[debiasio]

I have an oil burner with a tankless coil. No separate water heater. It has two dials on the side, see attached picture.

Is the grey knob on the left a tempering valve? I can't turn it. Is there a reason for that? I assume I loosen the screw to turn it.

If that is a tempering valve, what is the grey box on the right? It looks like its set at 165.

I have steam heat.

What are the optimal settings for summer and winter?

 

[beenthere]

The gray box, is your control to maintain the water temp in your boiler so you have hot water.

Yes, that is a tempering valve. Some need to be pulled out to turn them. Best to set it where it gives a constant hot water with minimal temp swing.

It would probably save you a lot of money to install an electric water heater, and not use teh oil boiler at all for your hot water.