Replacement for Navien CH-180 ASME

[Jac04]

My Navien CH-180 ASME (propane, modulating condension, combination) has been installed for 4 years, and it has been running fairly well after getting through some initial issues with gas piping size and getting the supply temp dialed in (thanks to this forum, especially Dana).

Well, I pulled the cover to clean the inlet screen and give things a once-over, and the heat exchanger is leaking. Really? After only 4 years.

The leaks are in the outer case of the secondary (condensing) heat exchanger. It appears to be a cast aluminum housing, and there are 2 pin holes with corrosion 'boogers' hanging off them.

I imagine the heat exchanger will be covered under the 10 year warranty. I'd like to do the install myself, but I guess I need to be prepared to pay to have a Navien servicer do it. I'm just not sure I want to go through this in another 4 years, because there is nothing to make me think that the next heat exchanger won't do the exact same thing. It just looks like the acidic condensate is causing this housing to corrode.

Anyhow, I want to be prepared with a secondary plan. So, I may just bite the bullet and replace the damn thing.

Knowing the the CH-180 works well in my application, what would you recommend for a replacement? I'm looking for something that I won't need to worry about for at least 15-20 years (other than regular maintenance).

 

[Dana]

Are you looking for another combi, or would a boiler + indirect work for you?

Stainless heat exchangers seem to go the distance better than aluminum (I thought the Naviens were all stainless too- are you sure it's aluminum?) , which can be more sensitive to the heating system water chemistry. HTP's EFT series combis might work, but NOBODY has 15- 20 years of experience on them- hard to say for sure.

Kiturami (the manufacturer of the EFT series) like Navien a Korean company, and competes head to head with Kyung Dong (Navien) in their domestic market, but it's hard to find long term reliability comparisons between them.

 

[Sponsor]

 

[Jac04]

Thanks Dana. With my limited space in the boiler room, it looks like the combi is the way to go.

Well, I'm not sure if the outer housing is aluminum, but it seems to corrode like aluminum, and it sure looks like cast aluminum. Like you, everything I have read says the Navien heat exchangers are stainless. However, maybe they are talking about the internal fin/tube part, and not the outer housing.

A knowledgeable tech from my propane company came out yesterday, and talked to Navien tech service. The plan is to replace this unit with an entire new NCB-180E. This unit has a space heating input range of 14,000 Btu/hr to 80,000 Btu/hr. The bottom part of the secondary heat exchanger (with the condensate port) now appears to be plastic. This is good, since I am also seeing lots of corrosion around the bottom of the existing housing where the condensate hose attaches.

The only thing I don't like is the warranty issue. I believe that my warranty 'clock' will not reset because this new unit will be a warranty replacement. My first CH-180 was replaced after a year and my current CH-180 had been in use for almost 4 years. That means the new unit will only have 5 years left on the 10 year heat exchanger warranty. Oh well.

Now, getting a little off the original topic, but ...

ODR Curve:
The NCB unit will finally give me some control of my ODR curve. The existing CH-180 makes me choose from pre-set curves, none of which work for me. The NCB-180E will let me set the curve, BUT there are some weird parameters that I must follow:
1) The minimum Outdoor Temp Setting is -4F.
2) The minimum supply temp has to be at least 36 degrees F less than the max supply temp.

With baseboards, I currently don't go any lower than 115F on my supply, and I use 115F for outdoor temps of 30F or above. From there, I ramp up linearly to 145F supply at -5F outside. (I currently have to do this manually, based on the forecast, what a PITA). So, I'll have to slightly tweak my supply temps, using 145F for the high (at -4F outside) and 109F for the low (at about 45F outside). That should give me a good starting point.

I'll try to keep you all posted on my progress.

 

[Jac04]

UPDATE:

A new NCB-180E is scheduled to be installed on the 18th.

 

[Jac04]

UPDATE:

New NCB-180E was installed. Everything seems good, BUT this thing is LOUD in high fire mode (like for the first 15-30 seconds of a call for DHW or heat). Have max fire limited to 50% for both DHW & heat, which is as low as it will go, but the noise remains. The noise is definitely vibration coming from the fan when the fan is at higher speed, which vibrates the sheetmetal case and the wall. Once the unit modulates down a little, it is very quiet.

So, my battles with these Naviens just keep on going ...

Anyhow, I may just replace the fan, since it's not that expensive (and far cheaper than a service call, since the warranty on this unit simply picks up where the original unit left off, so I'm outside the labor warranty). If that doesn't fix it, I'll most likely start a new thread on this issue.

 

[Jac04]

UPDATE - in case someone searches for the same vibration issue with a Navien NCB:

A new fan was installed under warranty and the unit is now MUCH quieter . Just a little vibration, much like the CH unit it replaced, but it doesn't vibrate the whole house like it used to.

The fan that came out has a significant 'wobble' to the fan. We inspected the new fan before installation, and it ran very true.