prototype 2 on 22/2/2

[solarbird]

A new, larger prototype for the wintertime heat/humidity recovery system for the dryer:


It's got four times the filtration surface area, and I've loaded it - if you can call it that - with a MIRV 1900/MPR 13 filter. That should be adequate for all the kinds of particulates we're going to need to care about from a dryer heat/humidity recovery system.

I've taken this step because I examined the previous, tiny-HEPA-filter based system, and found that not only had the charcoal completely reclogged across seven loads, the HEPA filter itself was pretty well at end-of-life, which explains the dramatically lower recovery rate over the last two weekends. Aand that's after only a month. Accordingly, we need something substantially longer-lasting, and a brute-force way to that is just to increase filtration surface size.

Also, such a short lifespan wasn't even really acceptable when that little filter cost $12. Now that it's costing $22 thanks to, well, everything - that seems a bit much.

So since we stock filters of this size anyway, I decided to try this one. It's a 14" square filter, actual size a bit less, and I'm calling the filtration area 13" square. That gives us four times - 4.1 times, specifically - the filtration area. If that gets us four months, I'm more than happy to call that an operating year, since really, you're not going to want this past March anyway. The question will be how much cleaning is needed along the way.

To that end, this version has a hinge on the bottom. Access to filter for cleaning is to take a layer of tape off the top, flip the filter down, and vacuum, which is obviously going to be a much better solution than in prototype nr. 1.

My biggest concern not already covered is the paper frame. The small filter had a plastic frame, which is one of the reasons I decided to start there. This one's paper, and even if I cover the outside with tape, the inside is still going to be, well, paper. Whether it'll stand up to the humidity is a very good question which we will very soon discover.

Of course, if this works in every other way, there's no reason that the filter we actually end up building can't more effectively enclose it, making its structural stability irrelevant. But, again: we'll see.

eta: Oh yeah, the black bits sticking out the sides of the filter are just excess charcoal I didn't bother cutting off. Nothing functional.

Comments

[armiphlage]

Would it be helpful to add a sheet of cheesecloth as a prefilter to catch the larger lint and extend the life of the MIRV filter, or would that reduce the airflow too much?

[solarbird]

I’ve certainly been considering something like that, yeah. I’m wondering if I could get ahold of some of the same material used on the old room air conditioners we had, and on the dehumidifier housemate Paul uses in summers. That would be perfect I think.

[solarbird]

Though that’s also what the charcoal prefilter I forgot to mention this time (except obliquely at the end) is partly for. That and scent control.

But I’ve been considering some kind of purely mechanical layer to make that easier to vacuum clean.

[stickmaker]

When I was experimenting with this concept I used a Kirby HEPA-rated sweeper bag (new, of course). I taped the dryer vent hose to the inlet of the bag (which was nearly the same size) and put this inside a pillow case, closed around the hose. Very little lint escaped, and the heat and moisture came into the house. However, it made the whole house smell like drying laundry. Also, as a single person I don't do all that much clothes drying. So I eventually reconnected the dryer hose to the standard vent.

[solarbird]

That’s what the charcoal prefilter is for. Works well, too. Probably helps that none of us use scented laundry anything, of course.

Also the difference between this system and anything else I’ve seen is the dual outflow. It makes the system a lot more controllable - and a lot safer in the event of too much outflow resistance!

[stickmaker]

Yeah; Tide Free, Bounce Free, etc.