Tankless in an unconditioned NJ attic

[Noth Jersey]

I really wanted to colocate the heater with the water softener and the blasted flow restricting sediment filter, but they sit in the corner of the house with the main entry door, porch, windows on both walls, and sidewalks below (this is a largely above-grade walk-out basement). If I ran the vent along the rim joist, I'm not sure I could maintain clearance from combustible materials. The twenty-foot run would also require a five-inch drop for condensate drainage.

So the whole freeze protection to -30 is inaccurate? The advice I got was post-purchase from the Rheem folks. They seemed pretty convinced that it would operate OK in the attic. Macplumb 777 told me about a freeze kit from Paloma, which apparently owns Rheem. I don't like the sound of having the coil freeze solid.

*UPDATE*

Well, the freeze kit thing is not available for any new models.

At any rate, I just called Rheem again and they assured me that the water heater would survive -30 amibient temperatures. They said the only real concern is having a vent that is sufficiently long. They recommended a cold-weather vent kit with a damper-style end cap.

[master plumber mark]

*UPDATE*

Well, the freeze kit thing is not available for any new models.

At any rate, I just called Rheem again and they assured me that the water heater would survive -30 amibient temperatures. They said the only real concern is having a vent that is sufficiently long. They recommended a cold-weather vent kit with a damper-style end cap.

I dont think I would trust anything that Rheem says.
never trust a Techey that teaches theory.....


yes, -30 that is pretty damn cold, but it dont take that to freeze pipes
....

you had better be installing that unit with some sort of drain pan under it. Something Like a washing maching pan with a drain to the outside...

....just in case those Rheem techs are wrong....


Also, I dont understand how the water lines going to and from this unit in that -30 temp area attic in New Jersey are supposed to keep from freezing and flooding your home either...


are they telling you to run heat tape on all the lines
all the way to the unit???


and if the unit sits without comming on for a whole day
in those harsh conditions, wont that coil get a little frosty??


is their some sort of fail-safe on this ??

Being installed the attic of your home,

I would be very hesitant about this....


.

[Noth Jersey]

I dont think I would trust anything that Rheem says.
never trust a Techey that teaches theory.....


yes, -30 that is pretty damn cold, but it dont take that to freeze pipes
....

you had better be installing that unit with some sort of drain pan under it. Something Like a washing maching pan with a drain to the outside...

....just in case those Rheem techs are wrong....


Also, I dont understand how the water lines going to and from this unit in that -30 temp area attic in New Jersey are supposed to keep from freezing and flooding your home either...


are they telling you to run heat tape on all the lines
all the way to the unit???


and if the unit sits without comming on for a whole day
in those harsh conditions, wont that coil get a little frosty??


is their some sort of fail-safe on this ??

Being installed the attic of your home,

I would be very hesitant about this....


.

Yeah, the attic won't be hitting -30 here. -15 would be a record setting day. We don't go negative very often. The average low during the coldest part of the year is 14.

At any rate, I'll be running the 1" pex underneath the insulation. The only exposed area will be the 18" portion up to the water heater. Maybe I'll just run the heat tape for the last few feet. I probably will put a drain pan under the unit. The problem with putting the unit in my basement is supplying air for combustion. 199k btus requires a little more volume than we have down there.

[master plumber mark]

[quote=Noth Jersey;198641 The problem with putting the unit in my basement is supplying air for combustion. 199k btus requires a little more volume than we have down there.[/quote]

if you can put it in your basement,
that is where it would be wise to do it...

getting combustion air to a applinace is as easy as
just putting in a dryer vent hose to
the outside....

someday over the next decade it will certainly freeze
up in the attic and its just a matter ot when..

[Noth Jersey]

if you can put it in your basement,
that is where it would be wise to do it...

getting combustion air to a applinace is as easy as
just putting in a dryer vent hose to
the outside....

someday over the next decade it will certainly freeze
up in the attic and its just a matter ot when..

What do you think about extending the house envelope to the attic, i.e., removing insulation between the ceiling and building an enclosure around the heater? I would have to put in a fairly large louvered vent in the door. I guess I could always put in a couple of thermostatic outlets for heat tape and a space heater.

[jadnashua]

There are all sorts of fire code and structural issues with moving something like this into the attic and opening up the space. At least a tankless won't weigh as much as a tank would up there - most ceiling joists aren't designed for that kind of point load of a tank.

Some of these things can be installed in small spaces like a closet...is there one near the master bath that could be usurpted for that use? You'd still have the makeup air problem, but that may be doable.

