Tankless Challenges

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Rrm8711

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Greetings
I Recently replaced a 20+ year old Takagi TK-3 with a Takagi 310U w/h. The original homeowner put this TK-3 unit in; I’ve only been in the house 4 years.

I am somewhat mechanically inclined and mounted the new unit up (it fit perfectly where the old unit did -did not have to do any adjustments for mounting or exhaust stack & used the same flex line gas feed.

I had a person that understands propane pressures and using manometer’s; he worked for Cummins generators and CAT.

We spent about three hours trying to get this thing to fire up and it would not & threw the towel in. No problem cycling, it would always go to trouble code 111

I then called my propane supplier & they sent out a tech to check the second stage regulator ( checked ok) then they poked and prodded the water heater and for no rhyme or reason, it fired up. The tech left thinking it was good to go.

Now my somewhat problem: out of the factory, this tankless water heater is set at 120°.
If I go to increase the temperature on the control panel (125°, 130°,etc ) it will not fire up and will show trouble code 111 - it does the same thing if I adjust the dip switch that goes from 120° to 140°.

Now, I don’t know if these newer models with their improved technology are more finicky with gas flow and pressures.
My propane supplier recommended shortening the flexible gas line and incorporating more hard pipe, meaning put a hard pipe tailpiece coming out of the water heater which would shorten the flexible corrugated gas line. Whether or not that would make a difference, IDK, but I’ll try it just to rule it out.

In talking to the manufacturer of the second stage regulator (Rego), they said the lifespan of the regulator is about 25 years , which mine is close to that, so I’ll probably have that replaced just to rule that out also.

So, any of you folks out there have the same experience? & any recommendations?

Also, looking through the site glass, when the burner’s on, the flame is good throughout the burner, but is rather small.
With tankless water heaters, when the temperature is increased, does the flame get bigger like it would on a propane barbecue? I’m just curious how the heat is increased, so if anyone has info on that and can pass it along, that would be appreciated.

A rather long post- any input and thoughts are greatly appreciated.

Thank you
 

GReynolds929

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What's the gas pressure, and pipe size? The model listed ships set up for natural gas. Has the unit been converted to propane?
 
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Rrm8711

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What's the gas pressure, and pipe size? The model listed ships set up for natural gas. Has the unit been converted to propane?
Thx for the reply.

The service technician from my propane supplier said he set it to 11” static.The manual says between 8-14.
I need to call the tech and verify dynamic pressure reading.

Pipe size coming out of wall is 3/4” hard pipe, then 3/4” flex to water heater.

Yes, coming out of the factory, this model is set up for natural gas.
It provided nozzles to convert to propane. I should’ve included that info in my opening post -my bad.
The model that was replaced was out of the factory ready for LPG- no conversion necessary.

I may just have to be content with the factory setting (120°), but if there is an easy way to do it, I’d like to tweak up the temperature some.
I’ll reach out to Takagi tech-support some more and see what they have to say.
 

Rrm8711

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Thx for the reply.

The service technician from my propane supplier said he set it to 11” static.The manual says between 8-14.
I need to call the tech and verify dynamic pressure reading.

Pipe size coming out of wall is 3/4” hard pipe, then 3/4” flex to water heater.

Yes, coming out of the factory, this model is set up for natural gas.
It provided nozzles to convert to propane. I should’ve included that info in my opening post -my bad.
The model that was replaced was out of the factory ready for LPG- no conversion necessary.

I may just have to be content with the factory setting (120°), but if there is an easy way to do it, I’d like to tweak up the temperature some.
I’ll reach out to Takagi tech-support some more and see what they have to say.
Update:
Just to play around with the control panel, I bumped up the temperature to 125° and the unit fired up.
I let it run for about a minute or two just exercise it, then turned it off.
Turned the faucet back on and unit is back to trouble code 111 on five different tries.
 

