Suburban IW60 on demand hot water problem

[Biggjb]

hi,


We have a 2018 3920FB, which has a full bathtub in the front. I am guessing this is the reason for an on demand water heater. We have the Suburban Nautilus IW60 on demand water heater. We have been recently having problems getting and maintaining the flow of hot water. About 90% of the time we don't get hot water and when we do the flow last for only a few minutes. I went on YouTube and found only one video about a spider web in the venture. That is not my problem. So took the side panel off the water heater and voila hot water each and every time. Putting the side panel back on and once again no hot water. I am thinking there is a safety device malfunctioning but as I have no manuals there is no way to test. I am lost and need help...any ideas?

[Bourbon County]

It's either not getting adequate fuel or adequate air for combustion. The fact it works with the cover off indicates lack of air. Carefully check the vents and openings in the cover. That's a big burner and it has to breathe.

I don't know if this has a safety switch on the cover or not, that might be another possibility. A door switch should be working just opposite of what you're experiencing though.

[rohrmann]

https://library.suburbanrv.com/
Click Download on the bottom item for the manual.

[Mikendebbie]

When you say you removed the side panel - do you mean you took the metal side of the water heater box off? Or did you remove the basement bulkhead wall which exposes the side of the water heater? Pic below is the sidewall of the water tank for my unit.

When you are listening to it - do you hear the burner fire and then turn off (which would be when you loose hot water)? Or you could feel the heat blowing out of the burner exhaust vent outside.

Are you the original owner?

[Biggjb]

Originally Posted by Mikendebbie

When you say you removed the side panel - do you mean you took the metal side of the water heater box off? Or did you remove the basement bulkhead wall which exposes the side of the water heater? Pic below is the sidewall of the water tank for my unit.

When you are listening to it - do you hear the burner fire and then turn off (which would be when you loose hot water)? Or you could feel the heat blowing out of the burner exhaust vent outside.

Are you the original owner?

Mikendebbie, I mean the side panel of the water heater and not the bulkhead wall. When I listen to heater, I can hear it trying to ignite but the burner does not ignite. I can also smell the propane being pushed out the burner exhaust. Even when I turn it off an on the same thing happens.

[Biggjb]

Originally Posted by Bourbon County

It's either not getting adequate fuel or adequate air for combustion. The fact it works with the cover off indicates lack of air. Carefully check the vents and openings in the cover. That's a big burner and it has to breathe.

I don't know if this has a safety switch on the cover or not, that might be another possibility. A door switch should be working just opposite of what you're experiencing though.

Bourbon County, this is my thought as well. The only vent in the cover is the exhaust vent which seems to be used as both intake and exhaust. I was thinking of cutting a large hole (3 inch diameter) in the side panel I removed and cover it with a mess. As there is no warranty left I hope it will work. Any other ideas?

[ChuckS]

I would remove the metal access panel and observe the flame thru the inspection window as noted in the images below.

If no constant flame while water flows then I would remove the flame sensor/ignitor and clean it and gap the ignitor

If you hear it the ignitor firing but contestant flame it’s where I would look

Image from internet ..

[Biggjb]

Originally Posted by ChuckS

I would remove the metal access panel and observe the flame thru the inspection window as noted in the images below.

If no constant flame while water flows then I would remove the flame sensor/ignitor and clean it and gap the ignitor

If you hear it the ignitor firing but contestant flame it’s where I would look

Image from internet ..

Thanks ChuckS but the flame is constant and full and heats the water really fast. I am really thinking the vent cover on the outside of the trailer is not big enough for complete combustion. We have always had problems with the water heater every since we bought the trailer, but it seems to worse now.

[Bourbon County]

You've already answered my next question if this is a new problem or long term.

