Outdoor tankless okay to install in crawl space?

[Tyson M]

I'm looking into getting a Takagi outdoor tankless unit and I'm thinking about installing in my crawl space.
The crawl space is conditioned but the access to it is outside, so temps can get pretty cold down there.
I wanted to do an outdoor unit to eliminate the existing venting up into the attic from the current tank water heater. The whole purpose of installing the tankless is to knock out the closet that currently houses the tank water heater and all of it's plumbing and move everything out of sight to the crawl space.
I want to get an outdoor as opposed to an indoor because sometimes the water lines do freeze in the crawlspace when it gets extremely cold and the outdoor tankless units have freeze protection. Is this a bad idea to install an outdoor unit down there? I live in Colorado so summers are typically hot and dry and winters are fairly cold.

Thanks!

 

[Jadnashua]

A unit designed for outside installation may have freeze protection for its internal parts, but that won't necessarily do much of anything for the supply and outlet line to/from it! It very much depends on how those lines are run whether it might work out.

Given where you live, the winter-time incoming cold water can be close to freezing...take that into account when evaluating whether a tankless system would provide enough hot water. Most of them are based on incoming water at 50-degrees and you have to read the fine print to find out what it can do when it's close to 20-degrees colder. It all depends on how much hot water you need at any one instant (gpm) and how much it needs to warm it. Think of waving your hand through a candle flame...a gallon of water weighs a bit over 8#...now, try to heat that up maybe 80-degrees as it flows past the burner...it only works when you have a HUGE burner, or you dribble the water through. WOrks much better in the summer when the incoming water is warmer, but if you have a deep well, it may never warm up much!

 

[Sponsor]

 

[Tyson M]

I guess what I'm concerned about is the exhaust. Is the exhaust going to be a problem if it's in the crawl space? Will it be a fire hazard?

 

[Terry]

If it freezes in the crawl, then the water lines will also freeze.
The exhauset needs to vent outside, not in the crawl space. We're talking carbon monoxide. Not a good thing to breathe.

 

[BadgerBoilerMN]

First, air seal and insulate the crawl space. There is no reason for a ventilated crawlspace in any part of Colorado.

Second, read, understand and follow the manufacture's installation manual, failure to do so may lead to properly damage, personal injury or death.

Finally, and to the point. Seek sound, experienced advice on the proper application of any gas-fired appliance you are considering. Most tankless water heaters are not good replacements for most tank-type water heaters when peak loads, gas piping and proper venting are considered.

In a closet, confined spaces and otherwise tight installations, a sealed combustion, direct vent, (plastic intake and exhaust) are the safest and most reliable, in terms of providing combustion air from outdoors, types e.g. NPE 240A, NRCP 1112, RUC98iP or the TH3DV TH3 Series 199000 BTU, if you must.

 

[Dana]

Listen to what the Badger says- a ventilated crawlspace is nothing but a liability in Colorado. It's a big heat leak for the house, and makes the plumbing susceptible to freezing. A ground vapor barrier and exterior wall insulation, with no permanently open wall vents is the way to go. The details of the wall insulation (and any ground insulation) depend on your actual climate. Colorado spans US climate zones 4B through 7B, so your location matters.

An outdoor tankless Takagi will freeze up just as quickly (or faster) than an indoor version would. They both are equipped with resistance electric heaters for freeze control on the heat exchangers, but if it can get below +10F down there forget about it. Just send Takagi some extra money now and save the installation expense- they won't warranty against that damage.

Not to mention, exhausting a gas burning appliance into a crawl space under the house would violate every clearance rule in the book. Even if it didn't gas you to death right away or set the house on fire, the condensing exhaust in the enclosed space would be a mold problem.

Installing a sealed-combustion interior unit inside of conditioned space makes the most sense, using a combustion air duct that's inside the insulation boundary of the house (or sealed insulated crawlspace) for at least 3', and with at least 3' of exhaust vent fully inside the insulation. With ultra-short runs even a light breeze can take out the heat exchanger when it's in negative double-digits F outside.