Condensate Trap Sediment

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Jac04

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Back on 9-18-17, I had new Navien NCB-180E combi boiler installed at my house. It replaced a 4-year-old CH180 unit.

Background: The CH180 unit always (from day 1) had grey colored condensate, and the trap always had heavy grey/black sludge in it. Navien told me this was normal, but the outer casing of the heat exchanger failed after 4 years. The grey/black material turned out to be the outer aluminum housing of the heat exchanger corroding away.

OK, back to the 1-year-old NCB-180E. After installation, I cleaned the condensate trap a few times over the first few weeks and found nothing but a few shavings leftover from when the intake & exhaust PVC pipes were cut. The condensate was clear, and I was relieved.

I checked the condensate trap on 2-25-18 and found some sediment (see pictures). I didn't think too much of it at the time, as there was very little sidement. I saved the sediment, cleaned the trap & re-installed it.

I checked the trap on 4-25-18 and found more sediment (see pictures).

Here's my concern - the sediment is magnetic! The only magnetic parts that are in contact with the condensate are inside the heat exchanger (as some of the stainless heat exchanger parts are made from a magnetic grade of stainless steel). My concern is that the heat exchanger on this unit is slowly corroding away, just like the fist unit.

The intake screen is clean. The condensate water is crystal clear. Being on the condensate (combustion) side of the heat exchanger, this issue is independent of the water being supplied to the unit.

What do you guys think? Is this a problem? Normal?

Thanks, Jeff
 
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Jac04

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Well, I guess I'll just keep an eye on this and see where it goes.

Reached out to installer, but no reply.

Reached out to Navien Tech, but they told me that condensate doesn't contact anything other than the plastic parts of the heat exchanger unit and the exhaust piping. I had to explain to them what the stainless steel secondary heat exchanger actually does. Not exactly confidence inspiring. Oh well.
 

Jac04

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Update FYI:
Finally got someone at Navien Tech to tell me:
Thank you for contacting Navein. I have reviewed the email thread below and I agree with you, this is a concern. The magnetite is a product of corrosion typically caused by oxygen and carbon dioxide. However, if you have a unit that is less then a year old the only plausible cause could be, build up. The system you had in place before our unit released enough of this to stick to the venting. All that is now running down. Flush your venting thoroughly and monitor the condensate. Also, as a precaution, ensure that your water quality is within spec.

Well, all of the intake and exhaust 'venting' was replaced with brand new components when the unit was installed, so the theory of previous build-up is out the window. That leaves heat exchanger corrosion as the likely source.

By the way, I also like how they throw in "ensure that your water quality is within spec". They tried to blame my first heat exchanger failure on water quality, which is 100% unrelated since the part of the heat exchanger that failed does not come in contact with the circulating water. If I know Navien, they are trying to set me up for blaming this issue on water quality.
 

Stuff

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What kind of gas/propane are you using? Maybe it is not matched to the burner orifice so is over firing.
 

Jac04

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The unit was converted to propane at installation. It is supplied as a NG unit and the propane orifice is included with it. The installer checked combustion with an analyzer after it was installed. I get propane from my local supplier, Superior Plus Energy Services.

I was thinking the same thing as you - that the corrosion may be due to improper combustion. I have notified the installer, and will hopefully hear from them soon.
 

Jac04

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UPDATE:
I wasn't able to get any response from my installer.
Navien Tech basically told me 'everything is fine'. Needless to say I'm going to keep this email for when the unit fails. Luckily I have the person's full name. Here's what he said: "Flush your venting thoroughly and your unit will be just fine."
 

Jadnashua

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I'm assuming that this is a closed combustion device that gets its intake air from outside? If so, where is your intake?

Condensate is naturally a bit acidic, but it can become a lot more corrosive if there's some contaminants in the intake air.
 

Jac04

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I'm assuming that this is a closed combustion device that gets its intake air from outside? If so, where is your intake?

Condensate is naturally a bit acidic, but it can become a lot more corrosive if there's some contaminants in the intake air.
Yes. My intake is at the back of my house. I can't think of anything that would cause contamination, other than dust outside from mowing the lawn or blowing the leaves.
 

Kris

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Yes. My intake is at the back of my house. I can't think of anything that would cause contamination, other than dust outside from mowing the lawn or blowing the leaves.
Is it a good venting location, with good separation between exhaust and intake? If caustic exhaust recirculated back through the intake, it could cause corrosion at many points in the combustion chamber and heat exchanger
 

Fitter30

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Ph from a condensing water heater is between 3 & 4. For around $12 can purchase a ph meter from amazon to check it to see if its more acidic.
 

Jadnashua

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A common hiccup is if the intake is anywhere near the dryer outlet, especially if you ever use some bleach.
 
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