rinnai

cmac

I was reading through "Rinnai woes" and have an issue that relates to one asked before but didn't find the answer.
Just installed RU98i condensing typical horizontal flue kit, pitched back to unit, condensate tube to outside. 3/4 gas line. 3/4 cold/hot main, 1/2 to fixtures. Whole house filter.
Shower goes cold often. I can turn off the flow then back on and it will be Ok, sometimes it will go cold again.
This has happened from the first day. I've taken the flow valve out of the shower head, but didn't make a difference. It does the same thing with just filling the bath. Faucet on full, half, tried different flows. When the shower is working right I can flush the toilet and it won't go cold. I tried hooking up a hose at the unit but can't make the burner turn off with the water flowing.
I have noticed the hot water pressure fluctuate a little and the temp gets hotter then tappers off.
The manometer readings are good and stable. Water inlet pressure around 55psi. I get a lot of condensation.
I did find the inducer fan very loose and one screw missing (shipping) Thanks Chris

Tom_133

How is your condensate piped? Why I am asking is the only problem I have seen with these units is the condensate wasn't getting out fast enough due to no vent on the condensate pipe and halfway thru a shower it would lock out and send cold water. Just a though.

cmac

Thanks Tom, I have a plastic hose going directly outside. The WC is on the outside of the house. I didn't think of venting it. I know putting a loop trap doesn't work.

Jack

Have to run right now, but that unit is internally trapped. Put an indirect drain on the condensate line. Also what are your flow rates on the various fixtures? You can read them within .1 gpm on the touch pad.

cmac

Thanks Jack, ya the touch pad has its own agenda, can't get it to give up the info.
I install these units and recommend customers to them, have had very few problems until I put this one in my own house.
What better way to gain knowledge and a cold shower to boot.

cmac

Still having issues with the tub faucet only. Know matter how we turn it on it won't let the tub be filled with hot water. The shower head works fine. It's like it just has to much flow. The unit is only about 7ft. away from the valve. I did get the condensate line connected vented/indirect.

Tom_133

any pictures of the setup would help

icesailor

Remember, in a shower, with a Pressure Balance valve, if the water is too hot, and you cool it down or have it adjusted so that you don't get scalded, the hot flow through the valve can be very low. If you have the Rinnai set too high, it might be cycling on and off. It can be a real problem with thermostatic mixer shower valves because they need high flow and hot water to mix properly. If the hot water isn't hot enough, you can't slow the cold down enough for the thermostatic part to work properly.

I'm not saying that's what's wrong with your valve, but it is something to consider.

Been there, done that.

cmac

The shower doesn't have a pressure balance valve so to speak, it has a two handle valve with a check valve on the spout. The shower head isn't the problem. I have the unit set at 115 which is fine, so no cold water is used. Using the tub spout is the issue, the water comes out full force and the unit appears to regulates it because the pressure slows down a little & some warm water comes out then the unit stops regulating the output and it goes cold.
Tom, what pics would help?
Thanks for the replies. Chris

icesailor

Understand, when using 8" Center tub/shower valves, the cold will ALWAYS have more flow pressure than the hot. The HOT will be overcome by the cold with its higher pressure. You have to turn back the cold to get it hot. That's why Pressure Balance valves were developed. The balancing spool automatically adjust and balances the pressure. That's why in most Jurisdictions, you can't replace a 8" Center tub shower valve that can be set to make the water come out of a shower head. And that includes hand sprays. Most codes specifically state that any device that can spray hot water on a human body must first pass through a single lever mixing valve that opens in the cold position and is pressure balanced.

cmac

But I'm not using any cold water

icesailor

Put a 5 gallon bucket under the spout and time it while it fills. See how many GOM's it passes. Maybe its exceeding the capabilities of that heater. Its not supposed to, but you're going to figure it out.

When the tub spout goes cold, does the outlet water from the heater get cold too? If it doesn't, you might have some odd H/C cross connection.

cmac

icesailer thanks for your input.
I have found that if I have the cover off the unit the hot water will stay on at the spout. So I took the inducer fan off and checked for clogs and see if it spun freely checked the flue etc.
I think the fan motor may be slowing down under load with the door installed. I don't have enough experience working on these units. The unit was purchased on line (new) and delivered to me.
The plumbing/heating shop I work at Part time is in another state, thats why I didn't get it there I wanted it delivered.

cmac

Icesailer; you also got me thinking about that odd crossover possibility. I have a chillipepper on-demand recirculation pump under the kitchen sink and just beyond that it tee's off to a outside hose bib.
Get this, I was using the hose and noticed the water was warmer than it should be. With the hose on it seems to be pulling enough water from the hot side at the tee on the stop for the chillipepper to turn the rinnai on. Go figure, another conundrum to figure out.
So #1 is the tub spout no hot water unless the unit cover is off
#2 figure out where to tee in the outside hose bib to not start the hot water heater.
Chris

icesailor

I heard an engineer tell me that water doesn't care where it goes. In his connotation, he was wrong. Water and electricity don't care where they go as long as gets to where it wants to go with the path you provide for it.