The manual rohrman linked is just the users manual and didn't help very much. That single vent appears to be a concentric vent/intake. Look at the slots in the piece behind the screen, that's your air intake. This is a common practice for residential furnaces and tankless water heaters. The theory is that by pulling the intake air across the exhaust tube, it will preheat it a little and in cold weather operation help prevent some condensate that has to be drained off. Please note that I said in theory, I've always doubted the effectiveness of these given the velocity of the air movement.

Maybe start by removing the screen and see if you can see any leaves, insect nests, or other debris in the air intake chamber, maybe even try to put a shop vac on it. It would take very little to obstruct the airflow. I don't know how big that vent is, but it looks pretty small for a 60K BTU burner. It's very likely there is a pressure differential switch or some other type air flow switch that has to prove air flow before it ignites. Your description makes me believe that's what is shutting you down, it's probably doing it's job.

Keep us updated

[ChuckS]

If you don’t have the service manual it may provide some useful info

[Bourbon County]

Thanks ChuckS, that helped a lot.

I was totally wrong about a concentric vent. I was looking at a pic and the extension on the exhaust tube is to allow for the distance from the water heater cabinet and exterior wall on the camper. Disregard my previous comments.

It's a little confusing because it's shown on one drawing in the manual, but not on another one, but it shows the left side access panel in figure 9 having 20 perforations of unknown size. Note, they call it the left side as viewed from the rear of the water heater where the water and gas connections are. I'm going on the assumption this is where combustion air is meant to be pulled in.

Is it possible to pull the exterior cover off and look in there with a flashlight or a borescope? Since you say this problem has been prevalent since you bought the Montana, I'm now suspecting maybe it's installed a little close to the bulkhead or maybe a piece of insulation or some other material has fallen against the panel.

If you don't find an obstruction, maybe your idea of punching a vent hole in the outer cover might be the best fix. It's hard to believe, but if the outer cover is caulked in, the compartment is just too air tight. I doubt you need a 3" vent, a 2" should be adequate. If I'm looking at the drawing correctly the perforated panel should be on the right hand side looking from the camper exterior. I would punch the hole lower than the exhaust and favor the right side as much as possible. You don't want to set up a scenario where the intake is trying to pull in the exhaust gases. Try to find some kind of screen to cover it, maybe order a replacement for the exhaust and use that, it would look better.

Are you getting any error/fault codes on the controller when this happens? The table shows an E6 error for air pressure fault, and an E2 error for accidental stall which is without flame during combustion. I would think one of these would come on.

The gas you're smelling before ignition and after burner cycles off might be normal. This unit has a 20 second post purge after the burner goes off. The draft induction blower runs over to purge unburnt gas and will also help purge any carbon monoxide, it's a really good safety feature. When the combustion cycle starts, the draft induction fan is the first thing to start and should there be any remaining unburnt gas in the burner, it would purge before the burner fires.

I was looking at the specs on the Suburban model and was surprised to see it's only 1.5 GPM. The Fogatti rates nearly twice that with a slightly smaller burner. You're probably right in that it was installed because of the tub, but the shower must be very weak.

[Biggjb]

Originally Posted by Bourbon County

Thanks ChuckS, that helped a lot.

I was totally wrong about a concentric vent. I was looking at a pic and the extension on the exhaust tube is to allow for the distance from the water heater cabinet and exterior wall on the camper. Disregard my previous comments.

It's a little confusing because it's shown on one drawing in the manual, but not on another one, but it shows the left side access panel in figure 9 having 20 perforations of unknown size. Note, they call it the left side as viewed from the rear of the water heater where the water and gas connections are. I'm going on the assumption this is where combustion air is meant to be pulled in.

Is it possible to pull the exterior cover off and look in there with a flashlight or a borescope? Since you say this problem has been prevalent since you bought the Montana, I'm now suspecting maybe it's installed a little close to the bulkhead or maybe a piece of insulation or some other material has fallen against the panel.

