To flush or not to flush Navien NHB-150

[Mev]

I have gotten 2 different opinions on flushing my Navien NHB-150 boiler during annual service. The installer, who no longer services or installs boilers, would flush the system during maintenance. A new plumber who came out says it is not necessary to flush. I looked at the Navien website, manuals, and blog. Those resources say a tankless boiler or combo boiler needs to be flushed during service. I can't find any recommendations on flushing a NHB boiler other than when specific issues happen. First, is what I've said correct about flushing the NHB series. Second, if correct, why wouldn't flushing as a general maintenance item help with longivity of the boiler. It still has a heat exchanger, still can get scale. Just confused. Thanks

 

[Reach4]

If you don't add water, you are not adding hardness materials.

I am not a pro, but if the system stays sealed, flushing seems undesirable to me. A water heater, on the other hand, passes new water. That would need periodic removal of deposits.

 

[Sponsor]

 

[Mev]

Thanks that makes sense. A tankless has the domestic water flowing thru the heat exchanger whenever someone turns on the hot faucet. Simple, but I could not understand it on my own. Thanks again.

 

[Fitter30]

Its a heating boiler. If the system was flushed and maybe boiler glycol 30% should ownly need a sample of the water once a year couple of oz.. The minimum glycol mix is 30% for the inhibitor package. Boiler glycol doesn't need to be protected for a hard freeze only slush if the 30% is met.
On a combi the dhw side needs to cleaned at least once a year with vinegar to clean the minerals out of it.

 

[John Gayewski]

Water is the best thing for your boiler. Once it has been heated the air and minerals have been mostly removed or mitigated. Adding new water only makes things worse.