Have to turn on heat to get hot water in shower!

[JK New York]

Hi!

We have oil/steam heat. No separate hot water heater.

Lately, the only way we can get a hot shower is if we turn the thermostat for the heat up a few degrees higher than the room temperature so that the boiler kicks on. This works great. We have long hot showers this way.

If we do not do this, we either have no hot water in showers, or very hot water for about 2 minutes and then cold.

Thanks for any help!

JIm

 

[Mitchell-DIY-Guy]

There's an aquastat or similar kind of flow sensor that's supposed to turn on the boiler when there's hot water demand. That's not working, but you are fooling the system into firing by turning on the boiler itself.

Find that sensor or stat, and locate the troubleshooting sequence at the manufacturer's web page...

 

[fixitron]

You would have a small tank inside the boiler and inside that tank is a coil connected to your potable water system. The boiler keeps that tank hot, typically around 180 degF. When a hot water tap is opened, the cold water is heated by the hot water in that tank. When it cools down, the aquastat turns on the boiler to heat it back up. The reason that you only get hot water for 2 minutes is that the boiler had recently fired to provide heat, which also heated the water in the tank. Your aquastat senses the temperature in that tank. It is a metal box (typically gray) connected to the face of the boiler near the coil (the pipes to the coil will be connected to a mixing valve nearby). The aquastat has failed.