Navien NCB-240 Combi Boiler - Not prioritizing DHW

[CM3939]

Hi All -

Having an issue with my NCB 240 combi boiler that I'm hoping someone can help with.

The boiler is not recognizing a call for hot water from our kitchen sink however this only happens when we have the radiant heat in the basement turned on and both sides of the boiler active. The strange thing is if I go to the basement and turn on the hot water in the laundry room sink (which is only a few feet from the boiler) the hot water will work there but then will also work in the kitchen sink afterwards. Also the kitchen issue seems to happen most frequently first thing in the morning after we wake up and haven't been running water in the house for several hours.

I'm fairly handy and would like to address this myself before paying for someone to come out if possible. I'm guessing it's either a pressure issue at the kitchen sink (although the water pressure is perfectly fine) or there is a part in the boiler which is supposed to recognize/prioritize DHW that is going bad.

Any help here would be very much appreciated.

Thanks!

Charlie

 

[Fitter30]

Can't call for dhw and heat at the same time. Is there only one zone for heat? If not how many? What are we they radiate, and or radiators. Is there a zone controller?

 

[Sponsor]

 

[John Gayewski]

Gpm of your kitchen sink?

 

[CM3939]

Can't call for dhw and heat at the same time. Is there only one zone for heat? If not how many? What are we they radiate, and or radiators. Is there a zone controller?

Thanks for the response.

This is a combi-boiler for DHW on one side and heating the water for radiant floor heating on the other.

 

[CM3939]

Gpm of your kitchen sink?

Hey John,

Thanks for the response.

That would make sense however it was working perfectly fine for almost a year after I put the faucet in. I took off the nozzle w/ built in sprayer to clean and soak in vinegar. Maybe it was dirty and able to slow down the water flow just enough to where the boiler isn't recognizing it. I can't think of what else it would be unless there is a part I'm not aware of inside the boiler going bad.

 

[John Gayewski]

Hey John,

Thanks for the response.

That would make sense however it was working perfectly fine for almost a year after I put the faucet in. I took off the nozzle w/ built in sprayer to clean and soak in vinegar. Maybe it was dirty and able to slow down the water flow just enough to where the boiler isn't recognizing it. I can't think of what else it would be unless there is a part I'm not aware of inside the boiler going bad.

Measure the gpm

 

[Fitter30]

Under E can see flow rate of dhw. Need .5 gpm for dhw.

 

[CM3939]

Under E can see flow rate of dhw. Need .5 gpm for dhw.

Perfect. Thanks for the heads up. I cleaned out the aerator and it seems like that may have been the issue.