This is by no means an actual recommendation, and I have no idea if it would meet any building codes (though I don't see why it wouldn't). I'm just thinking aloud of what might work.
The biggest problem with tankless water heaters in an area like mine (S. Ontario Canada) is that the incoming cold water pipe is COLD, year-round. Probably 10 degrees Celsius year round here, and perhaps even colder for some people in some seasons.
This creates a problem for tankless water heaters that have to heat water another 40 degrees Celsius on an ongoing basis.
So, here's what I propose: Don't throw out your old water heater tank, instead, leave its piping (but not its power/gas) hooked up, rip the insulation off and then connect the "hot" pipe to the tankless water heater. Over a period of hours (which is reasonable, 95% of the time you're not using hot water), the water in the tank will warm up to room temperature, and as an added bonus, this is more efficient. So now the tankless heater is working with room-temperature water rather than chilly municipal water. The water in the tank will pull heat (and humidity, watch out for drips!) out of your home, which is great during summer (free a/c!) and ok during winter. If your home is heated using natural gas, it is more efficient to indirectly heat up the water in the tank using your household furnace than the tankless water heater, because the tankless water heaters are not as efficient (whether natural gas or electric).
Of course, the other solution is to just size your tankless heater appropriately for your incoming cold water temperature :)
The disadvantage with this proposed method is that the very reason you might be considering a tankless is because your tank is broken, and buying two systems just isn't in the budget. Space may also be an issue.
The other big issue with any tankless water heater is the delay, which is usually not an issue for showers, but it is for faucets/taps. The greater the volume of piping between the faucet and the tankless heater, the greater this problem will be. One should ideally install a small point-of-use water heater that just keeps a small quantity of water heated at all times. Also, their peak flow rate is limited, so good luck if you want to shower, do laundry and wash dishes at the same time.
Tankless water heater improved
It is great to think outside the box. We have a tankless system (Rinnai Ultra) running at about 95% efficient. The idea you are suggesting is not bad but aside from the space drawback you mentioned the other area of risk is if the tank breaks as old tanks (15+ years, some up to 25) tend to do. I would advise against using a tank in this way. If you want to preheat the water you could install a heat exchanger ($500 and up) this is one model i have seen used by many builder in Ontario http://www.renewability.com/power_pipe/
A conservative estimate would be that it saves about 30% on water heating costs. Basically it exchanges the heat from the outgoing water to the incoming water. It is super simple and has no moving parts. You can get them from home depot dot ca and other retailers. Union Gas might even have an incentive.
Tankless water heater improved
It is great to think outside the box. We have a tankless system (Rinnai Ultra) running at about 95% efficient. The idea you are suggesting is not bad but aside from the space drawback you mentioned the other area of risk is if the tank breaks as old tanks (15+ years, some up to 25) tend to do. I would advise against using a tank in this way. If you want to preheat the water you could install a heat exchanger ($500 and up) this is one model i have seen used by many builder in Ontario http://www.renewability.com/power_pipe/
A conservative estimate would be that it saves about 30% on water heating costs. Basically it exchanges the heat from the outgoing water to the incoming water. It is super simple and has no moving parts. You can get them from home depot dot ca and other retailers. Union Gas might even have an incentive.
Post new comment