Several years ago Judy and I bought a cottage on the Lake of Bays in the Muskoka lakes area of Ontario. The main reason that we purchased this particular property was that it is next to the cottages owned by Judy’s brother and her step sister. Judy spent all her childhood summers in the area as her brother’s cottage was originally build by their father, a school teacher, and for as long as Judy can remember they used to “head for the cottage” as soon as the school summer holidays started at the end of June and head back to Coppercliff just before the beginning of the school year at the start of August.
From the time I was inducted into the family Judy and I watched the adjacent Northcott property and dreamed of one day buying it. Eventually, after some 30 years, it finally happened and we ended up with half an acre of waterfront property next to sister Jan and brother Charles.
Unfortunately within those 30 years the cost of lakefront property in Muskoka had risen some 15 fold and we have ended up with a huge investment in an asset which is only of use for about 6 months of the year at best. This is because the cottage started out as a typical un-insulated summer residence in the 1940s and, despite the huge amount of money spent on “improvements” and additions by the previous owner can still only be used during the warmer months.
We have considered all sorts of ideas as to what would be the best thing to do with the place. The property is very small and a new “Development Permit By-Law” has meant that one can only build a house of about 700 square feet on the lot without applying for a by-law amendment.
However, after much to-ing and fro-ing, and although we can hardly afford it, we have decided to demolish the existing structure and build a new four seasons dwelling.
For me a major consideration for the new home is how to heat it. There are lots of pine trees on the lot which provide plenty of shade in the summer but completely eliminate any possibility of solar heating. As there is no natural gas supply in the area unless I intend to stay there all winter and stoke a wood stove our options seem to be propane, oil or electric heat.
I spent quite a bit of time studying geothermal systems but the capital cost and marginal return on investment just did not add up.
Pretty early on, after hearing and studying Ontario’s new Smart Meter plan I decided that off peak electric heat was the way to go.
The Smart Meter plan for Ontario will deliver electricity at the rate of $0.042/kWh + + during the off peak hours of 11.00p.m. until 7 a.m. The actual cost, when other variable charges are included works out to $0.0612/kWh which works out to be almost exactly the same cost as natural gas. A very good energy cost comparator which can be used to calculate this here.
Of course the obvious problem becomes how are you going to heat your house when you can only use electricity for the purpose between 11p.m. and 7a.m.
I decided this could easily be done, and has been done, by storing the heat some way. There are several options for this, everything from bees wax to rocks but, considering that we were into new construction here, I decided that water was the best storage medium for our circumstances.
I figured that something around 900 gallons of water heated to 80°C would store sufficient heat to keep the house up to 22 °C for 48 hours and keep the house above freezing for almost 6 days in the worst conditions that we get in the area (your results may vary).
Once this decision was made the next question was what to use as a tank. I studied this in detail for a considerable period and after looking at plastics and stainless steel decided on concrete. Brooklin Concrete who operate a manufacturing plant near the cottage were able to supply a custom modified oil separator tank for just over $1000 which was ideal. This type of tank, unlike their septic tanks which are clam shells with a seam in the middle, is a tank with lid construction thus eliminating any concerns about sealing the joint. I got some special concrete to concrete silicone sealant which they inserted between the lid and the tank and they delivered the tank when the foundation was poured.
We set the tank on 6 inches of special high load bearing polystyrene foam and will add 6” of similar foam around the walls and over the lid once the installation is complete.
The next issue was how to get all that heat into the tank during the off peak hours. Although the house has excellent insulation (R55 ceilings R48 walls) it has a lot of windows so the heat loss is fairly significant. The worst case heat loss would be around 60,000 BTU/hr but we figured the normal winter heat loss for the building will be around 25,000 BTU/hr so if the energy had to be loaded into the tank is 8 hours we would need to heat the water at the rate of 75,000 BTU/hr or about 22 kW.
Note: If we happen to be there for a prolonged period during atrociously cold weather we will have a Vermont Castings high efficiency wood stove and a propane fireplace to supplement the electric heating.
We only have a 220 volt service so 22kW works out to 100 amps. Various options were available to do this including pool heater or perhaps a bank of hot water heaters but the ideal one was an electric boiler. Luckily a search of Kijiji and $500 turned up a slightly used Monitron EH25 boiler which was ideal for the job. It turns out that one issue with electric boilers is that of corrosion of the cast iron boiler when oxygenated water is heated for a prolonged period. This is termed an “open” system and is not recommended by the manufacturer Slant Fin. Additionally the manufacturers of the required circulating pump would not guarantee their product if it was used in an open system.
With all my experience in the automotive field I felt that this problem could easily be solved by replicating an automotive cooling system for this circuit. One of the things we had discovered when testing engines on a rolling road was that a car’s cooling system efficiency could be improved enormously by spraying water onto the radiator during dyno sessions. I had a Nissan Stanza copper radiator especially modified and that was installed near the water tank to act as a heat exchanger.
22kW is only about 30 BHP and the radiator of a Nissan Stanza could easily handle that in a liquid to air installation so liquid to liquid should be no problem. An expansion tank was also included in the circuit to maintain the required 4 – 5 p.s.i. required at the circulator pump inlet to prevent cavitation at the temperatures we would be using.
I purchased all the parts and spent a happy day cutting and soldering pieces of 1 ¼” copper pipe to produce this.
After testing all the joints for leaks and having the electrician wire up the electric boiler we bled out all the air pressurized the system to 7 p.s.i. and fired the system up. After about 3 minutes the boiler, which starts up in a sequence to prevent sudden electrical loads on the supply, had the water in the supply side circuit up to 90°C. So far so good.
The output side of the system will consist of 3 zones. The first zone will be the basement with 5 loops the second will be the main floor, also with 5 loops and 2 loops on the third zone which is my garage. The basement was easy. First a two inch layer of Styrofoam was laid on top of the compacted sand floor. On to this was laid reinforcing steel mesh after which the positions of the partition walls were marked out and then the oxygen barrier pex tubing of the 5 zones was attached to the mesh with plastic ties.
90° one inch conduit bends were used to protect the pex tubing where it emerged from the concrete directly below the first zone manifold. The manifolds I purchased from PexSupply in Farmington, NY together with the pumps and various other parts. Although I agree with supporting local merchants as much as possible when I was quoted prices of 250 -400% higher than those in the U.S. the limits of my patriotism are strained.
The Mr Pex manifolds are a thing of beauty and very simple to use. They have integral throttling valves and flow meters for each loop which should greatly simplify the final tuning of the heating system.
Once the concrete basement floor was laid over the heating loops I gathered all the parts together to build the delivery side of the system. This was considerably more involved but a couple of days of cutting and soldering pipes had a second radiator installed in the top of the tank and connected to one Honeywell mixing valves, one Grundfos circulating pump and one Mr Pex manifold for each zone.
The size of the second radiator is something that I’m really having difficulty calculating. I have talked to a number of people in the heat exchanger business and the general consensus seems to be that a radiator immersed in a tank is not likely to be able to absorb enough energy to heat the house. Most seem to think that a plate heat exchanger is the only way that I‘m going to get this to work. I have given the subject an enormous amount of thought but I have decided that I just don’t have enough information to make an informed decision. Perhaps someone out there in cyber space has a computer program that will model heat exchanger performance that they would just love to run my numbers through.
For the present I have installed the distribution side manifold and intend to run the system to see what happens. After all several people told me that the input side would never work with the Stanza radiator but it seems to perform admirably.
In my next posting I’ll let you know how it works out.