I have a 10 year old Slant Fin boiler with tankless heater. I'm on a well with hard water,at one time experiencing "black water" from apparent shale contamination. No solids,just a blackish film for a time. It has since cleared up,but I noticed over a couple years my hot water wasn't as hot as it used to be,it cooled quicker,and the pressure was far from adequate. Assuming correctly the coils interior was plugging with debris,I shut the boiler down in the fall,removed the coil,and thoroughly cleaned it with muratic acid. Knowing what this acid is capable of,especially on something with some years on it, I pressure tested it overnight. Being a mechanic, I accomplished this with the proper fittings and the help of a radiator pressure tester. It held 50 psi perfectly.
I have the HI/LOW/DIFF settings at 160/190/25. My hot water now measures 175,180 degrees F. which is plenty hot,scalding actually, and the pressure is terrific, which is the way it used to be when new,but it doesn't last long at all.
There in lies my problem. My wife showers longer then I,but I'm a Vietnam Era vet,so still take my Navy showers. Even with that,I can feel the water cooling quickly,my having to cut back the cold water mix continously,until the cold is completely off,with the water warm at the most,and this is with the boiler firing up for hot water about 2 minutes into a shower.
Assuming the coil is fine,my settings are correct(per InspectAPedia),and all the peripheral parts are good or working properly, I can't figure it out.
Any suggestions would be appreciated. My wife is getting very irritated with me.