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FiReSTaRT
Premium Member
join:2010-02-26
Canada

FiReSTaRT to tp0d

Premium Member

to tp0d

Re: Water Heater Brand Recommendations

Tankless units are almost an "all or nothing" kinda deal. If you just want luke-warm or a trickle of hot, you might not get it, so I'm not a big fan of them, unless you install a storage tank, but then you might as well just go with a standard unit and make sure your tank is sized right for the load.

Condensing (high efficiency) tanks have higher flue gas temperatures than most manufacturers are willing to admit. If it's not already in the specs, pay the few extra bucks and have the first 5' of venting in CPVC as it's rated for higher temps than PVC. Same amount of time and material cost, after markup should still be under $100 extra. Well worth it if you don't like the idea of flue gases escaping into occupied (by you and your family) space.

macsierra8
Baby Newfoundland
Premium Member
join:2003-11-30
Minden, NV

macsierra8

Premium Member

said by FiReSTaRT:

Tankless units are almost an "all or nothing" kinda deal. If you just want luke-warm or a trickle of hot, you might not get it, so I'm not a big fan of them, unless you install a storage tank, but then you might as well just go with a standard unit and make sure your tank is sized right for the load.

Condensing (high efficiency) tanks have higher flue gas temperatures than most manufacturers are willing to admit. If it's not already in the specs, pay the few extra bucks and have the first 5' of venting in CPVC as it's rated for higher temps than PVC. Same amount of time and material cost, after markup should still be under $100 extra. Well worth it if you don't like the idea of flue gases escaping into occupied (by you and your family) space.

Your observations are completely different from those of us here who have and regularly use top brand tankless heaters. I have no trouble adjusting water temps high or low volume.

As for flue pipe and gas temperatures I have no data on that but the Rinnai PVC 5" OD flue pipe I use is metal lined pipe. With the cool flue gas temps I've experienced coming out of the heater I doubt the gas escaping enigma & melting the pipe is a problem with OEM pipe.

FiReSTaRT
Premium Member
join:2010-02-26
Canada

FiReSTaRT

Premium Member

The units in question were Rinnais but who knows, maybe they never bothered with proper adjustment, just put'em in and forgot about'em (the guys who did that don't usually play with residential appliances). They probably just needed hot water, space at a premium, insulating pipe too much work, so they slapped a couple on the wall and called it a day.

As for the flue gas temps.. Tankless units usually need special venting, while regular condensing HWT's and Cat-IV boilers are normally vented with PVC. Those are the units I'm talking about. In most cases, PVC isn't rated for the flue gas temps that those units put out, so you need to go with CPVC.
XXXXXXXXXXX1
Premium Member
join:2006-01-11
Beverly Hills, CA

XXXXXXXXXXX1

Premium Member

said by FiReSTaRT:

The units in question were Rinnais but who knows, maybe they never bothered with proper adjustment, just put'em in and forgot about'em (the guys who did that don't usually play with residential appliances). They probably just needed hot water, space at a premium, insulating pipe too much work, so they slapped a couple on the wall and called it a day.

As for the flue gas temps.. Tankless units usually need special venting, while regular condensing HWT's and Cat-IV boilers are normally vented with PVC. Those are the units I'm talking about. In most cases, PVC isn't rated for the flue gas temps that those units put out, so you need to go with CPVC.

My Quietside has PVC piping for intake and exhaust venting. I attached a pic. It's been a great unit thus far!

FiReSTaRT
Premium Member
join:2010-02-26
Canada

FiReSTaRT

Premium Member

said by XXXXXXXXXXX1:

My Quietside has PVC piping for intake and exhaust venting. I attached a pic. It's been a great unit thus far!

Intake doesn't matter, you could even run the black stuff without any issues. For exhaust, I'd run the first 5' in CPVC. Water heaters and boilers have hotter flue gases than your typical Cat-IV forced air furnace. The PVC product that I've dealt with is rated up to 149, the CPVC product was rated to 190. If the flue gas temperatures exceed the rating, it causes too much expansion/contraction and it may eventually separate the joints, which causes flue gas spillage into occupied space. If you run CPVC for the first 5' of the exhaust, the flue gases cool down enough by the time they reach the PVC run that they're within specs for the material.

By the way guys, if you see your condensing appliances vented with the black stuff, get it changed out ASAP.. It's not rated for hot flue gases, the cement is weak and joints separate almost by looking at'em.