Navien 210 combi heat exchanger leak?

Safari65

My Combi has a recurring pressure loss issue. It'll run fine, sometimes for a day, sometimes just a heating cycle. Then the pressure drops 2 psi or less. I had an old bleeder screw that was leaking but has been repaired, but the pressure drops continue. I've put eyes on all the visible piping and can find no evidence of water. Yesterday a pal and I were spitballing what it could be, and he asked if there was a way to isolate the loop (single loop system) and watch for a drop. I thought i could. I attached a gauge (with tell-tale needle) to a valve in the loop, turned off the t-stat, put 20 psi into the loop / system. I then closed the valves to the boiler at the flush valves. The loop does not lose pressure, but the boiler begins dropping immediately, down to 2 psi or less. As soon as i open the valves, however, the pressure pops back up in the machine. There is no visible water leaks in the machine. When I had a tech out recently, they replaced the flame rod assembly as it was worn. The only thing making sense now is a leak from the heat exchanger into the burner? Am I missing something?

kcopp

If it is leaking you will see the condensate drain leaking water.
Pull the hose out and dont have the boiler run. If it stats dripping/ streaming thats the issue.

Safari65

kcopp, thanks for the suggestion. So i did that. put about 20 psi into the loop / boiler. I closed off the boiler at the flush valves. Guage on the loop read about 18 psi, machine readout said 20.1 psi. I put the condensate line into a mason jar and left for work. Almost 10 hours later i got home. There's maybe 1/8 cup of water in the jar from the condensate line. Oddly, the loop rose in pressure almost 10 psi. When I restarted the machine, i started getting water from the condensate line right away. I missed a couple teaspoons, but the line is back in the jar and i'll see what happens.

Safari65

I left it to run today. stuck the condensate drain line in a bucket. 9 hours later there's a little over 4 quarts in the bucket. That seems high to me. Can anyone comment on this?

kcopp

That depends on a number of things.
How often did it run? How cold outside? What is the operating temperature when it runs? (is this hooked up to an outdoor temperature sensor)... the lower the operating temperature the more condensate.

hot_rod

Does it ever drop to zero psi?

Safari65

Kcopp i couldn't say how often, or even how long it ran. It had dropped pressure before i got home. I'm in NJ where it's currently 30 degrees f.

Hot_rod, yes, it repeatedly drops pressure to less than 2 psi. That's the problem I've been fighting.

Safari65

24 hours later, about a gallon of water from condensate line, dropped to 0.0 psi twice.

Safari65

update, condensate line drips whether the machine is running or not, and also after the pressure drops to zero.

HVACNUT

Any part of the house on a slab, or pipes run through an inaccessible crawl space?
Does the boiler have the hydraulic seperation manifold with isolation valves? If so, can you isolate the boiler and leave everything off for a few hours. Don't even use the domestic hot water. There's the digital readout on the display, and a separate tridicator gauge on the space heat side so you can easily check both. Leave the feed valve off.
Where is the low water cut off?

Safari65

hvacnut, I did this last week: I isolated the boiler by closing the backflush valves at the bottom of the boiler. I had a gauge on the space heat side with a tell-tale needle. Space heat side actually rose in pressure over 8 hours. But the boiler was powered off. The house is on a slab. The piping only goes into the slab under the front and back doors. Piping at the front door is new pex with no connections under slab. Rear concrete is visible and shows no sign of moisture. Low water cut off is inside the boiler itself. I'll give it a fresh try in the morning. Thanks!

Safari65

I did a test. twice. T-stat off, boiler on. I put 20 psi into the system and had a gauge with telltale needle on the baseboard heat loop. I closed the backflush valves to the boiler and also the house feed line into the system. the condensate line went into a mason jar. Test One, 2 hours. The boiler dropped to 0.0 psi withing 30 minutes. The baseboard loop lost about 3 psi over 2 hours, which i think may be from the water cooling, since it was almost 160 degrees at the start. Condensate line put half a quart of water in the jar. Test Two, 2 hours. The boiler dropped to 0.0 psi within 30 minutes. The baseboard loop lost maybe 1 psi over 2 hours. Starting water temp was 110 degrees. The condensate line put half a quart of water in the jar. I know what I think, but I am far from an expert. What do you all think?

kcopp

You need to get someone there (preferably the installer) to start a warranty claim.

Safari65

kcopp, it's 4 years out of warranty and the installer went to Florida (I'm in NJ). I'm going to call the manufacturer and see what they say. I don't have my hopes up, though.

kcopp

I think you would be better off working w/ a contractor on this. They have some pull and have people in the supplyhouse that can work on your behalf...
If you call... they dont know you from Job...