Hot water goes lukewarm and then scalding hot

[CP]

Hello all,

I have a two stage boiler that is connected to an Everhot Hot Water Tank (Coil). Feeds hot water and heat to a building. In one of the tubs in the building the symptom is: If the hot water is turned on to a desired temperature along with the cold water, the water coming out goes to lukewarm after a minute and then five seconds later it goes to scalding hot, with no changes in the hot and cold stem settings in the tub.

The hot water tank is an Everhot one, with a Aquastat in the cylinder of the tank, a Taco Circulator and a Tempering Valve. Where should I look for the source of the problem?

[Jeff Wisnia]

If the problem is limited to just that one tub the source is likely to be in the valves on that tub.

A loose component (perhaps just a rubber faucet washer) in one of the valves can cause that sort of trouble.

Take the valves apart and inspect them for oddities.

Jeff