Registered: 1475273629 Posts: 1
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I built a house with the plan to put in radiant floor heat and a hot water preheater for domestic. I am using the $1k plans from build-it-solar as my jump off point.
What I've done so far-
I tried something I saw somewhere once on the internet- I placed the pex tubes between 2x4s laid flat, filled the surrounding space with tamped sand, and laid hardwood plank flooring over the top. There is a manifold for the first and second floors. I put in 1" pex supply and return lines for the panels that go through the walls and under my house into a 5' tall crawl space, where I plan to put the storage tank. I laid thermostat wires in the walls leading to the areas where I think I need sensors for control, before drywalling.
I am now ready to build the panels, storage tank, install pumps and controls...and I feel a little overwhelmed by options, and I'm hoping for some suggestions. 1. Collector panels- I am considering 9 panels (3x8) with vertical risers. I chose this size basically because I have some extra steel roof panels left over and thought they would make a good/light box bottom. (As a side note, is sandwiching a copper pipe layout between two roof panels a waste of materials vs. efficiency rather that a flat bottom and aluminum fins?) a. Are there pressure issues when hooking panels together like this? Will panel 9 receive any water at all, or should I move the input from one end to the center (which would be significantly more difficult). b. For mounting on a roof, do most folks use solar mounting racks (like Unirac, etc)? Has anyone ever used the S-5! ribBracket to mount onto an exposed fastener roofing panel? 2.pumps- I will have one pump to pump from the storage tank into the radiant system (8 runs of 225ft. Maximum head 16') and another that runs into the collector plates (70 feet of 1" header/footers, 580' of 1/2" riser. Maximum head will be close to 28'). a. Since the storage tank will be below the house, and in an uninsulated area, I thought submersible pumps would be best, to prevent freezing here in Iowa. I am having problems finding one that is inexpensive and has a 30' head. b. Can one adjust the current to a pump to reduce its flow rate? c. I have a grundfos circulating pump that seems like it should work for the flooring, but I would worry again about freezing, can I put another pump in the tank to keep the grundfos primed if it sits inside the house?
3. controls. I ran wires for a thermostat, control unit, a tank sensor and a panel sensor. Any recommendations for a control unit that can handle that set up?
As I write, I feel dumber and dumber, so please forgive any of my questions that seem completely ignorant.
Registered: 1352981942 Posts: 2,311
Reply with quote #2
Hi Jonathan, and welcome!
You have a great project ahead of you. It looks like you have done your research and your plans are well thought out. I'm sure there will be answers forthcoming as we begin to feel colder temperatures, as there has been a definite increase in traffic here on SimplySolar. Where are you located? Greg in MN
Registered: 1421647630 Posts: 15
Reply with quote #3
I have a system like yours. I built my house in 1981-82 and put pipes under the lower level floor. First I put down 2" of high-density insulation, then 1" black plastic water pipe(about 500'), then 6" of sand, then 4" of concrete. Around the of the outside of the foundation is about 400' of the 1" black pipe. I was not aware of PEX pipe back then. This pipe is outside of the insulation and about 7' underground. The side walls are 8" poured concrete with 4" of high-density insulation on the outside. The house itself is super insulated with an R40 in the walls and R100 in the ceiling. The main part of the house(two stories) is 44' by 50' with a 44' by 48' garage/shop on the North side. I have estimated the mass inside of the insulated envelope the be about 250 tons, mostly sand, concrete, sheetrock, and lumber. 480 sq. feet of glass makes up the south wall of a two story sun porch. In the 1970's, my family bought a semi truck load of glass made for sliding doors 45" x 75". They were seconds and had minor scratches on them. They are gas filled double pain. We have built three solar houses with them. The sun porch is 8' wide north and south and all sides are well insulated. I keep the mass inside the sunspace very low so that when the sun comes out the temperature rises quickly and when the sun is gone the temperature falls quickly. My goal is to keep the glass as cool as possible because the efficiency of a collector is determined by how much energy escapes out the front, sides, back, etc. of the colloctor. The total solar energy striking the collector, minus the energy losses from the collector equal the energy into the house. Take the energy that gets into the house and divide it by the energy striking the collector and that is the percentage of efficiency. The actual amount of solar energy available is what it is, I can not change it. The only thing I can control is the energy loss out of the collector. So my goal is to move the available energy out of the sunporch as fast as possible and keep the glass cool. To do that, I have two systems, one air, and one water. The air system has a two fans with automatic doors. The one on top of the sunporch blows air into a duct that takes the air to the northwest corner of the lower level. The air passes thru the lower level to the southeast corner and the other fan blows it back into the sunporch. this works well because the lower level loses/needs more heat than the upper level. At first, I had one fan, but it could not move the air fast enough. I also have two walk doors upstairs and two walk doors downstairs that can be opened to let the heat in, But they are not automated so someone has to be there to open and close them, and opening them can overheat the living area. Other than adding the second fan the air system has not change much in 34 years. The air system comes nowhere close moving enough energy out of the sunporch. I have a solar energy sensor that records the solar energy entering the sunporch in watts/sq.m. On a sunny December day, it has recorded close to 1000 peak watts per square meter. It is vertical like the glass, so 1000 watts X 44 sq. meters equals 44,000 watts peak entering the sunporch, I would guess that half of that goes out through the glass. It is getting late. I'll post more latter. Tom
Registered: 1421647630 Posts: 15
Reply with quote #4
Jonathan, I really like your drawings. What App did you use to draw them? Tom
Registered: 1421647630 Posts: 15
Reply with quote #5
The 44,000 peak last for a very short time. I think that on an average good day 25 to 35kw of energy will enter the sunporch. This is more than enough to meet the needs to heat our superinsulated home. I believe that if the sun would shine every other day, we could maintain the temperature above 70* all winter. But of course, the sun doesn't shine every day. To make up for fluctuations in the amount of energy available, a comfortable and safe solar home needs a lot of energy storage and a backup heating system the size the house would need if it didn't have solar heat. And if it is a large two story house, ductwork is needed to keep the air from stratifying, both the heating and cooling. This is especially true in a home with small children or older people, like my wife and I. We use small electric space heaters in the rooms that feel chilly. When building the house, I was not sure if ductwork would be needed. Now I'm glad I did. We went the first seven years without air conditioning. We could keep the house cool by opening the windows during cool nights and turning on the "whole house fan. The fan pulled air through the windows, through the house, out the back door, and up through the ceiling of an unheated room. The problem was that the humidity could get quite high. It would start feeling muggy. I finally bought and installed a used air handler in the lower level and hooked it up to the ducts already in place. The air handler had five electric heating coils in it. I disconnected four of them. the last one was rated at 20 amps, so I wired it to a 30 amp breaker. That used air handler is still running fine today. I have been thinking about getting a new motor for it so that I would have one on hand when it goes out.
Jonathon, I have some comments to make about your project, but I wanted you to know of my experiences first. I cover the water system and the controls soon. Tom