Rinnai I-series tankless combi intermittent E430

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Nhandojo

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Hello,

I have a fairly new (~8 months old) Rinnai that just recently started throwing E430 (low/high water pressure error). This happens intermittently when there's a demand for DHW or CH. It can be reset and the unit would work again for a few hours and then would error out again when there's demand for hot.

I can sort of trigger it to happen by inducing a large DHW demand, e.g. filling a bath, and I was watching the performance data display on the unit when this happen. The displayed water pressure is reading close to 0 PSI (it fluctuates when there's a demand for hot, but settles as soon as the unit reaches temperature), so I think the controller is doing what it is programmed to do, which is protecting the unit from boiling over when it thinks there's no make-up water. The trouble is, the external pressure gauges are all reading ~22-23 PSI, and there's no leak.

I had checked the circulator motor spins freely, DHW input filter screen is clean, CH filter is clean, etc. Any ideas what might be wrong? Should the boiler's internal pressure display dips below steady-state pressure when the boiler is activating? I can't think of the reason why this internal pressure gauge would dip low when the unit is starting to heat.

Thanks for reading,
Nick.
 

Fitter30

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E430 minimum 13lbs max 30lbs on the boiler side. Need to hook up a external gauge to the system. Possible one of two problems sensor is bad or expansion tank charge is wrong or bladder is bad. Fill pressure set the same as bladder pressure on a.cold to warm boiler.
 
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Nhandojo

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Thanks for the insight, fitter30. I did check the expansion tank, and it is not waterlogged, though I haven't check its bladder precharge pressure with the tank isolated yet. Need to get a hose to be able to drain the tank without spraying water all over the place.

I suppose the only other thing to check is the pressure sensor in the boiler itself. There's an external pressure gauge on the supply side of CH loop and it reads a consistent pressure, 22-23 PSI.

Since this error happens also with only DHW active, I would have thought that the CH loop is not "in the loop", therefore isolating the problem to be internal to the boiler. Is this sane?

EDIT: forgot to mention, changing pump speed to low makes error more reproducible. Just as an experiment, the pump speed should be set to high as per Rinnai.
 

Nhandojo

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Yes, I have the manual and am well aware of the steps the outlined there. The original installer agreed to come over on Tuesday and have a look, hopefully we can get to the bottom of this then.
 

Plumber69

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Hello,

I have a fairly new (~8 months old) Rinnai that just recently started throwing E430 (low/high water pressure error). This happens intermittently when there's a demand for DHW or CH. It can be reset and the unit would work again for a few hours and then would error out again when there's demand for hot.

I can sort of trigger it to happen by inducing a large DHW demand, e.g. filling a bath, and I was watching the performance data display on the unit when this happen. The displayed water pressure is reading close to 0 PSI (it fluctuates when there's a demand for hot, but settles as soon as the unit reaches temperature), so I think the controller is doing what it is programmed to do, which is protecting the unit from boiling over when it thinks there's no make-up water. The trouble is, the external pressure gauges are all reading ~22-23 PSI, and there's no leak.

I had checked the circulator motor spins freely, DHW input filter screen is clean, CH filter is clean, etc. Any ideas what might be wrong? Should the boiler's internal pressure display dips below steady-state pressure when the boiler is activating? I can't think of the reason why this internal pressure gauge would dip low when the unit is starting to heat.

Thanks for reading,
Nick.
Did you figure this out. Exactly the same thing is happening to me
 

John Gayewski

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Very first thing to do is call Rinnai. They might have a varified issue that they know about. I've heard of some with them. No specifics though.
 

Nhandojo

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Did you figure this out. Exactly the same thing is happening to me
I'd forgotten about this until now when it happened again. Long story short, Rinnai replaced my unit under warranty and gave me the option to get another installer to install the replacement unit as I have lost confidence in the original contractor. The new installer didn't find anything obviously wrong with the original installation itself (only that some black iron fittings have been used where brass should've been, and those were replaced).

The replacement unit ran flawlessly from Jun 3rd 2021 until today (Dec 21st, 2022) when the same (E430) code popped up. I power cycled the unit and watched the pressure indicator on the unit itself. If memory serves, the new one is behaving similar to the old unit. When DHW is demanded, there's a pressure drop in the digital reading, only sometimes the drop is far enough to trigger the error code.

I have not had to refill/touch the CH loop since it was installed ~1.5 year ago. The pressure gauge on the expansion tank dropped ~0.5 psi during that period, so there is no leak and I've no reason to suspect waterlogged expansion tank, though that is the next thing to check in the morning.
 

John Gayewski

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Can you take a picture of your system with the unit, piping, circulator(s), expansion tank(s) etc.?
 

