Maintaining a Sengoku Kerosene Heater

This is my fourth winter using only kerosene heat in my Indiana house and the 15K BTU Sengoku OR-77 I bought in 2011 is still in use although I trade up to a 23.5K BTU model for the really cold days. I’m three years past the warranty expiration on the smaller one and I’ve run into enough maintenance issues that I understand the importance of having a backup. Things do go wrong and they tend to go wrong on the days when you need the heater. After this much use I can totally recommend the product, brand and concept, so here’s a link to Sengoku Kerosene Heaters on Amazon.

Maintenance issues come up in predictable stages. The worst problem, a water-logged wick, can be delayed if you filter the kerosene through a water filter funnel like Mr. Funnel, something I use all the time now.

I used to recommend putting a spoonful of pure isopropyl alcohol like HEET in every tank of fuel, but over the years I’ve noticed that it has no effect on wick life. In fact, the more HEET I use in the fuel, the faster the wick waterlogs. I became so convinced of this that I did some research. HEET was developed to remove water from the fuel systems of internal combustion engines, not the wicks of kerosene heaters. In a car engine, when alcohol mixes with water and fires off in the piston chamber, the water turns to steam and exits through the exhaust. In a kerosene heater’s wick there’s no mechanism to expel the water. The alcohol burns off but the water stays behind. If you put HEET into a kerosene heater’s tank, it picks up water off the bottom of the tank and carries it to the wick. So don’t do that. Use a water filter funnel and skip the HEET.

After a few tanks of fuel have burned you’ll notice the stove behaving differently. The flame won’t burn as perfectly no matter how much you mess with the wick height. This is when you need to let the stove burn out thoroughly, and you can only do that outside the house. When the tank runs low, turn the stove off and take it outside. When it cools, siphon as much fuel back into the storage container as possible. Then light the stove and let it burn dry. This could take several hours and the low flame will produce dangerous fumes, so do this in an open space. When the flame is completely out and the heater is cool, raise the wick as high as possible and brush the wick clean with an old toothbrush. All the black tar should have burned away, restoring the wick to nearly pristine condition.

If this doesn’t fix the problem, it’s time for a new wick. Locally, one of our hardware stores offers to do this for twenty dollars and the wick costs about the same, so I do this myself but I don’t recommend that everyone do this themselves. The original manual is a little misleading and the procedure is awkward. Click here for a revised and much more sensible version of the original Sengoku OR-77 Owner’s Manual. Follow this link for a complete list of replacement Sengoku Heater Wicks

When I replaced the wick the first time, two years ago, I found three problems. The wick holder ratchets up and down in a vertical shaft and the back side of this shaft had some corrosion on it that kept dragging on that part of the wick. I polished everything with emery cloth but I’m sure it’s only a temporary fix. Teeth on the adjustment gear were wearing down, making the safety shutoff very touchy but still usable. The heater filament for the electric starter had also burned out. Fireplace matches were a cheaper solution than a new electrode.

Putting the heater back together wasn’t easy. Seems at first that you need three hands and even so there’s no answer to the problem, but if you persist and read the manual several times it is possible. I followed directions precisely and the stove exactly met specs, but in spite of this it did not work right. After disassembling, assembling and testing it a half-dozen times I finally made it work right but I had to play with standards a bit.

If I followed instructions precisely and set the wick in the holder so that the inked line was level with the holder top, even at maximum height the flame was too low. Best setting, achieved by trial and error, was 1/8 inch higher. This might be a printing error on the wick.

When reattaching the burner base to the stove, with the four wing-nuts, don’t over-tighten them. Just put them on finger-tight and check to make sure the wick holder sits exactly in the center of the shaft well. If it’s canted even slightly to one side the wick will drag there and the flame will not burn evenly.

So, having done this myself and having learned all the problems that can arise, would I trust this to somebody working in a hardware store’s repair shop? No. I would definitely do this myself because I check things and make sure they are right. For twenty bucks, someone else would replace the wick, but it probably would not be right the first time.

Five years seems like enough to expect from this heater, and when some of the essential parts need replacement I will buy a new one. The most important lesson I’ve learned from using kerosene heat the past several winters is that these stoves have to work right. If the flame is too high or too low, you can’t breathe the air in your house. It’s cheap, efficient heat — last winter I paid $120 for fuel — but you can’t ignore problems.

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About JTHats

Avid backpacker and outdoorsman with old skills and interests in old ways of doing things; equally fascinated by electronics, from the days of Sputnik, to the Zilog Z80A, to the present day of black box circuitry. Sixty years of experience with growing my own food and living simply. Certified electronics technician, professional woodturner, woodcarver, and graduate of two military survival courses -- Arctic and Jungle.

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