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  • by Aki Yoshimizu

    “The party went on till past midnight but the heater remained hot forever…”

    Triple Skin Contraflow Heater in Japan

    See report, above, for details on the construction of this heater, built in July 2013 by MHA members Brian KIipfel and Norbert Senf. It is the MHA Portfolio 22″ contraflow, hybridized
    with the Austrian Triple Skin System.

    Below is an initial performance report from Aki Yoshimizu, who attended the 2013 MHA Meeting at Wildacres and invited Brian and I to Japan.


    November 29, 2013

    Hi Norbert,

     My apology that it took so long, as I have been flying around lately.  It’s been so eventful the last couple of weeks.
     Here is how I operated the heater during the weekend:
    Friday, 1 pm    Outside temp 7-8 C, inside temp 4-5 C (colder inside) Loaded 25-30 lbs and tried to fire up but failed.  I opened the clean-out door to check draft then smoke blew into the house.  (that’s when above the loading door got dirty with smoke, even some smoke leaked thru the gap of the door / air intakes of the loading door.  So I will need more gasket around the door, )  I should have checked the draft first.  I then pre-heat the pipe with a torch for a few minutes until it started sucking air in, then second attempt was successful.  The fire went out in 120-150 mins and after  I made sure that there was no charcoal left I shut off the damper.  Started feeling warmth around the firebox in 60 mins and the area spreaded bigger in six hours or so.  By 10 pm the heater surface was reasonably warm but not enough to heat the house at all.  I was still cold even if I stood by the heater.  I had to put on one of the kerosene heaters to make it habitable.
    Fire 2:
    Saturday, 8 am   Outside temp 3-4 C, inside 14-15 C.  The heater surface was slightly warm but colder than the night before.  Loaded another 30-35 lbs and it started right away with no struggle.  The firebox was very warm to begin with.  Took 150-180 mins to burn out, and the facing got pretty hot by noon and started heating the room nicely.  Inside the oven was too hot to touch.
    At 4 pm the guys started showing up, and I loaded 3 lbs of seasoned beef in the oven.  They were shocked to find out that the heat was from the morning fire.  It was comfortable with a T-shirt already.
    Fire 3:
    At  5 pm? Outside temp 6-7 C, inside 20-22 C   I loaded 30-35 lbs (filled the firebox all the way up to the  box ceiling with dry wood with some air space) it burned well.  I knew that it was too early to lite up in order to maintain the same temperature, but I wanted to show the guys the heater with fire.   By 6 pm the surface got too hot to keep touching, and within 3 feet from the heater it was so hot that we had to stay away.  I shut off the damper again at around 8 pm.
    The roasted beef was done by 5:30 pm (cooking time 90 mins) and all the four guys, Yuji Kada(gardener from Nagoya),  Shinobu(Fiskars), Eiji(stripe shirt at the workshop in summer), and Ono gathered by 7ish.  I shoved a small tray of Nacho chips with cheese and cooked it for 5-7 mins, and then  a big piece of sea food pizza for 15 minutes.  Pizza crust did not get so crispy but the cheese got deliciously browned with bubbles.  The food was so enjoyable and I kept receiving admiration.
    During the supper it got so warm that we had to stay away from the heater, or even opened the patio door for fresh air.  The party went on till past midnight but the heater remained hot forever.
    At around 9 pm I went upstairs to turn on the inline fan  and opened the damper for the radiant panel of the bedroom in the middle.  (just one panel for that weekend, as I was keen on keeping the maximum heat in the heater in a way…) The room’s floor had been warmed up so it was warm enough to begin with in the bedroom.  We all went back there in an hour or so to check the temperature of the panel.  The cement board was nicely warm and the steel frame was too hot to touch.  The whole room was comfortable to sleep.  However, I noticed that some water kept dropping from the joints of the duct.  It was obviously condensation but I suspected that inside the heater was still super wet.  Will keep an eye on for the next time if the water is from the heater’s moisture or just general condensation.
    Fire 4:
    At 9 am Sunday, the heater was still very warm from last night but the facing was touchable.  Yuji loaded 30-35 lbs and ignite just for the picture taking and cooking lunch later.   At the same time  I boiled some water for soup, and toasted a dozen bagels for breakfast and it worked well from the remaining heat.
    At 2 pm I cooked 4 lbs of lasagna in an aluminum pan and it took 40-45 minutes.  It got nicely browned with sauce bubbling, and inside was also cooked well.  We enjoyed the last meal together and the guys left after the late lunch.
    It kept heat through the night, I was comfortable the whole night without firing.
    I left early Monday morning but the heater was nicely warm and the room was warm too, probably 18-20 C when I got up.  I was reluctant to leave anyway.
    It had not hit the coldest period yet, but I’m positive that the heater would be more than adequate for the house through the winter.
    The weekend was above zero the whole time, 2-3 C at night 6-8 C with plenty sun shine at day time.  In January it can get -15 a couple times in the season, normally -10.  I’m so looking forward to going back to use the heater again especially when the real winter comes.   The beauty of it is that everything in the room gets warmed up:  walls, floors, door handles, even china in the cup boards.  Our body was warm internaly, it felt like standing in the sun.    All the guests were owners of a wood burning stove but they were all astonished by the masonry heater’s performance.
    Well, that’s about how it worked.  If you have questions or if I missed any results that you wanted to find out, please let me know.
    Warm regards,
    Clockwise from closest person:
    Shinobu Seki: ????
    Eiji Daigo: ??????
    Takeo Onozawa: ??????
    Aki Yoshimizu: ?????
     Yuichi Kada: ??????