[Dana]

What do you think about extending the house envelope to the attic, i.e., removing insulation between the ceiling and building an enclosure around the heater? I would have to put in a fairly large louvered vent in the door. I guess I could always put in a couple of thermostatic outlets for heat tape and a space heater.

A 200kbtu/h burner needs much more than a dryer hose for combustion air unless it a sealed-combustion setup. Backdrafting or lean operation due to wind-driven and exhaust fan pressure differentials are real possibilities (even in forced-draft models.) Good luck passing inspection if you're just plopping in a dryer hose into the space. (Good luck with getting it INSURED too.) 200kbtu/h is more burner than many/most home heating boilers or furnaces in NJ, and needs to be treated accordingly.

Usually the freeze protection on these suckers relies on having reliable power. If an ice storm took down all the lines an you're out of power for a few days in winter (as happened to me this past December), if the unit is outside the thermal envelope of the building you're basically screwed. (Which DIDN'T happen to me. My HW heater lives in an insulated conditioned basement, it never got below 40F even on nights when it was 10F outside.)

There are many good reasons (well beyond the scope of a hot water heater discussion) for converting attics into sealed, insulated-rafter conditioned or semi-conditioned space and dispensing with attic venting. It's both easier and better than you might think. A condensed encyclopedic overview of published research lives here:

http://www.fsec.ucf.edu/en/publicati...CR-1496-05.pdf

There are also very good reasons for going with sealed-combustion water heaters & boilers, especially if you have tightened up the place a lot (or plan to.) Takagi makes sealed-combustion kits for all of their hot water heaters, and other manufacturers have models/kits that are sealed combustion as well. Backdraft preventers on the venting offers quite a bit of freeze protection from wind (assuming it's inside the thermal envelope of the building) but can only be used on forced-draft models, (which would be most models over 100kbtu/h- I'm less familiar with Rheem, but I'd be surprised if it wasn't.)

[master plumber mark]

What do you think about extending the house envelope to the attic, i.e., removing insulation between the ceiling and building an enclosure around the heater? I would have to put in a fairly large louvered vent in the door. I guess I could always put in a couple of thermostatic outlets for heat tape and a space heater.

the last time I re-did an attic, I sort of remember it being a lot of nasty , dirty , hot and
god awful grimey work......

and you are wanting to do all this just to get your tankless unit up there...


basically you are going to increase the overall area of your home that needs to be heated , increaseing your yearly heating bill and cooling bill,
I suppose that is a good thing if you ahve been wanting to do this anyway someday...


but to go through all this work just to be able to
save a few dollars a month with your tankless water heater...???


Why not put it in the basement, and simply put in a large enough
vent to the outside of the home for air>???



anyway, enough on this topic,

you do whatever makes you happy,

[ChuckS]

Here is the heater I have. It is rated down to -30. It has a built in heater.

http://www.tanklesswaterheaters.com/waiwelaph28ri.html

[Noth Jersey]

The plumbing inspector said he'll probably want me to open up the attic to the conditioned portion of the house. I don't think he realized that my home will likely not provide sufficient combustion air for a 199k btu water heater. I could place the water in a basement utility room next to the water softener and the expansion tank, but boring a 5-1/2" hole for combustion would cause the same sort of freeze problem as putting the unit the attic, right?

Is a buying a direct-vent unit my only practical option at this point?

[master plumber mark]

dryer vents are 4 inches round and no one complains about them....

you want it to be faceing downwards towards the floor... no different than many closets with
a pipe from the attic going down to the floor for air...


A 50 power vent is probably a better choice...

the bradfords are energy star rated too...

[Noth Jersey]

I'm afraid I'd need a 150 gallon tank heater for my 215 gallon bathtub. I'm not even sure a tank would fit in that closet. What type of vent material would you use to draw air from the attic? PVC? Flexible aluminum vent? Rain gutters? Since this closet sits in an exterior corner directly beneath the entryway to the house, I would have to run 7 pieces of 3" round duct up an exterior wall to provide sufficient air. What would be the consequences of notching my bottom plate to that degree?

[Noth Jersey]

Actually, I guess I would need 7 vents since it's a vertical duct, correct?

Required free area of duct:
199,000 btu/4000 btu/in² ≈ 50 in²

Area of 3" duct cross-section:
1.5²*3.14 = 7.077 in²

[ferd]

Better check your math.

[Noth Jersey]

Nice catch! Thanks.