PEX solar panels

[xpertpc]

That looks pretty nice so far and went to town with 10 copper pipes, what did you use as a backer board to screw the plates to? don't forget to mount with a slight slope so the tubes will drain.

 

[2.beans]

first i used a scrap piece of 1/2 inch plywood, then topped that with 1 inch foil back insulation, then laid the wirsbo plates on top and screwed them down thru the insulation to the plywood. i ripped down the scrap insulation and lined the inside sides with it. i just need to paint it and drill and screw the glass door on and im done. what did you mean to keep it tilted so the tubes will drain? thanks

 

[Wallyworld]

Looks nice, are you going to paint the inside with flat black barbeque paint?

 

[Wet1]

It looks nice (although quite costly for DIY)! What insulation did you screw the plates down to? The reason I ask is because the panels will reach temps in excess of 250° and your insulation will need to be rated above this temp since they are in direct contact with the plates.

You'll want to tilt the tubes or collector so everything has a slight slope to it, this way everything drains back during the coldest weather... The bottom headers MUST be sloped so everything drains back.

Since you've gone top of the line with this collector(s), you might want to spend the extra money on a selective coating rather than black bbq paint.


Nice job, I'm looking forward to your seeing your results!

 

[2.beans]

im at $226 so far. thats with buying enough screws and 1/3 of the wirsbo plates to build the next one. im not sure on the heat rating of the insulation, i didnt put that much thought into the 250 plus temp. thanks for pointing that out. i dont know if i could change it now without breaking something. i already bought the high heat paint and used some so i guess ill stick with it. if it fails i can always take the glass front off and repaint. thanks for the much needed input.

 

[2.beans]

without sounding too dumb about the drain back, i planned on draining this in the winter. this would give me room to add treatment to my system every spring. each collector holds 1 and 1/4 gallons of water. the collectors are going to be at my shop which is 250' from my 1000 storage tanks. when my super store tank (dhw 45 gallon tank) calls the panel will directly heat the dhw, if there is no call it will dump into the 1000 gallon storage. i guess im not to sure on how the drain back works. i wasnt planning on doing it with a drainback because i burn wood in the winter. in the worst case if this doesnt work like i hope i can put the panels down at my pool and try to heat that. thanks.

 

[Wet1]

im at $226 so far. thats with buying enough screws and 1/3 of the wirsbo plates to build the next one. im not sure on the heat rating of the insulation, i didnt put that much thought into the 250 plus temp. thanks for pointing that out. i dont know if i could change it now without breaking something. i already bought the high heat paint and used some so i guess ill stick with it. if it fails i can always take the glass front off and repaint. thanks for the much needed input.

Regarding the cost of the solar system, checkout the following link. It does a good job showing how big of an impact cost is when considering the payback. You'll need to know some basic info about your system to get accrate numbers, but either way it's kind of neat to see how build cost impacts payback.

The heat paint should be fine. The idea of using the selective coating is to increase efficiency, but you'll be fine w/o it... and it should hold up well over time.

without sounding too dumb about the drain back, i planned on draining this in the winter. this would give me room to add treatment to my system every spring. each collector holds 1 and 1/4 gallons of water. the collectors are going to be at my shop which is 250’ from my 1000 storage tanks. when my super store tank (dhw 45 gallon tank) calls the panel will directly heat the dhw, if there is no call it will dump into the 1000 gallon storage. i guess im not to sure on how the drain back works. i wasnt planning on doing it with a drainback because i burn wood in the winter. in the worst case if this doesnt work like i hope i can put the panels down at my pool and try to heat that. thanks.

You kind of lost me here. How are you going to configure your system? Is it going to be a batch, thermosyphon, drain back, or closed loop system? Here is a LOT of info on solar hot water heating design which you might find very helpful...
http://www.builditsolar.com/Projects/WaterHeating/water_heating.htm

Also, if these panels are going to be located 250' away from your storage tanks, I would think you would have huge losses given the delta T and distance.


BTW, those small panels will not do much for heating a pool, unless it's pretty small.

