Big mistake "upgrading" to Rinnai RUR199i from RU180i?

[Tankless-one]

We very recently had a Rinnai RUR199iN installed in our home. It replaces a RU180iN. The RUR adds the crossover recirculation capability.

They installed a thermal bypass valve at what we think is the furthest point in the circuit, which is at a sink in the master bathroom.

It's not working out exactly like I had hoped. (Long story short, the builder and/or subcontractor neglected the install of a dedicated recirc line, as was contracted, so this is the secondary option. The lack of a dedicated line was discovered at house completion. Obviously we are not happy with that).

A couple of issues:
1. The water heater revs up loudly basically any time we use hot water, even when the recirc function is turned off. I think this is the pump turning on? But why does it need a pump when it's not recirculating?

This sound definitely did not happen with the RU180iN model, which I'm guessing doesn't have the same internal pump mechanism?

The water heater is installed on a wall in the garage, which unfortunately is connected to a major structural wall of the home. This sends that rumbling and low hum into the living room and the entire 2nd floor.

Even when we disable the recirc function altogether on this model, the pump still revs loudly anytime hot water is pulled. I was hoping with the recirc function off, this wouldn't happen.

Is there any chance this is because of a poorly configured water heater?

Is there a way to isolate the sound better? Maybe a way to alter the water heater mount on the wall?

The vibration + sound is so bad we are thinking of reverting to the RU180iN and forgoing quick hot water.

Issue 2. Our kitchen sink now has very warm/hot water that comes out when set to cold, when recirc is turned on. Have to run it for 10-15 seconds to get cold water.

I knew this would be a compromise, but I thought that it would be only at the faucet with the bypass valve?

The faucet is a Brizo with a touch-sensitive on/off mechanism. We use the touch mechanism exclusively. Is this part of the problem, or not at all? Not sure if there is a different way it shuts off water flow when using the electronic system, that allows mixing hot and cold if hot water is pushed through with a pump.

I have a feeling the hot water is getting pushed through this faucet instead of the one in the master bath. That one takes nearly the same amount of time to get hot water as with the prior water heater.

Is there a valve that can be installed to mitigate this issue?

Appreciate any thoughts.

EDIT: Discovered the installer shut off the cold water line at the bypass valve and never turned it back on again, negating the function of the bypass valve. Turned it back on and this faucet gets hot water the way it should. But the kitchen sink still has very warm water when turned to cold.

EDIT2: I tested my theory on the electronic shutoff for the touch-sensitive valve and I believe it's correct. There is no warm water coming from the cold side when I turn off the faucet by moving the handle to the physically closed position and run a recirculation cycle. So the electric touch valve probably closes something further downstream of where hot+cold mix. This probably means a check valve on the cold side before it enters the faucet will prevent hot water from filling it.

 

[Breplum]

Your negligent contractor should install a fully dedicated insulated recirculation line on their dollar.

 

[Sponsor]

 

[Tankless-one]

Your negligent contractor should install a fully dedicated insulated recirculation line on their dollar.

Yeah, that would have been nice. How possible is that now that drywall and everything is in place? There is a substantial crawlspace where the first floor plumbing is probably accessible, though it's hidden under insulation.

Actually, given how many errors this subcontractor has made, I cannot allow them any more access to my house.

1. Did not install a condensate line with the initial water heater. Dripped condensate all over the garage for a month+ before I discovered it
2. Did not check for leaks when they installed the bypass valve. Wife fortunately discovered it immediately and had them fix it right then and there.
3. Did not check the gas line to the water heater for leaks. Builder ran back in to fix it after they left.

The less I have to deal with these guys the safer I am.

Hence part of my hope something is misconfigured or wrongly installed that will save us from swapping out a perfectly new water heater.

Edit: just discovered the installer left the cold water turned off at the bypass valve faucet, effectively negating the function of the bypass valve

 

[wwhitney]

Is there a way to isolate the sound better? Maybe a way to alter the water heater mount on the wall?

Yes, you can mount it on isolators, I used a style that looks like this:

https://vibrasystems.com/center-bolted-mounts.html

For seismic regions you want to be sure to use a rebound or snubber washer, basically mount it in a way that if all the rubber disintegrated, it would still be captive due to the large washer.

I believe I ended up rigidly mounting a couple bars on standoffs to the structure, and then I mounted the tankless through the isolators through large holes in those bars.

Cheers, Wayne

 

[Tankless-one]

Yes, you can mount it on isolators, I used a style that looks like this:

https://vibrasystems.com/center-bolted-mounts.html

I believe I ended up rigidly mounting a couple bars on standoffs to the structure, and then I mounted the tankless through the isolators through large holes in those bars.

Cheers, Wayne

Do you have any photos of your setup?

 

[wwhitney]

Here's a slightly off-angle shot of the top pair of mounts, looking down from above. This on the outside of a house, the white cabinet is the rear top of the tankless heater. I should have used the pair of holes one to the left on the tankless brackets, an oversight I never bothered to correct, not an intentional choice.

Note the large washers on the back; they are larger than the holes in the red bar. And those holes in the bar are smaller than the diameter of the visible rubber; that's the design of the mount. The net result is no metal to metal contact between the bar and the heater.

Cheers, Wayne

 

[Tankless-one]

Thanks, that's helpful. Ours is inside on a garage wall, but the idea is the same. Now to see if there are any plumbers in the area willing to consider this.

 

[bingow]

If you haven't already, check that none of the supply or recerc piping is touching the wall. Also, if two crossing pipes are in contact. Separate (if possible ) with a piece of foam pipe insulation.

 

[Tankless-one]

None that I can see. Here's a photo of the connections below, which seem well separated.

 

[bingow]

Nothing there that should cause what you described. Above mentioned mounts may be worth your trouble. I had a lesser noise problem that a touching PEX pipe caused; a foam separator helped. I did consider injecting expanding foam behind the drywall, but wouldn't recommend trying it without some on-the-spot advice. Good luck.