Rrm8711

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Update:
Just to play around with the control panel, I bumped up the temperature to 125° and the unit fired up.
I let it run for about a minute or two just exercise it, then turned it off.
Turned the faucet back on and unit is back to trouble code 111 on five different tries.
 

GReynolds929

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So the nozzles were replaced. Was the manifold pressure checked and reset as needed? Here is the conversion instructions if needed. All steps need to be followed, especially setting the dip switches and manifold pressures. LP is denser than NG, if the manifold pressure is off then the fuel air mixture will not be right and the unit will have trouble with ignition.

Weren't you having the same code with the previous unit? That points a finger at the fuel supply maybe. I would get a dynamic pressure reading, your old second stage regulator could be failing and need replacing.
 

Rrm8711

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So the nozzles were replaced. Was the manifold pressure checked and reset as needed? Here is the conversion instructions if needed. All steps need to be followed, especially setting the dip switches and manifold pressures. LP is denser than NG, if the manifold pressure is off then the fuel air mixture will not be right and the unit will have trouble with ignition.

Weren't you having the same code with the previous unit? That points a finger at the fuel supply maybe. I would get a dynamic pressure reading, your old second stage regulator could be failing and need replacing.
That is in the back of my head and I’m always circling back to it: getting that second stage regulator replaced as it’s at the tail end of the manufactures recommended life span- 25 yrs.

If I get that replaced, then start over from the beginning- have the tech check all the inlet and manifold pressures & dialed in, etc….

One question I have and maybe you’ll know the answer:
Is the inlet gas pressure checked 1st and then the manifold?
In the LPG conversion instructions (Which is a separate pamphlet from the Installation manual & Owners guide) , after installing the LPG manifold nozzles, it says to fire up the unit until a consistent flame is seen through the site glass.
It then says to verify static and dynamic gas pressures for the water heater at the inlet port.
Then it says to check for manifold pressure’s as described in the instructions.
All the above is taking into account that my unit will fire up, period- which is not doing on a consistent basis.
I’m thinking, get that 2nd stage regulator replaced, then start the process.


But to address your ?’s-

I do recall the tech taking dynamic manifold pressure reading’s and him mentioning (surprisingly) it went from 11” to 4”, but came back up. I don’t recall what he said it came back up to , but the manufacturer of the water heater recommends no more than 1.5” of drop.

Yes-I was getting the same trouble code 111 on my old unit, but after tearing it down and taking out the burner (which had a bunch of crud) - on the backside of the combustion area, it was corroded and rotted and there was corrosion on the bottom of the heat exchanger assembly, so I figured that was my problem, but as you mentioned, maybe it was my second stage regulator that was on the out’s.

I’ll reach out to my propane supplier and schedule a replacement of that second stage regulator.

Thanks so much for your input and taking the time.
I’ll provide follow up.
 

Rrm8711

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Yes, this is an lp unit; I left that out of my original post- my bad.

My propane supplier tech was out a week ago this past Friday & measured inlet pressure at 11” at the water heater- static.

Under load/dynamic, it went from 11” to 4” ,but then it leveled off- what it leveled off at, I didn’t get that number -manufacture say’s 1.5” drop maximum.

Whatever the number was, it got the water heater running for a week, until this past Thursday, when I tried to increase the temperature from 120° ( set at factory / default) to 125°.
Then the unit started throwing trouble code 111 , which it had been doing prior to it running for the past week.

The old LP unit I replaced was throwing out the same trouble code 111, but it is about 23 years old and when doing a tear-down, discovered the combustion chamber had a lot of corrosion & crud as did the heat exchanger.
That led me to think that is why it was throwing the trouble code 111.
But if my new unit is throwing the same trouble code, maybe it’s the 23 year old second stage regulator that might be the culprit.
In talking to the manufacturer of the regulator (Rego), they said 25 years is the lifespan & to replace it.

So just to rule the regulator out, I think I will have the propane supplier come out & replace it and then have him take measurements again & have another go at the water heater.
 

