How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Pitsch Plumbing Your Own Question
Pitsch Plumbing
Pitsch Plumbing, State Certified Plumbing Contractor
Category: Plumbing
Satisfied Customers: 370
Experience:  25 years in the trade. new Construction, remodeling, repairs ect. Business owner. 2nd gen plumber
Type Your Plumbing Question Here...
Pitsch Plumbing is online now
A new question is answered every 9 seconds

Aqua star tankless heater mod # aq 125 bng thomatsat not working

Resolved Question:

Aqua star tankless heater mod # XXXXX 125 bng thomatsat not working causing heater to stay on exploding out going water line filling the room with hot water and steam i got a bad burn shutting supply water off and turning off gas
Submitted: 6 years ago.
Category: Plumbing
Expert:  Pitsch Plumbing replied 5 years ago.

Pitsch Plumbing : Sounds like the flow sensor is stuck and possibly a thermostat issue also. My suggestion to you, since you've already injured yourself and the unit has cause damage to your home, is to call a qualified tech to asses the unit, decides if you want to repair or replace and if its repaired a good tech will put it back into service safely.
Customer: replied 5 years ago.
the unit has no flow sensor nor is it thormostat controled so sorry you were no help
Expert:  Pitsch Plumbing replied 5 years ago.

I'm sorry, but you are incorrect. My terminology might of been off, but any tankless heating unit has some kind of flow sensor(water valve or whatever the manufacturer chooses to call it) to tell the unit when to fire and when not to fire. PERIOD. And it sound like your unit thinks it has flowing water and thats why its not turning off. The fact that the water lines blew off leads me to believe that the install was incorrect or the T&P valve malfunctioned also or the T&P outlet was simply left open and not piped away from the unit.

The Aquastar 125B has a gas control that modulates burner

input in response to hot water flow. Its purpose is to ensure

that the hot water temperature will remain steady, although

the water flow demand may vary (down to ½ gal/minute).

Also, depending on the unit's adjustable gas control slide

being set in the single flame ( ) or three flame ( )

setting, the 125B can produce and control comfortable hot

water temperatures as seasonal ground water temperatures


To adjust the temperature on the heater, turn on a hot water

tap. At the water heater, turn the temperature adjustment

knob (see Fig. 9) all the way to the right (clockwise) and set

the gas control slide to the three flame ( ) setting. This

will produce a temperature rise of approximately 90F at flow

rates between 0.5 and 2.0 gallons per minute. Given that

average incoming water temperatures are 50F in winter

months; this heater will produce approximately 140F water

at these flow rates. Turning the dial all the way to the left

(counterclockwise) will produce a temperature rise of

approximately 45F for flow rates between 1.1 and 3.7 gallons

per minute. When setting the gas control slide to the single

flame ( ) setting and positioning the knob fully clockwise,

the heater will produce a temperature rise of approximately

55F at flow rates between 0.5 and 2.0 gallons per minute.

Turning the dial all the way the counterclockwise will produce

a temperature rise of approximately 33F for flow rates

between 1.1 and 3.7 gallons per minute. It is safest to select

a comfortable temperature and not have to mix in a

considerable amount of cold water. The positions you select

will depend on the temperature of the incoming water (50F

is average in the U.S.). In warm weather regions where the

incoming ground water is generally warmer, or during hot

weather months in other areas, a single flame ( ) setting

may be best. During the colder months, or in cold climate

areas, a three flame ( ) setting may be best. NOTE: The

knob setting will affect the activation point of the heater;

fully clockwise will allow the heater to activate at 0.5 gal/

minute. Fully counterclockwise will allow the heater to

activate at 1.1 gal/minute.

Do not supply the 125B with preheated water. For this type

of application, use the solar back-up model 125B LPS or

125B NGS.

If the inlet water temperature to the water heater is very

warm the heater can produce temperatures that may be

found to be too hot. A temperature balance shower valve

can automatically mix in cold water to reduce such hot water

temperature, in the event of any temperature instability with

the use of a temperature balance shower valve, refer to

shower valve manufactures instructions for internal

adjustment setting. Adjustments should be made to the

hottest setting in the shower valve. Additionally the

temperature control of the heater can be adjusted to produce

a more comfortable hot water temperature.



Water Valve (Part #(NNN) NNN-NNNN: The water valve on

this heater should be serviced periodically. Lubricate

component #23 on page 19 with a small amount of silicon,

faucet or lithium grease every two years to keep its o rings

fresh and pushrod sliding smoothly. Every 3-5 years replace

component #23 on page 19. The frequency will depend on

the mineral content of the water and conditions of use or

whenever signs of corrosion appear at the gas and water

valve joint. Periodically check that the water inlet filter (#25

on page 19) is clean as well.

NOTE: If water valve is removed, be sure to also inspect the

o ring seal on the end of the right hand side water pipe

before re-installing. Lubricating the o ring with lithium or

faucet and valve grease is recommended

Edited by Pitsch Plumbing on 10/30/2010 at 8:42 PM EST
Customer: replied 5 years ago.
I replaced the 125 B with a brand new unit from lowes it is a aquastar that was built to replace the 125B it is a 1600 H NG it was properly installed with the PSV that was supplied with the unit and piped in with steel pipe but the pilot is operated by a water flow generator when the water is turned on the ing. starts to spark the pilot will come on for a second and go back out over and over but the main burner will not come on. It has been two days of turning the water on and off to purge any air from the lines when the pilot lite does come on it is a nice blue flame but it only cycles on and off without lighting the main burner all electrical connection are in place and tight even used a butane lighter to help heat the sensor to make the unit come on but no luck wit that at all
Expert:  Pitsch Plumbing replied 5 years ago.
I have to head out on a call, But since its brand new, dont open it up or try and fix it. Thats an easy way out for the manufacturer to cry foul. Call lowes today and ask for a manager or call Bosch in the morning and they will get someone out to you. We do warranty for Rheems, which uses, sometimes, Paloma for their units and they get us out there quickly to take care of warrant claims. Double check the tags in the unit and make sure they didnt give you an LP unit too. It does sound like the unit isnt seeing the pilot lite and shutting down. I will be back in about 3 hours. Have 4 pool heaters to service now
Customer: replied 5 years ago.
I do have Bosh's tech support phone # XXXXX it cannot be repaired over the phone i will box it up and return it to lowes
Expert:  Pitsch Plumbing replied 5 years ago.

Thats your best bet. You shouldnt have to repair a brand new 600 dollar item. maybe look around for a beter brand. here are some reviews, note a few had the 125 and like it and went to the replacement and didnt. if its in your budget, Rinnai or Rheem or noritz are some nice units.

Pitsch Plumbing and 2 other Plumbing Specialists are ready to help you

Related Plumbing Questions