What type of check valves

Waterlogged

Hello,I have a Navien NFC-250 that is fitted with an external Grundfos pump on the recirculation circuit. I've had mixed results with the different recirculation settings but for the most part it's been fine.

The other night the wife complained of no hot water to the shower. There where no error codes so I rebooted the boiler but still had no hot water. I did notice that the recirculation line was back feeding cold water short circuiting the hot side. So think of it as reversed flow.

Looking at the manual I see there should be one way check valve installed between the recirculation pump and the cold inlet side of the boiler. So there must have been some sort of thermodynamic vodo that caused the back wash.

Long story.. short ask.. what type of check values should be used to prevent this. Just a standard 3/4" rubber seat type or something more robust?

Thanks

hot_rod

what was the error code that had to be cleared? Many of the small circulators have check valves inside them, or shipped in the box with them. The pump manual might show what that looks like.

Who installed the recirc pump?

The Navian manual may shop the correct piping and check location.

Aftermarket check should be a small spring check, rated for potable water use.

An example of a small serviceable check valve.

109A_5

If your system was operating normally, then changed for the worse.

If your system is similar to this, the Recirculation Pump may have a built in check valve that has failed.

https://www.freeboilermanuals.com/assets/pdf/Navien/nfc_h.pdf

109A_5

An example of a check valve in a circulator pump.

Waterlogged

Oh yeah. I forgot those Grundfos pumps have a valve in them.

I'll pull it when i do the descaling and check it. Thanks for the reminder.

Kaos

I've had those check valves disintagrate on city water in a couple of years. Looks like hot water plus chlorine eats the plastic and the rubber over time. I would not bother with an IFC but install an easy to replace in-line check valve. If you can get one with Viton seals, it will last longer.

hot_rod

while the IFCs solved a lot of issues especially with zone pumping.. The check is in the absolutely worse spot, right at the pump discharge

Even in clear air free water they seem to rattle around.

If you install a separate check go about 12D from the pump discharge

Waterlogged

Sorry, the reference 12D is not something I'm familiar with. Is that 12x the diameter of pipe used?

mattmia2

yes