 

[2.beans]

its going to be a closed loop system. im going to try to ball valve my boiler off or out of the system, and circulate the water thru two panels with a taco 011 to the storage. the undergroud piping is 1" pex. i would like them down at the house but i dont have a real good place for them besides at the pool. that also is an option, id have to dig up the lawn and run a new line into the house. you think ill loose too much heat in 250' feet with a 011? i dont loose any with the wood boiler, i know its apples and oranges though. ive been reading on build it solar, i did find one estimate for a yearly payback. at that rate it could pay for itself in a coulple years if i run it the way id planned. thats good right? if it gave me june, july, and august off from messing with wood that would be priceless. i think im enjoying the learning part more then any savings that this could offset. ive definitely wasted more money on worse things.

 

[Wet1]

Well if you're doing a closed loop system, drain back/tilting the collectors is irrelevant. I would suggest using a non toxic antifreeze, but since you switch over to wood in the winter, there's no point... just make sure it's easy to drain the solar system.

I would think you'd have a lot of heat loss running that distance. Remember, this is something that only runs a few hours each day, so it's not steady-state like your wood boiler basically is. If the collectors are over sized enough for your application, then you can probably get away with it, but I would think it's far from ideal when you consider the flow and amount of time these solar systems operate at.

Your payback of a couple years could be right, I have no idea what your numbers are. With that said, the delta T on the DHW during the summer is much lower than it is in the winter, plus you're only talking about three months of the year, so I would think the payback might be significantly longer... especially when you factor in the cost to run the Taco 011 for several hours each day. BTW, watch the flow rate with that pump and those relatively small panels.

Either way, it looks like your panel is coming out very nicely. It's a neat project and a real slick learning experience, I'm looking forward to seeing more pics as the project progresses. :coolsmile:

 

[2.beans]

i have my system setup with a three way zone valve at the tank side if the 250' run. the zone valve is controlled by the boiler temp or the panel temp. i im installing a temp sensor on the panel thats immersed in the water so it will only turn the circulator on when it hits its desired temp. then when the circulating water is to temp it will open the three zone valve. i dont know yet what to adjust things to but im sure that will be a learning curve on its own. so until the zone valve opens id be heating maybe 10 gallons of water. does that make any sense? i do this to stop the mixing of the water in the storage tanks. it seems to help my stratification by only letting hot water into the tank. i filled my panel with water to check for leaks and fixed the two that i had. i was going to paint it but now im getting chicken. im thinking i need to add some pressure to it to make sure im really all set.

 

[Wet1]

I see what you're doing. That should work fine in theory. What I suspect might happen in reality is the circulator and zone valve might end up being cycled a lot due to the losses from the long run and the relatively low temps we're talking about with two small panels and high rate of water flow with that circulator. Either way I'm sure it will work, you're just going to be taking a pretty significant hit in efficiency/performance.

Since you're using a closed loop system, you should absolutely pressure test your panels since they will see pressure in the field... it will be a PITA to fix leaks within the panels once they are painted and buttoned-up.

 

[xpertpc]

I pressure tested mine (just the grid) while sitting in the full sun for several days, one leak didn't show up until the grid expanded and contracted many times. My pump is a 4 gpm and although it seemed to work it was slow to heat, I throttled it down to 1 gpm and it worked much better. Most commercial unit specs I have looked at were rated between 0.5 - 1 gpm.

Are you putting street water or tempered preheated water back into the collector? The 250' pipe will hold 10 gallons and may not completely empty into your dhw tank if the collector cools down and pump stops. I see exactly what Wet1 is saying in the above post happening. At least you would be preheating the dhw inlet and should save a bit of money.

To stop short cycling you would need a temperature controller with hysteresis so you can turn the pump on at 120F and off at 90F or there about or maybe even an off-delay timer to keep the pump running for 10 minutes after the temperature is satisfied, neither would work in a open dhw loop unless you are recirculating that water too.

 

[Wet1]

I would think he'd want around 2 gpm flow rate for his system.

xpertpc... he's using a closed loop system with a HX in the tank(s). His system will not be draining into the tank, it will be pressurized.

 

[2.beans]

to correct the gallon per minute flow thru the collector i can install a smaller pump that is just controlled by the temp controller on the panel. it will be pushing thru the 011 that would be off. ive read that taco said that that wont hurt the 011. i have a 006 bronze that i could use. that would really slow things down in a 250' run, then maybe id have some heat loss in that length of run. the water is pre heated that goes back into the collector. the temperature controllers i use are ranco's. they can be set for heating or cooling, operate from 30 to 220 and the differential can be set from 1 to 30. the controller can be up to 400 feet away from the sensor.

