1. Preferred Utilities Manufacturing Corp
Electrical Energy &
Fuel Savings Using
Advanced Boiler Controls
This presentation is designed to be a general seminar on combustion. It not only deals with controls as supplied by Preferred, but general topics on boilers, burners, emissions, etc. While not designed to be “commercial,” it uses Preferred products as its base for descriptions. (indicates advance slide)
Preferred Utilities Mfg. Corp.
31-35 South St. • Danbury • CT

2. Introduction Introduction Fuel Savings Electrical Savings
Stack Losses
Electrical Savings
Fan Basics
Fan and System Curves
VFD Basics
Savings Summary

3. Introduction
This discussion focuses on upgrading existing burners from Jackshaft Control to FD Fan Variable Frequency Drives (VFD) Speed Control with Oxygen Trim to Save Energy and Provide Rapid Payback.
VFD are currently being applied to motors through out industry.

4. Typical Applications Firetube Boilers over 400 Bhp Watertube Boilers
Boilers with Seasonal Load Swings:
Hospitals
Universities
Prisons
Airports
Military Bases

5. Fuel Savings

6. Combustion Efficiency

7. Combustion Theory Chemistry: Air = O2 + N2 Fuel = C + H
3O2 + N2 + 2C + 4H Þ 2CO H2O + N2
Time + Temperature + Turbulence
Excess Air
 The chemistry of combustion is gone over.  Air consists primarily of oxygen and nitrogen as individual molecules.  Fossil fuels contain primarily carbon and hydrogen, though they can include other elements such as sulfur, nitrogen, etc.  The formula given is the ideal reaction; in reality, there are other reactions that occur, some of which will be discussed.
 Combustion requires time, temperature, and turbulence. Enough time for the reaction to occur, sufficient temperature to ignite the fuel and start the process, and turbulence to assure mixing of fuel and oxygen. The formula given assumes all fuel comes into contact with all oxygen.  We introduce extra air to assure that this happens. Too much excess air will cause good combustion but low efficiency as you will be heating this air rather than the water in the boiler.

8. Excess Air Required for Burners

9. Excess Versus Deficient Air

10. Variations in Air Composition
“Standard” air has LB. O2 per FT3
Hot, humid air has less O2 per cubic ft
20% less at 95% RH, 120OF, and 29.9 in. Hg
Dry, cold air has more O2 per cubic ft
10% more at 0% RH, 32OF, and 30.5 in. Hg
Combustion controls must:
Adapt to changing air composition or
Allow at least extra excess air at “standard” conditions

11. Variations in Air Composition

12. Variations in Air Composition
At these ambient conditions the burner has extra O2 & N2

13. Control System Errors
Combustion control system can not perfectly regulate fuel and oxygen flows. Therefore, extra excess air must be supplied to the burner to account for control system errors…
Hysteresis (non-repeatability): linkage slop, valves, dampers, and fuel pressure regulator
Fuel flow for a given valve position varies with temperature and pressure

14. Combustion Control Objectives
Maintain proper fuel to air ratio at all times
Too little air causes unburned fuel losses
Too much air causes excessive stack losses
Improper fuel air ratio can be DANGEROUS
Always keep fuel to air ratio SAFE
Interface with burner management for:
Purge
Low fire light off
Modulate fuel and air when safe to do so

15. Jackshaft Fuel-Air Ratio Control

16. Electrical Savings Fan Basics Fan and System Curves
Motor & Electrical Systems Basics
VFD Basics

17. VFD System Basics Variable Frequency Drive
The Inputs are a 4-20mA FD Fan Speed Demand and Motor AC Voltage
Output is a “Variable Frequency” AC
Motor speed follows the 4-20mA input
Motor manufactures strongly recommend a Motor rated for Inverter Service for long life
These motors can with stand higher surge voltages

18. VFD System Basics VFD provides Electrical Energy Savings due to:
Oversized Fans
Oversized Motors
Partially Loaded Boilers
Minimizing Damper Hp Losses

19. Centrifugal Fan Exploded View
Reference 1

20. Vortex Dampers
Inlet vanes give an initial spin (or vortex) to air entering a centrifugal fan. By adjusting angle of vanes the degree of spin and volumetric output are regulated.
Vortex dampers are only on the inlet of a fan.
Vortex Dampers spin the air as it enters the rotating fan wheel.
These dampers consume less kWh than a parallel blade damper.
Upgrading to VFD control provides moderate kWh savings.
Vortex dampers are round with pie shaped blades that rotate about radial shafts.
Reference 3

21. Inlet Control Vanes
Reference 2

22. Inlet or Outlet Dampers
Inlet or opposed blade dampers assure even distribution of air immediately downstream from the damper. By adjusting angle of blades the volumetric output are regulated.
Parallel Blade Dampers can be on either the inlet or discharge (or both sides) of the fan.
This damper adds pressure drop (and motor kWh usage) as the flow decreases.
These dampers consume more kWh than Vortex dampers and VFD's.
Upgrading to VFD control provides large kWh savings.
Cleaver Brooks firetube & watertube fans generally have discharge dampers.
Older Coen register burners generally have discharge dampers.
Webster burners use a parallel blade inlet damper.
Reference 1

23. Flow vs Fan Hp Non-Vortex Dampers Vortex Damper Speed Control
Reference 1

24. Fan Hp Summary
Dampers substantially increase Fan Hp and Fan kW Consumption.
Dampers are Evil!
Inlet Vortex Dampers waste less Hp than any type of inlet and outlet Blade Dampers.
Variable Speed Fans Control air flow with minimum fan shaft Hp.
Variable Speed Fans have been field proven in thousands of HVAC air handler applications.