Rrm8711

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Yes, this is an lp unit; I left that out of my original post- my bad.

My propane supplier tech was out a week ago this past Friday & measured inlet pressure at 11” at the water heater- static.

Under load/dynamic, it went from 11” to 4” ,but then it leveled off- what it leveled off at, I didn’t get that number -manufacture say’s 1.5” drop maximum.

Whatever the number was, it got the water heater running for a week, until this past Thursday, when I tried to increase the temperature from 120° ( set at factory / default) to 125°.
Then the unit started throwing trouble code 111 , which it had been doing prior to it running for the past week.

The old LP unit I replaced was throwing out the same trouble code 111, but it is about 23 years old and when doing a tear-down, discovered the combustion chamber had a lot of corrosion & crud as did the heat exchanger.
That led me to think that is why it was throwing the trouble code 111.
But if my new unit is throwing the same trouble code, maybe it’s the 23 year old second stage regulator that might be the culprit.
In talking to the manufacturer of the regulator (Rego), they said 25 years is the lifespan & to replace it.

So just to rule the regulator out, I think I will have the propane supplier come out & replace it and then have him take measurements again & have another go at the water heater.
 

Bannerman

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What size is the LP tank, and how much fuel does it contain?

LP is supplied in liquid format, but it is the propane vapor above the liquid that is supplied to and is utilized by your propane appliances.

To rapidly vaporize enough liquid to supply the 190,000 BTU input for your tankless unit, requires a large propane tank with sufficient liquid fuel in contact with the tank walls, to absorb enough heat from the air surrounding the tank.

Although a smaller tank may supply sufficient vapor to supply a lower input appliance such as a cooking range, tank type WH or Forced air furnace, the tankless units initial 190,000 BTU demand on startup, maybe causing the pressurized vapor at the top of the tank to become substantially depleted. The reduction of vapor pressure will then cause additional liquid to more rapidly vaporize, but the initial pressure reduction is likely causing the startup issue.

As liquid fuel is vaporized, the amount of liquid fuel in contact with the outer tank walls will be reduced, thereby reducing the vaporization rate, just as will occur during cold weather temperatures. A tank of sufficient size while more than 50% filled with LP, may not be capable of supplying the same high input appliances when the liquid in the tank is only 30%, or during a cold snap.

The link below, is to an article and charts pertaining to this subject.

Propane Tank Sizing
 
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Rrm8711

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What size is the LP tank, and how much fuel does it contain?

LP is supplied in liquid format, but it is the propane vapor above the liquid that is supplied to and is utilized by your propane appliances.

To rapidly vaporize enough liquid to supply the 190,000 BTU input for your tankless unit, requires a large propane tank with sufficient liquid fuel in contact with the tank walls, to absorb enough heat from the air surrounding the tank.

Although a smaller tank may supply sufficient vapor to supply a lower input appliance such as a cooking range, tank type WH or Forced air furnace, the tankless units initial 190,000 BTU demand on startup, maybe causing the pressurized vapor at the top of the tank to become substantially depleted. The reduction of vapor pressure will then cause additional liquid to more rapidly vaporize, but the initial pressure reduction is likely causing the startup issue.

As liquid fuel is vaporized, the amount of liquid fuel in contact with the outer tank walls will be reduced, thereby reducing the vaporization rate, just as will occur during cold weather temperatures. A tank of sufficient size while more than 50% filled with LP, may not be capable of supplying the same high input appliances when the liquid in the tank is only 30%, or during a cold snap.

The link below, is to an article and charts pertaining to this subject.

Propane Tank Sizing
LP tank is 1k gal @ 85% capacity.

Just some footnotes:
-The previous tankless water heater that I replaced was 199K BTU unit and was 21 years old.
-The previous owners had the dip switches set to 140° (Default on this older model is 122° ,according to the manual).
So the unit ran fine at 140° for 20+ years.
For whatever reason, it stopped working.

