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Old 01-31-2009, 02:40 PM   #1
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tankless in walk-in closet?


Remodel and addition has bathroom within 3 ft of cold water line but nearest hot water is 30 ft away in crawl-space behind a lot of ductwork. Simplest solution would seem to be a tankless at POS, likely a Seisco 18 kW. Cold water line terminates currently within 1 ft of the walk-in closet for the new master bedroom, which is very near the new bathroom. Does code allow a tankless (electric) in space adjoining a bedroom? Only other possibility I see is putting it in cabinet in bathroom (space available between tub and toilet). Is that allowed? There are other issues (SE load and slots) but before getting to that is a tankless even an option?

Thanks, Phil
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Old 01-31-2009, 05:22 PM   #2
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You may end up with a seperate service just for the tankless. You will need to consider that cost before you go any further. Some may take 3 60 amp 240 circuits.
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Old 01-31-2009, 06:18 PM   #3
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18 KW at 240 volts = 75 amps.

If your main breaker is 100 amps or less, this simply will not work. If it's 200 amps, it'll be OK if your water heater, and cooking appliances are gas. If the house is all electric, even a 200 amp would be questionable at best, especially if you have air conditioning.

You'll also need at least 4 or more likely 6 unused spaces in the panel.

Most people don't realize just how much of a strain tankless water heaters put on an electrical system.

Rob
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Old 01-31-2009, 06:21 PM   #4
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Jim -- The 18 kW heater takes two 40 A circuits, and as I said there are SE load and slot issues. But is it even legal to put it in a room adjoining a bedroom? I read the AFCI part of the code again and all it says is that any outlets in the bedroom need to be AFCI protected. The heater would not actually be in the bedroom so maybe it's ok?

As for the SE, I almost certainly would have to install a subpanel adjacent to the SE, but that's no big deal. The service is 200 A and my max kWH/month last year was 3900 (in February = 28 days) or about 140 kWH perday. A 200 A service running full tilt would use over 1000 kWH/day, if I can still do arithmetic. So it doesn't seem like the additional load would be a problem, but the house is all electric so I'd want to go over the load calcs with you good folks on this forum.

Phil
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Old 01-31-2009, 06:29 PM   #5
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what kind of heating system do you have and where app. do you live?
I think different regions of the country will have different solutions
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Old 01-31-2009, 06:33 PM   #6
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Why not just run the hot water pipe the 30ft and insulate it real good? That would be so much cheaper than what you are suggesting.

FW
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Old 01-31-2009, 07:09 PM   #7
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House is electric heat in Willamette Valley, Oregon. Mean water temp here is I'd guess about 50 F.

Why not just run the hot the 30 ft is a very fair question. It's a crawl space and the whole floor got retro insulated underneath by a local contractor paid for by my POCO. The insulation is glass wool bats shoved up into the joist bays and held in place by lathe stapled to the joists. There's wool hanging down everywhere. They also insulated the heating ducts really well and I just busted a rib trying to slide under one of the suckers. (Admittedly, I don't think the rib should have broken and I'm going to get a bone density scan next week but that's another thread.) I'm 5'9' and 160 lb and if I can't slide under the ducts, my plumber friend isn't going to have it any easier. Bottom line is it's worth say $500 extra to me to avoid the crawl space work. But not say $1500.

More details:
Existing 200 A SqD QO30-40 is absolutely full. There are maybe two 20 A branch circuits I could combine onto a single circuit but Id rather just leave them as they are. Almost entire right side of panel is 240 V circuits: water heater (30A breaker), dryer (40A), forced air furnace (two 60 A), shop circuit (40A), range/oven (40A), and two well pumps (30A).

Given all these 240 V circuits, Im nowhere near the 40 circuit limit and the panel is marked for tandems (twins) in 12 of the lower slots. However, the mounting rail doesnt accept the hook style SqD tandems, and I was quoted $60 a pop for the snap-on style SqD tandems. Thatd be $240 just to free up the 4 slots. Does all that sound right? If so, Im thinking maybe I can put in a subpanel for a lot less, and I could use the extra slots regardless.


Pitch in with advice, folks. I appreciate it and pretty much all options are still open.

Phil
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Old 01-31-2009, 11:28 PM   #8
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I was born and raised in Albany, Oregon. Small world, huh?

Here are a few quick load calc.s

1) New tankless water heater = 75 amps.

2) Existing water heater. Usually 4500 watts, if so 19 amps.

3) Furnace. If it's 2-60 amp breakers, it's likely 20KW. If so, 83 amps.

There's a pretty fair chance that all of these would be on at the same time, if so the load is 177 amps. This doesn't count lights, well pump, cooking, etc. The well pump will almost certainly be on at some point when you're using water.

This will be pushing a 200 amp panel pretty hard, it might hold, it might not. Having the main breaker trip while you're in the shower (which will turn ice-cold quickly) will not be much fun. This is also when the load will be the highest for the longest time.

Unfortunately, the Square D tandem breakers that don't have the cam are indeed expensive.

The arc-fault requirement applies only to 15 and 20 amp circuits.

Rob
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Old 01-31-2009, 11:44 PM   #9
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I'm not aware of anything that prohibits the installation of an electric tankless unit in a bedroom closet. A gas tankless would be prohibited for sure (as are gas furnaces and regular water heaters) because the code says you can't access fuel burning appliances via a bedroom.

The code prohibits the installation of any electrical panel in a clothes closet, but I can't think of anything that says you can't put an electric appliance in there.

Manufacturer's installation instructions and requirements would be enforced by any inspector, so be sure that the manufacturer doesn't prohibit such installations.
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Old 02-01-2009, 10:33 AM   #10
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Rob, KC - Thanks, that's what I was looking for. I'll check nameplates on furnace and water heater. But water pump is actually two pumps, one to holding tank and one to pressure tank, so I suspect that if your load guesses are even close, and with a few lights on, I'd blow the main. That's obviously not acceptable even if it's legal. The obvious half-assed solution is to crank down the furnace thermostat whenever I use the new bathroom. For bath or shower that's practical but not for say washing hands.

I'll have to get back to plumber, see if he's willing to crawl for me. Maybe we just disconnect the duct(s) since the HVAC folks will be out here anyway once the plumbing rough-in is done.

- Phil
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Old 02-01-2009, 11:28 AM   #11
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Why 18 KW for one bathroom? Did you calculate this or did a salesperson tell you that 18 KW is needed. I don't know much about tankless systems, but a point of service tankless at 18KW seems like more than you need.
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