As many tales begin, once upon a time.... I decided to take deLight to Europe. One of the issues to deal with was the difference in electrical power. Europe is 220v 50 cycle while the US is 110v 60 cycle.
Since all of the deLight's continuously used item were 12v, my idea was to buy a 80A battery charger that ran on both 110v and 220v, install a minimal 220v system (battery charger and a few outlets) and use my 1200w inverter to power my intermittent 110v electrical requirements (power tools and kitchen appliances).
I purchased a conversion kit with electrical adapters, plugs, etc. designed for travelers. In this kit was a 1500w 220v to 110v converter. It was a small square adapter so I took it apart to see what it was. It was a simple TRIAC circuit exactly like a lamp dimmer set to 1/2 brightness. Hmm... I could use this for my water heater instead of replacing the element.
I set all of this up and tested using a 240v outlet at the marina before I left. Everything worked fine. The little TRIAC converter nicely provided power for the water heater, the 80A battery charger and 1200w inverter provided 110v whenever it was needed. I was ready to go!
Well, I decided to cross the North Atlantic, Halifax to Horta, in October -- 28 days - 27 of which were storm rigged. I arrived in the Azores wet and exhausted. I plugged the boat into shore power and discovered that neither the battery charger nor the 1200w inverter had survived the trip. No power for my tools to repair them either.
After a few days in a B&B to recuperate, I purchased a 1500w transformer to replace the 1200w inverter and returned to a normal life. The little TRIAC converter was working fine so I had 110v power AND hot water.
Trouble -- The subject of this post -- started not long after. The little TRIAC converter was made for intermittent use on things like hair dryers. Powering a 1200w water heater for an hour or more was not what it was designed to do. It would overheat and blow its fuse. So, I whacked out a big chunk of aluminum heat sink from my dead 1200w inverter and mounted the little circuit board and TRIAC to it. By this time, I had added a small 220v electrical panel to the boat and I replaced the circuit breaker I had used for the water heater with a switch and fuse. I figured that the circuit breaker was too slow to protect the TRIAC by itself. A fast blow fuse would work.
Success -- for a while -- occasionally (every few months) the fuse would blow for no apparent reason. I decided that the problem was probably the TRIAC. It was rated for 15A and I thought 10A continuously in hot weather was maybe too much for it. So, I bought a 25A TRIAC and the next time the fuse blew, I replaced the TRIAC. The more powerful TRIAC had a higher gate current so I had to replace the resistor and capacitor with different values. I had a good stock of resistors and used a couple of capacitors from my junk box.
It worked fine -- for a while -- The next time the water heater quit (a couple of years later), I went to check the fuse, it was blown and and the fuse holder crumbled when I took it out. I purchased a couple of 0.1uf ceramic disk capacitors to replace the ones from my junk box which I considered questionable. I put them in and modified the circuit slightly to improve its stability.
A couple of years ago, the fuse and fuse holder were again blown and crumbled. I replaced them and changed the resistors so that the voltage output which read on my meter as 100v was reduced to 70v. As I thought that the problem might be related to the capacitors not being temperature compensated, I ordered some 1% film capacitors to replace them.
Last October shortly after I returned to the boat from a summer away, the fuse blew and the fuse holder fried. I went to replace the capacitors and discovered a cold solder joint on one of the capacitors. I decided that was the problem and just fixed the solder joint.
This morning, I awoke to the smell of burning electronics. Guess what -- my nose lead me to the fuse holder on the 220v electrical panel. I burnt my finger when I touched it. The fuse holder was cooking but the fuse was not blown -- badly warped but not blown. Again I replaced the fuse holder. I replaced the ceramic disk capacitors with the 1% film capacitors. I reduced the measured output voltage to 50v and replaced the 15A fuse with a 10A one.
I am going to order a diac as it is the only component (of the 6) that has not been replaced in the 10 years I have been dealing with it.
What I do not understand is:
Why does the fuse holder get hot and burn up without blowing the fuse? When the water heater is running, the fuse holder is slightly warm to the touch. I would expect it to be. There is contact resistance in the fuse holder and the fuse itself has a little resistance.
If it is a temperature issue, It should happen whenever it gets hot. It seems to happen when it warms up although having a year or more between incidents makes it difficult to remember the exact conditions in which it happened previously.
A mystery!
OK, In my previous posts I wrote about things that have worked and stood the test of time. The TRIAC converter sort of worked but definitely did not stand the test of time. I only continue to deal with it because I purchased and installed a 1500w transformer. In hindsight I should have installed a 2500w transformer. There is not physical room where I mounted the 1500w transformer to replace it with a 2500w one without major rework.
Besides, life would be boring without a few mysteries to solve.
Max
