Remodeling Tips and Reviews

Bosch 2400ES Aquastar Tankless Water Heater

Bosch 2400ES Aquastar Tankless Water Heater

Jan 10, 2012

Bosch makes some of the most respected tankless water heaters on the market. They recently came out with a new unit .  Their high capacity product is the Aquastar 2400ES. It is available in both Natural Gas and Propane versions. Unfortunately it has not rated well on line. It looks like several people have had issues with the unit and Bosch’s customer service is severely lacking.

Here are the specs on the 2400ES unit:

  • Power Input NG: 19,900-175,000 Btu LP: 19,900-175,000 Btu
  • Minimum Flow to Activate (gpm) 0.65 gallons per minute (gpm)
  • Flow Rates 90° F rise  3.2 gpm 77° F rise / 3.8 gpm 65° F rise / 4.6 gpm 55° F rise  5.3 gpm 45° F rise  6.4 gpm
  • Energy Factor NG: .82 LP: .82
  • Thermal Efficiency NG: 82% LP: 82%
  • Dimensions: H: 30 ½” W: 17 ¾” D: 11¼”
  • Weight 67 lbs.
  • Modulating Gas Valve Yes
  • Ignition Electronic (120V plugs in)


This unit unfortunately has not had very good reviews online. People are say that Bosch’s support is terrible and and you spend extraordinary amounts of time on line. Here are some quotes:

This is the worst Tankless water heater, I may not get any hot water during a shower. I alway get the error code EA. I tried to call their service department. They are the worst person in this world to help you to resolve any problem. They are useless.

Sheesh. We’ve had a plumber/technician here FIVE times. Yes, FIVE times. And this water heater has been nothing but a headache. Various problems include NO hot water or the gas light going out just to name a few. DON’T BUY THIS WATER HEATER.


The units also appear to have loud sound issues and leak issues. I recommend the Takagi TK series as the most reliable.

One comment

  1. Natano /

    The odd thing about this appliance is that i’ll pry always remember this model number – GWH 635 ESN. I didn’t have to go down there and look it up, no, i’ve been down there enuf to wear my basement stair treads out. Here’s a sad story (i’ll keep it short) i went skiing on Mt Hood. It was cold, sunny and the snow was the lightest they’d ever recorded. It was last March. Then my dang meniscus rips and now my knee is mad at elevation change. Every other time i take a shower i have to go down 2 flights of stairs to reset this stupid P.O.S. due to an EC error code. It only took me 4 painful years to find a random tech that knew these crap boxes will only raise the water temp 60°. We have 45° tap water here (i run it thru my slab to cool off my basement in the summer) so if i push it another 3 or 4° it doesn’t like it. Now i’m getting an EA error reading, which means not enuf gas or a clog or something. I put a bigger gas line in, shortened the exhaust run, and took the whole thing apart to check the screens and make sure there weren’t spiders in the new gas line and there wasn’t any debris. No visual problems. So now all i have to do is get someone out here with a spectrum analyzer and a manometer for $109/hr and pay them to tell me that i have a piece of crap hanging on my wall that should be replaced by something that actually works. It’s a shame these exist. It just gives nay sayers an “i told you going green would suck hard” the permission to do so. I’ve had this thing for 8 years and it’s been nothing but a headache except for 3 months. Yes, those were the good months. I turned on the shower, water got warm, stayed warm most of the time and i got out of the shower and dried off. I felt normal during that time. Now however, i get to relate more to the pioneers by heating large pans of water on the stove and taking bucket showers. Those pioneers went thru a lot, and i have to thank Bosch for introducing me to a little slice of life of the pioneering past. I can now relate to those brave hardworking people a little better.