25. Variable Frequency Drives
Adjustable Frequency Drive (AFD)
Adjustable SPEED Drives (ASD)
VARIABLE Frequency Drives (VFD)
VARIABLE SPEED Drives (VSD)
Inverters
Frequency Converters
Drives
Different names for the same thing.

26. Motor Speed Control

27. Pulse Width Modulation (PWM)
On or Off, voltage does NOT modulate.
PWM allows IGBT’s to run cool for long life, so all VFD’s use PWM.
However, PWM dV/dt causes spike voltages

28. Voltage Spikes dv/dt - Change in Voltage over Time
Poor Drives - up to 3500V/us
Good Drives - 900V/us on 500 feet
Lower Peak Voltages Extend Motor Insulation Life

29. Do we need a VFD rated Motor ?NO
230 V Motors
Strong Probability: NO
460 V motors with: < 50 ft wire run, good drives almost eliminate problems.
However, you can NOT guarantee it. Motor age and heat naturally degrade the motor wire insulation. The customer should know that there is a small risk.
If motor insulation fails, the VFD is not damaged, but the user must pay to have the motor re-wound or replaced.
YES
575 V Motors

30. Combustion Air Fan Hp Savings
Damper Control
HP Savings
Motor Power(HP) Input, % Full Load
Variable Speed Control
Combustion Air Flow, %Full Load
Reference 1

31. Savings Summary
Fuel
Savings +
Electrical
Savings

32. Energy Savings Fuel Savings: Electrical Savings:
Seasonal Air Density and Humidity Changes
Fuel Pressure and Temperature Changes
Fuel Btu and Viscosity Variations
Worn Linkage Components (Hysteresis)
Electrical Savings:
Minimizing Damper Pressure Drop - damper is 100% open for maximum kWh savings, (Partially closed at low fire to maximize burner turndown)
Oversized Fans
Oversized Motors
Partially Loaded Boilers

33. Advanced Burner Control

34. Energy Savings Important Factors Boiler Size? Loading Service?
Exit Gas Temperature? (Boiler Pressure Determines)
Electrical Cost? (10 cents, 4 cents?)
Fuel Cost?
Utility Rebate?

35. Unique Energy Savings Tool
Savings Estimate Based on:
Boiler size
Motor HP
Air Damper Type
Current O2 Level
Projected O2 Level
Flue Gas Temperature
Seasonal Loading Data
Fuel Cost
Electrical Cost

36. If You Can’t Get Field Data

37. Conservative Assumptions
% O2 Improvement = %
Heating Boiler Seasonal Loading =
Boiler Firing Rate 0% 20% 40% 60% 80% 100%
% Per Year 25% 5% 20% 15% 30% 5%
Process Boiler Seasonal Loading =
% Per Year 5% 5% 20% 20% 30% 20%
Natural Gas Cost $4.50 / 1000ft3
Fuel Oil Cost $0.90 / gal
Electricity Cost $0.75 kWh
Flue Gas Temperatures - 10 psi-350 F, 120 psi-475 F

38. Things You Need To Know Utility Energy Rebates
North East Utilities, CL&P - offers a 50 % rebate of the VFD price and cost of installation.
They use standard numbers.
They require paper work to be submitted
Local VFD rep will be able to give the local rebate offer.

39. Large Firetube Scenario
Steam Boiler: 600 bhp 10 psi (193 F), 350 F flue gas temp.
20 ppm, 60 hp fan motor, parallel blade outlet damper controls air flow
Utilities Cost: Fuel Gas: $4.5 / 1000 ft3) / Electricity: 5 cents / kwh
Operation: Process boiler, 50 weeks a year service,
Shutdown - 10 % of year / 20 % Load - 20 % of year
40 % Load - 20 % of year / 60 % Load - 20 % of year
80 % Load - 20 % of year / 100 % Load - 10 % of year
Oxygen Trim Improvement: Field service engineer has determined that the burner excess air performance can be improved as follows:
20 % Load - 6% to 4.5 % O2 / 40 % Load - 6% to 4.5 % O2 Wet
60 % Load - 5% to 3.5 % O2 / 80 % Load - 4% to 2.5 % O2 Wet
100 % Load - 4% to 2.5 % O2 Wet
Utility Rebate: 50% of VFD Cost and installation
(use VFD list price as an estimate)
Existing Jackshaft Actuator: 150in-lbs

40. Large Firetube Scenario

41. Large Firetube Scenario

42. Installed System Payback

43. 300 Bhp Payback vs.O2 Decrease

44. Preferred Utilities Manufacturing Corp
For further information, contact...
Preferred Utilities Manufacturing Corporation
31-35 South Street. • Danbury • CT
T: (203) • F: (203)