I have been asked over the years “What is a boiler horsepower” and what is the design criterion of square feet of heating surface per boiler horsepower.

 To understand boiler horsepower it is necessary to review the genesis of the term “boiler horsepower” (Bhp). The term originally related to the quantity of steam necessary to operate a one horsepower steam engine. Due to variations in engine efficiencies, this quantity of steam was itself a variable. Tests conducted in 1876 on a modern (for the time) steam engine determined that it took approximately 30 pounds of steam per hour to produce 1 horsepower (mechanical) of work. In 1889 the American Society of Mechanical Engineers (ASME) standardized the term “Boiler Horsepower” as being based on a conventional steam engine steam rate of 30 pounds of steam per hour (PPH) at 70-psig pressure and feedwater of 100 degrees F. This definition was later modified to: “Boiler Horsepower = the unit of capacity expressed as equivalent evaporation of 34.5 pounds of water per hour from and at 212 degrees F (33,475 Btu per hour.)”

In the early days of brick firing surfaces the rule of thumb was that it took 10 square feet of heating surface to create 1 boiler horsepower. In todays modern boiler designs the heating surface necessary to create 1 boiler horsepower has been reduced to 5 or in some cases less that 5 square feet of heating surface.

HORSEPOWER ?

As we all know before machines we did all the heavy work… then “Joe” one day hitched a horse to a rock to move the rock. Without knowing it at the time “Joe” created the term motive power. Motive power is a term used to describe something (air, water, steam, or the horse) that has the energy (power) to create movement in something else. So, as steam engines replaced the horse as a means of motive power steam engines were were rated in horsepower instead of “Joe Power”. Sorry Joe !

Hope you enjoy this bit of horsepower history.

We have written many articles about flame safe guard controls on Control Trends but we have not really given an explanation on the basic principles of these controls.

The programmer, (also called the blue box, the FSG, the fire eye and the brain) is the mastermind that controls the starting sequence and the firing cycle of a burner. The programmer controls the operating sequence of the blower, burner motor, ignition system, fuel valve, and all other components also called interlocks in the control system.

The programmer also provides, if necessary, a suitable purge period before ignition and after burner shut down allowing for the removal of explosive combustibles. The programmer is designed to de-energize all fuel valves within 4 seconds after loss of flame signal. In addition, the programmer automatically restarts a new cycle each time a temperature controller or pressure controller closes or after a power failure, lock outs must be reset manually after any flame failure.

Example of basic operation of programmer on steam boiler:

When the steam pressure within the boiler drops the pressure controller, (like Honeywell L404F1102), completes an electric circuit which starts a timing sequence in the programmer. The first timing sequence closes and starts the burner motor that rotates the primary air fan. The primary air fan blows air into the furnace to purge any unburned fuel present in a gaseous condition in the furnace.

This process is called pre-purging the furnace. By pre-purging the furnace before pilot ignition, the danger of a furnace explosion is reduced. The purge cycle is controlled by the time card (ST7800) in most programmers and can last varying lengths of time depending on the furnace size.

The programmer is still operating and when the second timing sequence contact closes, the circuit to the ignition transformer (similar to Donagan AO6-SA) is completed. The ignition transformer creates a high voltage spark in front of the gas pilot tube. At the same time, a solenoid valve is opened in the gas pilot line, allowing the gas to flow through the gas pilot tube and be ignited by the transformer spark. The scanner ( like the C7027A1023 or similar) is located on the front of the boiler and positioned in such a manner to sight the flame from ignition.

Sighting the pilot through the will verify that the pilot is lit. This process is called proving the pilot. The programmer timing sequence is still operating and the next contact closes to complete the circuit to the main fuel valve, which opens only when the scanner proved pilot. The main fuel valve is then opened and the fuel enters the furnace and is ignited by the pilot.

The programmer continues to operate for a few more seconds, securing circuits to the ignition transformer and the gas pilot. After the circuits are secure the programmer stops. The burner is now regulated by the pressure control and modulating pressure control. If the scanner senses a flame failure, the system is purged and secured. The programmer is then manually reset to restart the cycle.

The programmer needs very little maintenance. Most common failures are due to heat and moisture causing corrosion to the contacts of the programmer. Care must be taken to eliminate these factors. Check all wiring to the programmer sub-base for loose damaged connections or cracked wiring.

NOTES:

Please be aware this is a GENERIC ARTICLE on the workings of a burner programmer. There are MANY variations of these controls and many applications using these controls. Extreme care must be exercised when working with FSG CONTROLLERS and refer to factory and manufacture’s guides when working with these controls.

