We have a Triangle Tube Phase III Indirect Fired Hot Water Heater, Model TR-45. It was installed just before we bought the house, approximately six years ago.

Normally, when we get in the shower in the mornings, we crank the hot water all the way up, and the temperature stays perfect throughout the shower. There has never been any need to turn down the water temperature on the faucet. That has been the typical operation in the winter for the past six years. In the summer, as expected, the first person to run the water typically has to let it heat up for several minutes before getting in the shower.

This pattern changed about a six weeks ago, however, and I'm trying to figure out why. Since March, when we turn the water temperature in the shower all the way up, it quickly becomes scalding hot. We've tried turning the temperature down on the water heater itself, but that doesn't seem to have helped. It is currently turned down as low as it will go, and yet the temperature on the water heater reads at about 170F.

When the oil company did the annual service on the boiler/water heater a few weeks ago, the technician informed us that we needed a new thermostat and that he would order it. After not hearing from him for over two weeks, I called the oil company and was told by a manager that we actually need a domestic water mixing valve. He told me that, according to code in CT, these have been required for about 10 years. Oddly, our water heater, which was installed six years ago, does not have one.

However, I am not sure I believe the manager at the oil company for a couple of reasons.

1) Yes, the water is supposed to be hotter in the winter, but this "scalding" situation did not start until spring.

2) If the lack of a mixing valve is the problem, it would seem that we should have had a problem for the past six years. It doesn't make sense that the problem would have just started.

Does anyone know what the real reason for this sudden change in water temperature could be? Could it be the thermostate on the water heater, or could the lack of a mixing valve really be the cause? I've received helpful advice regarding other appliances on this website, so I thought I look here for answers. I'd appreciate any advice you can give.

Thanks!
Stacy

Why now is right ? Anyhow here is a little information, I will be researching my library to add more. Also talking to people in the oil industry that I have direct contact with still.
How Phase III Works
When the Phase III thermostat in the inner tank calls for heat, the boiler and circulator start. Boiler water is circulated around the outer tank and heats the domestic water in the inner tank. After transferring its heat, boiler water is returned to the boiler to be re-heated. When the thermostat in the inner tank reaches its pre-set mark, the boiler and circulator shut off.

Please download and read page nine: http://www.triangletube.com/document...0manual%20.pdf An automatic mixing valve is recommended.

My question is it it is recommended by the manufacturer, why was it not installed originally ?

Thanks, Icehouse! Do you think, though, that it could be the thermostat?

And yes, I agree...if it was recommended, why was it not installed initially? Good question. Unfortunately, I think the builder who flipped the house before we bought it was trying to cut corners or something.

The purpose of the mixing valve is to allow a certain amount of cold water to mix with the hoe, although you say till now it has been ok. Try the thermostat first.

A manager from the oil company finally came out to take a look at our hot water heater. He took one look at it, said "Oh! You have an indirect water heater! You do need a thermostat." and left. It took all of a minute! Could have saved us a month of irritation had they figured this out on Day 1.

Thanks again for the help, though, Icehouse!

"Duhh" some company, I'd switch.

This situation is dangerous. Your water temperature is over safe limits. This situation can cause severe burns, or even death. If this were my system I would have a third party inspect the complete water heater installation. You should not have to tweak the thermostat for showers. At the temperatures that you are reporting, you are:
1: Risking severe burns.
2: Risking thermal damage of pipes/unions.
3: Wasting oil needlessly.
4: Risking tank rupture.
The water heater thermostat is probably one of your problems. I would have all pipes and circulators and valves checked for flow direction and capacity. You should have sufficient hot water without tweaking before showers. A thermostatic temperature valve at the tank would take the thermo load off your plumbing and add safety to the occupants. This should be a top priority. It is an extremely dangerous situation.
My $.02