Nhandojo

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Can you take a picture of your system with the unit, piping, circulator(s), expansion tank(s) etc.?
Thanks for taking a look at this. I'm pretty sure the flex piping is ~2in in diameter. I upgraded the dirt trap to magnetic trap also. The water entering the system is also treated with one of those water treatment siliphos (anti-scaling) cartridge.
 

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John Gayewski

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Something that is jumping out at me. What is this piping system? Hydronics works in very small pressure differentials. I see that there's some kind of pex hooked directly to the air seperater. It looks small is it 3/4? Also that flex piping. What is it?
 

Nhandojo

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The pex piping is 3/4", and the flex piping is stainless steel I think. It's what the installer used, I didn't choose the materials. Perhaps I should've been more critical, but at the time I didn't have reasons to suspect.

I do agree with you that the piping is unusual, but the hydronic has been working fine for ~2 years, water is circulating to the air handler next to it (not pictured).
 

GrumpyPlumber

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Something that is jumping out at me. What is this piping system? Hydronics works in very small pressure differentials. I see that there's some kind of pex hooked directly to the air seperater. It looks small is it 3/4? Also that flex piping. What is it?
Same, at a glance it looks like CSST was used for hydronics.
 

John Gayewski

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If I were trying to figure this out it would be a very long call with rinnai. A low pressure error on the boiler side sounds odd. I didn't realize the boiler monitored pressure instead of water level. Corrugated piping can lose a lot of pressure and there's not much to loose on a hydronic system. But the circulator should be shooting right at the boiler as I think it's internal. So the individual sensor I would think. Maybe it's a known bad component and no matter how many you change your gonna have trouble?
 

Nhandojo

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I don't think the corrugated piping plays a role, this pressure drop happens when DHW demand starts, and water is circulating solely inside the boiler (the 3-way valve circulates water from primary heat exchanger to secondary heat exchanger). I can isolate the boiler by closing the CH in/out valves and operate DHW to prove this point.

Took a video of the symptom. The E430 isn't currently being triggered as the pressure drop isn't as low as 0.5bar (7psi), but I think its only a matter of time before that happens (I would really like to be wrong on this...)


If/when the error code crops up again (hopefully not during holidays/gigantic winter storm) I'll be on that long call with Rinnai tech support, and will post whatever the resolution is here.
 

Phil L

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I don't think the corrugated piping plays a role, this pressure drop happens when DHW demand starts, and water is circulating solely inside the boiler (the 3-way valve circulates water from primary heat exchanger to secondary heat exchanger). I can isolate the boiler by closing the CH in/out valves and operate DHW to prove this point.

Took a video of the symptom. The E430 isn't currently being triggered as the pressure drop isn't as low as 0.5bar (7psi), but I think its only a matter of time before that happens (I would really like to be wrong on this...)


If/when the error code crops up again (hopefully not during holidays/gigantic winter storm) I'll be on that long call with Rinnai tech support, and will post whatever the resolution is here.
As Fitter30 mentioned, the problem may be a sensor. I had an E430 error on my combi boiler. External gauge pressure was fine around 22 psi despite the digital reading showing 6 psi. Tech came and called Rinnai. Rinnai advised him to clean the water pressure sensor (part number 807000185) which is above the internal pump. This fixed the problem. I think what happened is that the installer didn't flush out the existing pipes on my system before installing the new boiler. The residue in the pipes gummed up the sensor. The tech removed the sensor, cleaned the sensing area with a cloth, and then re-installed the sensor. Apparently, a dirty sensor triggering an E430 error is not an uncommon problem. Hope this helps.

 

Fitter30

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Boiler is piped wrong heat side. It needs hydraulic separation and constant flow through it. The built in pump flows enough for one small zone but not the three or four. Primary secondary loop is needed with built in pump just for the boiler another for the zones with some headers instead of all the tees. Are there zone valves?
 

Nhandojo

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As Fitter30 mentioned, the problem may be a sensor. I had an E430 error on my combi boiler. External gauge pressure was fine around 22 psi despite the digital reading showing 6 psi. Tech came and called Rinnai. Rinnai advised him to clean the water pressure sensor (part number 807000185) which is above the internal pump. This fixed the problem. I think what happened is that the installer didn't flush out the existing pipes on my system before installing the new boiler. The residue in the pipes gummed up the sensor. The tech removed the sensor, cleaned the sensing area with a cloth, and then re-installed the sensor. Apparently, a dirty sensor triggering an E430 error is not an uncommon problem. Hope this helps.

Yep, the problem's definitely dirty sensor. I flushed the dirt trap a couple weeks ago, and although I have not opened the boiler itself to clean the sensor directly, the problem has slowly fixed itself. The transient dip in pressure reading when DHW starts is now almost gone.

Thanks for confirming that pressure sensor issues is not uncommon with these boilers!
 
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