Model # AT-900-04

Internet #205515505

ATMOR 3.8kW/240-Volt 0.56 GPM Electric Tankless Water Heater with Pressure Relief Device, On demand Water Heater


3.8kW/240-Volt 0.56 GPM Electric Tankless Water Heater with Pressure Relief Device, On demand Water Heater

  • Continuous on demand hot water heater, no hot water tank
  • Electric water heater for single sink hotwater application only
  • Requires 20A, Single Phase, DP Breaker, 12 AWG Wire, 240V
$13389 /each
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Product Overview

ATMOR 900 series Electric Tankless Water Heaters revolutionize hot water heaters with technology that provides you with unlimited hot water when you need it, without the wait or worry of ever running out. By automatically activating once water flow is sensed and shuts off when it stops, you'll lower your water consumption and eliminating costly water waste.  The ATMOR Electric Tankless Instant Water Heater is the eco-friendly, efficient and convenient solution you have been looking for, delivering an endless supply of hot water instantly at the point of use only when you need it. It is suitable for both residential and commercial applications, even in your RV, so you can enjoy a continuous flow of hot water whenever you want. Best of all, unlike a gas water heater, the compact design requires no venting, giving you the flexibility to install anywhere inside your home or garage.  The compact footprint of this device can be installed against the wall either under the sink out of sight or near the point of use, where its elegant design blends into your home environment among other appliances. Remember inlet temps vary by location and seasonality. Selecting the right water heater depends on your incoming water temperature, flow rate, and desired output temperature. To help with making sure this unit is suitable for your need, please see our selection guide below or call our support team at 888.783.6082.

  • Designed for single sink application
  • Requires 20A, singlephase, double pole breaker, 12 AWG wire size, 240V
  • Includes a pressure relief device
  • Standard 1/2 in. NPT (straight thread) fittings
  • 2 year limited warranty, 7 years free from leakage
  • Instant and endless hot water on demand without the wait or worry of ever running out
  • Save up to 50% on your water heating costs
  • Conserves energy - activates only with water flow at 0.5 GPM
  • Eliminates the wait for hot water and water wastage
  • Ideal for commercial or residential, single sink applications
  • Compact, eco-friendly design, made up of recycled material, installs neatly underneath sink
  • No venting necessary
  • Certified LEAD free
  • Inner workings (ie canister) of this ATMOR unit is primarily constructed with a commercial grade, heavy duty, heat resistant polymer composition reinforced with a fiber glass compound to complement its durability, stiffness, finish and strength, such thermoplastic materials are increasingly used across the automotive, consumer industrial, medical and energy markets, to enhance product performance and increase consumer safety
  • Note: unit must be professionally installed into electrical supply
  • Reference our guide to confirm if this is the right tankless water heater for your area/needs, to help with this, please see our selection guide below or call our support team at 888.783.6082

  • Use our buying guide to choose the right tankless water heater for your needs

    Tankless Electric Water Heater

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Info & Guides

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Product Depth (in.)
Product Height (in.)
Product Width (in.)
Water Connection Size (in.)


Amperage (amps)
Application Type
Point of Use
Electric Product Type
Point of Use
Energy Factor
Finish Family
Flow Rate @ 35 F Rise (gallons/min)
0.74 gal (US)/min
Flow Rate @ 45 F Rise (gallons/min)
Flow Rate @ 55 F Rise (gallons/min)
Flow Rate @ 65 F Rise (gallons/min)
Fuel Type
Heat Exchanger Warranty
2 Year
Maximum Temperature (F)
Minimum Activation Rate (gpm)
Minimum Temperature (F)
Product Weight (lb.)
Required Volt Connection
Uniform Energy Factor
Water Connection Location
Water Heater Features
Overheat Protection,Wall Mountable
Wattage (watts)

Warranty / Certifications

Certifications and Listings
1-UL Listed
Labor Warranty
No Warranty
Part Warranty
2 Year

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Customer Questions & Answers

Does it typically go inside a cabinet & stay turned on all the time?

Asked by: Jesse
It can go under a cabinet and it does stay on but only uses power when the hot water is running so it saves money.
Answered by: Cutworm
Date published: 2016-06-02

What about the shower?

Where would this be installed if it were needed for the water in a shower/bathtub?
Asked by: KJ
This unit is rated at .5 gpm. Depending on where you live it would work. Up north probably not so well.
Answered by: Cutworm
Date published: 2016-02-10

Could this product be used for point of use hot water until the home water heater water reaches the bathroom?