When your needs turn to the flame safe guard control please give Stromquist and Company at call at 1-800-241-9471.

Stromquist and Company does not sell fire tube boilers but we do sell a vast amount of controls for these boilers from manufactures such as Conbraco, Honeywell, Asco, McDonnell & Miller, Maxitrol, and numerous other control manufacturers. The understanding of these boilers is a major concern in our continuing efforts to keep our readers informed.

FIRE TUBE BOILERS:

In a fire tube steam boiler, heat and gases of combustion pass through the tube surrounded by water. Fire tube boilers steam boilers maybe either high or low pressure boilers. The three types of fire tube steam boilers are horizontal return tubular boiler, scotch marine boiler, and vertical fire tube boiler.

All fire tube boilers have the same basic operating principles. The heat produced by the gases of combustion pass through the tubes while the water surrounds the tubes. However, fire tube boilers have different designs like 2 pass, 3 pass, and 4 pass based on application and installation considerations.

Fire tube boiler tubes are always measured by their outside diameter (O.D.). Fire tube boilers are usually designed for pressures up to a maximum of 250 psi and approximately 750 horsepower.

HOW THEY WORK:

When water is heated, it increases in volume and becomes lighter. This warmer water, now lighter, rises and the cooler water drops to take its place. The steam bubbles that eventually form break the surface of the water and enter the steam space.

The addition of tubes inside the drum containing the water increases the heating surface. The heating surface is that part of the boiler with water on one side and the heat and gases of combustion on the other. By increasing the heating surface, more heat is taken from the gases of combustion. This results in a more rapid water circulation and faster formation of steam bubbles.

When larger quantities of steam are released, the thermal efficiency of the boiler increases. Thermal efficiency is the ratio of the heat supplied from the fuel to the heat absorbed by the water. Modern fire tube boilers with improved design and heat transfer rates have achieved thermal efficiency rates as high as 80% to 85%.

Placing an internal furnace within the boiler shell greatly increases the heating surface allowing for maximum absorption of heat thus reducing the time to create steam.

BOILER SAFETY:

Because of the large volume of water fire tube boiler contain, disastrous explosions may occur. Explosions may occur because of a sudden drop in pressure without a corresponding drop in temperature. Knowledge of basic principles of boiler operation can prevent serious accidents.

Water will boil and turn into steam when it reaches 212 degrees F at atmospheric pressure.

The higher the steam pressure, the higher the boiling point of the water in the boiler.

As steam pressure in the boiler increases, there is a corresponding increase in temperature.

When a steam boiler is operating at 100 psi gauge pressure the temperature of the water and steam will be about 337 degrees F. If there is a sudden drop in pressure from 100 psi to 0 psi without a corresponding drop in temperature, the water at 337 degrees F flashes into steam. When water flashes into steam its volume increases tremendously. This can result in a disastrous explosion.

It is imperative that maximum care is exercised in the operation and maintenance of the fire tube boiler. This includes annual boiler inspections of the waterside and fireside of the boiler. Controls such as the low water cut off, relief valves, flame safeguards must all be in correct working order.

Proper boiler blowdown is an essential part of firetube boiler operating proceedures. It is necessary to control the amount of TDS (total dissolved solids) in the boiler water.The total TDS should not exceed 3500 parts per million in a scotch marine boiler. If the blowdown is not controlled, excessive dissolved solids will have a tendency to increase and concentrate to a point that will cause a foaming or a carry over condition which will contaminate the  steam.

High concentrations of TDS in firetube boilers have a tendency to collect as SCALE on the heat transfer surface. Scale is an excellent insulator and its collection on the heat transfer surfaces of a boiler reduces the efficiency of the boiler. Scale thickness between 1/50 of an inch to 1/9 of an inch depending on the type of carbonates or sulfates present can reduce boiler efficiency between 3.5% to 16%. As you can tell just a small amount of scale build up can cost thousands of dollars a year on fuel costs.

Boiler blowdown frequency and duration is recommended by the water treatment contractor and can be accomplished either manually or automatically or both. Manual blowdown involves the operating personnel opening the boiler blowdown valves for a predetermined length of time at proper intervals. Automatic blowdown can be accomplished by many means. The most common method is the use of a surface blowdown skimmer attached to a calibrated blowdown valve which permits a continuous preset amount of boiler water to be blown down.

