Hello, I was excited to build my new rocket mass heater and before I cobbed it all in I decided to give it a test. We could not get it to draft so we stuck a hair drier in the clean-out and warmed up the pipe and even started another fire with the hair drier still in the cleanout (Cover on). Then it would draft and start to heat nicely. When we took the hair drier out we thought it would continue to draft but it didn't, no matter how long we did this it still did not want to draft. Smoke just came rolling out. The stove is in an L shape,6 inch pipe, 11 feet on one end and 8 feet on the other. Distance between heat riser and top of barrel is 1 1/2 inches. Heat riser is 8 inches wide. We have it piped out the side of the house 9 feet up. Any Ideas what I can do? Thanks!

Attached are 3 pictures.

Hi Mark, first thing to check is that your chimney/pipe has a good natural draft. If the chimney is taller than the tallest portion of your house roof, then the chimeny pipe should have a noticeable draft present at the bottom most clean-out that attaches to your RMH's bench pipe.

Is your RMH built in a basement location by chance? Such tends to be problematic for achieving a good chimney draft.

1.5" riser top to the barrel top is a minimum for a 6" system. However, most prefer to go for a 2" gap at that point, especially when using an 8" I.D. heat riser.

What are the inside dimensions of your J-tube, i.e. feed opening, and burn tunnel height and width?

Thanks Byron, the RMH is in the basement and is vented out the side of the house just below the floor on the second level.

1.85 " riser to top of barrel 8" riser.

Feed opening is 6" x 7", J-tube is 6" wide 4.5" high and 27" long.

Thanks!

I am no expert ,but I have three thoughts on this looking at your pictures.First you might try taking 2 sections of pipe off near the 180 degree turn.This could improve your draw by shortening the overall length .Also as a general rule the chimney should be 2 feet above anything within 10 feet.If its still possible to shorten your burn tunnel that could help too.

Mark Meier : A basement location is more than problematical! Google Stack Effect and Whole House Stack Effect! This is not a Nice to know exercise -but a real world condition

that you are bumping your head up against .

I am glad that you tried your system before you cob'd everything in, As a working rule you should Count on no more than 30 horizontal feet for a 6'' RMH System, and 50'

for a 8'' system. Every Horizontal Elbow counts 5' against your system ! This includes horizontal connections in your final vertical chimney.

Your RMHs Final vertical Chimney needs to rise to a point at least 1 stove pipe length above the peak of your roof, ideally it needs to be on the lee or downwind side of your house.

Because your RMHs present location is in the basement make sure all windows and doors are closed, and do not run your clothes drier, or any Fossil fuel fired hot water heater

that is vented to the outside OR the exhaust fan over your Cooking Stove or the exhaust Fan for your Bathroom !

Especially if these steps cause your problem to go away- you seriously need to reconsider your RMHs location ! For the good of the Craft ! Big AL

Mark Meier : You really need to remove the outside barrel to the out doors and burn or grind the paint of off it Before you make any further attempt to

run your RMH with the original pant on its outside ! This nasty stuff will give you and other family members a Massive Headache and will reduce everyones desire

to ever want to use this heating system ! Big AL


Late note and a link to a Barrel prep video ! ///// Link Below :

OK, I suspected that this was a basement build, which are very difficult in most cases to achieve satisfactory performance from an RMH. In any "normal" installation having a good naturally drafting chimney system is an important criterion. Once the chimney problem is addressed, then I'd heed the advise the guys have presented before proceeding with the build.

A few notes, adding to that already mentioned by the guy's posts above.

Since the feed (opening) measures 6 x 7 inches, the burn tunnel should be the same. 6 W x 4.5 H burn tunnel will be susceptible to clogging with ash and coals. Better to have the burn tunnel taller than it is wide if it must be unsymmetrical. Since this is a 6" system (bench ducting size) I'd go 5.5 x 5.5 to 6 x 6 inches throughout the feed and burn tunnel. Doesn't have to be exact, and even 5 x 6 inches (width x height) will work.

When an RMH is working correctly and come up to full operating temperature, any paint left on the outsides / top of the barrel will burn and out-gas toxic fumes. So do clean the barrel of paint, at least the exterior, if that hasn't already been done.

Al is correct about the bench being to long for 6 inch ducting. The size of your layout is more along the lines for an 8" system (8 inch J-tube rocket with 8 inch bench ducting). Otherwise, if you intend on staying with 6" bench ducting, I'd shorten the bench run by removing the two long parallel pipe sections that connect to the 180 hairpin turnaround. HTH.

Thanks guys, I will first work on shortening the horizontal length and less bends to see if that makes any difference. Then look at the burn tunnel. Thanks, will let you know what happens.