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HVAC and Plumbing Distributor
Steven Simmons

Steven Simmons

Technical Services Manager
Southwest District

All About Heaters

At first glance, a residential strip heat kit could look intimidating. I want to break down the operation and troubleshooting in a way that should give you confidence. Be careful and keep safety in mind while performing the tasks mentioned in this article because the power will have to be on to make these checks. Although different brands will look slightly different, the concept and troubleshooting will be the same.

Here are the different parts of a double (10kw) heat kit:

  1. High voltage terminal block
  2.  DC Heater relay with an AC to DC rectifier attached
  3. High temp auto resettable limit
  4.  High temp fusible link
  5.  Electric heater

Okay, let’s break this heater down even further and discuss each of the 5 different parts in depth for proper operational checks when a heater kit isn’t working:

1. High voltage terminal block:

The terminals should read the rating voltage displayed on the heater at all times. In this example the kit is rated for 230v. It is common for heat kits to have a separate power source and this voltage should be confirmed to ensure a breaker wasn’t tripped.

2. DC Heater relay with an AC to DC rectifier attached:

-LOW VOLTAGE-This heater relay consists of two parts, the actual relay and a rectifier. Notice the voltage on this relay is 28vdc. Some relays can be 22vdc.

Verify that the rectifier is receiving 24vac. Once this has been proven, the rectifier can be removed to confirm proper output voltage. In this example, the output is reading 33vdc. If the voltage output were to be zero, then it would indicate a faulty rectifier. When the relay receives the correct voltage, the relay should close its contacts.

-HIGH VOLTAGE- These relays consist of two set of contacts. One set is located on the top left of the relay and another on the top right. When the relay doesn’t have proper low voltage to energize the coil or if the coil is faulty, the contacts will read 240vac. If the relays close correctly with applied low voltage, then the contacts will show 0vac when checked in this manner:

3. High temp auto resettable limit:

This limit, like many other limits, is displaying its tripping and resetting temperatures. This information can be used when selecting a universal limit or when troubleshooting if the limit is opening/ closing at the right temps. The resettable limit and the fusible link test and function in the same manner EXCEPT that the limit will reset itself and the fusible link cannot. Troubleshooting and operation for this limit will be under #4 fusible links.

4. High temp fusible link:

Fusible links are the “backup limit” for when the resettable limit fails or the heater draws too many amps. They typically have a melt/open point of around 300F. Here are the two most common fusible links: The link that is wire only will actually melt and therefore open the power circuit physically and can be seen but, the link that has a device on the wire will internally open and will not alter its look when tripped.

If a limit or fusible link is suspected for a heater not functioning, then simply check the voltage with a meter to ensure that the voltage drop across it is 0vac in the same manner as the contacts were checked on the relay. If a meter were to read 240v, then the limit is open/ or the fusible link has been melted/opened.

5. Electric heater

The electric heater is the star of the show and the easiest to check. This is the meeting place for both 120vac power legs and SHOULD read 240vac. If your meter reflects the heater has 240vac but the current (amps) is zero (assuming the amp clamp is accurate) then this would indicate the heater has failed and is “electrically open” and should be replaced. The meter leads should be placed in this manner for this test:

Keep in mind that parts do fail from simple wear and tear from normal usage, but repeated failures usually happen for a reason and these repeated failures should be investigated further to find the root cause.

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Alabama Locations

Anniston (256) 241-3026 105 E D St, Anniston, AL 36201
Auburn (334) 734-8011 2295 1st Ave, Opelika, AL 36801
Birmingham (205) 250-7714 516 31st St N, Birmingham, AL 35203
Dothan (334) 836-1035 205 Wedgewood Dr, Dothan, AL 36303
Gulf Shores (251) 968-2660 820 Commerce Dr, Gulf Shores, AL 36542
Huntsville (256) 859-2691 391 Nick Fitcheard Rd NW, Huntsville, AL 35806
Loxley (251) 964-2707 30020 Co Rd 49, Loxley, AL 36551
Mobile (251) 476-2220 5522 W Commerce Blvd West, Mobile, AL 36619
Montgomery (334) 262-4855 861 Plantation Way, Montgomery, AL 36117
Muscle Shoals (256) 383-6904 107 Commerce St, Muscle Shoals, AL 35661

