Tom M's posts

Bob, a drainback system does make sense in your scenario. You are heating up a very large tank of water. Having a heat exchanger that is large enough could be an issue. I have seen some large homemade tanks with many coils/ft of copper used for a heat exchanger. So heating that much water directly would be more efficient, just like heating a swimming pool.
 You mention you use antifreeze. If your holding tank is 500 gallons, how much of that is antifreeze?
 It also sounds like you only use the solar for heating. If you added domestic hot water to the loop, then I would definately reccommend using a heat exchanger to keep the circulation water separate from the domestic water. 

Steve, if all you want to do is heat the slab, skip the tank and the drainback scenario and just pump an antifreeze solution directly from the panels into the slab. You can incorporate a thermostat, differential controller or manual switch to turn the pump on when sun is available.
 You do not mention if you will be using a tank, so I am curious as to the location and type of drainback system you plan on using. Are the panels to be located below the level of the garage? If so, you could use themosyphon techniques.
 I would think that if you planned on purchasing SHW panels and some sort of storage, to be used along with a drainback SHW system, from which you will circulate water to heat the slab, that you would try to use the same system to gain domestic hot water.
 I usually install heating in series or in parallel with the SHW loop. I use the residual heat returning from the domestic hot water tank, returning to the panels, and send it into a heating loop. You can set up a bypass with a couple of valves for the summer and/or hook it up with it's own controller or aquastat and pump.   
 

Keith, sounds like you are looking for something like the "solar wand". Just do a search. Just be sure your outlet and inlet are at the top of the tank.

Kieth, sounds like you pretty much got it. As far as the fan installation location goes, as you said, bring the glass structure up just over the top of the foundation wall. This should allow you to drill into the framing into the crawlspace. Drill two holes, probably 3-4" one at either end of the sunspace. Mount the fan in/over one of the holes. You can leave the other alone or use PVC pipe or dryer duct to blow or suck the warm or cold air from whatever location you want.
 You can even add a hole or duct in the room above to deliver hot air into that space also.
 Good idea to use a small PV to power the fan. (Radio shack has decent 12 volt fans). You can add a thermostat in line also to make sure the air is hot enough. (Use cooling mode).
  As far as the black surface. Just use foundation sealer. This will also aid with moisture problems should the glazing structure be a little leaky.
 Glass or plastic, whatever you got. Double up if you can. Find some old doors or windows.....
 Also check your sun angle for maximum gain...think about using snow a a reflector.....

Elbie, does the hot tub have a heat exchanger or does it heat the water in the tub directly? If it is indeed a heat exchanger then your idea will work. If it does not have a heat exchanger then you may have to rethink.
 You said you are in a freezing zone so I would think that you would use an antifreeze loop. If the tub has a heat exchanger, then do as you said. Send the heated antifreeze into the domestic hot water heat exchanger tank and then send the return water into the hot tub, then back to the panels. Install bypass valves for those times you do not wish to heat one or the other.
 If the tub does not have a heat exchanger then you may have to draw the water directly from the tub to be heated. It should have a drain somewhere. Pump the water from the drain into the panels and back into the tub using a hose so you have an air gap to prevent syphoning. Modifying components may void warranties.
 Using this scenario, you could skip the domestic hot water and only purchase the panels, pump and piping.
 If you do not use the tub year round, add a tank, flush out the piping and panels and switch over to solar hot water the rest of the year.

Kieth, the best way to get your wife to agree on using some passive heating is to make her pay the utility bills. Then maybe she will agree to do things that will save money, despite aesthetics. I do not know of any links that show the method I mentioned, but it is pretty straight forward. Basically a small green house structure. Figure the foundation and the base would form an "L" shaped structure then add glazing along the diagonal closing it in. You can build it so it can be removed or so it is permanent. You could also use it as a hot box in the spring, if you have a garden, by installing the glazing so it can be opened and making the interior accessible.

Kieth, I usually do not recommend using solar to heat up the water directly from an electric tank. The two end up competing with each other. If the water is cold before the sun comes out, then the electric heats up the water. Then, if the water is already hot from the electric, the solar will not kick on. Best to keep the solar in it's own tank. If you live in a cold climate, then you would most likely have to use an antifreeze loop for the solar. This would require you to have a closed loop heat exchanger, either external or internal. Some modern heat exchanger tanks are stainless steel and have a lifetime warranty, so they should last. Then you would just have to deal with replacing the cheaper electric tank should it ever fail.

Howard, I would think inside would be better, or cover it up to keep out ice and snow.

