Good you have done some home work. You should have asked this before you built. Why? The 2 inch foam board below slab was not a good investment. Insulation saving is based on the delta temperature, 50 vs 70 is called never pays pack. Dry ground is an insulator, why below ground homes were popular. Side walls as you go up should have been thicker, specially above the frost line and the exposed area should have same R value as outside walls.
Based on your perceived goals my feedback: (I agree with zeusmorg post above).
Tank is too small, heat storage is less than one night at worst case conditions. No antifreeze in the tank, need double walled heat exchangers for most codes. Using potable water in the tank a single walled heat exchangers will pass. (as long as you can prove always potable water).
Nothing wrong with wood tank if it has a liner. Difficult to make water tight.
Since I do not know your numbers estimate based on mine. My home in Michigan has insulation near yours, 1350sqft. 92% 76KBTU/hr forced air furnace, worst day -23 deg F five days in a row, Furnace run time 23.5hr/day. My basement walls have 1 inch above grade and 4 ft down. Payback was too long to go lower. Broke when completed my house.
Natural gas Tank less hot water is 117kBTU/hr. Unlimited hot water great:-) Can make for nice backup heat. I not setup for it yet.
18,000 gal pool. Heater 140KBTU/hr raise temp 1 deg F per hour. Very expensive to heat with electric, no wonder your interested in Solar heat!
Largest heat load is the pool, only used for a few months a year...
Have you checked out the links at www.builditsolar.com?
Have fun, Scott.
You say 2 inch styrofoam is not worth it and above gradee it is not enough. Our soil is rather humid. We cannot assume the slab would have been dry. Above grade is only 6 inches.
You say the tank is too small. I guess it is time for me to actually pickup the calculator and actually calculate load. I think the way I should do this is by analysing my electric bill. Will post again on that. The tank I plan to use is in my mind pretty big (4 x 4 x 8 ft)! That would surely take a fair bit of space in my technical room...
Regarding code and antifreeze, from what I understand, canadian code requires double wall heat exchanger unless there is more pressure in the domestic water line than in the antifreeze side. That is why I assumed it was OK.
MartinEau, soleil, le vent[ Parent ]
You suggest a 128 cubic foot tank. That's 3.6k liters of water at 4.2kJ per liter per degree C or 15.1 million joules per degree C. But that is only 15.1k BTU per degree C. A (small) 100k BTU/Hr heat load will "eat" over six degrees out of that tank every hour.
You need a bigger tank or a phase change material like sodium acetate trihydrate.[ Parent ]
Here is a plot my electric bill for the last 4 years.
Base usage in the Summer is approx 1000 kwh/mo (a lot of work to be done to lower that uh??)
Peak monthly usage in the Winter is around 4500 kwh/mo but lowered to 3300 kWh/mo with partial wood backup. If I substract the base usage, I get a peak monthly heating load of 3500 kWh/mo or 2300 kWh/mo with wood backup. So I guess, if I planned for 2300 kwh/mo, I would be OK. That would mean an average of 77 kWh/day which is equivalent to 3.2 kW.
Is this ok? where do I go from there? I guess I need to account for cloudy days and inherent variation in solar input...
French Eau, soleil, le vent =>Water, sun, wind
As you noticed, many considerations. Knowing your local code requirements is Very important. Codes are not written for necessarily normal operations, must deal with when things are not working.
Solar heat collectors. Drain back for cold climates seem to be the best.
Pool must be a new requirement, energy use does not show during the summer.
Tank Have a porch? Put the tank under it, insulated of course! Www.papercrete.com
All electric home? Then 1Mwhr/mo includes the hot water not so bad. My use 764Kwhr this month, with gas. Have too many computers running (4-5) cost $6 each to run.
Have fun, Scott.[ Parent ]
In fact "Eau, soleil, le vent" means "Water, sun, wind" but it is a word game because in French in pronounces like "Au soleil levant" meaning in English "to the rising sun"
I am not French from France. I am French speaking from Canada, originally from the province of Québec and now living in Edmundston (90% French speaking), northern New Brunswick. Minus 25 degrees C is about the coldest is usually gets. This week we turned off the electric heat for the Summer and I did a small fire this morning. We had over a meter of snow before it started to melt this winter. We still have over a foot in the woods still (April 24th).
Pool is not heated so far but season is short here.
Our consumption also includes clothes dryer year round. That should change next summer with the new clothesline.
Thanks for the calculations on tank sizing. That would mean at least doubling what I had planned. Do you think it is better to make two 4 x 8 or make a bigger one? Based on another contributor, I will probably separate dhw from heating, so there could three tanks, the dhw one being smaller though.
I realized just after I sent it could be Canada, my wife's family is French from Quebec.
