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Importance of ESP, Gas Pressure, and Voltage for

Gas-Fired UnitsPresented by

Bruce Standerwick

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Importance of ESP, Gas Pressure, and Voltage for

Gas-Fired Units

Part 1: The Importance of ESP

on Gas-Fired Units

Two Cases When Actual ESP not Equal to Design ESP

Case A: Actual ESP > Design ESP Case B: Actual ESP < Design ESP

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44,100 cfm

2.1”

TSP – “

W.C

.

CFM in 1000’s

Design Point

54,100 cfm

2.1”

TSP – “

W.C

.

CFM in 1000’s

Actual Operation: Case A

2.6”

3,780 cfm

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Case A: Actual ESP > Design ESP Solutions:

1. Adjust sheave if possible 2. Change sheave and possibly belts

74,100 cfm

2.1”

TSP – “

W.C

.

CFM in 1000’s

Actual Operation: Case A

2.6”

3,780 cfm

3.0 BHP

2.6 BHP

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Case A: Actual ESP >Design ESP Solutions:

1. Adjust sheave if possible 2. Change sheave and possibly belts3. Need (1), (2) and possibly larger motor

size with new motor controls -- Will motor fit?

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Motor Compartment of DFC

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Case A: Actual ESP > Design ESP Solutions:

1. Adjust sheave if possible2. Change sheave and possibly belts 3. Need (1), (2) and possibly larger motor

size with new motor controls -- Will motor fit?

4. Shaft deflection may require larger shaft and bearings

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Fan Assembly Under Construction

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Motor Compartment of DFC

133,900 cfm

TSP – “

W.C

.

CFM in 1000’s

Operating Point

Design Point

New Operating

Point

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Fan Assembly Under Construction

This dimension is smaller on a fan with a narrow housing

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Case A: Actual ESP > Design ESP Solutions:

1. Need sheave change 2. Need (1) and larger motor and controls3. Need (1), (2) and possibly larger motor

size with new motor controls -- Will motor fit?

4. Shaft deflection may require larger shaft and bearings

5. Different fan because new cfm/TSP point is not in operating range of fan in unit

164,100 cfm

2.1”

TSP – “

W.C

.

CFM in 1000’s

Actual Operation: Case B

4,550 cfm

1.6”

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Case B: Actual ESP < Design ESP

Solutions:1. Adjust sheave if possible 2. Change sheave and possibly belts

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When Actual ESP is Different From Design ESP Conclusions:

● It’s easier to slow a fan down than to speed it up

● It’s safer to overestimate the ESP than to underestimate it!

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Importance of ESP, Gas Pressure, and Voltage for

Gas-Fired Units

Part 2: The Importance of Gas

Pressure for Gas-Fired Units

Typical Gas-Fired Pipe Train in Piping Compartment

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Typical Direct Gas-Fired Pipe Train

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Main Gas Pressure Regulator

Main Gas Valve

Auxiliary Gas Valve

Maxitrol Modulating Gas Valve

Test Port

Test Port

Test Port

Pilot Gas Shutoff Valve

Pilot Gas PressureRegulator

Pilot Gas Valve

Orificed Needle Valve

Pilot

Gas manifold; start of factory furnished and piped components

Main Gas Shutoff Valve

Direct Gas-Fired Burner in Burner Compartment

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Direct Gas-Fired Burner at Full Fire

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Typical Direct Gas-Fired Heater RatingPlate

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Max. Gas Inlet Pressure

Min. Gas Inlet Pressure

Two Cases Where Actual Gas Pressure not Equal to Design Gas Pressure

Case A: Actual Gas Pressure > Design Gas pressure

Case B: Actual Gas Pressure < Design Gas pressure

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Case A: Actual Gas Pressure > Design Gas Pressure

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Main Gas Pressure Regulator

Main Gas Valve

Auxiliary Gas Valve

Maxitrol Modulating Gas Valve

Test Port

Test Port

Test Port

Pilot Gas Shutoff Valve

Pilot Gas PressureRegulator

Pilot Gas Valve

Orificed Needle Valve

Pilot

¾” I.P.S. gas manifold; 5 psig actual gas pressure instead of 10-14” w.c. per design

Main Gas Shutoff Valve

Solution for Case A:Actual Gas Pressure > Design Gas Pressure

Install a High Gas Pressure Regulator

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Case B: Actual Gas Pressure < Design Gas Pressure

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Main Gas Pressure Regulator

Main Gas Valve

Auxiliary Gas Valve

Maxitrol Modulating Gas Valve

Test Port

Test Port

Test Port

Pilot Gas Shutoff Valve

Pilot Gas PressureRegulator

Pilot Gas Valve

Orificed Needle Valve

Pilot

2” I.P.S. manifold; 10” w.c. gas pressure instead of 1-2 psig per design

Main Gas Shutoff Valve

Case B: Actual Gas Pressure < Design Gas Pressure

Solutions:1. Add section to burner2. Modify sheet metal in burner

section

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When Actual Gas Pressure is Different From Design Gas Pressure

Conclusions:● It’s much easier in the field to add a

high gas pressure regulator than to rebuild a gas train/burner

● It’s safer to underestimate the gas pressure than to overestimate it!

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Importance of ESP, Gas Pressure, and Voltage for

Gas-Fired Units

Part 3: The Importance of Voltage

on Gas-Fired Units

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Motor Compartment of DFC

Components That Could be Affected by a Voltage Change Disconnect Switch and/or Distribution Block Fuses and Fuse Blocks Circuit Breaker Transformers Starter and Overload Contactors Motor(s) Wiring and conduit to motor(s) Wiring diagram

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Relationship Between Volts and Amps

HP is proportional to volts times amps If : HP1 = HP2 then:

(volts x amps)1 = (volts x amps)2 or (volts1/volts2) = (amps2/amps1) Amps are inversely proportional to

volts at constant horsepower.

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Two Cases Where Actual Voltage not Equal to Design Voltage

Case A: Actual Voltage > Design Voltage

Case B: Actual Voltage < Design Voltage

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Case A: Actual Voltage > Design Voltage

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Disconnect Switch and/or Distribution Blocks

No change

Fuses and Fuse Blocks Fuses probably change; fuse blocks also if different fuse type required

Circuit Breaker Probably need to change so it will trip when necessary.

Transformers Must change unless original transformer is tri-voltage (208/230/460).

Starters No change

Overload Contactors Probably need to change so it will trip when necessary.

Motor(s) Must change unless original motor is tri-voltage (208/230/460).

Wiring and Conduit No change

Case B: Actual Voltage < Design Voltage

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Disconnect Switch and/or Distribution Blocks

Non-fused disconnect may change; fused disconnect will change

Fuses and Fuse Blocks Fuses probably change; fuse blocks also if different fuse type required

Circuit Breaker Doesn’t change because it’s downstream of transformer

Transformers Must change unless original transformer is tri-voltage (208/230/460)

Starters Must change

Overload Contactors Must change

Motor(s) Must change unless original transformer is tri-voltage (208/230/460).

Wiring and Conduit May change depending on original amp rating

When Actual Voltage is Different From Design Voltage

Conclusions:● Fewer components are likely to need

changing if the voltage goes up (amps go down) rather than if the voltage going down (amps go up)

● It’s safer to underestimate the voltage than to overestimate it!

Wiring diagram, specification sheet and rating plate must be replaced if the voltage changes 38

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Importance of ESP, Gas Pressure, and Voltage for

Gas-Fired Units

The EndThank You!