CF Series troubleshooting.

Trouble shooting for electricians

CF series ….Electromechanical heater models

CF-12, CF-15, CF-18, CF 24, CF- 27, CF-36, CF-48, CF-54, CF-72, CF-81, CF-90, CF-108, CF-120, CF-144

These instructions are only for qualified electricians.

There are three main working parts in these heaters….elements, thermostats , and contactor. There also is a safety mechanism called a pressure switch(#9 on the picture below) and delay switch (#8 below) that will delay the heater turn on if there has been a water pressure loss. The delay switch on all eyewash or safety shower heaters must always be set to -1 which means no delay in unit turn on after there is 3 PSI to the heater. This delay switch is there to delay turn on of the heater up to eight minutes(actual delay depends on the setting) after a pressure drop to less than 3 PSI. If the heater is not turning on at all check the pressure switch for impediments ….dirt or whatever and replace the pressure switch . All heaters have basically the same parts and the larger units just have more and larger elements.

The picture below shows our CF 144 unit in a non NEMA 4 box. The same parts exist in all CF series units.





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

Download and print the product manual from the website. All operating manuals are published on the
tanklessheaters.com website. They can be located as part of the troubleshooting area or in the product
specifications area for the unit you purchased. In that manual is a troubleshooting area for each type unit.

Read the manual -especially the trouble shooting area and view the heater in operation so you can respond to
questions from the factory.

Download manuals here

CF Series Manual


The optional lights on the sides of the units are to show which elements are engaged. If you have a NEMA 4 unit you have only a pilot light outside. You will have to open the door to observe the units operation.


The pressure switch and optional flow switch are part of the control circuit. If this control circuit is satisfied the contactor will pull in and power can flow thru the thermostat and on thru the elements to ultimately heat water.


The thermostats activate the elements. With normal operation at maximum flow or when you first turn on the switch all elements will be as long as there is water pressure coming to the unit. The lights will go on or off in series as the elements are engaged. The heater is designed to only use the thermostats and elements necessary to heat the water needed at any given time.


Fluctuation in temperature can often be remedied by a simple adjustment of the outflow valve on the left side of the heater or it can be a more serious problem. Fluctuation in hot water, lukewarm water, or no hot water at all,are almost always signs that indicate element or thermostat failure.


The units are not wired in series so failure of one part does not debilitate the whole unit. The heater will not perform as well as it should.


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 1: Turn off all power supply CAUTION FAILURE TO TURN OFF ALL POWER COULD RESULT IN SERIOUS 
           INJURY OR DEATH FROM ELECTROCUTION.

Step 2: Check for any loose connections, properly operating breakers, etc.

Step 3: Turn off the switch to the heater.

Step 4: Purge the heater. Run water thru the heater to cool it down. This will reset the thermostats.

Step 5: Turn the water flow on. Turn the main breaker back on. Turn on the heater switch.

When you first turn on the switch the contactor should pull in. If that is the case then proceed to step 7. If the contactor does not pull in ….lights do not go on


Test the pressure switch continuity across the posts.

Step 6: Testing the thermostats.

Turn off the power supply at the main breaker and the switch to the heater. CAUTION FAILURE TO TURN OFF ALL POWER COULD RESULT IN SERIOUS INJURY OR DEATH FROM ELECTROCUTION.


The thermostats have two functions: one to regulate the turn on and off side of the units and two to act as a safety in case of overheating. The thermostat can fail if 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. 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 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 some or 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 7: Ohms Test:

If the contactor is on 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
5.3 KW 208 volts= 8.2 OHMS
5 KW 240 volts= 12.2 OHMS
4.5 KW 240 volts= 13 OHMS
4 KW 240 volts= 15 OHMS
3 KW 240 volts= 19.5 OHMS


Step 8: 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.

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 7
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.

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 info@hotwaterheater.com 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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