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Old 03-07-2010, 07:37 PM   #1
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Location for new Tankless water heater?


I'm a newbie here. Hoping someone with some experience installing tankless systems might be able to help me.

My old hot water tank just sprung a leak. I have decided to install a tankless hot water system. The old tank is adjacent to a bedroom and the exterior wall is shared with a garage. The new building code won't allow me to install a gas powered tank unless it is directly vented outside with an intake and exhaust. This is mainly because of the adjacent bedroom -- building code requirements won't allow you to sleep in a room where air is being drawn for a gas appliance.

I have attached a floor plan which should make understanding my suggested install easier.

I'm thinking of running the cold water supply line and gas line from the existing furnace room/tank area to the back of the house (through the ceiling of two closets). Once at the back of the house, I would like to install the new unit against the outside wall -- thereby allowing it to vent directly outside. I am also thinking i might as well install a bbq natural gas line at the same time since that back corner of the house has my deck. The hot water return would travel back to the exisiting furnace room/hot water tank area.

Does this seem feasible? The new location would not have a drain. Do you think this is a problem? Do the tankless emergency relief valves tend to be used? How about for servicing, is there a need to have a drain nearby? If I do not use this installation, I'm not sure what my alternatives are -- unless i revert back to an electric tank - ouch.

Any ideas/suggestions???
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Old 03-08-2010, 12:28 AM   #2
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Location for new Tankless water heater?


What about putting the tankless where the tank was? What would the vertical height be for a concentric "B" vent from the existing water heater room to the roof going through the garage? Your tankless units are all power-vent units and as such many run a 2" stainless or PVC flue for 15 to 25 feet. If you go beyond these numbers you have to go to 3" or 4" diameter pipe, but you will be able to extend your flue better than twice the distance legally. Also tankless units are condensing heaters and as such require a drain for the discharge of the exhaust condensate.

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Old 03-08-2010, 09:35 AM   #3
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Location for new Tankless water heater?


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What about putting the tankless where the tank was? What would the vertical height be for a concentric "B" vent from the existing water heater room to the roof going through the garage? Your tankless units are all power-vent units and as such many run a 2" stainless or PVC flue for 15 to 25 feet. If you go beyond these numbers you have to go to 3" or 4" diameter pipe, but you will be able to extend your flue better than twice the distance legally. Also tankless units are condensing heaters and as such require a drain for the discharge of the exhaust condensate.
The unit I am having installed is not a condensing unit. It is a Rinnai direct venting unit so from what I'm told, it cannot be set up on a B vent -- it must directly vent outside. From the diagram you'll see that the garage prevents me from venting in the same place the existing tank is located. Also, I can't move the unit toward the front of the house because that wall has a window on it and you need any direct venting unit to be 3' from any window.

My understanding is that the only way the unit will let out water is if the pressure relief valve is triggered. Annual maintenance/flushing only requires a bucket be attached to the unit to flush out any residue.
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Old 03-08-2010, 09:44 AM   #4
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I installed a Noritz exterior mounted unit and reclaimed the space that my previous tanked water heater was occupying. Rather than a direct vent interior model, would that be an option for you?
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Old 03-08-2010, 09:59 AM   #5
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I installed a Noritz exterior mounted unit and reclaimed the space that my previous tanked water heater was occupying. Rather than a direct vent interior model, would that be an option for you?
Exterior mounting won't work for me. I live in Canada so the water lines would likely freeze.... plus, the wall where it would need to be mounted is in the garage, which I suspect would fail any building code requirement since it would still be venting in an enclosed space.
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Old 03-08-2010, 10:08 AM   #6
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Location for new Tankless water heater?


If I were you I would replumb your hot/cold lines to that new heater from below. If you run new lines to tap into the old lines you're adding what, 25-30 feet im estimating of new piping, but you're moving the heater closer to the bathrooms. Doesn't make much sense to wait even longer for hot water.

Edit : Pressure relief valve needs to exit to the exterior of the building in some manner.
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Old 03-08-2010, 01:25 PM   #7
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Sam, the "B" vent is just an over sized flue with concentric layers. If it is stainless material you will be able to use it to go vertically through your garage ceiling and the roof if there is no living space above the garage. The other thing you mentioned about the Rinnai not needing a drain is or has not been true in all the installations I've done. The fact that the tankless heaters are hi effiency means that they are wringing out all the heat they can from every BTU you consume. As the temperature is dropping in the flue the moisture in the flue gases condenses and has to go somewhere. So to protect your heater from flooding during normal operation, in the fire box, a condensate drain is provided on the unit. Sometimes it is on the bottom of the cabinet and sometimes it is provided right at the flue adaptor on top of the unit. Be sure your guy hooks it up to a sanitary drain or you will have problems down the road. If all else fails and you want a second opinion contact Mike Holmes. I forgot to mention that Noritz and rinnai are considered direct vent in that they are to vent to the outdoors as directly as possible. They are also called power vent units because they both operate/vent with small squirel cage blower.

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Old 03-08-2010, 01:31 PM   #8
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Sam, the "B" vent is just an over sized flue with concentric layers. If it is stainless material you will be able to use it to go vertically through your garage ceiling and the roof if there is no living space above the garage. The other thing you mentioned about the Rinnai not needing a drain is or has not been true in all the installations I've done. The fact that the tankless heaters are hi effiency means that they are wringing out all the heat they can from every BTU you consume. As the temperature is dropping in the flue the moisture in the flue gases condenses and has to go somewhere. So to protect your heater from flooding during normal operation, in the fire box, a condensate drain is provided on the unit. Sometimes it is on the bottom of the cabinet and sometimes it is provided right at the flue adaptor on top of the unit. Be sure your guy hooks it up to a sanitary drain or you will have problems down the road. If all else fails and you want a second opinion contact Mike Holmes.
Thanks for this. I'm getting a bit worried about the lack of drainage near the new location. I'm tempted to just put in a conventional tank for a couple of reasons:

1. the issue of drainage. The current location has a drain very close by which turned out to save me from a flood when the existing tank started leaking

2. The extra piping to and from the new location (approximately 25 feet) will delay the hot water from getting to the end user. I suspect this additional use of hot water might negate any savings

3. The new set up will require new water lines and a new gas line -- all of which is disruptive to the tenants I have living down there.

If I can just get someone to swap out the old tank with a new one. This might be the path of least resistance.
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Old 03-09-2010, 07:35 AM   #9
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Location for new Tankless water heater?


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If I can just get someone to swap out the old tank with a new one. This might be the path of least resistance.
Well, this is exactly what I ended up doing -- went to Home Depot and got a new 50 gallon tank and just swapped it with the old one. Ultimately, I was concerned about bringing new water lines and the water heater to an area of the house that has no drain and is fully carpeted. The old location has worked fine for at least the 17 years the old tank was in that location so here's to another 17 years!!

Thanks to all for your input/advice.
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Old 03-09-2010, 10:09 AM   #10
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so here's to another 17 years!!
hope ya don't try to hold your breath. They don't make things like they used to and now we're seeing them last to just beyond their warranty age(usually 6 yrs), and sometimes up to 10 or maybe 11 years before they start failing.

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