Proper blowdown rate can be easily figured when two factors are known. It is necessary to know the TDS in the feedwater and the amount of makeup water the boiler is using. The amount of TDS in the feedwater can be determined from a water analysis. The quantity of make up water is determined by installing a water meter in the make up water supply line that serves the feedwater unit. The correct amount of boiler blowdown, as a percentage of feedwater can be figured with the following formula.

TDS in feedwater / 3500-TDS in feedwater X 100. For example if the TDS in the feedwater = 200 divide this by 3500-200 or (3300) the result is .06 the multiply .06 X 100 for the amout of 6% of makeup water for proper boiler blowdown. I hope this is clear as the mud you will now be removing from your boilers.

NOTE: Because of the many variations of boiler plants, boiler, valves, pumping systems, and control systems proper maintenance of these systems should follow manufacturer’s recommendations and federal, state, and local laws that govern these proceedures. Boilers and Boiler maintenance can be dangerous and should only be preformed by Boiler professionals that have the proper training. When in doubt defer to the Boiler manufacturer.

The following is a list of what causes a LWCO switch to malfunction taken from the McDonnell & Miller Service Guide.

   1. Burner motor having greater power requirements than the LWCO switch

   2. Feed pump is not properly balanced for the required fill rate resulting in rapid cycling of the switches.

   3. Shorting of power wiring in control circuit.

   4. Switch submerged in water

   5. Lightning striking electrical service to building, causing electrical overload

   6. Overloaded circuit in building, resulting in low voltage conditions which in turn causes higher amperage draw and consequent switch failure

   7. Other limits like pressure controls, relays, thermostats, etc., may short circuit, overloading all switches in the same electrical line.

   Pump motor having a dead spot, may stall and generates heat, causing overloading of switch

The most common cause of switch overload is incorrect application. Check the electrical ratings of the switch against ratings of the equipment controlled.

If ypu have any other questions about McDonnell & Miller controls please call Stromquist at 1-800-241-9471 in Atlanta or 1-800-678-7828

Fault codes are used on the Honeywell RM7800 series of boiler burner flame safeguard controls. These codes help the service technician identify problems that occur with the relay or the components that are wired to the relay.

These fault codes are sent to the S7800 display as so known as the KDM (keyboard display module) that can be mounted on the main RM7800 relay or remotely. The S7800 display will show operation and fault information along with other features

Over the years Stromquist and Company has been selling Honeywell controls and explaining these numeric fault codes to various clients. As luck would have it the other day I received a phone call from a client asking about a fault code that was showing up on his S7800 display. I searched the fault code references I had from Honeywell and could not locate the fault code the client was reading off the display to me. His fault code was 33Z. I have, in all my time working with clients, never saw or heard of a fault code ending with a letter value.

After several telephone calls to find an answer/solution to this problem I finally got an answer. It seems I forgot to ask one small detail about the client’s system.

When working with a RM7800 system and you get a bazaar fault code ask the client this question “Is there an S7830 Expanded Annunciator installed”. If there is a S7830 installed you need to look at the expanded fault code lists for the S7830 and there you will find the fault code number and in some cases this fault code number is followed by a letter giving you the proper diagnostic information.

I don’t know about you but this “ole dog” learned a new trick hopefully you can add this one to your bag of tricks.

More Boiler Burner Information:

http://www.controltrends.org/2011/09/rebuilt-flame-safeguard-controls-penny-wise-pound-foolish/

http://www.controltrends.org/2010/07/2061/

Honeywell Burner Boiler Flame Safeguard Training Classes

Stromquist and Company is inviting you to our Honeywell Boiler Burner Flame Safeguard Training Class in Jacksonville, Florida.

Date: Tuesday October 4^th 2011

Time: 9:00 am till noon

Location: University of North Florida (University Center) Bldg. 43 Parking Lot 16 on Alumni Drive. http://www.unf.edu/map/

Cost: FREE

Host: Stromquist and Company

Featured Speaker: Dave Krause Honeywell’s Burner Boiler Factory Representative.

Attendance Requirements: Representatives from your facility whose responsibilities are or include the boiler and burner controls and systems.

Registration: http://www.controltrends.org/training-classes/

Questions: Call Bill Jones at 904-334-5938

We have registrations for the Duval County School Board, University of North Florida, and Mayo Clinic so REGISTER SOON to reserve your spot !!

Free Training!  Free Training! The Stromquist/Honeywell Flame Safeguard Training Blitz is on.  I recently posted about the classes being held in Tampa and Orlando, and since then we have added 8 more classes in 8 different cities.

