability.
(2) The wave shall have a fundamental frequency of 520 Hz +/- 10 percent.

Now we fast forward to 2013.

Note that the (2013) NFPA 72 Fire Alarm and Signaling Code requirements are the same found in Section 18.4.5.3

Now lets break it down.  There are a lot of code sections so stay with me.

The Annex A of NFPA 72 (2013) section A18.4.5.3 lets us know that this section does not cover the audible requirements of single and multiple station smoke alarms and instructs us to consult chapter 29 for said requirements.

If you refer to Chapter 29 "Single and Multiple-Station Alarms and Household Fire Alarm Systems" section 29.3.6 it states the following: "All audible fire alarm signals installed shall meet the performance requirements of 18.4.3, 18.4.5.1, 18.4.5.2 and 29.3.8."  Please notice that this section does not include section 18.4.5.3. This may lead one to believe that single and multiple station smoke alarms for dwelling units do not need to meet the new 520 Hz low frequency requirements.

The key section to pay attention to here is section 29.3.8 which states "Notification appliances provided in sleeping rooms and guest rooms for those with hearing loss shall comply with 29.3.8.1 and 29.3.8.2, as applicable."

Section 29.3.8.1 "Mild to Severe Hearing Loss.  Notification appliances provided for those with mild to severe hearing loss shall comply with the following:
(1) An audible notification appliance producing a low frequency alarm signal shall be installed in the following situations:
    (a) Where required by governing laws, codes, or standards for people with hearing loss.
    (b) Where provided voluntarily for those with hearing loss.
(2) The low frequency alarm signal output shall comply with the following:
    (a) The waveform shall have a fundamental frequency of 520 Hz +/- 10 percent.
    (b) The minimum sound level at the pillow shall be 75 dba, or 15 dba above the average ambient sound level or 5 dba above the maximum sound level having a duration of at least 60 seconds, whichever is greater."

Section 29.3.8.2 "Moderately Severe to profound Hearing Loss.  Visible notification appliances in accordance with the requirements of 18.5.5.7 and tactile notification appliances in accordance with the requirements of section 18.10 shall be required for those with moderately severe to profound hearing loss in the following situations:
(1) Where required by governing laws, codes, or standards for people with hearing loss.
(2) Where provided voluntarily for those with hearing loss.

What does this mean?  
System Sensor Low Frequency Sounder Internal View


If we read section 29.3.8 very carefully you will notice the word "AND" between sleeping rooms and guest rooms for those with hearing loss.  This is telling us that the requirements of section 29.3.8.1 and 29.3.8.2 apply to ALL sleeping rooms including guest rooms for those hard of hearing.

How does this effect your design?

To this date there are no UL listed UBC smoke alarms that can produce an audible tone at 520 Hz.  In fact the only manufacture that has a UL listed 520 Hz low frequency sounder appliance is System Sensor.  This means no more mini horns in the sleeping rooms of R-1, R-2 and R-2.1 occupancies.  The only way to accomplish this is by installing a System Sensor HW-LF (low frequency sounder) in place of all mini horns.  This will give us the required 520 Hz in all sleeping areas during a general alarm condition.

How do we accomplish 520 Hz when the Single or multiple station smoke alarm is activated?

Since there is no such thing as a low frequency LISTED smoke alarm, I propose installing addressable system smoke detectors in all sleeping rooms and guest rooms.  On top of this an addressable control module will need to be installed for each residential unit.  The control module will then need to be wired so that it controls an individual NAC (Notification Appliance Circuit) for that particular unit.  Through programming we can activate this individual control module upon activation of any smoke detectors within the unit.  Lastly the control module for each unit will need to be mapped to activate during a general alarm condition.  This way we are activating the in room low frequency sounders via the in room smoke detectors as well as any building wide general alarm device.  This method allows us to accomplish the requirements of section 18.4.5.3 as well as 29.3.8 with listed equipment and methods.

How does this effect your final cost?

Obviously there is a lot more equipment needed to perform this requirement such as addressable system smokes and control modules.  On top of this the low frequency sounders are more expensive than mini horns.  Also note that the new low frequency sounders draw more current than mini horns which will decrease your total allowable appliances per NAC ultimately increasing the number of required remote power supplies.

This is going to be a huge adjustment for our industry which will ultimately comes with a large learning curve.  I suggest your contact your local AHJ (Authority Having Jurisdiction) and find out what their interpretations on this subject are.