What led me to think that the old unit was kaput was that while taking a shower , there was a quick hiccup in the water temperature, going from hot to cold back to hot.
The next time I took a shower, water temp went from hot and then cold, never to recover to warm or hot, with trouble code 111, which is ignition failure in the owners manual.
So I troubleshot: cleaned the filter , the igniter & flame rods- that didn’t work.
Then I did a tear down: pulled the burner out - it was corroded some ; some slight blockage in the passages on the manifold.
But then after pulling the burner out, on the backside of the combustion chamber area, it was very corroded and a lot of crud as there also was some corrosion on the bottom side of the heat exchanger that led me to think that the unit was toast.

But now I’m rethinking it’s possibly the 20+ year old second stage regulator, which according to the manufacturer, has a lifespan of 25 years.
Both the new and the old water heaters were/are spitting out trouble code 111 and the only thing between the first stage regulator and the water heater is the second stage regulator.

So, to rule out the 2nd stage regulator, I am scheduling my propane supplier to come out and replace it and then go from there: recheck the inlet pressures (static and dynamic) and do the same at the manifold.
 

Rrm8711

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LP tank is 1k gal @ 85% capacity.

Just some footnotes:
-The previous tankless water heater that I replaced was 199K BTU unit and was 21 years old.
-The previous owners had the dip switches set to 140° (Default on this older model is 122° ,according to the manual).
So the unit ran fine at 140° for 20+ years.
For whatever reason, it stopped working.

What led me to think that the old unit was kaput was that while taking a shower , there was a quick hiccup in the water temperature, going from hot to cold back to hot.
The next time I took a shower, water temp went from hot and then cold, never to recover to warm or hot, with trouble code 111, which is ignition failure in the owners manual.
So I troubleshot: cleaned the filter , the igniter & flame rods- that didn’t work.
Then I did a tear down: pulled the burner out - it was corroded some ; some slight blockage in the passages on the manifold.
But then after pulling the burner out, on the backside of the combustion chamber area, it was very corroded and a lot of crud as there also was some corrosion on the bottom side of the heat exchanger that led me to think that the unit was toast.

But now I’m rethinking it’s possibly the 20+ year old second stage regulator, which according to the manufacturer, has a lifespan of 25 years.
Both the new and the old water heaters were/are spitting out trouble code 111 and the only thing between the first stage regulator and the water heater is the second stage regulator.

So, to rule out the 2nd stage regulator, I am scheduling my propane supplier to come out and replace it and then go from there: recheck the inlet pressures (static and dynamic) and do the same at the manifold.
 

Fitter30

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Tank 1 stage reg should be set at 10 lbs. Second stage at house 11". Did you see the on the conversion manual last page has burner side lp pressure.
 

Rrm8711

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Tank 1 stage reg should be set at 10 lbs. Second stage at house 11". Did you see the on the conversion manual last page has burner side lp pressure.

Thank you for your reply.


If you are referring to the/these manifold pressure numbers, then yes
310U Indoor: Max: 2.42 to 3.00/ Min: 0.41 to 0.52.

When my propane supplier tech comes out to install the new 2nd stage regulator, I’ll have him verify the 1st stage.

Then will have him check and verify all inlet ,manifold pressures/ static and dynamic.

I’m really hoping and thinking that the 20+ year-old second stage regulator is the culprit/suspect.
 

Michael Young

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So the nozzles were replaced. Was the manifold pressure checked and reset as needed? Here is the conversion instructions if needed. All steps need to be followed, especially setting the dip switches and manifold pressures. LP is denser than NG, if the manifold pressure is off then the fuel air mixture will not be right and the unit will have trouble with ignition.

Weren't you having the same code with the previous unit? That points a finger at the fuel supply maybe. I would get a dynamic pressure reading, your old second stage regulator could be failing and need replacing.
I agree man. sounds like a regulator issue. I'm wondering if that regulator is rated for LP
 
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