Posted by Bill Brown on Mon, Nov 14, 2011 @ 01:13 PM
Is your electric heater working properly? Check it out before the first "Big Freeze" blows thru and leaves you out in the cold.
When winter storms strike, heater repair services and heater component part suppliers are overwhelmed by demand. It becomes difficult to schedule repair appointments and even more difficult to find heater replacement parts such as heat sequencers, fusible links, contactors, limit switches and elements. 
Taking a few minutes now to assess the condition of your electric heater will ensure that when the thermostat is turned up, your heater will respond. Adequate heat will help protect your property and ensure your office or household's comfort.
Don't delay. If your heater is in need of maintenance or replacement parts, act now and have the work performed by a licensed HVAC contractor.
Posted by Bill Brown on Tue, Sep 21, 2010 @ 12:56 PM
From the Desk of: Larry Clever, Production Manager, Bel Thermal Units, Inc.
Having come up through the American education system, most of us, (if we are old enough), are familiar with the "three R's" - Reading, Riting, and Rithmatic. (Was spelling important?) These were considered to be the core subjects of a 'good' education.
Today's core revolves around information. We live in the, "age of information". So what effect has this change had on the manufacturing world?
In the business world information is critical to success. When manufacturing duct heaters, it is essential. I have spent my entire working career in the engineering arena, and have been both a "creator" and a "recipient" of information.
Virtually everything done in a manufacturing environment involves information. The process begins with a Customer, who conveys his needs to Sales. From Sales that information goes to Engineering and from there, on to Production. Ultimately, the Customer receives a quality product, at a fair price and in a timely manner. (Hopefully!)
While it seems obvious that delivering a quality product, on time and at a fair price should be the goal, there are many things that can disrupt the process. Faulty information is often the leading cause, and can be one of the biggest obstacles a business must overcome.
Over the years, many "quality gurus" have introduced concepts intended to help businesses deal with the problem of inaccurate information. Zero Defects, Kaizen, and Lean Manufacturing are but a few of the methods implemented by manufacturing facilities to tackle this issue.
It seems much simplier to me. What we need is information that is: Correct, Complete and Clear. (Tadaa.....The 3C's). Anytime information is incorrect, incomplete or unclear, mistakes will be made and time is lost getting a duct heater to market.
As we all know, time is money. When information is inaccurate the result can be a duct heater that has to be reworked, either during the manufacturing process, or worse, when it has been returned from a customer. (Ouch!). The result, an unhappy customer who takes his business elsewhere and/or frustrated employees who stop striving to build defect free heaters.
Each business has it own unique set of products, processes and systems, and thus its own 3C issues. As long as people are involved in the process, we will never achieve perfection. Thus, eliminating the attitude of: "It is not my problem", is critical. The disbursement of Correct, Complete & Clear information is the responsibility of everyone within an organization.
Years ago, someone figured out how start a fire, make a spear and use a wheel. We are fortunate that, along the way, others have improved on these things and have passed that information on to the rest of us in a correct, complete and clear manner.
Posted by Bill Brown on Fri, Sep 17, 2010 @ 12:12 PM
Proper upkeep is the key to ensuring that electric duct heaters operate at peak performance. The following Maintenance Tips may be helpful in keeping your heaters in good working order.
MAINTENANCE GUIDELINES
- Disconnect ALL power circuits to the heater before any service is performed, (there may be more than one disconnect switch that needs to be in the off position).
- Ensure that all air filters in the duct and/or the unit are clean so that there is no restriction of air flow to the heating elements.
- If an air filter needs to be replaced, always use the same type that was originally installed.
- If dust or other material has collected on the heating elements, use low pressure air to remove the debris from the surface. The heater may need to be removed from the duct section for proper cleaning.
- There should be no dust, dirt or moisture in the control panel.
SERVICE TIPS
- Inspect all electrical connections to the power and control circuits to ensure that they are securely attached, they can loosen during operation.
- Check to ensure that the field voltage and phase rating match the heater information data plate.
- Check the full line amp draw of the heater against the rating on the heater information data plate.
- Check the operation of the heater circuits with the thermostat/controller to ensure proper cycling of the relays to the thermostat/controller set point.
- Inspect all internal wiring in the heater control panel for burned or broken wires.
- The heater panel cover should not be open or removed while the heater is being operated.
REPAIRS / REPLACEMENTS
- All wiring must be done in accordance with the National Electrical Codes and any applicable state & local codes.
- Ensure that correct field wire size and grade connect the heater to power circuits. There must be a proper ground wire attached to the heater.
- For a heater to operate properly, repalcement wire must be of the same gauge and rated at 105 degrees Celsius.
- Automatic and manuel resets MUST be replaced with the same components, i.e., the same vendor, part # and temperature rating. Using a reset with higher temperature ratings will void the 'Listing' and can damage the heater or even cause a fire.