 

[2.beans]

saturday morning i started out with 42* water, at the end of the day it was at 106*. we had a daytime high of 86* the tank is a 45 gallon unisulated tank so i dont know how much that heated up on its own. i started out with the pump at 1.5 gpm and around one o'clock i slowed it down to 3/4 gpm. that made the output water temp increase from 94* to 105* in a half hour to finally top the tank out at 106* today im going to add a gauge to the panel supply line and add the ranco controller to see if i can get the tank hotter.

 

[Wallyworld]

You need to use a differential controller, which I assume the ranco controller is. Mine turns on at 15 degrees warmer than water temp and kicks off at 5 degrees warmer. I have 2, 3 by 8 panels, copper collectors and I hit 160 degrees yesterday. I'd say your collector did pretty well

 

[2.beans]

You need to use a differential controller, which I assume the ranco controller is. Mine turns on at 15 degrees warmer than water temp and kicks off at 5 degrees warmer. I have 2, 3 by 8 panels, copper collectors and I hit 160 degrees yesterday. I'd say your collector did pretty well

so if your tank temps at 100* the pump turns on at 115* and shuts off at 105*? does it automatically rise as the tank temp rises? when you say that you hit 160* yesterday was the collector temp or storage temp? the ranco is a differential controller im not sure if its the best one for the this application though.thanks

 

[Wallyworld]

You need to use a differential controller, which I assume the ranco controller is. Mine turns on at 15 degrees warmer than water temp and kicks off at 5 degrees warmer. I have 2, 3 by 8 panels, copper collectors and I hit 160 degrees yesterday. I'd say your collector did pretty well

so if your tank temps at 100* the pump turns on at 115* and shuts off at 105*? does it automatically rise as the tank temp rises? when you say that you hit 160* yesterday was the collector temp or storage temp? the ranco is a differential controller im not sure if its the best one for the this application though.thanks

If the tank is a hundred my pump turns on at 115, if the suns goes in and the collector cools off, it would shut off at 105 assuming the tank temp is still 100. My tank temp got to 160 yesterday,

 

[2.beans]

what kind of controller is it? thats how id like to run it.

 

[Wallyworld]

Its a solarmetric, think they are out of business though. The controller is 18 years old. They make them now where you set the differentials you want. This one is one choice

 

[2.beans]

i adjusted the ranco higher and got the tank to 120* today with low sun until 2 o'clock this afternoon. i think im going to need a better controller and install the panels closer to the house.

 

[Wallyworld]

I heard my pump start running at 8:55 this morning and it was still running at 4 pm when I went out. Collectors' temps at 4 were around 152; tank temp in the high 140s.

 

[steviep]

I live here in NH and I plan on making solar heater for my DWH. I really like your designs and wouldn't mind looking at them but a better idea would be a list of materials. I am planning on putting a spare electric hotwater heater as storage in line before my gas hotwater heater. I would like to know what buy for a controler and where to buy it reasonable. I have also thought about getting a 12 volt circulator and running it off of a small solar collector .

 

[xpertpc]

what kind of controller is it? thats how id like to run it.

In Gary's article under "pumps and controls" he uses the Steca differential controller, They seem to be $100-$200 depending on needed features, I just google searched and came up with this (broken link removed to http://www.stecasolar.com/index.php?Steca_TR_0502_en)


http://www.builditsolar.com/Experimental/PEXColDHW/Overview.htm

 

[2.beans]

im going to look in getting one. ive wathched this work for a week now and achieved 120* in my uninsulated tank. on the hottest days we had it melted some of the plastic fittings off so i didnt get good results on those days. it was putting out 150* water onto the ground, it would have been better in the tank. i knew it was going to be slow but i didnt think it was going to be this slow. so with that said im going to put these down at my house and dig a ditch across my lawn again and add a second panel maybe a third and a second super store tank, or build one. heres some pics. ive have about 10 seconds into placing the panel so im guessing my results could be increased. thanks