DXMachina (dxmachina) wrote,
DXMachina
dxmachina

  • Mood:
  • Music:

Paging Dr. House...

What a lovely day. This morning, looking out my kitchen window at the large patches of lawn visible amidst the remaining drifts while the sun shone on my face, it felt like spring. Yesterday was very much the same. The temperature helped, as it got up into the low fifties. Shirtsleeve weather! Well not really, but I was able to do things like go to the mailbox, replace an exterior light bulb, and haul stuff out to the truck without wearing a jacket. So nice.

The warm temps let me do a couple of repairs that I wouldn't have done if it was colder. The first thing was to replace the weather stripping on the side door so I don't have to keep stuffing athletic socks into the gap between the door and the jamb on cold days. I'd put the old foam stripping on it the first winter I was in the house, and another layer on top of that a couple years later (and that's all on top of the plastic stripping that is part of the door itself), so it all had to be peeled and scraped off. The old stuff was 1/8" thick, so 1/4" thick total. I replaced it with some 3/8" thick stuff. We'll see how wind proof that is. One good sign is that I now have to lean into the door a little to close it properly.

The next warmth related thing I looked at was my heating system. You may remember that last year I had to replace the pressure relief valve on the system because the gasket had gone on the old one, causing it to leak all over my basement floor. I did finally find a new valve, but the new valve leaked as well, albeit not so much as the old one had. I just kept a bucket under the drain pipe to catch the occasional drop I was getting, and made a mental note to investigate further at a later time. Which I never did. Instead, I just lived with emptying the bucket every weekend.

Flash forward to Christmas, when I happened to mention the problem to my brother, who pointed out that if the relief valve was still leaking, then either I'd bought a defective valve (unlikely, but it was the only thing I'd thought of at that point), or else there was just too much pressure building up in the system for some reason, and the leaking gasket on the old valve was just a symptom rather than the cause of the problem last spring. D'oh! I felt exactly the same as I imagine Dr. House (such an appropriate name in this case, too) feels when he discovers he's yet again misdiagnosed a patient. (I have a long rant coming eventually about House, and yet I keep watching it.)

Anyway, I figured I could divine what the real problem could be at my leisure, i.e., wait until until spring, but unfortunately, winter finally went from cold to really, really, cold. With the system running almost constantly, I was having to empty the bucket almost every day. Clearly I had to do something about it. Constantly carrying buckets of water upstairs is murder on the back. Off to Google I went.

Our patient is a hydronic heating system, which is a fancy way of saying it uses forced hot water to heat the house. There's a diagram here that, although it differs in the location of some of the details, is pretty close to what's in my basement. Now here's the basic problem. The system is made up of sturdy copper pipes full of water, which is a liquid, and is therefore incompressible. That would be perfectly fine if the water stayed the same temperature all the time, but the whole point of the sytem is to heat the water, which causes the water to expand. If you don't do something about that expansion, those sturdy, not-terribly-flexible pipes will eventually burst. (Of course, the same thing happens if you freeze the water, except it's even worse, because ice expands a LOT. Water is tricky stuff.)

Anyway, one way to address this is to add our old friend the pressure relief valve to the system. The pressure of the cold water entering the system is usually around 12.5 psi. The pressure relief valve is triggered when the water in the system gets to 30 psi, which should be well below the point at which the pipes burst. That's good, except you wind up with water all over the floor, or in a bucket. You're also wasting energy, because the released water is already hot, while the water that replaces it is cold. If only there were some place in the system that the water could expand into rather than leaking out onto the floor.

Well, there is. It's called an expansion tank. It's a four gallon steel tank with heavy duty rubber diaphragm or balloon inside it, that acts almost like a tire tube. The balloon is connected to the outside world by means of a tire valve in the bottom of the tank. When it's installed, the balloon is pressurized to 12.5 psi, i.e., the same as the cold water in the system, so everything is in equilibrium. Then as the water gets heated, it expands into the tank against the balloon. Since the balloon is filled with air, and air is compressible, it compresses, allowing more water into the tank, until the air pressure inside the balloon matches that of the water. When the water pressure goes back down, the increased pressure in the balloon causes it to expand, forcing the water back out of the tank, until the system is once again at equilibrium. And since the water flows into the tank at much lower pressures than the relief valve triggering pressure, there's no water all over the floor. Pretty damn clever, those hydronic engineers.

The thing is, as anybody who rides a bicycle can tell you, even intact inner tubes can slowly leak air. Eventually the balloon can deflate, and there's nothing to push the water back out when the pressure goes down. When that happens, the tank acts like any other part of the rigid piping system, and the only way to moderate the pressure is by having the relief valve, er... relieve itself. Get out the wet-vac.

In my googling, I'd come across a list of the top ten reasons why pressure relief valves discharge, and four of the top five had to do with the expansion tank (and the fifth was a bad valve). So down to the basement to see if was the tank. The first thing I did was just tap the bottom half of the tank with a screwdriver to listen to the sound. A steel tank with only air in it should give a ringing sound when it's hit. All I got was a dull thud. Liquid dampens sound. Next I uncovered the tire valve in the bottom of the tank, and pressed the valve with my thumbnail. There was no pressure inside the balloon at all. I had a waterlogged expansion tank.

Now to fix it, all I had to do was repressurize it, but that can only be done if there's no pressure coming from the water side of the system, which means I had to turn off the furnace and release the pressure in the system. That's why I wanted to wait for a warm day to do it. So, I levered open the relief valve, attached my air compressor to the tire valve on the tank, and turned it on. Water streamed out the open relief valve. Yay! (Yes, I did have a bucket under the valve...) The meter on the compressor actually doesn't read low enough for 12.5 psi, so I kept it up until the needle moved off the 15 psi mark, figuring that I'd release some of the pressure when I was done. It looked like everything was going great. Then I put a tire gauge on the valve to test the pressure, and a bunch of water came squirting out of the valve. That's not good. It means the diaphragm/balloon itself is leaking, since there's no other way that water could get inside there, which means the tank is toast. Bother.

Fortunately, it seems to be a very slow leak. I closed up the relief valve, refilled the system with water, and turned on the furnace. Everything seems to be working so far. The relief valve didn't discharge at all overnight, and the tank still pings when I tap it. There's still a ton of air in the water side system which I have to bleed out, the result of the draining and refilling, because besides being a lousy conductor of heat, air in the pipes is annoyingly noisy. Come the spring, I'll get to reacquaint myself with my long unused mad sweat-soldering skilz. I was going to reroute the flow of the system anyway, so I can replace the tank as part of that project. Joy.

Afterwards I did some straightening up, this time in the living room. I finally took all the Christmas stuff up to the attic, and since I was up there, I hauled a couple boxes of junk down from the attic and out to the truck so I can toss them. There's still a lot to be done up there, but at least I've gotten started.

I also did some online shopping. I've been working on a mix CD of songs about baseball, so I ordered a used copy of the soundtrack from the Ken Burns documentary. And I finally found a place that not only sells my favorite style of sneaker, the super-comfortable Etonic Trans-Am Trainer, but also had my size (12W) in stock. I found them at Bob's Store a few years ago, and loved them, but they eventually wore out. Bob's doesn't seem to carry them anymore, and I hadn't been able to find them elsewhere. I ordered them from shoeseeker.com, which I'd never heard of before, but it turns out the site is owned by the wife of the CEO of Etonic. Bookmarked!
Tags: clothes, house, music, weather
Subscribe
  • 8 comments
  • 8 comments

Comments for this post were locked by the author