Watts 70a valve

Hi, new to the forum. Looking for some advice. Have a Watts 70a tempering valve on oil fired tankless boiler. This time of year the incoming city water gets cold enough that the tankless set up struggles to deliver warm water. Over the years I've wondered if there's something I can do to reduce the cold water blending into the hot. I am pretty sure the coil can handle the load but there's too much cold water mixing in. Actually, this valve has been on the cool side since it was new.

A few years back I opened the 70a but don't recall if I can add a spacer or change a spring to cut down the flow of cold mixing water? Any tips on getting more heat out of this valve? Thank you all for reading...

The purpose of the dial/handle is to set a temperature. It is up to the valve to regulate the cold water to maintain that setting. IF the valve is defective it will not work, and if the hot water is below the valve's setting, it should not even mix ANY cold water into it. You do NOT have to modify the valve, you have to get it working properly.

Thank you for the reply. I was betting that would be the answer. However I failed to mention this has been happening since new. And further, getting warmer water only really occurs in summer when the city water is proportionately warmer. The dial setting does nothing to help.

If I feel the pipes into the mixing valve it's obvious too much cold water is flowing into the mix. The valve is functioning consistantly but not giving a desired end result. I'm an old school fix what you have, not R&R unless absolutely necessary guy.

If anyone wants to tell me why I should replace the valve, please tell me of an available model that has a greater range of adjustment. Thank you for reading...

Sounds like the valve was not properly installed. This valve has a number of requirements that, if not met, will cause premature failure or prevent it from working right. You can pull the installation instruction sheet from the manufacturers web site yourself. If I had to guess, you are missing the throttling valve.