Navien CH-240 knocking/banging noise

giantsean

Hey All,

As if I didn't have enough trouble with my system, today I was powering up after a power outage and the boiler starts making a banging noise the likes of which I've never heard. I am neither an HVAC pro nor a plumber, but I know machinery and this was NOT a normal noise. I literally thought an animal had crawled in there and was trying to get out. It was a loud knocking/banging which was shaking the whole unit. The strangest part was that it persisted after I powered it down. It seemed to be coming from the top of the heat exchanger (upper right) near what looked to be some sort of solenoid. Not sure if this was stuck or if it was trying to push the mother of all air bubbles through but long story it was not working, first firing off error 16 (overheating heat exchanger), 01 (water boiling in HE), and 46 (abnormal thermistor). I tried cleaning all filters (both the water filters were clean) as well as the air filter (which was not as clean). Eventually after several on/off cycles it began working normally again.

I will say for sure that I have had the DHW inlet turned off for a few days (the house is still under some renovation)

Typically the unit will do the "singing pipes" routine which from what I understand is just from expansion. This was definitely not that. It also did not sound like trapped air (I hope!) but I guess it's possible. It went through an air purge cycle after I pulled out the supply filter. As I mentioned it works now, just wanted to see if anyone has seen this and whether there will be anything to watch out for in the future.

Thanks for any info!

njtommy

First off did you switch your supply and return lines on your hot water coil? If so did you see any changes?

What pressure was your boiler at when you turned it on?

Ironman

It sounds like there was steam flashing in the HX due no water flow. That could be from being air bound, a blockage or the circ not pumping. I doubt that it has anything to do with the domestic heating circuit.

giantsean

Thanks. It has not repeated since so maybe it was a fluke and just needed to work itself out.

@ Tom... no have not yet. It's been warm enough to leave well enough alone (have the rest of the house to make livable first). I have had a couple of guys look at it though and they seemed to think my biggest problem was the low CFM's that the unit puts out. Looked at all the flex and just shoot their heads lol.

Ironman

giantsean said:

Thanks. It has not repeated since so maybe it was a fluke and just needed to work itself out.

That's wishful thinking. Steam flashing is serious and happens for a reason. You need to get a COMPETENT tech to find the cause.

giantsean

Thanks Ironman... I was referring to the other problems I was having w/ my hydro air setup (not enough heat) vs. this problem. It sounds like I should have this specific problem checked though. Are there typical causes for steam flashing in a tankless boiler?

Just as a side question - would the fact that the noise persisted for quite a while after the power was cut be consistent with steam flashing?

Ironman

giantsean said:

Thanks Ironman... I was referring to the other problems I was having w/ my hydro air setup (not enough heat) vs. this problem. It sounds like I should have this specific problem checked though. Are there typical causes for steam flashing in a tankless boiler?

Just as a side question - would the fact that the noise persisted for quite a while after the power was cut be consistent with steam flashing?

I gave the most likely causes in my first post. As far as loosing power affecting it: did the boiler lose pressure when it happened? If not, the power loss may have simply given the real issue the opportunity to rear its head.

Posting some pics of the boiler, its piping and some of the system piping, would be helpful.

njtommy

I wonder if he has a backflow preventer

Ironman

njtommy said:

I wonder if he has a backflow preventer

That's what I was thinking. Or air in the system that worked its way into the boiler when circulation stopped.

giantsean

Pretty sure my system is the most photographed on The Wall by now (long story)

To answer the question about losing pressure, no, not that I know of. I heard the noise shortly after the power came back on.

njtommy

On the CH model I think there is a red cap on the internal pump if that is left up it will suck air in.

@giantsean every time you post this the more I want to rip my hair out. It's solid equipment with a crappy install. The pex drives me nuts.

njtommy

Also I wander if it was a problem with the propane.

Leon82

Is there a possibility it inhaled a bunch of exhaust? My water heater did that once and is was loud!

giantsean

Hey Tom if it REALLY bugs you, CT is not that far away from you lol.

kidding aside, is there anything in that plumbing that should concern me other than the PEX (that we all hate )?

njtommy

Just the pex and the condensate drain.
I probably would of ran 1" piping to the down stairs coil.

giantsean

Not too late for that. I can go over the top with some 90 bend supports and 1" PEX. What I really need though is more CFM's from this setup. Just not well designed.

The condensate drain setup is half my fault (at least the open untrapped portion - because I wanted to drop it straight down and they wanted to drop it into the reducer I told them to leave it and I'd do it later. It's # 457 on the list now

njtommy

Lol lists. I stopped making them or calling things projects.
I have things that just never get finished.

davidjbj

Giantsean,

You mention "singing" as if it is a common issue, I have a Navien
in my new home. I have an issue, mostly in colder weather, where after running the hot water for a bit, 5-10 seconds after shutting it off, there is a sound, like a musical instrument (flute type wind instrument) that slowly builds then trails off, coming
from the crawlspace. It is not coming from the heater itself, which is mounted in the Garage, and not from the tank or values in the crawl space (private well).

Is this the kind of thing you are mentioning? If so, is there a solution? Plumber who installed all the plumbing is clueless.

The system has the re-circulation pump in use with PEX 1 inch piping throughout the crawl/walls, reducing to smaller at each point of use. (not sure of size)

Thanks

Dave

the_donut

A whistling noise? Maybe air venting/sucking.

davidjbj

Thought about that, but it's not coming from the vent stacks, and it's only hot side cold does not do it, but thanks!

giantsean

> @davidjbj said:
> Thought about that, but it's not coming from the vent stacks, and it's only hot side cold does not do it, but thanks!

Hi Dave...sorry this is a year late as I'm not here often. My singing comes from the Navien itself and the copper around it. I'm pretty sure it's just vibrations from expansion in my case. But I also have PEX all over the house and when it goes from cool to hot it expands (more like literally stretches) and it can make all manner of noise, from ticking to groaning depending on what it's pushing against. If you have any running through joists I would guess that is the culprit. In your case maybe it's when the hot pipe is cooling and shrinking back?

Do you have a way into the crawlspace to check?