Clark711
New Member
My Rinnai V2532 Inline water heater makes LOUD cycling noise at night. It ROARS on a mostly repeated cycle. After much discussion with a Rinnai engineer, I believe the sound is caused by fluctuating inlet water pressure to the unit. SO, If I shut OFF the inlet valve overnight, there is no sound at all. I have recorded the sound overnight to see the sound wave, shown here. 
There are two separate types of spikes or cycles. The small sound spikes last about 3 1/2 minutes each. The large sound spikes did not begin until 3:30 in the morning. NO ONE was up then. NO ONE was using water. The large sound spikes then occur at ONE HOUR cycles after that, each one lasting about 25 minutes. They repeat not approximately one hour, but exactly ONE HOUR.
The Rinnai engineer said that the noise cycles were likely due to spikes in water flow into the unit. The unit has a flow indicator water turbine, which responds to an increase in water flow by starting up, heating the firebox. I have the recirculating pump completely shut OFF, so there is no on-purpose water flowing in.. There is NO ONE using water at those times of the night, especially not in the cyclic manner shown.
My water supply is city water, currently about 85-90 psi, probably lower in summer. It first flows through a pressure regulator in my basement, then through a check valve, then flows in parallel to a Flexcon Potable Water Expansion Tank, then through the block valve that I shut off, and then into the Rinnai.
As I said, the sound goes away if I shut off the inlet water valve at night. The sound also becomes much less if I change the pressure regulator setting so that the pressure is about 60 psi. The sound is still there, but much less. If I go back to 70/75 psi, the loud sound returns.
My guess is that the water pressure regulator is bad. It is not holding a steady pressure, but instead allows water pressure spikes get to the Rinnai. The Expansion Tank may not help.
Does anyone have thoughts about my problem ? Would you replace the inlet pressure regulator ?
Clark Johnson
There are two separate types of spikes or cycles. The small sound spikes last about 3 1/2 minutes each. The large sound spikes did not begin until 3:30 in the morning. NO ONE was up then. NO ONE was using water. The large sound spikes then occur at ONE HOUR cycles after that, each one lasting about 25 minutes. They repeat not approximately one hour, but exactly ONE HOUR.
The Rinnai engineer said that the noise cycles were likely due to spikes in water flow into the unit. The unit has a flow indicator water turbine, which responds to an increase in water flow by starting up, heating the firebox. I have the recirculating pump completely shut OFF, so there is no on-purpose water flowing in.. There is NO ONE using water at those times of the night, especially not in the cyclic manner shown.
My water supply is city water, currently about 85-90 psi, probably lower in summer. It first flows through a pressure regulator in my basement, then through a check valve, then flows in parallel to a Flexcon Potable Water Expansion Tank, then through the block valve that I shut off, and then into the Rinnai.
As I said, the sound goes away if I shut off the inlet water valve at night. The sound also becomes much less if I change the pressure regulator setting so that the pressure is about 60 psi. The sound is still there, but much less. If I go back to 70/75 psi, the loud sound returns.
My guess is that the water pressure regulator is bad. It is not holding a steady pressure, but instead allows water pressure spikes get to the Rinnai. The Expansion Tank may not help.
Does anyone have thoughts about my problem ? Would you replace the inlet pressure regulator ?
Clark Johnson
