Direct vent gas water heater... are 90degree angles allowed outside?

[dschroder]

I had a power vent water heater put in a few years ago. For some reason, the FV sensor decided to keep tripping this year. Not sure why, basement is a bit humid, kids are rummaging down there a bit more often, and perhaps there is some off gassing from old oil spills from the boiler. It's a mystery.

I put the power vent in because plumber said he couldn't get it close enough to wall. But now I see that some direct vent models allow up to 80" to wall, which I can make. And those don't have those FV sensors, right? The issue is that the highest point of cellar wall comes out about 6" above ground. I used a couple 90s to bring the vent up to about 3'. But all the direct vent models I see don't seem to "snorkel" like this? Is allowable, and does any body make vents for this?

 

[Mitchell-DIY-Guy]

I had a series of [three] power vent water heaters from the time my home was new in 1992 until I moved out in 2019. I believe the last one I installed was in 2012. I cannot tell you if they had FV sensors or not but they were not sealed combustion units...just regular water heaters with the power vent option.

With a direct vent water heater you are using a special wall cap that has both exhaust as well as input (combustion air) components. You must follow the manufacturer's guidelines on installation as well as any local codes. In looking at a common State (a common brand used here in NC) 50 gal model, there are a number of venting requirements, all easily found in their online manual. If you choose a different make/model of direct vent, they may have their own requirements. Safety cages are available to place over the vent cap, too, if the cap will be in a place subject to touching my people who cannot read the word "HOT" embossed on the metal. On this State model, the vent cap must be a minimum of 12" above grade, or 12" above highest anticipated snow level. As an inspector I've seen non-direct vent (they are clearly marked as Direct Vent or not) water heaters installed with direct vent caps, a huge no-no and safety issue generally caused by ignorance or more likely, from someone trying to save a buck by not buying a direct vent water heater as a replacement because they are more costly.

A power vent water heater is a great option with very flexible (not physically, but logically) venting options. Though the unit is about the same cost as a direct vent, it beats a direct vent because the venting is a whole lot easier and less costly.

Couple of things you may try: how about cleaning or replacing the FV sensor? I believe ALL water heaters are now FVIR, so they should all have FV sensors. This was a phased-in requirement that began in 2003. As a precaution, if this FV detector is going off, have you had the immediate vicinity of the water heater tested for flammable vapors by external tools? I carry a flammable vapor detector in my tool bag, but have yet to use it.

 

[dschroder]

I just ordered a cheapo FV tester from amazon. the WH is next to a 40 yo boiler, which has leaked at some point in the past... so there always is a bit of an oily smell... but nothing "flammable." Also reading a cat box nearby can trip those FV sensors. But plenty of people say humidity or dust can trip them as well. You can't clean those external silicon/graphite FV sensor discs, BTW. once they pop, they need to be replaced ($70 for OEM).

From what I read, the direct vent (non AC powered) water heaters have an internal FV system. I'm guessing DV won't work for me since I don't have the clearance and not seeing any that have an option to move the cap up the wall... though I'm seeing some two pipe power vent units which may be a better option if that means they don't need the external FV sensor.

 

[Mitchell-DIY-Guy]

I do believe you are correct in that there are some high efficiency power vent water heaters that have an external air intake much like a condensing furnace typically. I have not seen any in person, but have seen some specs on them and photos too.

Best to call a few professional plumbing supply houses locally to see what you can find. I think Rheem makes one, if you have any Rheem dealers around.

The power vent is basically a [sadly] forgotten water heater. They used them where I used to live since the houses all had wood burning fire places and condensing furnaces, so no reason to make a masonry chimney with a separate flue for the gas appliances. (You cannot mix gas/wood in a single flue). Some of the cheaper builders actually had two story B-Vents when they were too cheap to spend the extra 15% for a power vent water heater, and they had this vent stack running from the basement through the first and second floor before exiting the roof. The smart ones used a power vent water heater.

Here in NC, they prefer putting water heaters in attics (with all the problems that brings) or using electric water heaters when gas is available. It's like they never heard of a power vent...but I wouldn't expect them to when they think a water heater in an attic is a good thing. My neighbor's 3 year old home had his water heater fail. About $2,000 to replace it, and about $5,000 in damage to flooring and ceilings and drywall. Real smart. Thankfully my builder put it in the garage where it can do no harm.

 

[dschroder]

Just got a cheapo FV tester unit of amazon... $22, still smells like Guangdong province.

I maxed out when I got it within 4 inches of a open stove burner, and hit 50ppm from a fart, so it seems reasonably calibrated... got nothing from any reading in the basement. Methinks I just might make due with a 25K resistor in place of the FVsensor

 

[GReynolds929]

Saving $65 is worth the safety of you and your family eh....

 

[dschroder]

$70 every 8 weeks... yeah