Lochinvar NKC150N Water Temperature Problem

lochinvarproblems

Hello everyone,

We have a Lochinvar NKC150N in our home, installed 15 months ago. The other day, all of a sudden we started to get lukewarm water instead of hot. The water never gets as warm as it used to, and also it fluctuates.

I replaced the flow sensor, which didn’t make a difference.

What do you might be the problem here? Please ask me your questions for whatever other information you need.

Thank you all.

hot_rod

did you go through the maintenance steps in the manual?

There is a diverter valve that can get sticky from hard water deposits

lochinvarproblems

Hey, thanks! I hired a plumber initially, who said the problem may be a sticky diverter valve. He turned it back and forth for a while and water did get warmer than it does now. He left. My assumption is that he’s tried the maintenance steps, although I’m not sure.

Problem came back. He diagnosed the problem as the flow sensor. Replacing it didn’t solve the problem.

I hate to complain about this but I got laid off a while back and I just can’t seem to find work. The plumber naturally wants to be paid, can’t blame him, but I don’t have the money to keep paying $500/hour every time he eliminates a potential cause.

Do you think there are other “easy” potential solutions I can try myself?

GroundUp

Did the original installer install flush valves and/or an inline filter? These boilers have an internal plate heat exchanger that can easily get scaled/plugged up from poor water quality and cause the issues you're seeing, and flushing the exchanger would be a good start. A bad flow switch wouldn't have any bearing on temp, so it sounds like you didn't get a very competent technician unfortunately.

lochinvarproblems

Thanks GroundUp, I appreciate it. I don’t know if the installer installed flush valves or an inline filter. Do you know of any resources I can use to figure out how to flush the exchanger?

hot_rod

Service valves like this get installed under the boiler on the hot and cold piping. Then you connect a small pump with a citrus acid cleaner and run it for 20 minutes or more. Always do this first before replacing parts.

Depending on how hard you water is and how much runs through, it could take a yearly cleaning.

lochinvarproblems

Thank you hot_rod, I think you are talking about these guys, right?

I’ll try using the pump like you said. Anything else you think I should know before I do that?

GroundUp

Those are the ones, yes. You'll need to close the yellow handles (90 degrees from where they are, perpendicular to the pipe) first which will isolate the unit from the rest of the system, then remove the two caps facing the camera, then connect your pump and hoses to those ports. Once that's all connected, you can open the red and blue valves and plug in the pump to circulate your cleaning agent (white vinegar usually works well) for awhile then switch hoses and flow some more in the opposite direction. I try to run 20-30 minutes each way on really bad ones, sometimes it may be necessary to dump the vinegar and replace with new.

lochinvarproblems

Thank you very much guys, I really appreciate your help and sure hope this does the trick!

lochinvarproblems

Update: Flushing the combi worked! I used a descaling solution, and then white vinegar. I couldn’t believe the stuff that came out.
I changed the water twice, reversing direction each time and running for 30 minutes each time.

Ran with just water for a last time until I got clear water.

Water gets piping hot and stays that way now.

Thank you so much guys, you have no idea how happy we were to save so much money at a difficult time like this. God bless you all!

hot_rod

you may need to do that descale yearly