Rinnai Water Heater

John Fernandez_2

We istalled a Rinnai on demand water heater, due to architectural restrictions we could not mount the unit on an exterior wall, thus we vented the unit vertically using Rinnai vent components. We are lacking one piece of the vent system, which is a the termination piece, it is a 39" piece of pipe with a cap on top. I wanted to try the unit out and check its operation.... the exhaust pipe does not go through the roof actually it terminates about a foot below the roof, yes there is a hole in the roof for the new vent pipe, so the exhaust goes to atmosphere. My question is this........is it because of the lack of the termination piece of vent causing the unit to rumble upon call for heat ? Question 2....why is there cold water in the hot water line after a a normal hot cycle run, I think there would be residual hot water in the line......I checked for cross connections and found none.

JackFre

I'll try

Yes, it can cause a rumble because while it may seem that it is venting to the outside you are problably getting some recirc of flue gases back to the burner. Also, check your gas pressure. The #1 mistake on installs is inadequate gas line sizing. Go to www.rinnaisolutions.com for a gas line sizing program to confirm your sizing. Also, check the position of dip switch #1 on the pcb for proper setting for your vent length. It is in the manual. Do you have the condensate collector on the unit outlet?

As to the cold water in the line...Every time you turn off the water the unit has to initiate fire again upon the tap being opened. On the Rinnai that is the CW inlet turbine reads the flow and incoming temp, The pcb initiates the inducer, then the spark and then the gas to flame. You will get a short period of cool to cold water thru the unit while the unit figures out what it is seeing and responds. It is called the "Cold water sandwich" and is a characteristic of on-demand hot water heaters.

JackFre

Also....

Tech service is at 800 621-9419!

John Fernandez_2

Right on

Jack.............. you were 100% right about the vent and the cool water "sandwich" on the Rinnai water heater. It is working great. Thank you for the input.

John

JackFre

Cool, glad I could help!