Tankless water heater code question

[gsganzer]

I guess I'm putting the cart before the horse. My whole reason for looking into a the code issues on a "tankless" unit has to do with what someone told me about my existing tank heater installation.

When I remodeled the house, I added a utility room for the washer/dryer and pantry goods. I just stuck the water heater tank into the corner of this room. Now an aquaintance has told me that according to code, the tank must be isolated in a closet. If it does need to be in a closet, and had I known that, I would have laid the room out differently. If a "room sealed" unit doesn't need to be in a closet, then I'll just swap to one of those when I replace the tank type. Otherwise, I'll probably have to move some plumbing and gas lines around (not a big deal, I'm on a pier and beam with crawl space) to lay the room out the way I'd like it and add the closet.

My house is outside city limits, so I really don't have to worry about code enforcement, but I also have a wife and kids and I don't want an unsafe installation. I'll call the building inspector this afternoon.

 

[LC Brewing]

_RaT_ - I've had good luck with mine. Flow hasn't been an issue at all. My well water is consistent at 45~55 degrees (summer/winter/any time). Is your Rinnai the 2532 (larger)? I've had showers, dishwasher, and laundry all going at the same time with no problem at all. I was aprehensive (and worried) at first when I had such bad luck with the Bosch, but since switching to the Rinnai it has been great.

Layout and sizing of the water lines in your house may be a limiting factor too though - all of my main hot water lines (a loop in the basement) are 3/4" with only 1/2" branches to individual fixtures, whereas it is more common to see only a short run of 3/4" from the heater and then all 1/2" from there. This (staying with 1/2" pipe) is done to minimize the wait for hot water at the farther fixtures (1 second per foot for 1/2", 3 seconds per foot for 3/4"). Since I have a recirc loop, I opted for the larger main to be able to maintain higher volumes and flows in the main. Also, by having the larger volume in the main, there is less chance for a single upstream tap to steal flow from downstream lines. You can only get so many GPM through 1/2" pipe, so if the shower is at the end of that pipe, and you turn on another item between the source and the shower, you will start to starve the shower. The 3/4" pipe has about 2 1/4 times more capacity than the 1/2" pipe (2.25x cross-sectional area), so it sees less drop in flow from individual 1/2" drops being turned on.

gsganzer - If you are considering a tankless to replace a tank unit, you need to look very long and hard at the gas supply sizing requirements for the tankless, and the exhaust venting requirements. You CANNOT use standard flue vents (often PVC) for the tankless units - they require a special high-temp stainless steel vent for corrosion resistance and air-tight seal, due to the extremely high BTU output they have when operating. They also cannot be combined with any other gas appliance flue vents (such as a furnace). Also, you will find (again because of the high BTU output) that the standard gas supply line sizes will be too small for a tankless unit compared to a standard tank one. Tankless will require no less than 3/4" black iron pipe (larger if the run is longer or has more elbows/fittings or other appliances on it), whereas your standard 40,000 to 80,000 BTU tank heaters are 1/2" black or SS corrugated pipe.

A "room sealed" unit can be installed basically anywhere that is not going to be bothered by the noise (they produce a bit of a fan noise from the makeup blower on the heat exchanger/burner assembly). A dedicated closet or other special room is not required, although you do have some clearances that must be maintained above and below the unit (the top gets a bit warm, and the bottom has all the connections and the PRV valve). Also, the PRV valve must be routed to where it can drain without threatening to flood a finished floor or get blocked by possible flooding (just as with a standard water heater - per code leaving 6" air gap from the PRV drain to any floor drain or floor surface). The biggest factors in a successful installation, though, are the length and complication of the exhaust (more length = less efficiency and more $$$ to install) and the different gas line requirements. One contractor I talked with said they will often install the unit in the attic space of a house, since it makes a short straight run up to exhaust it out the roof, is easy to vent the PRV drain to an eave vent, is usually easy(er) to retro-fit a gas line to the attic - often through a garage wall, and the unit has a wired remote anyway (at least many of them do).

 

[Dargo]

I first bought a Bosch as well, but returned it before I ever installed it when I sat down and went through all the specs. I have had two Rinnai units installed for over two years. I have a standard 200k btu residential unit in my guest house and a larger commercial Rinnai (they are brown) upstairs in my main house. The commercial units will go up to 180 degrees on the remote control temp pad. I didn't realize how hot that is until after I tried it. That is way too hot. The residential units go up to 120, and they default to 108 degrees whenever the power goes out.

The unit in the guest house is installed in a small utility room that is sealed. I changed plans and mounted the Rinnai to the outside wall due to the cost of the intake/exhaust pipe required with the units. We have very strict inspectors and I had my units professionally installed from factory authorized Rinnai techs who were certified by Rinnai for installation. The installation in the small room passed inspection no problem. Also, we have been very pleased with both units. I have a large family and we have 6 showers that could possibly be on at one time. We have never been short on hot water. I still have a 70 gallon tank water heater for the lower portion of my main house. Whenever it gets old, it will be replaced with another commercial Rinnai.