Plumbers and heaters, have check valves. Electronics have their Diodes.

The outside sill cock is trying to draw more water out of the pipe than is available. You need to move something so that the hot water share isn't getting balanced by the hot water line. That pump and return recirculation set-up is a cross connection between the hot and cold when the pump is running. When you over draw the cold to the sill cock, the outside hose replaces the pump for the cross connection.

Where kitchen sinks can really drive you nuts with cross connections is with portable dishwashers, connected to the spout and the hot and cold are both turned on. You will have a direct cross connection through the kitchen faucet.

It can also happen with old Moentrol Moen T&S valves where the balancing spool gets stuck. Because the spool is always "live" and is pressurized whether the valve is open or not, you have a cross connection. Its a common sound to hear a "Click" behind a tub/shower with an old Moentrol valve when you open or close a hot or cold lavatory faucet. At least you knew the spool was working.

icesailor

@cmac:

If the unit runs better with the cover off, and not so when it is on, take the intake supply off and see if it improves like when the cover is off. If it does, look for an obstruction in the intake side. It could have leaves or birds living in the pipe if it is 3". Starlings like to nest in places like that.

If you see bird ship on the ground, they are residing close by.

cmac

Thanks again, nope no birds, the vent is concentric, although I haven't installed the bug screen set up. The unit is only 2 months old, so not a lot of time for bug build up so to speak.
What controls the fan speed? Flow or gas valve?
I can see how the side sprayer on a kitchen single handle could be a cross over also.
I recently re-piped the hole house from galvanized to pex so moving around the cold supply to the hose bib isn't quite as hard, with the exception of the belly crawl under the house.
But first this stupid Rinnai.

Jack

The unit runs with the cover off, but not with the cover on. There is a leak sensor in the bottom of the unit. If it sees any water/moisture accumulation in the bottom of the unit it interprets that as a leak and shuts everything down. It is possible, unlikely but possible, that there is condensation forming in the bottom of the unit when the cover is on given the air temps and at high flows, creates enough moisture to close the flow control valve and shut off the heater. With the cover off, you are getting warmer air. I would suggest that the vent be disassembled. Reassemble each joint on the floor getting maximum make in on each joint. Take a sharpie and mark that make in and when reassembling the vent make sure you are at the mark. That vent system has proven over 15 years to be excellent with Rinnai units. Having shut-down at high flows is a classic symptom of a cross flow from exhaust to combustion air. At low flows, there isn't enough X-flow to impact the flame rod. I'd hook up a DMM and check your flame current while operating the heater. Also, what is your gas pressure? That is always the first question on a tankless and your description mimics that symptom too.

cmac

Gas at 7.6-8 in. about a1in drop out with the unit running. took the whole flue apart twice, even changed the pitch a little. I started the unit with the cover on but the flue disconnected same thing. cover off, flue connected the tub OK. I had the shower go cold on me today, haven't had that problem sense fixing the condensation piping. didn't get a reading on the flame rod yet.

cmac

flame rod 28V

cmac

After messing with the unit Sunday it seems worse off and having a hard time with the shower too. The hot water flow is fluctuating and I have to turn it off and on to get it to work. I no were the turbine is but haven't checked it or no how to get to it. But if it wasn't spinning nothing would work, and I get good flow hot water at the service port. I should have taken up school on these units, but the school is to far away from my summer residence, rather than this kind of experience. I'm not working with a plumber at this time. I have more experience with large scale HVAC. But have installed more than a few rinnai's.
For a unit that boosts about 9+gpm I'm about to kick it to the curb.

Jack

...are you working with Rinnai tech service? 800 621-9419

cmac

my work hours don't help with the tech service, I have some time in the morning but its early the WC is on the side of the house, neighbor may think I'm evil and shoot me LOL
The spout(tub) say's 38 (key pad) when it's running the temp will get to about 100 and shut off. The shower head say's 18 and it will get to set point (115) but some times it shuts down too.