Georgia Locations

Albany(229) 432-5254205 Baldwin Dr, Albany, GA 31707
Athens(706) 548-2563105 Whitetail Way, Bogart, GA 30622
Atlanta(404) 875-77551290 Tacoma Dr NW, Atlanta, GA 30318
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Brunswick(912) 265-5193275 Rose Dr, Brunswick, GA 31520
Columbus(706) 322-38706201 W Hamilton Park Rd, Columbus, GA 31909
Conyers(770) 918-9132335 Gees Mill Business Pkwy NE, Conyers, GA 30013
Forest Park(404) 361-24745158-C Kennedy Rd, Forest Park, GA 30297
Gainesville(770) 297-93352472 Hilton Dr, Gainesville, GA 30501
Lawrenceville(678) 442-10602111 Cedars Rd SE, Lawrenceville, GA 30043
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Macon(478) 474-85445527 Thomaston Rd, Macon, GA 31220
Marietta(770) 426-05511060 Triad Ct, Marietta, GA 30062
Newnan(770) 239-210570 Enterprise Ct, Newnan, GA 30265
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Savannah(912) 232-1228103 Central Jct Blvd, Savannah, GA 31405
Statesboro(912) 764-8841126 W Parrish St, Statesboro, GA 30458
Valdosta(229) 245-8200363 Connell Rd, Valdosta, GA 31602
Warner Robins(478) 953-3727110 Byrd Way, Warner Robins, GA 31088

South Carolina Locations

Hilton Head(843) 689-34043715, 21 Hunter Rd, Hilton Head Island, SC 29926

Florida Locations

Fort Walton Beach(850) 244-201776 Beal Pkwy SW, Fort Walton Beach, FL 32548
Panama City(850) 913-05853012 Lisenby Ave, Panama City, FL 32405
Pensacola(850) 438-10054405 N. Palafox Street, Pensacola FL 32505

Mississippi Locations

Hattiesburg(601) 579-96701851 Lincoln Rd, Hattiesburg, MS 39402
Ocean Springs(228) 497-5090Sunplex Industrial Park, 5717 Suntec Drive, Ocean Springs, MS 39564

Commercial Sales

Norcross – North Georgia Hub
(800) 282-4911

Birmingham – North Alabama Hub
(205) 250-7714

Macon – Southwest Hub
(800) 342-9250

Loxley – Gulf Coast Hub
(800) 239-7419

Savannah – Southeast Hub
(800) 822-7617

Commercial Parts

 CompanyWeb AddressDescription
Airzonewww.airzoneinc.comCustom and Underfloor Air Handlers
Aladdin Metal Productswww.aladdinmetalproducts.comCurb Adapters and Roof Curbs
Aprilairewww.aprilaire.comIndoor Air Quality Products
Autaniwww.autani.comBuilding Automation and Controls
Bardwww.bardhvac.comHeat Pumps,Gas/Electric, and Wall Mounted Air Conditioners
Bryantwww.bryant.comCommercial, Industrial, Residential Heating & A/C Products and Controls
Carrierwww.commercial.carrier.comCommercial and Residential Heating & A/C Products
Data Airewww.dataaire.comPrecision Air Control for Data Processing Centers
 DXairwww.dxair.comPool dehumidification systems
 First Companywww.firstco.comFan Coil Units
Global Plasma Solutionswww.gpshvac.comAir Purification and Bi-Polar Ionization
 Greewww.greeusa.comPTACs
 Hayes Fluid Controlswww.haysfluidcontrols.comHose Kits and Control Valves
 iAirewww.myiaire.comCommercial Air Purification using ionization with energy savings
 IslandAirewww.islandaire.comPTACs, Vertical Units, Water Source Heat Pumps
 i-Vuwww.commercial.carrier.comBuilding Automation and Controls
 Magic Airewww.magicaire.comFan Coil Units
 Micro Metlwww.micrometl.comRoof Curbs, RTU Accessories, & ERVs
 Modinewww.modine.comGas-Fired Unit Heaters, Duct, Furnaces, Hot Water Cabinet Unit Heaters, Makeup Air, and Dedicated Outdoor Air Systems
 Network Thermostatwww.networkthermostat.comInternet Thermostats, Wifi Themostats, Ethernet Thermostats
Paynewww.payne.comResidential Heating & A/C Products
Rawal Deviceswww.rawal.comContinuous Capacity Modulation and Dehumidification for DX Systems
Renew Airewww.renewaire.comFixed-Plate ERVs
Totalinewww.totaline.comCompressors, Parts, and Supplies
United CoolAirwww.unitedcoolair.comModular All-Indoor HVAC Systems
 Warren Technologywww.warrenhvac.comElectric Heaters
 Wilo Pumpswww.wilo-usa.comPump Systems for HVAC and Water Supply and Sewage