I can't see any advantage to keeping a huge amount of water hot at all times after seeing how nice the tankless units are. I agree with the installers and the inspector in that the tank water heater will soon be a thing of the past. They are extremely inefficient when compared to the tankless models, and they take up so much more space. After a bit of research, I see that the U.S. is about the only place in the world that still uses the wasteful tank dinosaurs.

 

[_RaT_]

I first bought a Bosch as well, but returned it before I ever installed it when I sat down and went through all the specs. I have had two Rinnai units installed for over two years. I have a standard 200k btu residential unit in my guest house and a larger commercial Rinnai (they are brown) upstairs in my main house. The commercial units will go up to 180 degrees on the remote control temp pad. I didn't realize how hot that is until after I tried it. That is way too hot. The residential units go up to 120, and they default to 108 degrees whenever the power goes out.

The unit in the guest house is installed in a small utility room that is sealed. I changed plans and mounted the Rinnai to the outside wall due to the cost of the intake/exhaust pipe required with the units. We have very strict inspectors and I had my units professionally installed from factory authorized Rinnai techs who were certified by Rinnai for installation. The installation in the small room passed inspection no problem. Also, we have been very pleased with both units. I have a large family and we have 6 showers that could possibly be on at one time. We have never been short on hot water. I still have a 70 gallon tank water heater for the lower portion of my main house. Whenever it gets old, it will be replaced with another commercial Rinnai.

I can't see any advantage to keeping a huge amount of water hot at all times after seeing how nice the tankless units are. I agree with the installers and the inspector in that the tank water heater will soon be a thing of the past. They are extremely inefficient when compared to the tankless models, and they take up so much more space. After a bit of research, I see that the U.S. is about the only place in the world that still uses the wasteful tank dinosaurs.

The Rinnai will run without electricity? I have the older model, I think the 2350 or whatever it was called in 2001. Back then it did not come with a remote.

 

[LC Brewing]

The residential units go up to 120, and they default to 108 degrees whenever the power goes out.

I am (pretty) sure mine is a residential unit (2532 FFU) - white cover and everything - but I can crank mine up to 140-degrees. It defaults to 115 if I cut the power to the unit (unplug it from the outlet) and then turn it back on. I keep it at 125 and never change it...just too much of a pain in the butt to run down the the master bathroom to bump it up 10 degrees or down 10 degrees or whatever. That's why faucets have a hot AND a cold tap (or a mix control on the mixing valves). Besides, if I started to screw with it all the time, it would screw up my settings on the shower and bath temp valves - which could be dangerous when I've got little kids that like to start their own bath water.

 

[Dargo]

I am (pretty) sure mine is a residential unit (2532 FFU) - white cover and everything - but I can crank mine up to 140-degrees.

Yes, it is the next size up residential unit than what I have in my guest house. Rinnai color codes the units; white for residential and brown for commercial. Supposedly (other than size) the only difference is that most places do not want a residential unit to be able to go up to more than 140 degrees. After feeling how hot 180 is, I'd tend to agree.

My installer told me today that he thought that my residential unit was only 199,000 btu and the commercial was 250,000 btu. He also told me that he is now not allowed to install the commercial units in a residential location unless he changes a module that allows the temp to go over 140. In other words, you can get the same btu in a residential unit, only you cannot have it go up to 180 degrees. As I said, that really isn't a bad idea; especially if you have kids.

 

[Steve_Miller]

What's the take on electric models as there is no hope for NG in my area. The future for NG is very bleak where I am.

Steve

 

[LC Brewing]

I posted a short reply to CurlyDave's recent (yesterday) question on electric vs LPG vs tank water heaters. In a nutshell, my brother-in-law has an electric tankless and is generally satisfied with it. However, he has stated that when he builds his next house, he will probably switch to LPG tankless(he, like I, prefers to build out of town a bit where NG isn't available). His biggest issue is having to dedicate roughly 1/4 of his total electrical service (400 amps to his house total, 120 amps to the water heater I believe) to nothing but the water heater. Add to that the electric forced-air heat pump, and you've got a lot of high-amperage breakers that don't leave a lot for everything else.

 

[_RaT_]

I posted a short reply to CurlyDave's recent (yesterday) question on electric vs LPG vs tank water heaters. In a nutshell, my brother-in-law has an electric tankless and is generally satisfied with it. However, he has stated that when he builds his next house, he will probably switch to LPG tankless(he, like I, prefers to build out of town a bit where NG isn't available). His biggest issue is having to dedicate roughly 1/4 of his total electrical service (400 amps to his house total, 120 amps to the water heater I believe) to nothing but the water heater. Add to that the electric forced-air heat pump, and you've got a lot of high-amperage breakers that don't leave a lot for everything else.

Out here in California, you never consider electric as an alternative. I would go NG or LPG for sure. ELectric may be quite efficient as an end product, but to make that power, the efficiency changes rather fast. Don't count on electrical power being cheap in the future unless we go nuclear or solar panels get real cheap.