Be careful with playing with French words, the Le car did not go over well with the French gov:-)
Edmundston is about 5 deg north of me. -25 C is -13 F. Michigan rarely goes below 0 F, yet few years ago we had -23 deg F for 5 days, no sun. Furnace ran 23.5hr, 11pm setback for 6 deg, then ran continuously. After the second day we never made it to the temperature set point. Ran the burners on the stove for a hour to get it up to temperature. Wife learned just how cold the windows are!
Have you read the stuff over at www.builditsolar.com? Very good ideas for what your doing. Including how to build the tank. Round tanks have less surface area, then square then...
Tank - Needs insulation, one requires less for the same volume of water. Put a baffle so the new hot water stays in a small area for DHW, excess then flows to rest of the tank.
A year ago I had a nice response on clothes dryer. http://www.fieldlines.com/story/2007/4/24/14610/4873 Since your's is electric you should be venting into house during the winter. Without to much work, can reduce heat by 50% was my conclusion.
Pool - solar blankets help! Above ground? Quick calculations show 0.5 to 1 inch insulation is very cost effective. (unless have a cheap source of heat). At nigh in the spring and fall it goes below 60 F, with 80 F pool, it cools fast. My wife wanted 90 F pool, did it for a while, could not do laps was too hot. She hardly used it so backed it down to 80-82F. Bit cold for some, great for me.
I looked at the cost of the pool. Realized its expensive! Only getting two months use for the cost of water and chemicals ($300/yr or $5/day, later got the cost down to $100). Spending the money on a heater more than doubled the season, heating cost was $1/hr with gas. Early spring it was expensive to keep heated, not enough warm days to use it so backed it down to early June through October. Once the kids are in school not much use except on the weekends, so after a while stopped in September. Took pool out once they were in their teens, they could not keep the chemistry right so sold it. I only miss it now and then. Planing on a pool in my next home use it year round. No Cl. Pool cover removal is not fun alone. New pool will have a button to press to remove cover. Chemistry will be totally automated. Nice to be an engineer.
Bien le bonjour à votre épouse! "Be careful with playing with French words, the Le car did not go over well with the French gov:-)" I don't get it... please explain.
Yes I have looked at www.builditsolar.com. That is where I got the idea of a wooden tank. I like your idea of building one single tank with a baffle to separate the DHW storage tank from the main heating tank. However, the problem will be to fit all this in my technical room. From a previous post, I see that I need a bigger tank (at least 2 tanks 4 x 4 x 8 ft) plus the dhw heat storage tank. My technical room is about 12 x 14 ft but one full wall is occupied by the heating system valves and boiler, the second is occupied by heat exchanger, pressure tank and electric breaker box, third one has central vacuum and dhw electric tank. That leaves me a portion of third wall maybe just about 8 ft long and about 6 foot long on fourth wall on the other side of door. It seems like if I want a bigger tank, I need to make it taller than 4 ft high. Considering that space issue, I prefer square tank to round ones. I will have to check code for distance to breaker box.
So far, the pool is the least of my preoccupations. We got it for free except for the labor of removing it. I envision it more like a dump load for summer.
70's American Motors (AMC) imported a Renault vehicle they called "le car" for little car. I remember hearing the French gov did not like this name, if I got this right "The French do not like the butchering of the language like the Americans do"... What can I say I thought it was funny.
Taller tank looks like it will work for you. The weight of the tank is huge, make sure the slab its on can handle the weight without breaking.
I mentioned earlier do you have a porch without a basement under it? Great place for a large tank. Digging the hole by hand is not too bad. I have done the foundations for a home only took a couple days.
Solar collectors sized by the heat needed by the pool, everything else will be taken care of.
About the slab. Does anyone know how heavy a 4 inch thick slab reinforced with wire mesh can withstand?
I do have a porch but it is only 4 x 8 ft. I doubt it is worth the trouble of digging and making a hole in the basement wall, more difficulty to insulate the tank
If I split the tanks in 2 (within my technical room), I wonder how I could place the inlet and outlet vs heat exchanger coil... Connection between the two tank I guess should be at the bottom. Martin Eau, soleil, le vent[ Parent ]
If the slab was properly done, you should have no worries putting a water tank on top. Tap on the concrete to see if you can detect any hollow areas, if any are present then you have some worries.
Location of a pipe for balancing the water level isn't critical. Water seeks it's own level. Personally, I'd build one large tank with an insulation barrier between them. You create less exterior surface area that way and a lower need for heavy exterior insulation. The top is probably the most critical for insulation, as heat rises. That would save you from any additional heat load in your house in the summer.
Heat exchangers should be placed near the top for heating applications, (pool, DHW) and at the bottom for solar panels. In other words you want to utilize the hottest part for your heating applications and heat the coolest part. Of course if you go drainback, that is inconsequential, pickup at the bottom, and return at the top. [ Parent ]