Tallahassee, FL:  September 20, 3:00 – 6:30 (at Tallahassee Community College)

Albany, GA:  September 21, 9:00 – 1:00 (at Darton College, Albany)

Valdosta, GA:  September 22, 1:00 – 5:00 (at Wiregrass GA Tech College, Valdosta)

Orlando, FL:  October 5, 9:00 – 12:00 (at Stromquist, Orlando)

Jacksonville, FL:  October 4, 9:00 – 12:00 (University of North Florida)

Tampa, FL:  October 6, 3:00 – 7:00 (location TBD)

Athens, GA:  October 25, 10:00 – 2:00 (at Hilton Garden Inn, Athens)

Augusta, GA:  October 27, 10:00 – 2:00 (location TBD)

Dalton, GA:  November 1, 10:00 – 2:00 (NW Georgia Trade and Convention Center, Dalton)

Each training class will include lunch or dinner, depending on the time of the session.  There is no charge to attend, but you need to register in advance.  After you register you will be contacted with information regarding the exact location of your class.

Honeywell has announced they are introducing a series of integrated combustion panels to go along with the awsome Delphi release from last year. These new panels will incorporate Honeywell’s proven combustion technology into complete panels, making equipment upgrades a snap! All panels will be pre-wired, pre-tested, and a built in a certified UL panel shop. Made in the U.S.A.

The initial offering will include:

YP7999A1000 Control Links Fuel Ratio Control panel. Features:

Pre-wired and Pre-tested, Panel measures 24X24 inches, NEMA 12. UL508 approved. Includes Q7999A, R7999A1005, S7999B1000, remote monitor via modbus through S7999B touch screen, Alarm Light, Auto/Manual selector switch, Fuel selector switch, Reset push button, Emergency stop button. Order ML7999A actuators seperately.

YP7899A1002 7800 Series Burner Management and Fuel Ratio Control Panel. Features:

Panel measures 24X30 inches, NEMA 12, UL 508 approved, Includes Q7999A, R7999A1005,S7999B1000, Q7800A, RM7800L1087, Remote monitor via modbus through S7999B touch screen, Alarm light, VPS Valve Proving System capability via FSG control, Auto/Manual selector switch, Fuel selector switch, Reset push button, Emergency Stop Button, Burner on/off selector switch. Order ML7999A actuators, R78XX flame apmlifier, ST7800 purge timer, and appropriate flame detector separately.

YP7899C1000 7800 Series Burner Management Panel. Features:

Panel measures 24X24 inches, NEMA 12, UL508 approved, Includes Q7800A, RM7800L4087, S7999B100, (2) UDC2500 process controls. Order R78XX flame apmlifier, ST7800 purge timer, and appropriate flame detector separately.

The future addition of these new Honeywell Combustion Panels will make upgrading older boiler systems easier for all concerned from the client to the installer. We at Stromquist and Company are excited about these soon to be released panels and will update you here on Control Trends upon release or call us at 1-800-241-9471 in Atlanta or at 1-800-638-7828 in Orlando and we will keep you informed.

The Honeywell T775 Series stand alone controllers have now been on the market for several years. This diverse controller offers the technician a multitude of installation options on one small package.

This controller that stands 8 inches wide by 4 inches wide can be mounted anywhere within 1000 feet of its sensor location and be purchased as a standard enclosure or a NEMA 4X enclosure.

The T775 has an EEPROM that saves all values entered. The date and time values are retained for 24 hours after power loss. After power loss of more than 24 hours values may need to be reentered.

IMPORTANT:  If a high limit set point is entered into a T775 controller this value is IRREVERSIBLE !!

Features:

Voltage: 24/120/240 note: cannot be used for DC voltages

Set Point Range: -40 to 248 F

T775A and B models:  relay outputs from 1 SPDT to 4 SPDT (no analog outputs). Sensor inputs 1 to 2. Floating outputs 0-to 2

T775M models:  Modulating with analog outputs of 2-10Vdc or 0-10 Vdc or 4-20 mA or Electronic Series 90.  Relay outputs from 0 to 4 SPDT. 2 sensor inputs

T775R models:  RESET OPTION.. 0 to 2 analog outputs 0 to 4 SPDT relay outputs. 0-2 floating outputs.

Sensors: update display and controller every 1 second

Accessories:

C7031D2003 5 inch immersion sensor with well

C7030B1009 wall mount room sensor

C7100D1001 12 inch Duct Averaging Temperature Sensor

When the need for a standalone controller presents itself think Honeywell and let Stromquist and Company help you select the right controller for your needs. Give us a call… Atlanta 1-800-241-9471 or Orlando 1-800-638-7828