Things that Work Home Power tests the Heliotrope PSTT 2.3 kW. Inverter, Model WF-12- 2300 test conducted by Richard Perez & John Pryor In the past, inverters have been weak links in our power chain. They were very prone to failure, and didn't work well. Well, those days are past. Heliotrope makes an inverter that works extremely well, survives gross abuse, and costs less than its worth. We like this inverter; it's built like a battleship! Test Environment We installed the Heliotrope in our shop on a pack of two Trojan L-16W batteries (12 VDC at 350 Ampere-hours). We used low loss 0 gauge copper cables with a combined length of less than six feet to feed the inverter. One of these cables is set up for current measurement, so we can measure the amount of current going into the inverter. Other instrumentation present to monitor the inverter's performance is a battery powered oscilloscope, a Digital Multimeter (DMM), and an iron vane type expanded scale AC voltmeter. Packing, Installation Instructions, & Owner's Manual The Heliotrope arrived in good condition being heavily packed. After unpacking we had enough styrofoam peanuts left over to just about insulate a wall in the shop. Shipping containers are important. Nothing is more disappointing than taking delivery on an inverter and finding it damaged in shipment. Heliotrope is obviously spending the money for first class packing so that this doesn't happen. The installation and operation instructions provided with the inverter are adequate. They could be better. I have discussed this with Heliotrope on the phone and they assured me that a new manual is in production and will be included with future inverters. Complete and organized documentation is essential in complex items like inverters. The manual we received with this Heliotrope was definitely complete, but too technical and lacks photos. Inverter Physical Examination The first impression this inverter gave us was one of solidity. It's a large, solid, heavy unit. The case, heatsink, circuit boards, and everything connected with the inverter are made from heavy weight materials. Heliotrope has not scrimped on quality hardware. The inverter is 14 inches wide by 18.5 inches tall by 5.25 inches deep. It weighs 56 pounds, which for its power class is very heavy. The Heliotrope has the best and heaviest hardware of any inverter I have ever seen. All exposed metal parts and fasteners are well painted or plated to resist rust and salt water environments. Inverter Installation The Heliotrope is designed to mount on a wall. We liked this feature as there is more space available on vertical surfaces than horizontal ones around here. The heavy cables that feed the inverter from the battery are connected in a novel manner. Most inverters use a bolt. You must attach a heavy ring connector to the battery cables in order to bolt them to the inverter. Heliotrope uses power connectors like the heavy connectors in AC distribution panels. These 4/0 -250 MCM connectors are inside the inverter out of harm's (and shorts) way. These connectors are like sockets. The heavy copper cable is inserted inside the connector and a lug is tightened to hold the wire in place. No need for ring connectors and the result is a high contact pressure, low loss, connection that is easier for the user to make. We simply inserted the stripped ends of our 0 gauge cable into the connectors inside the inverter and tightened them down. Heliotrope also uses two small wires that connect the battery to the inverter. These are in addition to the heavy cables that feed the inverter its current. These smaller wires enable the inverter's logic to measure the battery's actual voltage directly, without the loss present when running large currents through the main cables. This is a very nice feature, allowing the inverter to better control itself by more accurately monitoring the battery's condition. This Heliotrope inverter has a feature that is unique among inverters of this large power size. IT IS REVERSE POLARITY PROTECTED. This means that you can hook it up to the battery backwards and while it won't work, it also won't destroy itself. Try this with any other large inverter and you're looking at hundreds of dollars in repairs. We investigated the manual and found that this reverse polarity protection is accomplished by two large series diodes in the main power line inside the inverter. We also learned from the manual that the voltage drop across these diodes costs us some 2% in efficiency. The manual has instructions for bypassing the diodes and gaining more efficiency. We did this before installing the inverter. The reserve polarity protection is an essential feature for folks who hook and unhook their inverter regularly. Those who wire it once and leave it are advised to get the polarity right the first time and increase the inverter's efficiency 2% by bypassing the diodes. The Heliotrope inverter has the best connection methods for getting the 120 vac out of the inverter. Most inverters give you regular receptacle type female ac sockets. These are present, times four, in the Heliotrope. What is also present are standard wiring connectors within the inverter that will accept regular, 12 gauge, copper wire. While some other inverters offer interior hardwiring of their output, no one else has the size and installation ease of the connectors Heliotrope uses. The Heliotrope is a programmable inverter. It has a number of user selectable features that allow you to set it for your own particular needs. The inverter protects itself against the following conditions: over temperature, over current, too low battery voltage, & too high battery voltage. Each of these protection functions can be either manually reset by the user or automatically reset by the inverter's logic. We chose the manual reset for the first portion of this test. This is easily selected on a small DIP switch on the inverter's printed circuit board. The Heliotrope has two operating modes. One is called "Standard Mode" and the other "Battery Saver Mode". In standard mode, power is continuously available to run very small appliances like micro nicad chargers, electric clocks, etc. In standard mode, no load power consumption is 5 Watts. In battery saver mode, a 5 Watt or greater load is required to start the inverter. In battery saver mode, the inverter's no load consumption is 0.4 Watts and this is very, very low. Being basically tight with the electrons, we configured the Heliotrope for battery saver mode. Once we wired up the inverter and selected our operating modes, we were ready to fire it up and see how it works! Inverter Operation We ran the Heliotrope WF12-2300 for about five weeks in what we like to call "user testing mode". This means that we just used it; we ran