December 6 , 2002
Trolls Under the Bridge
As I reported in the last journal, I discovered that the heating system was thermosyphoning from time to time. The fluid in the pipes is only suppose to go in one direction: from the solar collectors to the tubing in the sand bed. This is what occurs while the pumps are running, but at the end of the day after the sun has set, the flow sometimes reverses and the heat contained in the sand bed starts heading back out to the collectors. This should not happen though because of a simple device called a check valve. A check valve is nothing more than a piece of hinged metal that closes to prevent a back-flow from occurring. Some nights the system works just fine, while other nights things go wrong. I can only conclude that I must have trolls under the bridge.
So, when I returned last weekend I took the panel off of the box under the bridge to get a closer look at the check valve, much to my demise I discovered that both pumps were oozing the lifeblood of the system: glycol! Being the nontoxic variety of glycol, the stuff is not cheap and the thought of it leaking out of the pumps had visions of dollar signs running through my head. (Instead of sugar plums.)
It seemed to drip more frequently over night when the temperatures began to drop into the low teens. This leads me to believe that the bronze pump housings and flanges must warp just enough for the drips to begin as the temperatures drop. I tried tightening the screws that hold the pump housing together and discovered that brass screws don't like torquetwo of them snapped right off! So off to the hardware store to pick up some "C" clamps. The "C" clamps have temporarily stopped most of the bleeding, but not completely. It looks goofy, but at least it is helping.
I probably should have followed my intuition with these pumps a few years ago. They gave me problems from the beginning. One of the two original pumps wouldn't even turn and I had to dope up the gaskets to keep them from leaking the first time I installed them.
I called up the manufacturer of the pumps and found out that the pumps have not been manufactured for over ten years and parts are no longer available. I could try to fabricate new gaskets and drill out the broken screws, but I could do all of that and they still might leak. Plus, I thought when I purchased these pumps I could get replacement brushes, but such is not the case according to the manufacturer. So I either replace them now or later.
|Here's a photograph of the added loop with the check valve. The flow comes in from the top, down the left pipe, up through the check valve and then down the pipe on the far right. For this process to reverse, it's going to take a lot of work!|
So I have elected to do some major surgery and change out the pumps. The new pumps to be installed are much quieter and will be installed inside of the house instead of outside. (I'm not sure if extreme temperatures played a role in the demise of the pumps, but I'm not taking any more chances.)
Since I have band-aided the leaks for now, I may elect to wait a while to make this change. The system is running fine at the moment and the fluid loss is less than a teaspoon of fluid per day. The weather is also a factor. It's pretty darn cold as of late with low temperatures near zero. Doing plumbing outside when it's that cold is no fun. We'll see what mischief the trolls will bring for next week.
In the mean time, I did fix the thermosyphoning by installing a second (temporary) check valve inside of the house. When I built the system, I left an option to add a heat exchanger. (A heat exchanger is typically used to heat a hot water tank using a solar heating system. Plans are to install this handy device next spring some time.) To solve the problem, I used the pipe nubs to attach a loop of copper pipe with a new check valve. So far, the new check valve has stopped the thermosyphoning.
Unfortunately, I spent a lot of time working out the kinks in the solar heating system so I didn't finish the wall this week, but I did get a chance to try some more "experimenting". Without adding any sawdust nor paper, I attempted various amounts of cement retarder to prevent the mortar from cracking. No matter what formulas I tried, cracks still occurred. I believe this is the case due to the humidity levels inside of the house. With cold outside temperatures heated to 70 degrees, the humidity levels are similar to the desert. I was also quite frustrated by the lack of "stickiness" to the mixes. The mortar will not readily bond the wood. As far as I'm concerned, using cement retarder is a dead issue. Knowing what I now know about PEM (Paper Enhanced Mortar), there is no substitute and why use more chemicals when there are better alternatives?.
Speaking of PEM, after having a frustrating week, I decided Wednesday afternoon to mix some good old' fashioned PEM. The trick was going to be how to slurry paper (in a hurry) without making a mess of things. During the summer months, I soaked 75 LB bales of shredded newspaper in 55 gallon drums and then slurried half of the barrels at a time, leaving it to drain in another (perforated) 55 gallon drum. Once it was drained, I used a cement mixer to mix the sand, paper and masonry cement. This worked great outside the house, but to do this inside the house would make for a big mess.
to the slurry boardA new process
I decided to mix the paper fresh. No soaking, no overnight draining. Much to my surprise and delight, I may have stumbled on to something here. I use my 15 gallon barrel to slurry smaller amounts of water and dry, shredded paper. It takes a bit longer for it to slurry, but it does slurry. The drained, slurried paper is then mixed with sand in a wheel barrow with a hoe. Once the sand and paper are mixed, the masonry cement is then added. No water, there's enough in the drained paper.
I don't want to sound to euphoric here, so I won't...yet. I'll reserve my exclamations for later once the wall is set up. But I can say that the workability of this mix is astounding. It sticks to everything.
TREC - The Renewable Energy Cat