Suburban IW60 on demand hot water problem

[Bourbon County]

Originally Posted by 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.

Yes, that's exactly what I was talking about. I didn't realize it was inaccessible from that side, maybe possible from the other.

The pressure switches can and are used in lieu of sail switches in some applications and by different manufacturers; there are upsides and downsides to both. A sail switch requires some type of paddle mounted in the airstream that can sometimes be restrictive to air flow and not really accurate. The pressure switches can be produced to be accurate to some very tight ranges in both negative and positive pressures, or a 2 tube design that measures the differential pressure. As I stated, the pressure switches are prone to get condensate and fail.

Take a look at the spider nest video around the 12:15 minute point, you actually get a pretty good view of the fan box and the pressure switch. It's pretty brief and you'll need to pause and maybe zoom a bit.

Take a look at this video about a guy installing a Suburban tankless:

https://www.youtube.com/watch?v=hzFEz14J-D0

Look very closely around the 15:16 minute mark and you'll get a fairly good view of the vent, there's absolutely no question it's designed to be concentric. Look at the inner and outer sleeves on the vent insert that goes through the outer door.

While you're on Youtube, look at this video:

https://www.youtube.com/watch?v=AQaVcruN6hM

This is a concentric vent kit commonly used for residential gas furnaces and tankless water heaters. I realize this is not practical for an RV but the point I'm trying to prove is that there is some separation between the exhaust and the intake. It don't take much but the Suburban design has absolutely none. I'm thinking it's setting up a vortex like situation and preventing adequate amount of air to enter, or could be pulling in exhaust gases with depleted O2 content that would not support combustion; a properly fired burner with good fuel to air mix should exhaust air with nearly zero O2 content. A windy day could make this situation even worse.

I did a quick search of some other RV tankless models and the Fogatti, Ranein, Furrion, Girard, Trume, Precision Temp, and Camplux all have louvers punched in the outer door for combustion air intake. Some of them even have a baffle on the inside of the louvers to help prevent wind interference. I don't know if Suburban is right and the rest of the industry is wrong, or maybe vice versa? In looking at the specs on the other manufacturers, the Suburban is the lowest performing in GPM delivery of all. That is if they all use the same amount of temperature rise for their rating; they don't publish this data. I suppose Suburban has deep inroads to the RV industry with all the other products they supply and the lowest price will always win.

[ChuckS]

What I find interesting is all the other tankless RV water heaters have vent louvers ( as previously posted ) but I am really puzzled that Suburban also makes the ST40 and ST60 series on demand RV water heater and its exhaust door has vent louvers as well

https://suburbanrv.com/files/product...t%20111522.pdf

[Bourbon County]

Good observation ChuckS.

I wonder which model is supposed to be the "new and improved" one? I'm not having any luck researching that. It's common in most all industries to come out with a new model that has some slight cosmetic or performance changes visible to the consumer for sales purposes while the real reason for the new model was to correct mistakes in the previous model. Apparently the ST series is about $100 cheaper than the IW series.

In reading the information on the ST series it states that it can deliver 1.5 GPM of 120 degree water based on 70 degree water incoming temperature. That's very unrealistic unless you're camping in parts of FL, TX, AZ, or Palm Springs; I think the national average is about 55 degrees for ground water. It's a really poor performing unit. The ST series has a slightly higher flow threshold for starting the burner than the IW, 0.7 GPM vs 0.5 GPM.

[Biggjb]

I want to thank everyone for your support. I too watched the spider video and unfortunately my furnace is located on that side of the hot water heater. however, I have access from the other side as it is fully open. There are no error messages. Cutting holes in the side panel is not an option either as I have found that the burner only ignites when the panel is completely removed. Anything less and the burner will not ignite. As mentioned earlier, there are two areas inside the hot water heater, one for the burner and the other side holds all the electronics. They are completely separate. I will look at the diaphragm type single tube pressure switch and see if it is the issue.