whatever we liked off it without paying particular attention to technical details. The idea is to subjectively see how the Heliotrope performed in relation to other inverters we have used. We were not only surprised but very pleased with how well the Heliotrope worked. For one of many pleasant examples, Karen has a small hand mixer in her kitchen. No inverter we have ever used could spin this mixer as its ONLY load. At best, the hand mixer would sluggishly attempt to do its job. The Heliotrope not only powered this mixer, but ran it better than our ac generator could. This pattern of superb performance was carried through on all of our inductive loads. The Heliotrope inverter powers inductive loads better than any type I have ever used to date. Motors ran faster and cooler, the power supplies in our computer equipment ran cooler, and very small problem loads like electric scissors and electronic sewing machines ran as they never have before on an inverter. Well, after weeks of enjoying completely trouble free and transparent inverter operation we started to wonder how the Heliotrope worked in a technical sense. We went into the technical testing stage. We watched the inverter's waveform on the scope, in addition to making voltage and frequency measurements. We abused the inverter to see if it would, in fact, protect itself. It did. Here is a sample of the abuse we put the Heliotrope through. We used the following loads (ac load amperage draw listed in parenthesis): ShopVac (6 amps.), 7.25 inch circular saw (10 amps.), Blender (3 amps.), Split-phase bench grinder (5.1 amps. running over 25 amp. starting surge), and a motley collection of incandescent light bulbs (about 4 amperes worth). First we started out with the circular saw and the ShopVac for a total ac current load of 16 amperes. Then we started the split phase bench grinder. This is a brutal test. The inverter was already loaded to 84 % of its 19 ampere capability and we asked it to start the grinder. This split phase grinder motor is a real inverter killer, and draws in the neighborhood of 25 amperes when starting. The Heliotrope grunted once and the grinder started & ran. We were amazed. We then started ALL the aforementioned appliances, with the grinder being started last. We basically overloaded the inverter, demanded a super surge to start the grinder and it did it all! We were never even able to get the inverter hot enough to make its internal fan operate. The output waveform of the Heliotrope stayed incredibly stable over the entire test. Even when we grossly overloaded the Heliotrope, it did its job. We couldn't get it to change its output waveform no matter what, or how much, we plugged in. Voltage and frequency of the inverter's output are not only within Heliotrope's specifications, but according to our instruments better than their specs. In terms of gross wattage output, we were able to take well over the inverter's 2,300 watts out of the unit. By starting all the inductive appliances mentioned at the same time, we determined that the Heliotrope inverter does indeed supply surge power around 7,000 watts. The Heliotrope inverter's efficiency is just as specified. We measured input current and voltage and compared this to output current and voltage. On very small loads, under 50 watts, efficiency was around 85%. At about the 165 watt level the inverter was 95% efficient. At loadings in the 700 watt range the Heliotrope inverter produced efficiencies up to 98%. The Heliotrope inverter is as efficient as or more efficient than any make we have tested. We then tested the inverter to see if it would protect itself against too low or too high battery voltage. At about 14.5 VDC input, the Heliotrope shut itself off. On the low side, it turned itself off when the battery voltage fell to 10 VDC. Since the Heliotrope uses separate sense wires to the battery, these voltage switch points are very accurate and neglect losses in the main cables feeding the inverter. On the tech side The Heliotrope, Phase Shift Two Transformer (PSTT), inverter uses two transformers instead on one. The output waveforms of the two transformers are opposite and compliment each other. To quote their manual, "Depending upon the current draw, the phase position of each transformer is matched to provide a perfect push-pull for each cycle of the 60 Hz. power pulse..." The manual provides a very complete technical explanation of Heliotrope's new inverter design. What really counts to the user is that the PSTT design works better than anything now available with inductive loads like motors, power supplies, fluorescent lighting, etc. Inverter Overview and Other Stuff A thermostatically controlled fan is standard equipment on the Heliotrope WF12-2300, PSTT inverter. At 2,300 Watts, it is the highest output inverter we know of that has a 12 VDC input. It is very simple to operate. If automatic mode is chosen by the user, then there is only one on/off switch to deal with. The installation of this inverter is relatively simple and no one should have trouble hooking it up. No battery charger option is available with this inverter. All details of the inverter's operation are indicated by a series of nine LEDs on the front panel. Remote control of this inverter can be accomplished easily via terminals already present on the inverter's printed circuit board. Other inverters charge extra for remote control functions. Inverter Warranty Heliotrope has the following warranty for this inverter, and I quote from their manual. "These products carry a 10 year warranty. During the first year replacement of defective merchandise with a tested replacement will be made at no charge. For years 2 through 5 replacement will be made for a service charge not to exceed 25% of the current list price and for years 6 through 10 the fee will not exceed 50% of the current list price." Conclusion We like this inverter. The Heliotrope PSTT inverter powers inductive loads better than any type we have tested to date. Heliotrope's new two transformer inverter design concept really works! This inverter is beautifully made; every part in it is of the highest quality. Heliotrope has obviously spared no expense in construction of this inverter. It meets, and in many cases exceeds, Heliotrope's specifications. We tried to kill it by overloading and couldn't. This inverter has a retail price of $2,300, and is a very good deal. At $1. per continuous output watt, the Heliotrope is priced in line with other inverters. Considering its excellent performance and the very high quality of its hardware, the Heliotrope PSTT inverter is an excellent value. Write: Heliotrope General, 3733 Kenora Drive, Spring Valley, CA 92077, or call toll free inside CA (800) 552-8838, & toll free outside CA (800) 854-2674.