Kieth, tanks today are pretty well insulated and can hold their heat overnight. Some tankless heaters are better than others but installation and operation cost, as others have pointed out, can be high. Having endless hot water can be costly too. Since you do not use much hot water, using a tankless may be the way to go. But think of future consequences should units need to be replaced or fixed. Parts or manufacturers may not be available.
 Adding solar, to be used in conjunction with your existing electric tank, could work out better. You can go with a smaller system since your requirements are low. Start with a 40-50 gal heat exchanger tank and a couple of solar hot water panels and this should provide all your hot water needs. Use the solar hot water to feed into the electric tank. If the water is hot enough then the electricity should stay off. Then you have all day to make up another tank of solar hot water to be used the next morning and you should end up with 80 gal of available hot water for almost free. 

Kieth, you could also consider adding a sunspace along the foundation of the crawlspace. Basically use the foundation wall as mass and add an insulated pad of cement extending from the foundation. Paint the concrete black and add a small greenhouse type structure from which cold air from the crawlspace can be drawn into and hot air can be pumped out of and back into the crawlspace.

Matt, something to consider for both cost reduction and increased reliability is to use several pumps in parallel. Pumps in parallel share the load so there is less stress on each pump contributing to longer life. If one pump fails then at least there are others to continue doing the job. Smaller, more efficient and even DC pumps could then be considered.

A creek nearby? If you cannot take water from the creek directly, either because of contamination or volume of water present, perhaps you can use the water itself in a condenser. It would work the same as your very powerful refridgeration unit you plan on buying. But instead of pumping R12 and using several compressors, perhaps you can pump the creek water through tubing or fins. Then you can return the water back to the creek. The cooled tubing would create condensation just as the "dehumidifier" type of device you are planning on using. Pumping creek water may prove more cost effective power wise.
  If the creek has enough flow and volume to remove the required volume of water needed, solar distillation, water pasteurization and filtration may be an option at little or no cost for power. Distribution can be solved using smaller DC pumps each with their own small PV and/or battery.
 

David, I just checked the link you suggested for hot water components. It seems they sell Crystal Clear collectors with their kits. These are AET collectors. They sell them here at the Alte store also. All the other components they sell are readily available at any plumbing supply. The $5000 price he gives for all these components is close to my base price for a complete installation. His price doesn't include shipping, piping and installation. So comparitively speaking, it looks like you still paid too much for a system through these middlemen. 

Patrick, in the grand scheme of things, your system is small so major damage from a lot of power is not to big a deal. If the inverter has a ground then just use that. All other component are connected so they too are somewhat grounded. The gound is an emergency negative so you would probably hook up any grounding lines to the neg. If you cannot find information here, Home Power Magazine has a lot of schematics you can look at.
  You can also/should install circuit breakers or fuses in line anywhere you think a surge may occur to protect any equipment. Shut offs or disconnects are something to consider also, especially in larger systems.   

Rene, are you sure you are using your multimeter correctly to read amps. Most meters must be installed in series with the wire you are reading so the current passes through the meter as if it were a resistive load.
 One way to explain this is to cut one of the neg. wires coming from the panel. Attach the pos. side of the meter to the wire coming from the panel and the neg. side of the meter to the other cut end going to your load or controller. Then set your meter to read current.
  Some amp meters have a loop you can put around the wire.
 

Patrick, take a look at the "Learn" section here. It has a wire chart that will help you determine the gage wire you need and how far you can run it base on the amount of amps you are drawing or you can find one easily online.
 You mention you will grow your system. You may also consider using smaller dedicated systems, somewhat like what you have now, to operate specific loads. That way there if you purchase panels in the future, and they are not compatable, you can hook the two systems up separately and reliablity goes up.
 As far as the 230 pump goes, it is 3/4 HP, so 750 Watt/HP x .75 HP = 570 Watt  and 570 Watt/ 230 V =2.5 amp. Or 570/12 V = 47 amp. Look for a metal tag on the pump itself. It should have the specs there. There may be a surge or startup current that is a little higher than this. This would translate into approximately 1/2 hr to 45 min max that you can operate this pump without degrading the battery.
 Then it would take your current setup of 10 amps at 12 volts approximately 8-10 hrs to recharge the loss on the battery.
 Hooking up your batteries in parallel is the same deal as the panels, all the negatives and all the positives connected. There may be some battery diagrams here in the learn section. Start with the ground connection then neg then pos. This way here there is alway a connection to ground while wiring and hopefully and current will go that way first.