In-Duct Smoke Detector vs. Duct Detector for FSD

This question comes up more often than not:  "For fire smoke dampers, should I use an in-duct spot type smoke detector or a duct detector?"
Sampling tube style duct detectors are listed for a minimum air velocity of 100 fpm (feet per minute).  If you are to ensure the rating of the wall @ duct penetrations (dampers), you must provide coverage per CBC 716.3.3.2.  

716.3.3.2 Smoke damper actuation. The smoke fire damper shall close upon actuation of a listed smoke detector or detectors installed in accordance with Section 907.3 and one of the following methods, as applicable:
1. Where a smoke damper is installed within a duct, a smoke detector shall be installed in the duct within 5 feet (1524 mm) of the damper with no air outlets or inlets between the detector and the damper. The detector shall be listed for the air velocity, temperature and humidity anticipated at the point where it is installed. Other than in mechanical smoke control systems, dampers shall be closed upon fan shutdown where local smoke detectors require a minimum velocity to operate.
2. Where a smoke damper is installed above smoke barrier doors in a smoke barrier, a spot-type detector listed for releasing service shall be installed on either side of the smoke barrier door opening.
3. Where a smoke damper is installed within an air transfer opening in a wall, a spot-type detector listed for releasing service shall be installed within 5 feet (1524 mm) horizontally of the damper.
4. Where a smoke damper is installed in a corridor wall or ceiling, the damper shall be permitted to be controlled by a smoke detection system installed in the corridor.
5. Where a total-coverage smoke detector system is provided within areas served by a heating, ventilation and air-conditioning (HVAC) system, smoke dampers shall be permitted to be controlled by the smoke detection system.

The 1st method above states that you must provide a smoke detector installed in the duct within 5’ of the fire smoke damper, and that the smoke detector shall be listed for the air velocity.  If you shut down the fan, there will not be a minimum air velocity of 100 fpm to achieve the proper listing of a sampling tube style duct detector (System Sensor D4120 for example).  Notice that this same paragraph states that “Other than in mechanical smoke control systems, dampers shall be closed upon fan shutdown where local smoke detectors require a minimum velocity to operate”.
System Sensor D4120 Sample Type Duct Detector

What if we decide to use sample tube duct smoke detectors?
If we are using duct detectors for damper control, then whenever the fan is off, the dampers must be shut since the duct detectors such as the System Sensor D4120 require a minimum velocity of 100 fpm to operate.  Does this mean we then have to monitor fan status, and shut dampers upon fan shutoff, or shall the mechanical contractor have to inter-tie with all the dampers associated with that fan?  If we decide to monitor the fan, that creates another issue—per the CMC (California Mechanical Code), if a damper has automatically been activated to close, the associated fan must be shutdown.  Picture this scenario—AHU1 turns off, so we shut down the dampers.  The damper circuit we are controlling also serves dampers associated with AHU2, therefore we must shut that one down as well.  Since AHU2 is serving other areas of the building, we must shut those circuits of dampers as well, and so on until the whole building has typically been shut down for HAVC equipment including dampers.

In-Duct Smoke Detector Spot Type

What if we use spot type In-Duct Smoke Detectors?
On the other hand, if we are protecting the fire smoke dampers with an in-duct detector, you can have the fan shut down upon duct detector for the fan, and the dampers throughout the rest of the building may remain open and the other fans may remain on.  The damper is still protected with the in-duct smoke detector to ensure the rating of the wall to shut the damper upon detection of smoke, and if the in-duct smoke detector activates, then we go through the shut-down process of the fans and dampers throughout the building as exampled above.  Note that in-duct detectors have a listed minimum air velocity of 0 fpm, meaning that it does not “require a minimum velocity to operate“, therefore not requiring shutdown of the building upon a single fan being shut down.
Building owners really don’t like when their building heats up because they are servicing one of their fans, or one of the many fans in their building turns off due to a number of circumstances that are not necessarily indicative of a fire, and our fire alarm system shuts down all HVAC movement in the building.  Mechanical contractors don’t like it when they are forced to interface with individual dampers to close upon fan shutdown.  And finally, electrical/mechanical contractors really don’t like it when we force them to give us a true status of the fan via a Current or Differential Pressure switch when the fan is not a part of a smoke control system and it was not shown on their drawings or bid docs.

