Weird Rinnai Combi behavior

eblend

Hello all,

So I built my own home and installed the Rinnai myself, but I am now wondering if I did something a little bit wrong. There are a couple weird issues. I have created a diagram to show my system setup

Basically, the water comes in from the well, into a pressure tank, and then from there it does a Y, one half of the Y goes towards my yard hydrant distribution, and the other half of the Y goes up to distribute cold water to the house, and a T off that to feed the Rinnai i120cn boiler.

What I am noticing is, when I open an outdoor hydrant at high pressure, the Rinnai i120cn is turning on and starting to heat. It feels like it's detecting reverse flow in the pipe. I was thinking of throwing a check valve after the Y before the boiler, and I think that would resolve this issue, but am I missing anything else here?

Another issue I noticed is that if the system is doing floor heating in it's dedicated floor loop, and I go and take a shower, it all works fine and I have a normal hot shower, but if I go into the utility room shortly after, the Rinnai will flash E430 error code. Reading online that seems to indicate loss of pressure, but why. The heater does fire back up and the code disappears, but something obviously isn't right here. I never notice any pressure changes when showering or anything like that, and wouldn't have even known about the error if I didn't drop by the utility room right after to notice it once. I did the same thing yesterday and say the E430 flash again as well. My hydronic loop in this boiler is independent with a feeder tank that keeps that pressure, so I don't think it has anything to do with Hydronics side of things.

Any assistance would be appreciated. Feel like I have some fundamental issue here that I overlooked.

Jamie Hall

The diagram is nice — but nowhere near complete enough to begin to troubleshoot. Sorry…

Questions?. How is the hot water heat side connected to the domestic water side? Need to know all the valves and pumps and locations, as well as the expansion tank for the hot water heat and any air removal devices.

Are there any valves anywhere on the system? Need to see them.

What pressure does your domestic side run at when an outside hydrant is open?

Related, do your well pump and well have the flow capacity to handle the demand when an outside hydrant is open and something is also running inside? At what pressure?

For starters…

eblend

Hey, i don't have all the answers as I haven't actually gathered some of that data yet, but here is my system setup, hopefully it will answer some of that. Many of the questions you you are asking seem to be related to the CH side of the Combi, whereas I believe my problem is on the DHW side, but anyways, here is some pics of my setup:

In this pic, you can see the well water coming in on the left side into the pressure switch, and then on the right side it exits into the white PVC pipes, where it Tees off into PEX (covered with foam insulation). That PEX is where the first diagram I made basically starts. Ignore the few other valves further down, that's for future irrigation system. The PEX then runs inside the wall where there is a Y for water to flow to rest of the house on one side, and outdoor faucets on the other. There is a valve with a drain to shutoff the water to the outside in the winter

This picture is of the CH side of the setup before it was filled. I didn't have the well tank yet when this photo was taken, it currently sits right below the Rinnai. This is a closed loop glycol system, with expansion tank, pump, air eliminator, dirt separator, as well as the auto feeder, which feeds the system with 16-18PSI.

In this pic I overlaid my initial diagram

Hope that all makes sense. My understanding is that the DHW side of things will get pressurized by the well pressure tank, which kicks off at like 30PSI I think, and currently set to run until it hits 50 PSI I think at the moment.

My well can do 10 GPM. I only have a water pressure gauge on the DWH on the pressure tank, but haven't looked at it's behavior when water is in use. I will try to look at it next time my wife is taking a shower to see what it's doing.

GroundUp

Your system pump is pushing right at your expansion tank connection, which is causing system pressure to fluctuate wildly during a call for heat and likely causing the issue you describe. Move that system circ to the downstream side of the air eliminator/ expansion tank (and verify air side tank pressure while the system is drained) and the issue should cease.

Slimpickins

As Groundup said you need to move your pump so you're 'pumping away' from the expansion tank. As for the 430 code, Rinnai I boilers need higher pressures than others. They recommend 20 psi. After you move the pump, charge your expansion tank without pressure on it to 19 - 20 psi. I'm not seeing any purge valve unless you're using the drain on the dirt trap. When you're sure the system press is at least 20 psi and no air in the system, I'd check the pressure switch.

As far as your DHW, I would install a check valve after the tee to the hydrants and make sure your well pressure tank is properly charged.