Navien 240E Pressure Valve Discharge

[plumbershane]

Hey all,

Not a plumber - know just enough to be dangerous..

We just changed our water filters out in the house, and ever since our combo Navien 240e is discharging small amounts of water all day out the boiler side pressure valve. Boiler is off with summer (still using hot water side), but after I relieve pressure down to around 12 psi, it slowly climbs to just over 30 psi throughout the day as we use the hot water.

Doing a little research some have mentioned the expansion tank. Knocking on the side of it I can tell where there is air, then water...not sure if this eliminates the tank being the culprit...

System is less than a year old, and was working fine until we changed filters. I'm thinking there is air in the system? After I changed filters I heard air vent out the top relief valve, but then we kept receiving an "air" code. I kept trying to relieve air out the top relief valve until the air code went away. Now it's working fine just getting water out the boiler side relief valve.

Hopefully that all makes sense - I'm new to the Navien systems after we bought this house last October. Company that installed it is 4 weeks out and my other buddy who's a plumber hasn't worked on these systems.

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[ShaunCorbs]

Is there a service valve on the expansion tank ?

 

[plumbershane]

Not directly above the tank that I see - I updated the original post with links to pictures (uploaded to my ftp site).

 

[ShaunCorbs]

I would say the tank is low on pressure / needs checking

 

[plumbershane]

Thanks I'll see if someone can get it checked out.

Are the boiler and hot water sides isolated in the Navien system? If I shut off the valves on the boiler should the pressure increase in the system?

 

[ShaunCorbs]

There separate systems not connected eg not the same water

 

[plumbershane]

That's what I thought - so why does opening the relief on the boiler side reduce pressure on the hot water side? And if I shut the boiler valves off, the pressure climbs as well, quicker than if they're open. If I re-open the boiler valves, the pressure drops.

 

[ShaunCorbs]

How do you know it’s reducing the pressure on the hot water side ?

 

[plumbershane]

Sorry I was mistaken - the pressure indicator on the boiler is the space heating side.

It's just confusing to me because if I relieve water out of the space heating/boiler valve and drop it down to around 13psi, and shut the hot water side valves off, the pressure remains constant. But if we run the hot water the pressure slowly climbs. So just seems weird to me if they're separate.

 

[ShaunCorbs]

Sorry I was mistaken - the pressure indicator on the boiler is the space heating side.

It's just confusing to me because if I relieve water out of the space heating/boiler valve and drop it down to around 13psi, and shut the hot water side valves off, the pressure remains constant. But if we run the hot water the pressure slowly climbs. So just seems weird to me if they're separate.

Because it uses the heating water via a plate heat exchanger to heat the domestic hot water

 

[plumbershane]

Thanks for the diagram that helps!

I replaced the expansion tank and bled the lines (as best I could), still having issues. I adjusted the pressure reducing valve to make sure it was set correctly at 13psi, but it still climbs over time.

Seems like, when we run hot water, the pressure increases 1 - 2 psi every time once the system stops. After a few hours then it is back up to around 30psi.

Also - after running the hot water for a few minutes, then shutting the water off, the unit runs for another 3 - 5 minutes or so, turning on and off. Sounds like a dishwasher. I don't remember it doing this in the past.

 

[ShaunCorbs]

That’s strange and if you use no hot water is doesn’t rise ?

 

[plumbershane]

It rises, just slower, last night we were around 15psi, and this morning it was at 26psi.

Could there be anything wrong internally that would allow water to seep into the boiler side? Cracked heat exchanger?

 

[ShaunCorbs]

Yep sorry to say that’s my thought as well time to contact the manufacturer as it should be under warranty

 

[plumbershane]

Thanks, yeah that was my worry.. I'll contact them and see what happens.

 

[plumbershane]

It seems like there's a lot of "sloshing" / dishwasher sound coming from the bottom left pump. It also looks like there's a bleed valve on it. Is there a way to bleed the air out of it if it does have air in the pump?

I see there's a metal clip holding the (possibly) pump bleeder in. Could I drain the unit and remove this bleeder to make sure it's working fine? The bleeder at the top of the system was clogged a while ago (we have some sediment in our well water).

Just throwing out thoughts..

I have the DWH set to 117 F, and it seems the system overshoots to 130F. That's why it runs/oscillates after the water is off, seems to be trying to bring water temp back down to 117 before shutting off.

 

[ShaunCorbs]

Bottom right is the pump with an auto air vent on the left side if there’s a cap on the top of the air vent this should be loose but sometimes there’s purge valves below the boiler eg two 3/4 valves so you can connect a hose pipe on and give it a good flow through to remove any air

But also in the settings there should be a air purge mode