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Thursday, February 27, 2014

UBC Requirements for Smoke Alarms

The following is from the UBC Uniform Building Code.  Uniform Building Code Compliance Manual

310.9 Smoke Detectors and Sprinkler Systems.

310.9.1 Smoke detectors

310.9.1.1 General. Dwelling units, congregate residences and hotel or lodging house guest rooms that are used for sleeping purposes shall be provided with smoke detectors. Detectors shall be installed in accordance with the approved manufacturer’s instructions.

310.9.1.2 Additions, alterations or repairs to Group R Occupancies. When the valuation of an addition, alteration or repair to a Group R Occupancy exceeds $1,000 and a permit is required, or when one or more sleeping rooms are added or created in existing Group R Occupancies, smoke detectors shall be installed in accordance with Sections 310.9.1.3, 310.9.1.4 and 310.9.1.5 of this section.

Exception: Repairs to the exterior surfaces of a Group R Occupancy are exempt from the requirements of this section.

310.9.1.3 Power source. In new construction, required smoke detectors shall receive their primary power from the building wiring when such wiring is served from a commercial source and shall be equipped with a battery backup. 
The detector shall emit a signal when the batteries are low. Wiring shall be permanent and without a disconnecting switch other than those required for over current protection. Smoke detectors may be solely battery operated when
installed in existing buildings; or in buildings without commercial power; or in buildings which undergo alterations, repairs or additions regulated by Section 310.9.1.2.

310.9.1.4 Location within dwelling units. In dwelling units, a detector shall be installed in each sleeping room and at a point centrally located in the corridor or area giving access to each separate sleeping area. When the dwelling unit has more than one story and in dwellings with basements, a detector shall be installed on each story and in the basement. In dwelling units where a story or basement is split into two or more levels, the smoke detector shall be installed on the upper level, except that when the lower level contains a sleeping area, a detector shall be installed on each level. When sleeping rooms are on upper level, the detector shall be placed at the ceiling of the upper level in close proximity to the stairway. In dwelling units where the ceiling height of a room open to the hallway serving the bedrooms exceeds that of the hallway by 24 inches (610 mm) or more, smoke detectors shall be installed in the hallway and in the adjacent room. Detectors shall sound an alarm audible in all sleeping areas of the dwelling unit in which they are located.

310.9.1.5 Location in efficiency dwelling units, congregate residences and hotels. In efficiency dwelling units, hotel suites and in hotel and congregate residence sleeping rooms, detectors shall be located on the ceiling or wall of the main room or each sleeping room. When sleeping rooms within an efficiency dwelling unit or hotel suite are on an upper level, the detector shall be placed at the ceiling of the upper level in close proximity to the stairway.  When actuated, the detector shall sound an alarm audible within the sleeping area of the dwelling unit or congregate residence, hotel suite, or sleeping room in which it is located.

Conduit Bender Offset Reference Table

This is a chart to help you better understand the the shrink amount and the distance between conduit bends when performing a saddle with EMT, Rigid electrical conduit or any other type of electrical conduit. You will want to use the arrow mark on the conduit bender and refer to the degree markers along the side of the conduit bender head. Make sure the electrical conduit is always in line with the pipe bender to insure nice straight bends.


22.5° 22.5° 30° 30°
OFFSET DISTANCE BETWEEN BENDS SHRINK DISTANCE BETWEEN BENDS SHRINK
2" 5-1/4" 3/8"

3" 7-3/4" 9/16" 6" 3/4"
4" 10-1/2" 3/4" 8" 1"
5" 13" 15/16" 10" 1-1/4"
6" 15-1/2" 1-1/8" 12" 1-1/2"
7" 18-1/4" 1-5/16" 14" 1-3/4"
8" 20-3/4" 1-1/2" 16" 2"
9" 23-1/2" 1-3/4" 18" 2-1/4"
10" 26" 1-7/8" 20" 2-1/2"






45° 45° 60° 60°
OFFSET DISTANCE BETWEEN BENDS SHRINK DISTANCE BETWEEN BENDS SHRINK
2"



3"



4"



5" 7" 1-7/8"

6" 8-1/2" 2-1/4" 7-1-4" 3"
7" 9-3/4" 2-5/8" 8-3/8" 3-1/2"
8" 11-1/4" 3" 9-5/8" 4"
9" 12-1/2" 3-3/8" 10-7/8" 4-1/2"
10" 14" 3-3/4" 12" 5"