I have my 150 gallon tank in a family room that I dont use very often. Due to the less frequent use and the room being on its own heat zone, I select to keep that room at lower temperatures when not in use. Ultimately that room spends a lot of time under 55 degrees. This inevitably makes it more difficult to keep the tank at optimal temperatures.
I started out with (2) Two Marineland Stealth heaters rated at 250 watts each. These heaters would cycle on an off but when I checked the power consumption I was less than thrilled. I ran both heaters through a Belkin Conserve Insight for power data and found that the electric heaters were pulling ~$33/month @ 18 cents per kilowatt.
I decided to look at alternatives and thought about using some form of heat exchanger to transfer heat from my domestic hot water to the tank thus using the far less expensive energy source of natural gas.
I looked at heat exchangers used for solar pool heating and other applications and they looked great but I wasnt willing to put the money down for what was essentially an experiment at this point. I decided that making a simple, although clearly less efficient heat exchanger would be the best route for now. I placed the heat exchanger between an Ehiem 2215 with 2217 impeller and the tank which essentially turned this into a natural gas powered Hydor inline heater.
What I ended up constructing is a tube in shell heat exchanger. If you are unfamiliar with the principal here is a link to a photo: http://www.cheresources.com/invision...r_1_Image5.gif
I took 1.5 PVC and used Tee fitting on both ends that had 1 NPT female threads. I put a stainless steel pipe inside of the PVC and used compression fittings to seal the stainless steel pipe and PVC pipe. Hot water from the gas hot water heater flows into the stainless pipe from the top and exits the bottom. The water then makes a 180 degree turn and is pumped back to bottom of the hot water heater with a bronze Taco recirculating pump. The hot water system is at the same pressure as the city water.
Aquarium water enters at the lower Tee and flows from bottom to top while absorbing heat from the stainless pipe and exits through the upper Tee. From here it flows back to the tank for discharge.
The Taco recirculating pump is turned on and off by a Ranco ETC controller that has a thermistor (temperature sensing) probe in the tank. This controller allows you to set an offset of 1-30 degrees. I set the unit with a 1 degree offset and 80F setpoint. The controller calls for heat until reaching 80F and then allows the tank to reach 79F before calling for heat. If the offset were 3 degrees it would drop to 77F before calling for heat.
When I reviewed the electric cost of the new system I am running around $4 @ 18 cents per KW of electricity per month now since all of the heat is now coming from natural gas and the electricity is only the cost for pumping the hot water.
I started out with (2) Two Marineland Stealth heaters rated at 250 watts each. These heaters would cycle on an off but when I checked the power consumption I was less than thrilled. I ran both heaters through a Belkin Conserve Insight for power data and found that the electric heaters were pulling ~$33/month @ 18 cents per kilowatt.
I decided to look at alternatives and thought about using some form of heat exchanger to transfer heat from my domestic hot water to the tank thus using the far less expensive energy source of natural gas.
I looked at heat exchangers used for solar pool heating and other applications and they looked great but I wasnt willing to put the money down for what was essentially an experiment at this point. I decided that making a simple, although clearly less efficient heat exchanger would be the best route for now. I placed the heat exchanger between an Ehiem 2215 with 2217 impeller and the tank which essentially turned this into a natural gas powered Hydor inline heater.
What I ended up constructing is a tube in shell heat exchanger. If you are unfamiliar with the principal here is a link to a photo: http://www.cheresources.com/invision...r_1_Image5.gif
I took 1.5 PVC and used Tee fitting on both ends that had 1 NPT female threads. I put a stainless steel pipe inside of the PVC and used compression fittings to seal the stainless steel pipe and PVC pipe. Hot water from the gas hot water heater flows into the stainless pipe from the top and exits the bottom. The water then makes a 180 degree turn and is pumped back to bottom of the hot water heater with a bronze Taco recirculating pump. The hot water system is at the same pressure as the city water.
Aquarium water enters at the lower Tee and flows from bottom to top while absorbing heat from the stainless pipe and exits through the upper Tee. From here it flows back to the tank for discharge.
The Taco recirculating pump is turned on and off by a Ranco ETC controller that has a thermistor (temperature sensing) probe in the tank. This controller allows you to set an offset of 1-30 degrees. I set the unit with a 1 degree offset and 80F setpoint. The controller calls for heat until reaching 80F and then allows the tank to reach 79F before calling for heat. If the offset were 3 degrees it would drop to 77F before calling for heat.
When I reviewed the electric cost of the new system I am running around $4 @ 18 cents per KW of electricity per month now since all of the heat is now coming from natural gas and the electricity is only the cost for pumping the hot water.
