The following picture is of a water heater that is doubling as the heater for domestic hot water (sinks, tubs etc) as well as the hot water for the heating system. These systems are VERY common in my area and Seattle Home Inspectors find them on a huge percentage of Townhouse type structures that have hydronic heating systems. The jury is still out on the long term practicality of these systems as it makes the water heater work harder than a regular water heater. The jury is also still out on whether this dual function will result in shorter life spans for heaters that are also more expensive. I suspect that in about 10 years we will know the answer----mighty glad I missed out on that jury pool. But back to the picture. In this picture you can see pretty much all the components that should be there for the system to function. 1. The Heater Itself (big strapping white thingy). The system would not accomplish much without it. 2. Expansion Tank (at the very top center of the picture---just the bottom shows). These tanks (or at least some means of dealing with thermal expansion) are required in most jurisdictions by modern standards. So you will see these whether it is a space heating system or not---on newer installations. 3. Circulator Pump & Timer (green thingy). This pump circulates water through the system. It might go to in-floor pipes, in-wall heaters, or wall radiators. 4. Tempering Valve (grey thingy under the green thingy). While the heating system needs water around 145 degrees to do its job this temperature is WAY to hot to be coming out of your shower head. The tempering valve allows us to mix a little cold with the hot to regulate the temperature to fixtures throughout the home---typically not more than 120 degrees. In fact, in Washington State, Licensed Home Inspectors are required to note whenever the temperature is above 120 degrees and recommend appropriate action. Charles Buell, Seattle Home Inspector For those of you that have REALLY been paying attention you may be saying to yourself, “Where the heck is this ‘timer” he is talking about?” You mean you don’t see it? How can that be? First of all let’s talk about what the timer does. Since the heating system does not operate year round, we don’t want water to sit in the pipes for long periods of time. If we did, bacteria could grow in the pipes----including Legionella bacteria. With a timer we can circulate the water periodically whether the heating system is calling for heat or not. The timer can also be used to control circulation during the day or when we go on vacation. The system will function fine without it but then the circulator might run 24/7---or only when the thermostat called for heat---not the most ideal situation in terms of energy consumption. Sometimes “control” is a good thing. Now back to the timer location. If you don’t see it, I am not surprised----I had a hard time seeing it as well. It IS there however---behind the green circulator thingy---FACING THE WRONG WAY. This position makes it almost impossible to operate/set as needed. The following picture is looking up under the circulator toward the bottom of the expansion tank---and there is the timer---sitting on top of the green thingy. It is not difficult to relocate this timer to a more practical location---just needs an electrician and about an hour of his or her time.
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