If you don't find an obstruction, maybe your idea of punching a vent hole in the outer cover might be the best fix. It's hard to believe, but if the outer cover is caulked in, the compartment is just too air tight. I doubt you need a 3" vent, a 2" should be adequate. If I'm looking at the drawing correctly the perforated panel should be on the right hand side looking from the camper exterior. I would punch the hole lower than the exhaust and favor the right side as much as possible. You don't want to set up a scenario where the intake is trying to pull in the exhaust gases. Try to find some kind of screen to cover it, maybe order a replacement for the exhaust and use that, it would look better.

Are you getting any error/fault codes on the controller when this happens? The table shows an E6 error for air pressure fault, and an E2 error for accidental stall which is without flame during combustion. I would think one of these would come on.

The gas you're smelling before ignition and after burner cycles off might be normal. This unit has a 20 second post purge after the burner goes off. The draft induction blower runs over to purge unburnt gas and will also help purge any carbon monoxide, it's a really good safety feature. When the combustion cycle starts, the draft induction fan is the first thing to start and should there be any remaining unburnt gas in the burner, it would purge before the burner fires.

I was looking at the specs on the Suburban model and was surprised to see it's only 1.5 GPM. The Fogatti rates nearly twice that with a slightly smaller burner. You're probably right in that it was installed because of the tub, but the shower must be very weak.

ChuckS thanks for the manual.


Bourbon County, if you look at the picture provided by Mikendebbie the perforations you speak of are not really perforations but 20 small circles indented on the side. Perhaps I can cut them out but for now the panel is completely removed and it seems to work find. The concern I have with this is rodents getting inside and destroying the wires.


As for the shower, it is very weak and I must take it off the hook and use it like a wand.


I have extended warranty but it is a pain in the butt to call and get a technician (certified) to perform the repairs and most likely they will suggest the same thing that I have done...perhaps cut holes in the side panel.


Thanks everyone I will keep everyone updated.

[Bourbon County]

Suburban's design continues to puzzle me. I can't think of any good reason for the dimples, seems like it would just be an unnecessary step in the manufacture. If the panel is fairly large and made from very thin gauge metal, it can add some stiffness. Don't believe it's for aesthetics, nobody would see it after installed.

It's a physical fact that air is required for combustion, and I don't see where they've made any provisions for intake air. I think you have had the best idea all along. Good concern about rodent proofing. Maybe you can find some kind of vent with a screen at a big box or online?

[Biggjb]

Originally Posted by Bourbon County

Suburban's design continues to puzzle me. I can't think of any good reason for the dimples, seems like it would just be an unnecessary step in the manufacture. If the panel is fairly large and made from very thin gauge metal, it can add some stiffness. Don't believe it's for aesthetics, nobody would see it after installed.

It's a physical fact that air is required for combustion, and I don't see where they've made any provisions for intake air. I think you have had the best idea all along. Good concern about rodent proofing. Maybe you can find some kind of vent with a screen at a big box or online?

I fully agree with you on the design. I now have to determine how much ventilation is required to have complete combustion. Once I determine that I will then know how large of hole I need to cut into the side panel.

[Bourbon County]

You can't possibly make matters worse, and probably can't overkill it either.

I've tried to find some recommendations and the only thing I found was a recommendation of 1 sq in per 1K BTU burner. This is for naturally aspirated burners which yours is mechanically aspirated. For a naturally aspirated burner, 2 each 6" diameter openings would be very close. The draft induction blower has to pull in the same amount of air it exhausts and I believe your original idea of a 3 or maybe 4 inch would be quite adequate assuming the internal construction of the water heater will allow free flow to the blower intake.

[rames14]

I don’t know anything about the tankless water heater, but the furnace on ours exhibited similar behaviors. We looked at gas flow, sail switch. Finally had a mobile tech look at it. Took the whole furnace apart. Nothing. Finally, while putting it back together, he found the screw that holds the igniter was stripped. That also served as the ground. He installed a slightly larger screw, tightened it down and we have heat in Alaska.

