Compact Water Heater


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Old 12-02-09, 03:27 PM
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Compact Water Heater

Aloha All,

I just purchased a 730 sqft condo with 2 br/ 1ba in Honolulu. It needs renovating, and one issue I'd like to address is the space used up by the standard 30 gal tank water heater.

I thought that electric-tankless (Bosch AE115 or 125) would be the way to go. However, there's only 90amps flowing to my unit.

Given the 90 amp limitation, the best I can do is a Bosch AE12 tankless, 2 gpm for 120F water based on the 75F cold water input. 50 amps. I was thinking maybe I could combine that with an Ariston GL 6Plus 6-7gal point of source water heater (12.5 amps), but fear that it wouldn't be sufficient. Also, I'm already at 62.5 amps, with only 27.5 to spare . Am I stuck with a traditional space eating water heater?

I'm going to install a front loader washer, which ConsRep says takes 4gal hot water for a warm wash ( 1.5-3gpm); a 1.5 gpm shower head, 1.5 gpm kitchen faucet, new dishwasher (8gal per cycle), etc... you get the idea efficient appliances and fixtures all around.

Any thoughts?
 
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Old 12-02-09, 04:15 PM
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Using a low flow shower head with a shut off built in allows you to intermittently turn the water on and off while showering and can reduce use by another 50% or more. Singing in the shower not allowed.

With those limitations, my guess is you are stuck with the tank, but some of the pros may have other suggestions.

Bud
 
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Old 12-02-09, 04:19 PM
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Originally Posted by He'e_Pali

Given the 90 amp limitation, the best I can do is a Bosch AE12 tankless, 2 gpm for 120F water based on the 75F cold water input.
You input water is really 75 degrees? That seams really warm but then again, I'm in Minnesota and your in Hawaii

Originally Posted by He'e_Pali
Also, I'm already at 62.5 amps, with only 27.5 to spare . Am I stuck with a traditional space eating water heater?
For such a small condo I am surprised you would be at 62.5 amps. YOur electric bill has to be crazy! Are you running a lot of electric heat or other heavy appliances? The rating on your breakers/fuses in your panel has nothing to do with how much load in on your system. Can you list your major electric appliances?
Any chance of going to a gas on-demand heater?
 
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Old 12-02-09, 07:01 PM
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Originally Posted by Tolyn Ironhand
You input water is really 75 degrees? That seams really warm but then again, I'm in Minnesota and your in Hawaii
I measured it today, 76F. I ran it for a minute before measuring. If it makes you feel better, the condo cost $280k, and that was a major bargain. "price of paradise" Beer 4U2


Originally Posted by Tolyn Ironhand
For such a small condo I am surprised you would be at 62.5 amps. YOur electric bill has to be crazy! Are you running a lot of electric heat or other heavy appliances? The rating on your breakers/fuses in your panel has nothing to do with how much load in on your system. Can you list your major electric appliances?
Any chance of going to a gas on-demand heater?
I'm in Honolulu, the only heaters we have are for the water. Windows open year round

As for the amperage, I'll admit that I'm not an expert on this. The home inspector said that I could draw 90 amps at the circuit breaker, I assume that's a limitation of my building rather than the circuit breaker. The AE12 tankless water heater is rated at 50 amps. The electric tankless water heaters draw huge amperage because they heat the water as it's flowing through the heater, no tank. But they don't draw current unless the water is flowing The GL6+ point of use water heater has a small tank and is rated at 12.5 amps. I'm figuring that under max load just those two units could draw 62.5A. Let's say I'm doing laundry and the drier (40A), washer (20A), plus two water heaters (62.5A) might be running simultaneously. That's potentially more than 90A. In my limited knowledge of the subject, I think that without a breaker, if you draw more amps than wires can handle, they can fry. And even then, I'm not positive this combo of heaters would provide enough hot water.

There's no gas in the building, so no can there. I have the standard appliances, fridge, dw, stove, w/d, water heater.
 
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Old 12-02-09, 07:11 PM
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Originally Posted by Bud9051
Using a low flow shower head with a shut off built in allows you to intermittently turn the water on and off while showering and can reduce use by another 50% or more. Singing in the shower not allowed.

With those limitations, my guess is you are stuck with the tank, but some of the pros may have other suggestions.

Bud
I think you're correct on all counts Bud, but I'm holding out hope that I don't understand the amperage ratings on appliances and they hopefully draw less than what they are rated at. I think that if I could run the AE12 tankless to 2 point of use GL6+'s (one bathroom, one kitchen) it would provide enough hot water an I'd be able to tuck them in the dead space under the sinks.
 
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Old 12-02-09, 07:20 PM
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just read this again. I guess I'm not sure what my limitations are on water heaters given that the inspector told me that my service is 90A. I ordered a number of books from Amazon last night, one of them on home wiring. What do you think TI? What's the biggest tankless I could run? The next model up from AE12 is rated at 80 amps and might supply hot water to my whole condo without point of use tankers (2.6gpm).

Originally Posted by Tolyn Ironhand
You input water is really 75 degrees? That seams really warm but then again, I'm in Minnesota and your in Hawaii



For such a small condo I am surprised you would be at 62.5 amps. YOur electric bill has to be crazy! Are you running a lot of electric heat or other heavy appliances? The rating on your breakers/fuses in your panel has nothing to do with how much load in on your system. Can you list your major electric appliances?
Any chance of going to a gas on-demand heater?
 