Our bathroom is located at the opposite side of house than the water heater. It takes about 3 minutes before the hot water reaches the bathroom.
Asked by: Kerry
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Customer Reviews

3.8kW/240-Volt 0.56 GPM Electric Tankless Water Heater with Pressure Relief Device, On demand Water Heater is rated 3.1 out of 5 by 16.
Rated 1 out of 5 by from I install two of these and had nothing but problems. Relief valve kept purging when it wasn't eve... I install two of these and had nothing but problems. Relief valve kept purging when it wasn't even on. One would get hot just warm, and finally started leaking from inside, the second would'nt even come one, replaced it and it wouldn't shut off from getting hot when the faucet was closed. I would not but Atmor ever again.
Date published: 2017-08-04
Rated 1 out of 5 by from I bought two units the instructions are very poor.... I bought two units the instructions are very poor. I called for help no one answer the phone sent Emails no one answers The plumbing was installed correctly the electrical as well. BOTH UNITS would not go on !!!! Cost me a lot of money & time. Bottom line is they don't believe in their product !!!
Date published: 2017-02-14
Rated 5 out of 5 by from Be sure you understand what you are getting I just finished the installation today. I connected it to a bathroom faucet because our main water heater is located so far away from that bathroom that you used to be done washing hands before the hot water even got there. Now the hot water is ready to go. And I want one for the other bathroom. If I put one in the kitchen I will go with a higher wattage. However, some things you should know: the water temp depends on flow rate and on the temp of your cold water. I live in Louisiana and it is winter now. The cold water is cold enough that I don't want to stick my hand in it, but I don't know the temp. Anyway, If I turn the hot on full blast (about 1.5GPM), it is not as cold as the cold water but it is still cold. At about half flow (.75 ish) the temp and flow are nice for washing hands. The slowest flow that will keep the heater on is about .3GPM, and it is too hot for me to tolerate. You can estimate your flow rate with a stopwatch and a measuring cup to get an idea of what you need. See how many seconds it takes to run out one cup of water (8oz). Take 3.75 divided by the number of seconds, and that is your flow rate in GPM. There is no way this thing would heat enough water for a shower, in my opinion. Next thing to consider is cost. If you do it yourself, you need to buy wire, plumbing parts, and maybe a GFCI breaker, which is not cheap for a 240v circuit. The instruction said you must use a GFCI, but my local code does not require it so I left that off. Also, it requires a dedicated line, which means you need an available 2-pole spot in your breaker panel. Many people's panels are full; make sure you have room.
Date published: 2015-03-01
Rated 3 out of 5 by from underpowered for most uses Installation was simple for me, I'm a seasoned DIY-er. You need to run a new dedicated 240v line (so you will need 2 slots in your breaker panel). I was very disappointed at what a poor job the heater did at raising the water temperature, especially as I am in Texas where our ground water temperature is around 65 degrees. I read over the sizing guide again, and much to my dismay discovered why the heater wasn't doing its job. The guide details flow rates of just 0.5 gallons per minute. Either 0.5 gallons per minute for a single sink or 1 gallon per minute for a double sink (meaning two faucets at 0.5 gallons per minute each). I checked my faucets, none of them run this low. I checked online for flow rate information - Kitchen sinks are typically 2.2 gallons per minute flow, bathroom faucets can have aerators that restrict flow to 1.5, 1.2, 1.0, or even 0.5 gallons. So herein lies the problem. Unless you are restricting your water flow to a minuscule 0.5 gallons per minute, this heater is just not up to the job. At 0.5 gallons per minute I would find the faucet unusable at best. When sizing your water heater, you are likely going to need a unit that is 3 to 4 times as large as the guide claims, unless you are in the minority of people with 0.5 gpm restricted faucets.
Date published: 2016-02-02
Rated 4 out of 5 by from BE SURE TO READ PRODUCT DETAILS I have been wanting one of these tankless hot water heaters for a very long time. When I saw this one I was thrilled and excited to get it. Our guest bathroom's hot water is supplied by a too small hot water heater which results in GI with no wasted motions. This product arrived well packaged and in good time. However....Installing this unit IS NOT a diy project .The manufacturer suggests having it professionally installed. It is complicated. This unit is not an accessory to a hot water heater it is meant to replace a standard hot water heater. This particular unit heats less than a gallon a minute. Not enough for a shower. I should have read the product overview better. I'm not sure where to put this now. Maybe in my husband's shop. I am disappointed but it is my own fault for not paying better attention.
Date published: 2015-01-10
Rated 1 out of 5 by from Not so good Have it with a tub sink in the shop, Have the volume turned down to a trickle and the water in hot, turn it up to a reasonable pressure to wash your hands and it is not warm enough to use. Would noy be able to use with a shower.
Date published: 2016-05-04
Rated 4 out of 5 by from Instant hot water... I installed the Super 900 Series 3.8 kW/240-Volt Tankless Electric Instant Water Heater in a small bathroom that is well away from the primary hot water heater. Installation is straight forward and it is worth noting that this is the 240volt model so plan accordingly. I have read other reviews where people are disappointed with the performance of this heater but I have not had a poor experience. I liken this to the fact that I am using this with an eco friendly low flow faucet that doesn't use a large quantity of water. Water comes on hot in seconds as opposed to waiting for 3 gallons to flow through the pipes. Works as advertised. Be sure to check your requirements to determine the proper model for your installation / use case.
Date published: 2016-06-08
Rated 5 out of 5 by from Finally...HOT WATER!! Haven't had hot water in my kitchen (too far from the water heater) in years. Got this tankless WH and it works great. In about 5 seconds, water is HOT! Love it!
Date published: 2015-07-30
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