Troubleshooting-- Vacubreakers

This piece of equipment requires an experienced electrician to repair. Do not attempt to repair this unit without the appropriate experience

You will need the following items to test the units: continuity tester, Voltage meter, Amp meter, and Ohms meter.

The lights on the sides of the units are to show which contactors are engaged. If you have a NEMA 4 unit you have only pilot lights outside and the contactors will indicate their engagement or lack therof by the buttons on the contactors pulling in or not.

If the fluid passing the thermostats is below their setting the thermostats close and create a circuit and activate the contactors. With normal operation at maximum flow or when you first turn on the switch all lights will be on …. all contactor buttons pulled in as long as there is water pressure coming to the unit. The lights and buttons will go on or off in series as the elements are engaged. The heater is designed to only use the thermostats, contactors, and elements necessary to heat the water needed at any given time.

Note: Where the heater fails to maintain the desired temperature you may be running the water faster than the heater is capable of heating the water.

Use the following steps to diagnose a problem.


Step 2: Check for any loose connections,

Step 3: Turn off the switches to the heater.

Step 4: Check the fuses on the elements for continuity.

Step 5: Purge the heater. Run water thru the heater to cool it down. This will reset the thermostats.

Step 6: Turn the water flow on by turning on the 110 control switch and pump. Turn the main breaker back on. Turn on the heater switches.

Check to see which contactors pull in. When you first turn on the right side switch the two contactors on the right side should pull in. If that is the case then turn on the left side switch to see if the left side contactors pull in and proceed to step 8. If the contactors do not pull in ….lights do not go on or the buttons do not pull in on the contactors … do the continuity test as shown in step 6.

Step 7: Testing the thermostats. Turn off the power supply at the chiller and the switches to the heater. CAUTION FAILURE TO TURN OFF ALL POWER COULD RESULT IN SERIOUS INJURY OR DEATH FROM ELECTROCUTION.

Because the thermostats are in series any thermostat that fails will prevent any thermostat after it in the series to work and correspondingly any later contactor to pull in and connect the elements.

The thermostats have two funtions: one to regulate the turn on and off side of the units and to act as a safety in case of overheating. The thermostat can fail if the contactor fails to close in time and the water in the chamber overheats and if it goes over 260 degrees Fahrenheit the fuse side of the thermostat will burn and the thermostat will never work again. This slowness to close will happen after the contactor has 100,000 plus operations because the contactor spring will weaken over time and it will be slower to close than when it was new. The thermostat will have continuity if the fuse side of the thermostat is still good.

The thermostats condition is determined by a continuity check AFTER POWER IS OFF AND AFTER COLD WATER HAS BEEN RUN THRU THE HEATER TO RESET THE THERMOSTATS.

Continuity is tested between the arms on the thermostat. Occasionally, you get a false positive on a thermostat. It may read as good but have a weak connection.

If a thermostat tests as “no continuity” the thermostat should be replaced and either the contactor should be replaced or the technician should determine what else could have caused the thermostat to fail. It is possible for the operator to shut off the cold water supply to the heater and blow all the thermostats but that is an abnormal occurrence.

The unit has a pressure switch to shut the heater down in that case but there is no 100% protection against air entering the unit on its restart.

Step 8: Ohms Test: If the contactors are pulling in and you still have bad performance(not hot enough, fluctations) you may have a failed element. Check each element with an OHMs meter for correct readings. If the elements reads 0 or flickers it is bad and needs to be replaced. If the failed element looks like it was split from the inside it probably failed due to air in the heater and you need to check the water source for a problem.

6KW 240 volts= 10 OHMS
6 KW 208 volts= 7.2 OHMS

Step 9: Testing the contactors
The buttons or the lights will tell you if the contactors are engaging. The buttons on the contactors pull in when they engage.

There is no legitimate test to determine the age of the contactors for how much life they have left.

If the thermostat has continuity the contactor should pull in. If the buttons do not pull in then the contactor needs to be replaced. If a thermostat has failed the contactor that is controlled by that thermostat should be replaced as the thermostat failure is an indication that thecontactor may have stuck in the on position.

Step 10: Checking for leaks

If you have a leak there are four possible reasons

1. A plumbing leak that can be fixed at the site. Pipes not tight or valve not tight.
2. The o ring on the element failed.
3. The o ring on the thermostat failed.
4. Other leaks from the exchanger which is a more serious problem that will probably require a factory repair. This an extremely unlikely situation.

Turn off the main power and all switches.

Take paper towel and dry off the heater. Take another paper towel to find the leak source….either around the element or the thermostat. If the leak is at the element or thermostat; then

1. Drain all water from the heater
2. Take the element out and examine it for damage and test it for OHMS see step 8
3. Test the thermostat for continuity.
4. Order a new element or thermostat
5. Put in a new o ring if neither part failed but there is a leak at the part. You should have some in your spare parts kit. If you install a new element o ring be sure to not overtighten the element on reinstall.

If neither of these is the entire problem the unit will have to be sent back to the factory.

Call us at 800 826 5537 for assistance if you have any questions.

If the unit is still not putting out the temperature of fluid you expect you need to do the following tests.
Set the temperature to a high enough temperature and flow level that the heater will need maximum draw to fulfill the task.

Test for full load AMP draw with an AMP meter after referring to the engineering chart on page 3 that shows FLA by unit size and voltage.

Shut the unit off and do an ohms test on each element as shown in step 1 above.

If all elements are good re do the continuity test on the thermostats. If they all have the proper resistance they are good and are not the problem.

If all the above checks out and you do not get the output you should then you should call us at
800 826 5537 for help or at any other time during this process.


If you are still having trouble please fill out the Troubleshooting form.  Filling out and sending us the form at the right will enable us to determine the status of your warranty and also allow us to prepare for the call from your electrician. You can fax them at 941-755-6529 or email them to This will expedite the process of getting your heater back into optimum operation.

Tankless, Inc. 2060 Whitfield Park Ave., Sarasota, FL 34243 Phone: 1-800-TANKLESS 1-800-826-5537
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