Thanks for your time Jack

icesailor

"" But I'm not using any cold water ""

I just re-read your postings.

So hear me out FWIW:

It is my personal experience when filling a tub of water with any valve (8" Center valves are worse), if you turn just the hot on and try to fill the tub and then add cold water to temper it, you will run out of hot water and not have a warm tub but a cool one. If you "mix" the water to the proper temperature, you will fill the entire tub with warm water. If you turn on a shower, you can take a whole shower with warm water. Because the shower head is always restricted. Much more than the tub part of the valve.

We used to see similar things with oil boilers with dirty tankless coils that need to be cleaned. You said that "" and I get good flow hot water at the service port. "". You get good flow of hot water, but how many GPM? Did you measure it? Like timed into a 5 gallon bucket how much and at what temperature? If you have good and high flow out of the heater, but not equal in the tub, you have a cross connection somewhere. Turn on the HOT only in the tub as slow as you can maintain hot water. If it isn't close to the same as the tank, you have a cross connection. Rinnai Tech Support won't help you on this one. Trust me. When you find it, you will be training them.

Is there any possibility that you have anti-sweat valves on toilets? Especially the Milwaukee types that look like a big brass "H"? They were notorious for creating cross connections.

You've had too much good luck with Rinnai's. I did too. I don't have one to go look at, but it sounds like something is in the passageway that intermittingly restricts the flow of water and the high limit is shutting down the unit.

Are you sure that you don't have any Floaters that are getting into the cold water screen and restricting the flow enough to make the unit overheat and modulate down? I've seen debris come and go and drive one crazy.

Jack

Turn the controller to 104 and run hot only and see what happens. Figure out the touch pad. All your flow and output temp is there.

To enter or exit the maintenance monitor information mode:
Press and hold the down arrow for 2 seconds and THEN simultaneously press the on/off.

To display various diagnostic information press the up and down arrows. Example "01" which will then display water flow rate, or 02 which will then display outgoing water temp.

Code 1= water flow GPM in tenth so 21 +2.1 gpm
Code 2=outlet temp in F...or Centigrade and you can set that.
3=Hrs of operation X 100
4=Combustion frequency X100
5=Fan Frequency in Hz
6=system controller ID
7=water flow servo position: 1means servo is open, 2 closed, 0 is fluctuation between partially open/closed
8=inlet water temp F
9=fan current Unit 10mA
10=total bath fill vol
11=HEX Temp
12=bypass servo position (degree position)
13=Burner Thermistor Temp F
14=Intake Air temp F
15=Thermal fuse mV
16=Themocouple value mV
17=Frozen Sensor Temp 1 F
18=Frozen Sensor Temp 2 F

Note that not all codes will be present on every model indoor/outdoor or condensing/non condensing.

cmac

Thanks Icesailer, Jack
I did talk with tech service, he thinks as does Jack its in the flue, cross contamination. This is causing the high temp shut down at high flow. I can't see how it could be that sensitive being the way the exhaust and intake are so close at exit. I did get the touch pad to work and will spend more time with that. Sometimes I over look the simple part (reading instruction). The tech also said to check the forced low/high. This is something I don't have experience on performing. I started the procedure as it shows on the paperwork but the values didn't change so I left it alone for now. The readings are off from what the instructions show.
Personally I don't think the flue is bad but I'll order new pieces and see. The one gasket I see that may be a problem is the one inside (exhaust) on the top of the unit. I don't know what I could use other than the silicon grease sent with the kit.
The toilets have a flush master on it.

Happy new year

Jack

When assembling the flue pipe, I don't just push it straight in. I like to kinda twist and push. I think that reduces the tendency to roll a gasket. I would like to see a picture of that vent and termination if you can post it.

Before I purchase new parts I'd try to throw a dab of silicone caulk behind it and let it sit for a while to secure the gasket. Lubricate the gasket then and see if it goes together properly. Of course, I would understand wanting a fresh start too, based on what you have been going through.

Happy New Year!

cmac

I think resetting the low/high fire and sealing the 4 joints of the flue with silicon has improved the situation. I put the silicon on the top edge of the female ends on the inside exhaust, including the one inside the concentric termination. It was only about 40 deg. out so not sure how well it cured.

icesailor

Did you use High Temperature RTV Silicone?

cmac

No, the unit shouldn't put out any heat at 98% efficiency, plus I didn't think of it. Thanks