Patrick, those stores should have them. They may call them a junction box. Or just look for what I described, several smaller contacts connected to one large contact. Actually what you are dealing with isn't that big a deal. The ten small wires can be connected to a larger wire using copper wire clamps.
 As far as current draw. At best, you are making 10 amps per hour. That's only 50+ amps a day. You can't expect to draw 500 W or 2500 W at 12 volts (40 - 200 amps) for any length of time before you drain your 100 amphour battery.

Jack, is the roof the only location you have? If you have a good ground location you can mount the panels so you can change the pitch throughout the year. If you have a flat roof, you can purchase or fabricate racks/mounts that are adjustable also.....

James, you got it, use the sun as the sun shines. Same priciple applies to solar hot water and heating......

Patrick, twist all the positive wires together and then all the negative wires together. Then tie each of those two groups to a suitable gage wire that can handle the ten amps total. (Usually you use an electical combiner box that has screw contacts, a bunch for the smaller individual wires and one for the total output wire that will lead to your PV controller.)

Ronald, AET panels are pretty much the standard supplier for hot water panels here east of the Mississippi, for now. They sell them here at the AltE store also. Tying in solar hot water in combination with radiant heat can be a little tricky unless you plan out your system ahead of time and install it in such a way so you can take advantage of both systems. You should also consider using it for your domestic hot water as well.
 I work out of Lowell and service the north shore area as well. You can find me at solarinnovations.net in Lowell. Just do search and send me an email from there and perhaps I can help you in your endeavor.

Tom 

Henry, all you have to do is dedicate a few or install a few new radiators to work with solar hot water. I assume the radidators are the old cast iron type. Basically, if they are already converted to hot water, just cut them out of the loop, bypass, and repipe them so that solar hot water goes through them. As mentioned you can either use the existing heater or add some new ones. If you do add some SHW panels you may want to install a tank to be used for domestic hot water the rest of the year. You can even combine the SHW loop for domestic with the radiators. Just install the radiators on the return line going back to the panels for residual heat or add a second controller or aquastat and pump dedicated to the radiators. 

Jason and David, I have already hit the books. I am a Mechanical Engineer and a Journeyman plumber. I have also worked on many of these systems in my years working in the solar hot water field and have had more problems with these systems than any other. Perhaps you should get yourself a thermodynamics and physics book and refer to it instead of using specualtion.
 As far as a slower moving fluid, just think of heating up a pan on the stove. Pass a volume of water over it fast and pass the same amount of water over it slow. Which volume of water will gain more heat? Also, Q = K *A *(T2-T1), the smaller the temperature difference between the two fluids, the less heat gained and transferred! The smaller the area, A, the less heat gained. So if you have a volume of water that is not changing temperature, the less heat you can gain. You cannot add 100 deg. heat to something that is 101 deg.
 And the TANK has to have a vent. If you suck water through a straw, similar to pushing it up with pump, if you block one end with your tounge, the water will not come out. It needs air pressure to remove the water from the straw. If the system was sealed as you suggest, the water would not move at all, since once you pressurize the tubing, the air in the tubing would push back from being compressed. Simple physics, action and reaction. You can pump water out of a bucket and return it to the same bucket without the water spilling out of the system, as you suggest it would, which is basically what the drainback tank is. So basically, if it were not vented, it would be a closed loop system, and therefore no need for a tank. Also when you consider efficiency, each heat exchanger lowers efficiency through heat losses to the surrounding, unless they are super insulated.

Jason, the reason there is no real temperature difference in the drainback tank is because of the amount of water in the tank that gets sent up to the panels to be heated. If you notice, when the pump turns on, most of the water in the drainback tank is sent up to the panels leaving very little water in the drainback tank. This indicates that the amount of water to be heated pretty much equals the amount of water that the panels can hold. Since you are heating a small amount of water it heats up quickly. The other reason the temperature stays steady is the heatexchanger area. It is this area that determines the amount of heat that can be transferred. The heat exchanger, I assume, is 1/2" tubing surrounded by 3/4 to 1" tubing. So if you know the length of the 1/2 tubing you can calculate the surface area and thus the heat exchange area. Also since the hot water from the panels is in the drainback tank, the tank itself, if not insulated, can lose heat to the surroundings.

 The newer technology that I speak of are heat exchanger tanks in which the heat exchanger coil is inside the tank. These tanks are available in 45, 80 and 120 gallons. The most common of these today are "Super Stor" tanks. If you check their specs, you will see the size of the coils and will see that the surface area is much greater than your drainback coil. And since the coil is inside the tank and exposed to and surrounded by the water you are trying to heat, the efficiency is much better.   As far as a more powerful pump goes, actually the slower the water moves the better. This give the heating fluid more time to absorb and transfer it's heat.

