Any Boiler Techs on here?

[Hnthrdr]

So boiler went out at the family cabin, had a plumber come up and I was bummed when he said we couldn’t have cast iron/ steel (something about inadequate venting, we had double walled 4” but said 5” was necessary) installed a condensating boiler (navien combi units). Had it installed and it keeps throwing pressure codes. It’s a long shot, but wondering if anyone has experience with navien combi units. Would love to chat, was told we could shut the water to the place off and the boiler would run, what we used to do, but wondering if the condensation is causing the problem ie calling for more water supply and none to be had with the shut down water. Anyhow would love to hear from a boiler tech or anyone with one of these navien units, so far had it for about 2 months and I am not impressed :/

 

[StuckoYota99]

What error codes are you getting?

These newer navien probably have a water pressure sensor in them that wants to see a minimum water pressure on the heating side. 14 psi for example.
So therefore you cannot shut the water supply valve off and run the boiler.
The condensation comes from the boiler combustion process not the water in the system.

 

[Hnthrdr]

What error codes are you getting?

These newer navien probably have a water pressure sensor in them that wants to see a minimum water pressure on the heating side. 14 psi for example.
So therefore you cannot shut the water supply valve off and run the boiler.
The condensation comes from the boiler combustion process not the water in the system.

I am beginning to suspect that, it’s not ideal, since no one is there all the time but gotta do I guess unless people wanna show up to a frozen everything, thanks for the info!

 

[Jstumbaugh]

DM me if needed. I'm pretty knowledgeable on them. As long as you have no leaks in the system and you have supplied the minimum boiler pressure of 12psi (15-18psi target) you should be fine to isolate the feed side. Make sure your expansion tank is good or you will have drastic pressure swings. Low pressure code would be E302. I have a couple of these installed that have no feed connected to them. They are stand alone radiant systems in garage floors.

 

[strousek]

As mentioned above, as long as you have no leaks in the system the boiler will be able to run just fine with no fill water. It is very common practice to close off the inlet fill before the pressure reducing valve once a system is full and operating properly. especially if there is glycol in the system.

You should have a closed loop system with an expansion tank to regulate consistent pressure when temperatures raise and lower. It is possible that you have a bad expansion tank and when the boiler runs the pressure increases beyond the safety limit and releases through the pressure relief. As soon as that happens the system is no longer a closed loop and you will have low pressure when everything cools back down.

Another issue you could have is air in the system. If there are lots of p-traps and no air bleeders on the highest points of the system you get trapped air. The air compresses and absorbs pressure as it travels through the pipes. When the pumps run the air can be trapped for awhile and then eventually find its way through the system to wherever your air relief is located. As soon as the system burps out this air bubble that was compressed the pressure will drop. Once all the air is out however you will maintain a constant temperature.

First check the system for leaks. Fill the system to 15 psi and close off the inlet water. Do not run any pumps or the boiler a full day. Just let the system sit idle with the supply water off. Check after 8 hours or so and see if you are still at 15 psi. If you are lower you have a leak.

If no leak then check the expansion tank. Look for signs of water coming out of the pressure relief valve. The expansion tank should be roughly half water and half air. Tap on the tank up and down and you should hear a difference in the sound on where the water and air line is. You can also put a bike pump on the bottom air fill and read pressure on the unit. At idle the water pressure in the system should be equal to the air pressure on the bike pump fill side of the tank.

Next make sure that all the air is out of the system. Find your highest point and install an auto air bleeder if there is not one there already.

 

[Hnthrdr]

As mentioned above, as long as you have no leaks in the system the boiler will be able to run just fine with no fill water. It is very common practice to close off the inlet fill before the pressure reducing valve once a system is full and operating properly. especially if there is glycol in the system.

You should have a closed loop system with an expansion tank to regulate consistent pressure when temperatures raise and lower. It is possible that you have a bad expansion tank and when the boiler runs the pressure increases beyond the safety limit and releases through the pressure relief. As soon as that happens the system is no longer a closed loop and you will have low pressure when everything cools back down.

Another issue you could have is air in the system. If there are lots of p-traps and no air bleeders on the highest points of the system you get trapped air. The air compresses and absorbs pressure as it travels through the pipes. When the pumps run the air can be trapped for awhile and then eventually find its way through the system to wherever your air relief is located. As soon as the system burps out this air bubble that was compressed the pressure will drop. Once all the air is out however you will maintain a constant temperature.

First check the system for leaks. Fill the system to 15 psi and close off the inlet water. Do not run any pumps or the boiler a full day. Just let the system sit idle with the supply water off. Check after 8 hours or so and see if you are still at 15 psi. If you are lower you have a leak.

If no leak then check the expansion tank. Look for signs of water coming out of the pressure relief valve. The expansion tank should be roughly half water and half air. Tap on the tank up and down and you should hear a difference in the sound on where the water and air line is. You can also put a bike pump on the bottom air fill and read pressure on the unit. At idle the water pressure in the system should be equal to the air pressure on the bike pump fill side of the tank.

Next make sure that all the air is out of the system. Find your highest point and install an auto air bleeder if there is not one there already.

This is fantastic info! Thank you, I’ll check those leads

 

[Hnthrdr]

Also here is a picture of the boiler set up, if you guys with experience can ID any deficiencies. It looked like a clean install to me, but I don’t know much about these systems

 

[Jstumbaugh]

I don't see anything that stands out and looks like a solid install. I usually don't mount the expansion tank sideways as that's point to trap air. The relief valve blow off down spouts should end 6-10" from the floor but I'm assuming they run to a floor drain?

 

[Hnthrdr]

Yes the pvc at the bottom of the picture all run to floor drain about 30” from the wall

 

[strousek]

Little hard to tell from the picture but appears to be a primary secondary loop piping. If the boiler has its own circulating pump the valve with the red arrow in the picture below should be open. Currently this looks to be closed forcing flow through the boiler at all times. The primary loop should be free to flow with the main system circulating pump with any call for heat. Then the boiler secondary loop will pull return and supply hot water to that loop upon loop temp demand. Water should only flow through the boiler when the loop temp is below setpoint. Not saying this is your issue but if this is truly a primary secondary system that valve needs to be open. Otherwise looks clean. Agree with Jstumbaugh that the expansion tank should be mounted vertical. You should still be able to tap on the tank and hear a dull sound with water on the left side of the tank and a hallow ting on the air filled right hand side.

 

[Hnthrdr]

More great insight, I’ll make sure it’s open too! I appreciate all the help, once again Rokslide community delivers!

 

[strousek]

That valve should only be open if the boiler has its own built in circulation pump. If it does not then you need to keep it closed to force flow through the boiler with the system pump. That install would be very odd with only one pump however.