- Do not file down relays to stop chatter or to extend their lives, replace them.
- Element insulators that are cracked or broken should be replaced with insulators of the same size and type. If insulators on the element support frame are missing or broken, they must be replaced or a replacement frame assembly should be ordered.
- Broken heating elements must be replaced with elements of the same gauge, ohms and outside diameter size.
CAUTION
- For the safe operation of a heater, do not try to repair any of the heater's components. Broken parts should always be replaced with new ones.
- Modifying or altering a heater's construction can result in the warranty on the heater being nullified and/or its 'Listing' being voided.
Electric Duct heaters, installed following manufacturer recommendations and NEC/SMACNA guidelines, should require very little upkeep. However, to keep heaters operating at peak performance, a formal schedule of regular maintenance should be established and maintained.
Posted by Bill Brown on Tue, Jul 06, 2010 @ 10:03 PM
Many factors influence the reliability of an electric duct heater, the use of quality parts being the most significant. Contactors, transformers, manual resets and automatic limit switches are all essential to a heater's operation and are fairly easy to replace if they happen to fail.
This is not always the case with a heater's resistive elements. Elements are the most critical component of an electric heater and can be difficult to replace.
HEATER ELEMENTS
Open coil heating elements are made of a nickel/chromium alloy that radiate energy through their outer surface, or skin. The elements' skin can reach temperatures as high as 1700 degrees fahrenheit. When operated at such extreme temperatures, oxidation will begin to degrade the elements. To retard this process, and extend element longevity, surface temperatures of the elements should be kept as low as possible while still obtaining the wattage needed for the application.
WATT DENSITY
"Watt Density" is the rated wattage per unit of an element's surface area, i.e., "watts per square inch". To lower the "watt density", use longer and/or heavier gauge wire to increase surface area. The result will be elements that operate at cooler temperatures and therefore last longer.
TEMPERTATURE RATINGS
High quality resistive heating elements are designed to operate below their maximum rated temperature. When operating at 100% capacity they should appear to be dark or black in color with almost no red glow anywhere on the element.
A heater that is made with low quality materials, or that does not receive adequate air flow, will operate closer to its maximum rated temperature. In that case the resistive elements will appear to be dark orange to bright red in color, an indication that the elements are degrading and will need to be replaced earlier than usual.
ENSURE THAT YOUR HEATER HAS A LONG, REILABLE LIFESPAN
A well designed heater can be expected to deliver 15-20 years of reliable service. Ensure that this is the case by consulting with an HVAC design engineer prior to placing an order for equipment.
- Request that low "Watt Density" elements be specified in the heater's construction.
- Insist on the use of the highest quality parts
- Ensure that the CFM is correct for the heater's application
- Ensure that placement of the heater provides for adequate air flow
- Keep the air filters clean
Posted by Bill Brown on Wed, Feb 24, 2010 @ 08:11 AM
When specifying an electric duct heater an HVAC professional can help you save $$ and aggravation by designing the heater correctly the first time. The design engineer will need answers to a number of questions.
Information about the site
- Does the application allow open coil electric heat? Most HVAC installations do.
- What will the heat load be under the worst case conditions?
- Is "quiet operation" required? (ie: A classroom or doctor's office)
- Is the power to operate the heater available in the area where the conditioning is needed?
- What type of power is available? (both phase and voltage)
Duct system
To determine the appropriate kilowatts for the heater, the design engineer will need to know the duct size, the CFM and the temperature rise needed for the air exiting the duct. You may also want to consult with the engineer regarding staging. He can recommend the optimum number of stages, to help minimize surging of the building's power, for minimum cost.
How to save $$
Consulting with a HVAC design engineer regarding the number of kilowatts required for the job can often result in cost savings. For examlpe, a 20 KW heater at 240 Volts and 3 Phase can cost up to twice as much as a 19.6 KW heater with the same phase and voltage. This is simply because the 20 KW load is over 48 amps and UL requires circuit fusing for any load over 48 amps. You will save $$ if a 19.6 KW heater is adequate to do the job!
Other Considerations
- What is the control voltage and will it be supplied by the heater or another source?
- Will an Air Pressure Switch or a Fan Interlock be required? (to prevent operation of the heater in the event of low or no air flow)
- To ensure the safety of service personnel, the duct heater control box can be configured with a door interlocking disconnect switch. This saves on installation cost since a separate service disconnect may not be required in the area.
- Duct heaters are available with many options including: fan motor interlock relays, additional fan motor fusing, plenums, square to round construction, single point line connections, quiet SCR or mercury contactors and step controllers to name a few.
Make sure to consult with an HVAC professional before making any decisions about your heating requirements.
