Periodically, PRIMUS receives calls from the field concerning a “blown” boiler heating element or some other related malfunction.

Most, if not all, premature failures can be avoided by following routine maintenance guidelines and paying strict attention to detail when inspecting, cleaning, and replacing the heating elements.

The vast majority of premature “blown element” failures are due to 1) poor water quality causing excessive scale build-up and 2) failure to properly tighten electrical connections to the required torque.

Boiler electrical connections can become loose over time due to the
frequent heating and cooling cycles a boiler experiences. Because of
this thermal cycling, boiler connections must be checked on each PM.
Just because a boiler has been operating properly before the PM is
not justification for skipping this critical step.

The information below is specifically based on a Sussman 24 kW
ES24A boiler, but is also generally applicable to all Sussman boilers in
the types and sizes PRIMUS uses.

All PRIMUS steam sterilizers shipped with an integral or standalone
boiler include a boiler Installation, Operation, and Maintenance
Manual. The unit-specific manual should always be used as a
reference when operating, inspecting, and maintaining the boiler.

Element Description

Unlike gas boilers that have gas burners to heat the water, industrial electric boilers rely upon metal heating elements. These heating elements are made of metal (stainless steel in the case of PRIMUS boilers) and get hot from electrical resistance, similar to what is found in an electric cooking range.

A typical PRIMUS 24kW boiler uses industrial grade, heavy duty 0.420 inch diameter stainless steel heating elements equipped with one-piece resistance welded terminations for added strength and safety.

If the required quality feedwater is supplied to the boiler and routine boiler maintenance is conducted, the heating elements should last a significant period of time depending on the sterilizer usage rate. On the other hand, a poorly maintained boiler using high-hardness feedwater can fail in a matter of days.

Basic Maintenance Requirements

For a 24 kW boiler, always allow a minimum of 21 inches clearance for heating element removal. If this is not done, the time and complexity of conducting routine inspections and maintenance will increase severalfold.

A monthly inspection should be made of the internal wiring. All electrical connections should be checked for tightness. A check for water leaks should also be made and any loose fittings immediately tightened.

A loose connection increases the amperage drawn by the element and
can melt the potting material used to seal the connection points of the
element. This will cause a leak and potentially ruin the boiler controls
as steam leaks into the cabinet.

Every four months, the heating elements should be removed. If scale has begun to form, the element should be cleaned and the boiler should be drained and flushed.

New bolts and a gasket should always be used when installing a new
element or re-installing a used element to assure proper sealing.

Electronically Testing a Heating Element

Operational Test

Before turning off the power to the boiler, an operating electrical test can be performed to indicate if problems are developing with one or more heating elements. Using all electrical safety precautions, do the following:

Carefully remove the cover and make an amperage measurement with a clamp-on amp meter, such as an Amprobe, to each of the 3-phase wires leading to the heating elements. The measurement should be made when the heating contactor is energized. Extreme care needs to be observed when making this
as a substantial risk of electrical shock is present when the boiler is operating. The amperage measurement should be similar from one phase to another within 10%. Typically, an element that is pulling substantially higher amperage on one of the three phases indicates either a high resistance electrical connection at the heating element or a heating element that is failing. A substantially lower amperage or no amperage on one of the three phases indicates a failed element.

Shutdown Testing

  • Turn off the power to the boiler at the main power panel. Turn the boiler switch to the “OFF” position.
  • Close the water supply valve on the incoming water supply line.
  • Drain the boiler completely of water.
  • Open the boiler door to access the heating elements.
  • Disconnect the wire (electric) leads connecting the elements to the main power system of the boiler. Note the wire connections to facilitate re-assembly (see the wiring schematic on the inside of the boiler box).
  • Remove and discard the (6) bolts from the flange.

Do not reuse these bolts! If old bolts are reused, a bolt can potentially
break off inside the flange and have to be drilled out and removed with
an Easy-OutTM. If this is not done properly, the threads can be
damaged and a leak will occur. The only option then is to replace the
entire boiler!

  • Remove and inspect the heating elements.
  • Using a multimeter, test for the proper functioning of the heating elements by checking for an “open” or “closed” circuit (continuity).
    • Set the multimeter to “Ohms” and connect the red lead to one terminal and the black lead to the other terminal on the heating element.
    • If the ohm reading is 0, there is no flow of electricity through the element and it needs replacement.
    • If an ohm resistance value is seen, then the heating element itself is not bad. The problem is likely somewhere else in the boiler controls.

Replacing or Reinstalling the Heating Element(s)

Thoroughly clean the boiler flange of all foreign material. Be certain no part of the old gasket remains on the flange!

Apply Slic-tite® paste (or equivalent) to both surfaces of a new gasket.

Install the heating element flange assembly with the new gasket between the boiler flange and the element flange. In doing this, be careful to align the flange holes so the element’s wire connection terminals on the element assembly are in line with the previously disconnected wire leads to facilitate easy connections.

Observe the markings on the element flange. Install the element
marking “TOP” on top.

Use only new element flange bolts (these bolts will come with a new heating element or can be purchased separately from PRIMUS). Tighten all (6) element flange bolts to a torque value of 22 lb-ft each.

Connect all wires to the terminals. Tighten all element terminals to a torque value of 20 lb-in each. Make sure all wires are clean and bright to assure good electrical contact.

Check that the wires are correctly connected to the contactor terminals and are tightened to a torque value of 45 lb-in. Make sure all wires are clean and bright to assure good electrical contact.

Open the water valve to allow the water supply to reach the boiler feed mechanism.

As the boiler automatically refills, observe the new flange assembly for possible leaks. If water is noticed, the bolts must be re-tightened. Before doing this, turn the boiler off at the main power panel.

When the boiler reaches working pressure, check the flange assembly again for leaks and correct any problems.


When buying a replacement heating element from PRIMUS, the part will come with the gasket, 6 bolts, and the gasket paste.

Replacement Heating Elements

The following heating elements are available from PRIMUS:

PRIMUS Part #Heating Element Description
800073Heating Element 20 kW 208V 3PH
800074Heating Element 20 kW 240V 3PH
800075Heating Element 20 kW 480V 3PH
800076Heating Element 24 kW 208V 3PH
800077Heating Element 24 kW 240V 3PH
800078Heating Element 24 kW 480V 3PH
801309Heating Element 12 kW 208V 3PH
800206Heating Element 12 kW 240V 3PH
801338Heating Element 12 kW 480V 3PH
800234Heating Element 18 kW 208V 3PH
801416Heating Element 18 kW 240V 3PH
800293Heating Element 18 kW 480V 3PH
800985Heating Element 18 kW 380V 3PH

Heating Element Gasket Kit

The flange is the same size and configuration on all the above heating elements. Because of this fact, only one common gasket, bolts, and gasket paste kit is sold. This kit is needed when inspecting and cleaning (but not replacing) a heating element.

PRIMUS Part #Heating Element Description
801419Heating Element Gasket Kit (gasket, 6 bolts and Slic- tite® paste)

Have a question or having difficulties? Talk to Dave Schall, our PRIMUS sterilizer expert who is here to assist you anytime at 877.679.7800 extension 1212 or email at

Visit us at

Back to Blog