Jason, you are right. And as I and you said, most of these problems occur if the system is not properly installed. As far as the diff. temp., most systems operate on a 10-15 deg. differential regardless of where the sensors are located so there can be intermittent pump action. Try monitoring the system at startup to see if this is happening. The evaporation part usually stems from the drainback tank itself that has to be open to the atmosphere somewhere, usually in the form of a vent, in order for the water to drain back into the tank, otherwise the internal air pressure would not allow the water to return and refill the tank. The bleach scenario is correct too. The only drawback is if the heatexchanger coil has some rubber. The bleach will eventually eat it up. You can use antifreeze or a mix of antifreeze and water instead. This will reduce evaporation, bacteria build up and will keep your panels clean. It will also prevent corrosion on the inside of your panel piping that water can otherwise promote.
 Also I assume you have two pumps, one to circulate water to the panels from the drainback tank and one to circulate water from the storage tank to the drainback tank heat exchanger. So besides losing a little heat and efficiency, being an external heat exchanger, you are using a little more electricity running the two pumps.
 As I mentioned, these system do work and have worked for years. It's just that there is newer technology out there that increases efficiency over this older technology. Also if and when the time comes to service or replace the drainback portion of your system, parts may not be available.

The main thing I don't like about drainback systems is the startup. An empty panel get hot quicker. This turns on the pump. Once the water enters the panel it cools and the pump turns off and the water drains back. This cycle can happen several times before the water gets hot enough to keep the pump running and can lead to early pump failure. When draining back, syphoning can drain the water from the pump, if not properly installed, and can lead to pump failure also. If you are in a climate with freezing weather, trace amounts of water can be left in the collector which can freeze and cause leaks, once again if not properly installed. Most drainback systems are an external heat exchanges which can lower efficiency. Warm water in the drainback tank can also lead to bacteria build up if the water is not treated or changed regularly.
Water levels from evaporation from should be checked regularly to ensure that there is enough water for the solar loop. I usually say, "Use the system until it start to fail, then change over to a closed loop heat exchanger tank when the time comes."

James J., I believe in smaller dedicated systems myself. If you are just using the power gained for your own needs, why not have several, smaller, redundant systems operating instead of one, all purpose system. Then finding discontinued panels would not matter so much since each system would be specifically designed for a purpose and all panels could be purchased at that one time.
 Also, if one component fails in your combined system, then your complete system could be shut down. Smaller, simpler items for installation and operation may even cost less and last longer. Then component parts can be moved around if needed. Less complicated components may not be as fussy when it comes to adding mixed outputs.

Jerry, before you make your expensive purchase from the company you mention, check out the pricing here at the Alternative Energy Store for your panels and controller. Then check at your local plumbing supply for a double heat exchanger tank and other related plumbing materials needed. I think you will find that you can purchase and install a complete system for the price of purchasing only half the components needed from the source you are considering. At least then all the components will be locally purchased and easily replaced, rather than trying to deal with an overseas company, just in case anything is missing or goes wrong. Of course, check with your installer to make sure he is okay with your purchases or just hire an experienced plumber to help you with your purchases and/or installation.

Glad you got it going. Good idea with flare. I usually use a compression fitting with an insert to keep the soft aluminum from squishing. It may be cheaper and easier to use 3 or 4 ball valves in your piping instead of trying to find a 4 way valve. I usually set it up so you can use either your solar only, auxilary only or solar to preheat the auxilary. The condensation should eventually disappear with time as the panels get hot. It's probably from wet insulation that should eventually dry. Also, make sure the weep holes are clean and clear.
 It sounds like you have a tankless coil in your oil boiler. I usually install an aquastat control in the  domestic hot water line out to the house. I wire it to the incoming power to the boiler, bypassing the original switch. Then if the water is hot enough, the boiler stays off. Once the water gets down to 100 F or so, it turns the boiler on and the auxilary part of the system kicks in.

Frank, those panels are usually made with one contiuous piece of aluminum tubing run in a serpentine configuration. It is best to connect them in series so the water travels further through the collectors gaining more heat. This configuration will also prevent uneven water distribution between the two panels. Usually, the hardest part of installing these panels is finding a connector to attach to the aluminum tubing, since you cannot solder them. I service MA so if you have any further questions or problems just post here or give me a call. Tom, Solar Innovations, Lowell....just do an internet search.