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Old 12-02-09, 10:26 PM
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Forty amperes for a clothes dryer is really high, most run on a standard 30 ampere circuit and take about 23 or 24 amperes. A washing machine that does not have an internal water heater will take maybe 12 or 13 amperes when on spin cycle and less when on wash or rinse cycle. Also, you cannot add up the amperages of 120 volt (washing machine) and 240 volt (clothes dryer) to get the total amperage of the electricity being used. A much better method is to convert all amperages to watts by multiplying the amperage by the voltage. The 90 ampere electrical limit is 21,600 watts (90 amperes times 240 volts) which is often written as 21.6 kilowatts.

I usually try to dissuade people from installing electric instantaneous water heaters because they have such a limited flow versus temperature rise and they take a lot of power. In your particular instance however it might be okay. You won't be able to do much more than wash your hands when the washing machine is taking on water and probably not even that if someone is taking a shower and you for certain would not want to be in the shower when the washing machine (or a dishwasher if you have one) takes on water.
 
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Old 12-03-09, 12:28 AM
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surfed the net some more, it looks like i can hire an electrician to upgrade my electrical service connection to 200A. That would also require a new 200A circuit breaker panel and the electric company hooking up a new 200A meter. Looks like $1-2k, maybe . However, if I made these upgrades, I could install a single 4gpm tankless heater that would be more than enough for my condo. it all depends on how much the space is worth to me
 
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Old 12-03-09, 12:54 AM
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Originally Posted by furd
Forty amperes for a clothes dryer is really high, most run on a standard 30 ampere circuit and take about 23 or 24 amperes. A washing machine that does not have an internal water heater will take maybe 12 or 13 amperes when on spin cycle and less when on wash or rinse cycle. Also, you cannot add up the amperages of 120 volt (washing machine) and 240 volt (clothes dryer) to get the total amperage of the electricity being used. A much better method is to convert all amperages to watts by multiplying the amperage by the voltage. The 90 ampere electrical limit is 21,600 watts (90 amperes times 240 volts) which is often written as 21.6 kilowatts.

I usually try to dissuade people from installing electric instantaneous water heaters because they have such a limited flow versus temperature rise and they take a lot of power. In your particular instance however it might be okay. You won't be able to do much more than wash your hands when the washing machine is taking on water and probably not even that if someone is taking a shower and you for certain would not want to be in the shower when the washing machine (or a dishwasher if you have one) takes on water.
Hi Furd, thanks for your response. I'll work with the watts, as you suggest. i was hoping that if i had 12-14 gal of hot tank water plus the 2gpm from the tankless heater, that would handle at least 2 simulataneous hot water jobs. No? I want to have a heating system that delivers hot water as well as a 30 gal tank. Hot water is a high priority of prospective buyers.

I know this is fairly non-standard, but 730 sqft is not a lot of space and I'd like to trade the 30gal heater for a closet in the second bedroom or kitchen cabinet space (take your pick) - as long as I can still have reliable hot water.
 
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Old 12-04-09, 05:48 AM
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Sorry for my late reply's. This thread seamed to be "off my radar"
If you are willing to do the service upgrade to 200 amps that will pretty much solve all your problems. Then you could pretty much install what ever tankless you want. (The AE115 looks like a good fit if you do the upgrade) The price you gave sounds pretty fair for your location. Although, it would be nice if they could reduce the range a bit. ($1K range!?)

However, you should contact your power company and let them know your intentions of adding the on demand water heater. They may have to upgrade there transformer outside feeding your condo.
 
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Old 12-04-09, 05:03 PM
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Hey TI, $1000 would definitely be better I'll have to call some companies and get a quote. Thanks for the advice on the electric company. That's one part I'm worried about - this high rise was built in 1964, and who knows if the equipment leading to my service are legit for 200A .

For the heater, I was looking at the AE125. It doesn't cost much more than AE115 and flows 1.4 gpm more for my required temp rise. Do you have an idea of the cost of running a tankless vs a tank heater? You noted in your first post that you tend not to recommend the tankless.

Originally Posted by Tolyn Ironhand
Sorry for my late reply's. This thread seamed to be "off my radar"
If you are willing to do the service upgrade to 200 amps that will pretty much solve all your problems. Then you could pretty much install what ever tankless you want. (The AE115 looks like a good fit if you do the upgrade) The price you gave sounds pretty fair for your location. Although, it would be nice if they could reduce the range a bit. ($1K range!?)

However, you should contact your power company and let them know your intentions of adding the on demand water heater. They may have to upgrade there transformer outside feeding your condo.
 
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Old 12-04-09, 06:51 PM
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No, I can't really say anything bad about tankless water heaters I just have not had much first hand experience with them. I have wired one in my 8+ years and that one was fed with 120 amps of power. It made hot water but that meter was spinning! Most water heaters around here are either gas or the tank type.

this high rise was built in 1964,
I was a little in the dark of what type of condo you had. Since it is a high rise, upgrading your service is likely not going to be an option.

Another possible option is a compact tank water heater. (google compact water heater)

While I feel the AE12 might serve your needs (it has a rating of 42 degree rise @ 2GPM. That's 115 degree water) I can't quite bring myself to say go and get the AE12 because I'm a little worried if your cooking, got the oven on, running hot water, and doing a load a laundry that your service would handle it for sure. What you can do is write down all the nameplate ratings of your appliances (oven, dish washer, microwave, etc) either watts or amps are fine and post them here. Maybe we can figure out if your service will handle it.

Lastly, they say that you save money because you don't heat water when your not using it. But seeing the tremendous amount of energy to heat the water quickly I would think it would be quite while to recover the investment.
 
 

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