Gentlemen.

Can anyone come up with a soulution we have
with our inductive heating elements burning out. At present they are only lasting weeks as opposed to years. They are made from incaloy and are installed in potable hot water tanks. We have two theory,s the first is that we are overdosing the water with clorine and this is causing rapid deteriation of the element sheath, The other is that when we go onto emergency power the unstable
frequency is causing the elements to burn out.

 

Are you sure these heaters are inductive and not resistive? I have never seen immersion water heating done with other than resistive heaters. If they are resistive, unstable frequency will do them no harm. They couldn't care less if you fed them DC. If they are on a time proportioned PID control, or on/off control with poor choice of differential, resistive heating elements can fail from mechanical fatigue caused by thermal cycling. If the incoloy sheath is inadequate for the water chemistry, you might consider Teflon sheathed heaters.

Steve Myres, PE
[email protected]

 

Frequent Heter failure There is only one reason---High element temparature.
This might be due to.
1. Over Voltage to the heaters.
---The working voltage might be higher than name plate voltage.
2. Occational water level going down below heater level.
3. Contamination of deposits on the heater because of poor water quality.
4. Wrong heaters,
---The heaters may be of same wattage but operating temp. might be high reducing the life of the heaters.
If the heaters warp and bend in shape, it could be an indication of over temparature.
Watch for the puncture point if happens around the same place you may have some more clue.
Best regards,
sekar

 

Heating elements are resistive and the only thing that causes a high failure rate is excessive heat. Check the water temp. for over heating and check the tanks for mineral buildup. Elements also can be purchased with stainless steel as the covering from "http://www.seemaheaters.com/":http://www.seemaheaters.com/ they have a great trouble shooting guide for imersion heater problems.

 

I have never heard of induction heating in potable water tanks, but that aside, I'll assume you really are talking about inductive heating and not resistive heating. In inductive heating your heating power frequency must be tuned to your load, otherwise you will heat your element and not your target. Simply put, you inductively heat the target by inducing eddy currents in it, and if you are not tuned to do so then you will dissipate energy in your inductive heating coil, not in your target, causing hot spots in the coil. If you are truly doing inductive heating, then you will have an inverter supplying high frequency heating power to the coil, so refer to the documentation of that unit. It should contain instructions about load matching. SCR type inverters usually have a multi-tap capaicitor that must be retapped to adjust the capicitance in parallel with the coil to match the load. Some of the newer IGBT inverters have automatic load sensing and matching, so if you have a new IGBT inverter, it may be malfunctioning.