Lochinvar Noble NKG110N sn- 1828 111061305

ccstelmo

Problem here is that the customer suddenly experiences varying hot water temperatures throughout the house.

Customer initially discovered that the "whole house water filter" he'd ignored forever was full of silt and sand from the well. He went after it but acknowledges that some of this crud and corruption probably entered his domestic water supply piping. I surmised that some of it got sent into the DHW heat exchanger and/or nearby piping. I arrived and broke into both the "in" and the "out" of the exchanger and hooked it up to a reservoir of water in a five-gallon bucket and pumped into the heat exchanger, alternating from both directions. The volume of water through the heat exchanger was huge, leading me to believe that it was not plugged up with crud and corruption. I put everything back together and the problem persists.

Another guy shows up and tells the customer that tapping into the "in" and "out" the way I did did not guarantee the water was pumped thru the heat exchanger because there is some sort of internal bypass.

I have no familiarity with this boiler or the proprietary hardware around the DHW exchanger and so here I am, asking you guys.
Any thoughts?

GGross

You had the correct idea. That being said there is very like an inlet filter or screen, where the cold water enters the flat plate, if there is no screen there is likely to be some other restriction that gets plugged with stuff (a tight elbow or such) There is probably some stuff in that inlet side of the boiler

Sometimes the flow sensor or switch becomes fouled up, or defective, that can cause your issue. Beyond that you should check at each fixture for yourself, perhaps there is a particular shower that acts up that may have a valve issue?

While technically much of what is in there is "proprietary" The design itself is quite universal for modcon combi boilers. I would suggest you become familiar with the general operation of this type of equipment for future service needs.

Ironman

If a washing machine valve, proportional shower diverter or any other device that has a potential cross connection is leaking through, then you can have the symptoms you’re describing.