[Mikendebbie]

Biggjb - the unit is fairly easy to take out completely. If you think it would be beneficial to access the other side of the box, maybe to blow and test that thing from the spider video. There are a couple of screws anchoring the back panel to the floor, then simply unhook the water and gas, and slide it out.

[Bourbon County]

I'm changing my recommendation on the fix; at my age I believe I'm entitled to that.

The whole idea of a sealed combustion burner is that it uses outdoor air for combustion and exhausts back to the outdoors; it doesn't use any inside air for combustion. It's pretty important in newer more air tight homes so not to create a slightly negative pressure indoors. It's probably not nearly so important in an RV, but punching holes in that access panel would likely make the water heater draw it's combustion air through the access point inside the RV since the outer door is supposed to be sealed to the sidewall.

I will now recommend buying another vent assembly, looks like they make them in 4 different lengths, and another red rubber washer like on the exhaust vent. Cut holes in the outer door and in the end of the tankless housing. Alignment will be pretty critical but should be able to do it with a hole saw. I would keep the new hole as far away from the exhaust as possible. Maybe lower and to the right looking from outside. It looks like the pressure switch is low on the opposite side of the housing, check for any obstructions inside the unit before drilling. This would make this new vent a dedicated intake. You are correct about the cabinet having 2 different compartments as far as I can tell from drawings and videos. After you install the new vent assembly and put the outer door back on, this should give about 7 sq. in. of free opening directly into the compartment containing the burner, and insuring that it's only drawing outdoor air, not your conditioned interior air. It should also look like it's intended to be there. With this design even if you had a louvered door it would still have to have a path into the cabinet.

I still think there might be some obstruction on the air intake system. If you can't see anything in the vent assembly, how difficult would it be to remove the blower assembly? I would imagine that the wires are on a plug and maybe only a few screws to drop the whole assembly. The spider nest video gives you a pretty good look at the blower, notice that the air intake is around the outer part of the blower assembly. Give that a good look for obstructions as well as inspecting the squirrel cage blower for dirty, bent, or missing blades.

Once again I have to say this is a poorly designed product, and hearing about other RV manufacturers experiencing the same issues supports that. It looks like an assignment they gave an engineering student working as an intern for a semester and was never thoroughly tested before releasing.

[Biggjb]

Originally Posted by Bourbon County

I'm changing my recommendation on the fix; at my age I believe I'm entitled to that.

The whole idea of a sealed combustion burner is that it uses outdoor air for combustion and exhausts back to the outdoors; it doesn't use any inside air for combustion. It's pretty important in newer more air tight homes so not to create a slightly negative pressure indoors. It's probably not nearly so important in an RV, but punching holes in that access panel would likely make the water heater draw it's combustion air through the access point inside the RV since the outer door is supposed to be sealed to the sidewall.

I will now recommend buying another vent assembly, looks like they make them in 4 different lengths, and another red rubber washer like on the exhaust vent. Cut holes in the outer door and in the end of the tankless housing. Alignment will be pretty critical but should be able to do it with a hole saw. I would keep the new hole as far away from the exhaust as possible. Maybe lower and to the right looking from outside. It looks like the pressure switch is low on the opposite side of the housing, check for any obstructions inside the unit before drilling. This would make this new vent a dedicated intake. You are correct about the cabinet having 2 different compartments as far as I can tell from drawings and videos. After you install the new vent assembly and put the outer door back on, this should give about 7 sq. in. of free opening directly into the compartment containing the burner, and insuring that it's only drawing outdoor air, not your conditioned interior air. It should also look like it's intended to be there. With this design even if you had a louvered door it would still have to have a path into the cabinet.

I still think there might be some obstruction on the air intake system. If you can't see anything in the vent assembly, how difficult would it be to remove the blower assembly? I would imagine that the wires are on a plug and maybe only a few screws to drop the whole assembly. The spider nest video gives you a pretty good look at the blower, notice that the air intake is around the outer part of the blower assembly. Give that a good look for obstructions as well as inspecting the squirrel cage blower for dirty, bent, or missing blades.

