e.alleg wrote:Why is the pipe made out of aluminum instead of steel? Also, what are the holes in the top of the pipe for?
In the beginning and for a short time, a brass pipe was used. Shortly after, in the '50s, the pipe was made from aluminum. Richard gave a great answer. Also, from wet coal and the heat from the pot, the heated mosisture would quickly corrode the steel pipe. From being unused in the summer, the two similar metals would corrode/rust together and could not be taken apart.
The holes in the pipe, which are meant to face upward, are to safely vent any coal gas back into the combustion area. Many people use only the short pipe and feed from a 55 gal. drum. This can result in coal gas being forced back in the pipe and out of the drum into the air. For this reason, it is necessary to use both the short and the long pipes for safety. We realize that this isn't always done.
gaw wrote: I think the 700 & 900 were a superior design and yet they were discontinued.
What is (are) the differences between the 520, 700, and 900? I see the manual for the 900 on the EFM site. Looks like a nice boiler/stoker. I do notice the right angle bin feed vs. the thru the back setup of the 520. What are the respective specifications of each unit?
I'm not sure where you saw the 900 on the website ????? The 520 is the only stoker produced now. The gross BTUH output is 220K and the net output is 186K. It has a wide range of BTUH output, depending upon how much coal is fed.
The 700 and 900 models are still available as used models and many parts are available. Mark's in Shenandoah, PA is one who has this end of the line.
I questioned our two 40+ year vets in this business about the frequency of pipes burning. Both agreed that it was extremely rare and always from owner neglect. It sometimes happens after an owner gets a load of new coal from a new supplier which may not be the same quality as a previous supplier. Sometimes, owners will not clean the ashes and they build up around the pot after filling the entire base and the stoker now becomes a forge. Also, the inexperienced owner is not watching his pot.
A stainless steel bin feed and burner end pipe is available for users who want a long pipe life. I think they are worth the small additional price.