What does tankless water heating mean with our chicago plumbing. First off what you need to consider is the fact that in the winter time our incoming water temperature can be almost freezing. Many tankless manufacturers state the capacity of their units on a 45 degree temperature rise. Think about that. At a 45 degree rise, if we want to deliver 120 degree water, we need to start at 75 degrees coming into our home. In the summer time that is fine, but in the winter when the water coming in is closer to 35 degrees you can be looking at significantly less capacity. This is not all doom and gloom. The key is to make sure that your tankless water heater is sized for our low incoming water temperatures.
Is this the only thing to consider with your tankless water heater? No. In chicago most of our gas mains are what is called low pressure. All homes are low pressure as well. What that means is that careful consideration needs to be taken when sizing the gas pipe and gas meter. Most homes in Chicago have a gas meter that is about 250,000 to 275,000 BTU's in capacity. This is not enough for almost any tankless. First off you have to consider that the tankless alone is 200,000 BTU's, now you have to figure the furnace, gas dryer, stove top, log lighter and anything else that might use gas in the house. The meter will need to be changed. Any qualified Plumbing company will identify this and assist in getting that accomplished. The actual pipe will also likely need to be changed and this should all be done prior to the new tankless heater being put into operation. The results of a meter or piping that is too small is insidious. The heater will work, often times for years. The problem is that it will not be working efficiently and all the while it is damaging the unit. A tankless water heater can give you well in excess of 20 years of service if installed properly.
Your last consideration for your tankless installation is the combustion air. Combustion air is the air that is delivered into the unit and mixed with the fuel for the fire that heats the water. Many tankless' can use the air in your home for combustion but often times there is not an adequate quantity of air available for such a large BTU fixture. You are always better off drawing your combustion air from the exterior of the home. At John Baethke & Son Plumbing it is mandatory that when we install a tankless heater, we draw combustion air from outside. You will get better, cleaner, and sufficient air supply this way. The side benefit is that you will not cause your home to be drawn into a negative pressure either.
These pointers are just the tip of the iceberg when designing a proper tankless water heater installation. If you ever have any questions or are considering having a tankless installed just give us a call any time at 773-276-5430.
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John, I agree with the points you make about tankless heaters, however their is one other thing to consider, cost of operation. The tankless folks alway pitch, no standby loss. This refers to the time that a tank heater is not in use. Just sitting allows the water in the tank to cool down and kick the burner on. This of course is wasted energy. A tankless heater does not have "standby loss" as the water is heated instantly. If I have a 40 gal tank heater in my home, I should get around 30 gals of hot before the water starts to cool off. So, if my someone wanted to shower, they could go for about 10-15 minutes before the tank goes cold. That would not happened with a properly sized tankless. At 200,000BTU or better on a gas tankless, someone could stay in that shower as long as they wanted, never running out of hot water. A extra 10 minutes would chew up. 35000BTU which is about the amount of gas that the tank heater would use in a hour. Long showers could become very costly!