Sunday, 23 February 2014

DIY ventilation maintenance

A couple of weeks later I went into the machine room. I think that's the best name for the loft with the power conditioners and the ventilation heat exchanger. That's all that's in there so the only reason to go is for the monthly cleaning of the filters or if the batteries need changing for one of the temperature data loggers in there. And of course whenever there's a problem from leaking condensate.

I just learnt that word from the Stiebel manual, which I've been reading to find how to clean the heat exchanger. The manual says in one place that it must be cleaned every three years, but elsewhere that it should be cleaned every year. The suppliers of leaky ventilation systems mentioned a three-year maintenance, and wanted us to sign a contract with them, which we did not. The system has been leaking for about the third time, and two weeks ago they came to fix it, which they did not.

I'd left a bowl under the system where it had been catching drips. I knew there would probably be a bit more water to drip through as everything dried out. I didn't expect it to be overflowing two weeks later, and still coming out after I'd emptied the bowl. I called the builders once again to tell them that the problem hadn't been solved. It was still leaking, a little less than before so it wasn't urgent for somebody to come, and since it was a snowy Friday, the following week would be fine. I got a call back to say he was in the area anyway and would be there at 6pm. He also said that the ventilation experts had asked me to contact them directly, which I'd evidently forgotten, misheard or ignored. Then a few minutes later another call came to say they'd be charging us. I asked why they'd be charging us this time, when they were just finishing the job that they hadn't done properly last time. Then I told them there would be no need to come, and I'd be in touch if necessary.

The first thing I noticed as I was following the instructions to get the heat exchanger out was that he'd put the filter back in the wrong way round. This is probably not a big deal if it's a clean, new filter, but it had been filtering a few weeks of crap from the air coming in, and since he put it back the wrong way round, that crap was all going to go straight into the innards of the machine, which the filter was supposed to protect against. My confidence is not inspired if he didn't know which way the air was flowing, or couldn't read the arrow on the filter, pointing in the direction of airflow.
Maybe I'm being hypercritical. I shouldn't be so harsh on these people who are innocently going about their business of importing European technology to Japan without properly understanding how it works.
Removing the bypass unit from the ventilation system revealed a large pool of water in the bottom, with a drain in the middle that was not letting anything through. A screw driver helped unblock this.
Once it was draining through the drain, it became apparent that the system was not level. The housing of the ventilation and heat exchange is all expanded polystyrene. Underneath the diamond-shaped heat exchanger unit there is a small reservoir with a drain in the middle. If I'd been designing it, I would have made it slope towards one corner and put the drain there. A few millimetres of water were still settling towards the front, so it wasn't very effectively draining. You can see the effect this has had of leaving a dirty residue. I remembered their boss saying that it was a good idea to drain the bath every night since the Japanese custom of keeping and re-heating bath water is an invitation to legionnaires disease. I'm sure he'll be shocked to hear about the stagnant pool of water he has installed in my house.

I don't know whether their failed attempt at fixing our problem was a gambit to get us to subscribe to a maintenance contract, or a genuine failure to fix it, but either way I don't think we've even got to the stage of maintenance. We are still dealing with getting a suitable system that has been correctly installed.

It sounds like the manufacturers are also culpable. This system was designed in northern Europen, and I think works very well there. Apparently there have been a lot of problems in Japan with systems leaking in the summer. The diamond-shaped heat exchanger fits in the middle of the unit, with air coming from outside going from bottom right to top left, then the air being sucked out of the house going from top right to bottom left. There's a collector and a drain in the bottom left chamber for the air being expelled during the winter, when it will be precipitating moisture. There is no drain for air coming into the house in the summer. This is not likely to be a problem in summer in Europe, where it is not so hot and not so humid. When it is high in the thirties and close to 100% humidity in a Japanese summer, there is going to be some precipitation on the other side, and no drain for it to drip through. Since hotter air carries so much more water, this could result in a lot more condensate than in the winter.
Another issue is that Japan just seems to have a lot more bugs, germs, particles and general small crap. The average temperature is significantly higher and presumably this just multiplies a lot of stuff.
But the real question is, is anyone really interested?

If they are, then there are immediate and long-term solutions.

Long term, the system should have more rigorous drainage, so that it will handle regular and irregular condensate, both from expelled air in the winter and incoming air in the humid summer. Parts should be easy to clean. Build-up of crap in the heat exchanger itself is inevitable, and it may be that a lower-cost disposable material would be cheaper, long-term.

Short term, we need to get our system level, so that there is no pool of stagnant water in there. Another possibility is to put a collecting pan in there, that would funnel water from the heat exchanger through the drain.

Even more short-term, and probably medium-term, I need to contact the suppliers, the manufacturers, or their agents in Japan, and try to get someone to take this seriously since heat exchange ventilation systems are crucial to low energy building, and it is bad news if they are being driven around by cowboys.