Tom Ramcigam (magicmarmot) wrote,
Tom Ramcigam

The Big Broken Box™ has hydronic (hot-water) heat with old-school radiators. As much as I prefer that over forced air, there are some disadvantages with the system because it's a conversion from an old gravity fed system that reacted differently.

When we first moved in, we bought the house as-is, knowing that it needed some serious work. The first two weeks I spent redoing almost all of the plumbing from galvanized steel to copper, and I had to do some pretty major electrical work as well just to be able to live in the place. That being said, those were the immediate major things that had to happen; after that, there was some fiddling with a new water heater, having to install a new boiler (an expensive lesson in boiler operation, thankyouverymuch), tearing down the old garage, adding a new roof and the new front porch that have been taking up the huge chunks of house-time.

Jeebus, when I think about all that's been done to the house since I moved in, it's a whole hell of a lot. There's still more to do, but it's a much better house than it once was.

The first time that I tried filling the boiler, it turned out that the radiator in the kitchen was cracked and had to be pulled. What that means is there is no heat in the kitchen at all, except for what comes from the oven and filters through the rest of the house. And since it's on the opposite end of the house from the boiler, it stays colder than just about everything else. There's also only one thermostat for the entire house, which is really crap. When it's cold outside, the bedrooms and kitchen get nearly unbearably cold, and if it's reasonably warm, they get too much heat.

What I really need are heating zones. Each room should have its own thermostat (or something equivalent) and a control valve to regulate the flow of hot water to the radiator in the room. That way the heat will remain a lot more even, and the whole heating system will be much more efficient as it can deliver heat to where it's needed instead of trying to fill the whole house at once.

Of course, that sounds really expensive. That's because it is expensive. It means tearing out the existing heating plumbing (and the asbestos that's swathing it), routing new plumbing as necessary, adding zone valves (electrically-operated valves), thermostats, wiring, and a zone controller. It also means adding some heat-radiating devices to the kitchen (I'd really prefer radiant floor heat) and other rooms as necessary. Radiant floor heat in the bathroom sounds decadently delicious-- and since heat rises, that also means a warm toilet seat in the cold, cold winter. Faboo.

Now when I did the tear-out of the old boiler and re-did the plumbing for it, I designed it specifically for adding multiple zones and radiant floor heat. It was a bit of foresight on my part, knowing full well that I'd be making changes and expansions to the system as I went along, and I'm so very glad that I did now.

But do-it-yourself zome heating systems aren't exactly readily available. Ready-made zone valves are bloody expensive, and trying to find a zone controller is the internet equivalent of butt-ugly. Not to worry though, because my background is in control systems engineering, and I have the knowledge and a lot of tools.

I can make my own zone valves by retrofitting ball valves (that I can get from 'Nards or Home Despot) with gearmotors (that I can get surplus, amazingly just like the ones I got for the animatronic tentacles for last year's CONvergence facade, not that I bought ten of them for that very reason or anything) and a little bit of sensor/gate magic.

As for the controller (the "brains" of the system), doing embedded systems programming is my current career path, and has been for some time. If I choose to use thermostats, the controller is really pretty simple, and could be built with a few logic gates-- or even a diode array.

But if I choose to go with a thermal sensor in each room-- basically a digital thermometer-- I can do a more sophisticated controller that hooks to the network and can be set by accessing it through a web browser. It can be programmed to reduce heat during the day and bump it up at night before I come home, and I can add nifty features like looking at the outside temperature and humidity to see if bringing in outside air would help cool or heat the house instead of relying on manual flopping of the air conditioner and heater and the like. A whole environmental control system instead of just a heating controller.

And really, it's still a pretty simple system. The whole thing boils down into a state machine, with a set of inputs (temperature in each room and outside, humidity, a clock, etc.) and a set of outputs (zone valve and pump controls) with the programming to handle the state transitions. Hell, it's a single-thread infinite loop.

There are things to consider, like valve faults and power outages and boundary conditions, but those are the same in any system.

Blah blah blah blah Ginger blah blah blah...
Tags: Big Broken Box™, mcgyver

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