Once again I have to say this is a poorly designed product, and hearing about other RV manufacturers experiencing the same issues supports that. It looks like an assignment they gave an engineering student working as an intern for a semester and was never thoroughly tested before releasing.

Bourbon County I am of the opinion that my model of IW60 was probably one of the first and subsequent models have been modified to rectify many problems and this may just be one them.


I called a mobile repair tech who has worked on our trailer over the past couple years. When he looked at the issue and he felt the problem was lack of air flow. He looked at a couple senors and suggested to replace them perhaps one at a time to see if the issue was resolved. To me this would be very costly and time consuming. I eventually went with my initial idea of replacing the panel cover with a wire aluminum mesh (1/4 inch squares). I just hope it will keep the rodents out.


I want to thank everyone for your help, suggestions and documents. Here is picture of the final product.

[Mikendebbie]

Great idea…keep us updated

[Bourbon County]

Good call not to fire a parts cannon at the problem.

Have you tried taking a shower or at least run hot water for a length of time to see if it keeps burning?

[MattR]

Can anyone on here tell me if there’s any other way to adjust the temperature on these water heaters other than the dip switches? To get the 130 degrees I have all dip switches off except number 4 like the manual says but this one doesn’t seem to be near as hot as my last one. I wasn’t sure if there was another way to adjust as well like maybe adjusting the flame itself. If anyone has any answers I would greatly appreciate it! Thank you!!!

[Mikendebbie]

Hopefully forum member ChuckS will see this post and provide some technical information for you. I have never dealt with the questions you raise.

I thought it might be helpful to post the water temps I get at various outlets in my rigs. The screen shot below is from another thread about the IW60 Suburban water heater. I never get 130* water at the outlets - especially in winter (if that is what you are looking for). The city water supply will much colder in the winter - so the heated water discharge will be less than it would be in the summer.

Edit: I added a floor plan view of my unit to show the location of my water heater. The kitchen and half bath deliver hotter water possibly because they are closer to the source. Also a pic of my control panel with the IW60 controller showing "OF". When I turn it on - I leave it at 129*.

[MattR]

That’s maybe close to what I’m getting but probably not because I’m in Colorado right now and the city water is much colder than that I think. Don’t know for sure because I haven’t tested it but it’s not anywhere close to warm and I know that’ll have an effect on how warm it comes out as well. The main reason I’m asking is because I just replaced the unit and the old one seemed to get warmer than the new one.

[Bourbon County]

I looked at the manual for your model and apparently 130 is max setting with either dip switch setting or digital control. This is obviously for scald protection in the shower.

I highly recommend taking your digital BBQ thermometer and doing the same testing Mike did. Incoming water temp has everything to do with tankless performance. The residential models have a flow control valve built in and will throttle flow rate down to maintain temp set point. I don't see a flow control valve on the wiring diagram, it does have a flow sensor that I'm sure is used to start the unit and switching from high to low fire rate. None of the RV tankless manufacturers that I can find publish a chart or curve on how much flow they can maintain at different temperature rises. If your incoming water is around 40 degrees and you're asking it to raise the temperature 90 degrees, I seriously doubt a 60K BTU burner can do that.

[ChuckS]

Images from service manual for water too cold..

130 is highest temp setting either from dip switches or control panel if installed

[High5er]

Originally Posted by MattR

Can anyone on here tell me if there’s any other way to adjust the temperature on these water heaters other than the dip switches? To get the 130 degrees I have all dip switches off except number 4 like the manual says but this one doesn’t seem to be near as hot as my last one. I wasn’t sure if there was another way to adjust as well like maybe adjusting the flame itself. If anyone has any answers I would greatly appreciate it! Thank you!!!

The only other way I know of to adjust the temperature would be to install the digital control.

[prndl]

The instructions posted earlier say that these heaters can supply water up to 120Deg.
They also say there is scald protection to limit the output temp to 113Deg.

Confusing