[Mikendebbie]

About 90% of the time we don't get hot water and when we do the flow last for only a few minutes. I went on YouTube and found only one video about a spider web in the venture. That is not my problem. So took the side panel off the water heater and voila hot water each and every time. Putting the side panel back on and once again no hot water.

If I understand correctly - the OP thinks the problem is an air intake problem.
The burner flame comes on when water flow is detected and water is heated and delivered, but then burner flame goes out and no hot water is delivered. He took the "basement" side panel off the water heater box and the flame burns good and hot water is delivered. Put the side panel back on - and burner flame goes out after initial fire.

I have and IW60 on my unit and I have not had this issue. Bourbon Country stated that the single vent must be /concentric both exhaust and air intake. I could not find documentation stating where the combustion air comes from - so his theory seems correct. But I would love to know from the engineers how the combustion air gets to the combustion chamber for my own curious future use if I have issues with mine someday.

I have never taken the side panel off my unit - but I believe these boxes are wide open inside (2 chambers split by a divider wall). Looking at the screen shot below from the service manual - what widget lives on the left side that may interfere with combustion with the side panel on or off? I highlited a couple of widgets - but I would suspect the thing that ChuckS showed in the post above - the electrode/flame probe might be defective.

I would check that flame thing before I started drilling holes in the case for more combustion air. My IW60 operates without holes in the case.

[Bourbon County]

I watched a couple of videos on installing/repairing this water heater including the one with the spiders nest. After watching, I retract my previous retraction from post #11; it definitely is a concentric vent. the vent insert that goes through the outer door has an inner ring that I'm guessing is 2" diameter and an outer ring that appears to be 3" diameter. The red rubber gasket on the water heater seals against the outer ring, the inner ring slides into the exhaust tube on the burner housing. It's supposed to draw fresh air around the outer circumference of the vent screen in the outer door. It's not the best design I've ever seen, but they didn't consult me.

I seriously doubt the ignitor is an issue. It only operates until the burner fires and flame sensor detects flame, and this is not the reported issue. If the unit does fire properly and then drops out, it either loses air, fuel, water flow, or a bad flame detector.

I did notice in one of the videos that Suburban uses a diaphragm type single tube pressure switch to detect combustion air flow. These things are notorious for filling with condensate and failing. Looking from outside the camper, it' on the left hand side, need to remove that panel. It's on the negative pressure side of the fan and should be easy to test. Unplug the tube at the fan housing, put an ohm meter across the switch terminals, suck on the tube and see if the contacts close; also check for condensate in the tube too. You might possibly hear the contacts click if you don't have a meter. I would only jumper the switch for testing purposes only, do NOT operate long term with a jumper, very dangerous. According to the online manual this is part #233229 and I saw an online vendor had one for <$30

https://rvpartsexpress.com/product/s...switch-233229/

Although a possibility, I'm still not convinced it's the root cause. If it works with the cover off, the switch still has to work, it's just getting it's air from another direction. The most likely issue is blockage in the intake, screen, or venturi. It's highly unlikely to be an issue now, but those vent screens can freeze over in below freezing weather. The exhaust is very moisture laden and if the screen is very cold, condensate can start falling out and collecting on the screen. Once the water heater cycles off it can freeze over enough to block air flow.

[ChuckS]

A better price formthe pressure switch. If you determine it is needed..

https://www.adventurerv.net/pressure...h-p-36241.html

Sounds like you are making progress in this issue.

Over in the Alpine world the same water heater is causing many many owners similar issues as you are experiencing…

[Mikendebbie]

Does the control panel show an error message ?

He will have to pull the water heater out thru the front in order to remove the right side of the case. He might have to disconnect the water and gas to pull it out. There is no access to the right side because it sits next to the furnace.

Bourbon - the thing you are talking about testing/blowing into is shown in the spider nest video right? He might try to reach it from the left side - looking at those interior views I posted above maybe he can reach thru and get to it. Try that before pulling the whole box out.