Bosch AquaStar Indoor Natural Gas Tankless Water Heater with Vent Hood #125 Logo
Posted on Nov 22, 2010
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Hi i have installed a few bosch gas geysers at our lodge in mozambique.The problem is that the water gets hot when we turn the water on then the heat just shuts off and the water gets cold after a short while.i was told that the water pressure was incorrect so we resolved this by fitting a booster pump.The problem still persists even with good pressure .The water is hot when the tap is opened initially then gets cold,if you switch the tap off then on again the water again will get hot for only a very short while then cold.i have adjusted the settings but nothing helps

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  • Posted on Nov 22, 2010
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The problem with all that type of water heater is that once the hot tap is turned on sufficient flow must be maintained through the water heater to keep the main gas burner alight. If the heat adjuster is turned up to high, then the person using the hot water will turn it down to a low rate which means the main burner will turn off and result in cold water. Try setting the heat control to the lowest setting that still gives hot enough water. If you have a thermometer adjust control for a temperature of around 50 to 55 degrees Celcius. You may have to fiddle with fine adjustments to get the temperature and flow rates to maintain a constant output of hot water. You may still have intermittent problems. If the heater only supplies baths or showers you could set the temperatuer even lower (45 to 50) to ensure that the hot tap is used more than the cold which will maintain flow and therefore heat.

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1answer

Junkers gas geysers not heating water much

between 60 and 75 degrees c as any hotter will scald you. Have the gas specialist check it out as it may not be getting enough gas flow to the burner either a badly adjusted regulator or a blockage in the gas tap or line.. You control the temp by the amount of water coming out of the tap as you found out when you attempted to restrict the water flow.
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Hi I have a Bosch water wizard 10p & although i have the heat turned up to the highest it is still not hot enough! I was wondering if there was another way of increasing the water temp?

Open following link for Bosch troubleshooting resources:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html

Typical Bosch 10P manual shows temperature control illustration on Pg4, and includes low water temperatures on troubleshoot on Pg6
http://waterheatertimer.org/pdf/Bosch_10P-installation.pdf
Water flow rate too high, low gas pressure, faulty thermostat.

Two other things might be causing problem
Crossover:
http://waterheatertimer.org/Crossover.html
Lime build-up
http://waterheatertimer.org/pdf/Rheem-De-lime-tankless.pdf
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Our gas water heater (Rheem Optima Quick recovery 81 series) heats the water as evidenced by the steaming water we can release from the temperature and pressure relief valve but we get no hot water from...

Sounds like a plumbing problem.

Since no tap gets hot water, chances are good the problem lies in the hot water pipes between the water heater to the first Tee.
Look for sediment lodged in water heater hot water pipe.
Or sediment lodged in elbow or Tee.

Other problems can be in play.
Faulty check valve or mixing valve if these are installed.
Faulty recirculation system if this is installed.
Also crossover at single-handled faucet where the cartridge is bad and lets the cold water flow into hot water pipe whenever another faucet is turned on. If you are getting cold water out the hot tap, and you know the hot water heater has hot water, then crossover is suspect > in addition to sediment blockage at hot water heater.

Upvote the help.
And take advantage of fixya expert assistance live.
For a price, expert works with you while you work on timer or any do-it-yourself project.
Fixya is always less expensive than a service call.
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Failing ignition on Bosch Aquastar AQ125-HX tankless on demand water heater. Carefully followed all directions on device to best of ability. Gas supply is full and on. Water pressure should be...

Before calling service technician, open following links for Bosch troubleshooting resources:
http://waterheatertimer.org/Troubleshoot-Bosch-Tankless-water-heater.html
Resources at Bosch
http://www.boschhotwater.com/HelpfulResources/TechnicalSupport/BoschAquaStarModels/tabid/370/Default.aspx
Typical Bosch Aquastar manual:
http://waterheatertimer.org/pdf/Bosch-aquastar-170vp-manual.pdf

All tankless and tank-type gas water heaters require regular cleaning and maintenance.
It is unknown if your unit needs maintenance or repair parts, but catching up on maintenance using information from manual is good place to start.
Gas appliances are increasingly complicated and experienced technician is good resource to have in local area before installing tankless.
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I had our 1600ng Bosch water heater installed a month ago during warmer weather. It is not providing very hot showers. I use all hot no cold. how can io get more heat

on the front of the water heater down at the bottom there is a thermostat (usualy a blue knob) turning it clockwise will increase the tempature of your water
(good Luck)
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