Rheem (Ruud, GE) TRD Thermal Release Device failure

[RonAKA]

Helped my son get his atmospheric vent Rheem natural gas water heater going after it failed. It turned out to be that the TRD device exploded, I guess as it is intended to do if there is an over temperature in the burner area. Found a replacement and managed to get it back in place. However when it started up again the flame was fluffy and orange/yellow instead of blue. The vent seemed to be drawing fine on the exhaust. There seemed to be no obstruction of the fresh air supply to the heater. The vent outside did not have an ice build up.



While we were standing there discussing what to do about it, the flame all of a sudden turned blue and looked just fine. It seems to me that the poor combustion was the likely cause of the safety device failing as it should under high temperature (500 deg).

Any thoughts what may be causing the poor flame and why it would clear itself up suddenly? I looked at the gas orifice on the burner when it was out and it looked fine?

 

[Twowaxhack]

Sounds like it may be taking longer than normal to establish a draft.

Check your vent system. Post pics if you’d like me to look at it.

The heater needs plenty of combustion air.

How old is the heater and where in the home is it installed ? Dusty environment ?

 

[RonAKA]

It is a relatively new WH that was installed in 2018. The house is a bungalow with the WH in the basement. Prior to this the furnace was replaced with a high efficiency version with PVC intake and exhaust. A new WH vent was installed inside the old furnace and WH vent. We checked the vent draw with a cig lighter flame. It seemed to be drawing quite well and I could not detect any change between when it had the orange lazy flame and when it had the much more crisp blue flame. Here is a photo.

 

[Twowaxhack]

I don’t like your vent.

 

[RonAKA]

OK?
What I noticed about it is that it seems large. I have not had an atmospheric vent WH for 12 years or so. From memory I recall mine was not quite that big in diameter. I also remember that it was very hot to the the touch. This vent when it was running this afternoon was not real hot. You could leave your hand on it.

I'm wondering if some insulation wrap around the vent pipe would get it to heat up faster and get more flow?

 

[Twowaxhack]

A 3” vent would induce the natural draft quicker. I’d like to see the horizontal portion have more rise, I can’t tell if it has any actually. It may have enough.

Is the vertical portion of the vent that I can’t see properly sized or is it a oversized vent going out the roof ?

Any chance that some flammable vapors reached the burn chamber ?

 

[MicEd69]

Does the water heater vent into a chimney? If not, I assume it vents into the same vent in the roof as the former furnace and water heater combined did.

If either is the case, the water heater vent pipe is discharging into a larger flue that is filled with cold air. It appears that it is taking a few minutes for the hot combustion gases to heat up the flue to provide the proper draft. The pipe is already double walled just above the water heater draft hood and insulating it will not help as you are not losing that much heat in that pipe.

Some 50-gallon water heaters require a 4" vent, but if the water heater is designed for a 3" vent pipe, as Twowaxhack said, that would provide a quicker draft, assuming that 3" would go all the way through the roof. And also, as he said, while the horizontal portion needs to have at least 1/4" per foot slope, I too like much more than that, something like 20 degrees or so.

 

[RonAKA]

Does the water heater vent into a chimney? If not, I assume it vents into the same vent in the roof as the former furnace and water heater combined did.

If either is the case, the water heater vent pipe is discharging into a larger flue that is filled with cold air. It appears that it is taking a few minutes for the hot combustion gases to heat up the flue to provide the proper draft. The pipe is already double walled just above the water heater draft hood and insulating it will not help as you are not losing that much heat in that pipe.

Some 50-gallon water heaters require a 4" vent, but if the water heater is designed for a 3" vent pipe, as Twowaxhack said, that would provide a quicker draft, assuming that 3" would go all the way through the roof. And also, as he said, while the horizontal portion needs to have at least 1/4" per foot slope, I too like much more than that, something like 20 degrees or so.

Yes, I believe it is a 50 US gallon tank. And the vent is a 4" type B which is why it would feel cool, and agree that insulation would not help. The furnace was retrofitted to a high efficiency type before he bought the house, and from what I can see the water heater vent was replaced with a new 4" vent for the water heater only and goes up through the original chimney vent to the roof. That seems to be common practice here. From what I can see by eye the vent is 4" all the way up to the roof. Will have to check it closer along with the slope.

I have seen some comments on code requirement forcing the upgrades of 3" to 4", so perhaps that is why it was changed. Thoughts about the minimum straight vertical section height right above the water heater? I have seen 1 foot quoted. It would seem the easiest way to get more slope to the horizontal part would be to reduce the vertical height right above the water heater.

Thanks for the suggestions.

 

[RonAKA]

A 3” vent would induce the natural draft quicker. I’d like to see the horizontal portion have more rise, I can’t tell if it has any actually. It may have enough.

Is the vertical portion of the vent that I can’t see properly sized or is it a oversized vent going out the roof ?

Any chance that some flammable vapors reached the burn chamber ?

I think it is 4" to the roof. Will have to check the slope of the horizontal part. Don't see how any flammable vapours could get into the water heater combustion chamber other than natural gas. The burner assembly looked to be in good condition. Thanks for the suggestions.

 

[RonAKA]

A couple of more photos of the horizontal vent plus where it goes up to the roof. Pretty sure this is 4" type B that goes inside the original combined furnace and water heater vent right to the roof.

 

[Twowaxhack]

Yeah that’s the issue. It’s cold and the vent is oversized.

I bet the 4” is stuck up inside the 6” a little like a chimney.

 

[RonAKA]

I bet the 4” is stuck up inside the 6” a little like a chimney.

I don't think so. Pretty sure it is a 4" B vent right to the vent cap on the roof. But, yes, it is inside the original large vent pipe.

 

[Twowaxhack]

I don't think so. Pretty sure it is a 4" B vent right to the vent cap on the roof. But, yes, it is inside the original large vent pipe.

I’d check

 

[TomFOhio]

What is the diverter size? Measure the top of it.

 

[RonAKA]

What is the diverter size? Measure the top of it.

What do you mean by diverter? It is just a full 4" B-Vent and makes a right angle to go straight up to the roof inside the old 6"? vent. If you mean up on the roof, I won't be going up there until all the snow melts. Too dangerous. However by eye, it is 4" at the roof and not the larger combined vent size.

 

[TomFOhio]

The diverter is the piece on top of the water heater with the 4 legs.

 

[RonAKA]

I will have to measure it the next time I am over to my son's house. It would be the one that came with the Rheem Performance Plus heater.

 

[TomFOhio]

Correct. Just trying to determine if his 50 gal tank is a 3 or 4" vent

 

[Twowaxhack]

Correct. Just trying to determine if his 50 gal tank is a 3 or 4" vent

Either one is fine. 3 or 4”

I think the problem is the oversized vertical combined with the 4” they used and how it’s installed. Then It got really cold compounding the problem even further.

Circumstances/conditions got right and the TRD tripped and shut the air supply off to the heater. The burn chamber over heated.

OR

A flammable vapor was present.

 

[RonAKA]

Correct. Just trying to determine if his 50 gal tank is a 3 or 4" vent

It is 4" above the flare piece. The bottom of the flare is 6".