Installing an ICS Batch System for Mild Climates

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If you live in a mild climate, you can install a simple ICS system because you don't have to worry about freezing conditions and super hot conditions. Even if these conditions are rare, you can still install an ICS, if you take a few precautions.

Figure 12-2 shows a simple and effective system for preheating the water that goes to your existing domestic water heater. Over the course of a sunny day, the water in the collector heats up from solar radiation. Due to the insulation, heat doesn't exit the system anywhere nearly as quickly as it enters. Because of the thermosiphon effect, hotter water migrates to the upper copper tube (even when no water flows, the heat will flow) so that the water that ultimately flows down into your water heater tank (when a faucet is opened in the house) is the hottest water from the collector.

Whenever somebody opens a hot water tap in your house, that much water is pumped through the collector, into your domestic hot water tank.

Collectors heat the water directly, so they're a significant part of ICS. Figure 12-3 shows two different versions of typical solar collectors. The collector on the right-hand side shows the more common arrangement. It offers some distinct advantages. The large diameter, black finished, copper tubes beneath the glazed cover (and insulated from the frame) are connected in series so that water flows from the bottom to the top (such collectors are mounted at an angle). Each of the copper tubes can typically hold 10 gallons of water.

A 3' x 8'-unit holds 30 gallons of water and collects about 22,000 Btus for an average North American day. Cost is around $1,500 for the collector, about $2,200 if you add in the cost for pipes, installation hardware, and labor for installation. Larger units are also available: A 4' x 8'-unit holds 50 gallons of water and can collect 30,000 Btus per day. Cost is around $1,700, plus installation. Or you can expand to two batch collectors by plumbing them in series, but you need to mount the second system physically above the first in order to get a proper thermosiphon effect.

Batch Collector

Figure 12-2:

Batch water heater supplement system.

Batch Collector

Water Supply

Insulated Supply Pipes to Roof

Drain Valve

Hot Water Supply

Residential Water Heater Tank

Water Supply

Hot Water Supply

Residential Water Heater Tank

Insulated Supply Pipes to Roof

Drain Valve

Figure 12-2:

Batch water heater supplement system.

Complete kits include all the valves, plus the collector and its associated mounting hardware. If you do opt to do it yourself, give some serious consideration to how you'll lift the collector (even empty, they weight a lot) wherever you plan on mounting it. The collector can weigh upwards of 500 pounds when full of water (which means the units can withstand winds of up to 180 mph!). Make sure that your roof can take this weight. You don't want to find out the hard way that it can't.

If you mount heavy collectors close to the edge of your roof, the rafter load will be easier to handle because the load will be directly over a load-bearing wall. And if you mount one of these collectors right near your water heater, you can use as little as 8 feet of tubing to complete the system.

Here are some considerations to keep in mind concerning the valves:

1 Draining the system: Valves drain the water when freezing is a possibility for more than a day or so. Note the bypass valves, which allow water to bypass the solar collector and revert to normal, hot water tank operation. The valves may be controlled either automatically or manually.

Heat is a problem as well. These collectors can burst if the water gets too hot, so drain the system when experiencing extremely hot, sunny conditions. Or turn a hot water faucet on in the house (just a little will do) to be on the safe side. If you don't have a temperature probe in the water line up at the collector, you aren't able to tell how hot the water is. When in doubt, drain the system. Consult the user's manual for your collector to get some advice on when this is appropriate.

i Locating the drain valves: Make sure to locate the drain valves where children won't open them up and get scalded. For safe drainage, locate the drain valves outside; they may look exactly like a hose faucet. You may want to consider some kind of locking valve that requires a key to open.

i Controlling water temperature with a tempering valve: The tempering valve is critical. It mixes cold water with the heated water from the collector when the collector water exceeds a certain temperature. This prevents scalding water from entering your household plumbing system. Always use a tempering valve in your system and never buy a cheap one.

i Testing water temperature: You can always find out how hot the water in the collector is by sampling from the downstream drain valve. Learn your system performance, and you'll be rewarded.

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