Bosch propane 1600H with hydrostart.

by Guest7543  |  10 years, 12 month(s) ago

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The main problem is that the water is not hot enough even when it's 60-70 degrees outside, it is barely warm enough to stay in the water.  Also, when showering, the water sometimes suddenly becomes cold for 10-15 seconds before warming again. The flame is set on high.  Water is set on lowest.

 Tags: 1600H, Bosch, hydrostart, propane



  1. amomipais82
    originally installed my Bosch Aquastar 125X tankless water heater in early 1999. In those years (1980s - early 2000) a company called Controlled Energy Corporation ( was the USA distributor for Bosch Aquastar tankless water heaters. At some point in the past few years CEC HOT must have been bought out by Bosch and now Aquastar tankless water heaters are distributed directly by Bosch in the USA. The below page was first posted in 2001 and has several (now inoperative) links to CEC HOT's website which has since ceased operation. Web information on Bosch Aquastar tankless heaters can be now found at As of 2007 they have introduced a replacement for their 125HX model called the 1600H (still utilizes their fabulous battery-less piezo electric hydro start pilotless ignition with a maxium 117,000 BTU rating). I would recomend staying away from their 1600P as no gas appliance should ever have a standing pilot light (unnecessary waste of natural gas). The 1600H still has a lower 0.6 GPM (Gallons Per Minute) turn on (Bosch's initial posted specs had originally noted the same 0.5 GPM as their previous 125HX, they must have just revised this specification). Bosch has a higher output (175,000 BTU) 2400 model but due to the higher 0.8 GPM turn on requirement I would recommend going with Noritz as their turn on is a low 0.5 GPM. Takagi used to have a higher 0.75 GPM turn on for their TK-1 and TK-2 units but recently they've released a TK-3 that has a lower 0.5 GPM. Unfortunately Takagi doesn't appear to list the turn on rate anywhere unless you call.

    If I were to install another tankless (and I'd never consider a tanker water heater from its energy waste perspective = more CO2 global warming emissions, higher lifetime operational cost, far shorter life requiring replacement every decade) I would choose from the following tankless heaters in this order. The beauty of the Bosch Aquastar 1600H is its simplicity (no computer, least cost, no battery, no 120 VAC power required). A friend just upgraded to the Bosch Aquastar 1600H tankless water heater and found it for $598.99 at Lowes. If you need more flow rate (realize most shower heads by law are restriced to 2.5 GPM flow rate) look at the Noritz units. With any of these heaters you will need to have adequate natural gas supply (3/4" gas pipe feed ideally from a larger main house 1.25" gas pipe). All of them will require some sort of flue upgrade either to 4" or 5". The Bosch Aqustar 1600H isn't a forced vent model and passively vents via a 5" galvanized steel flue (my preference is to install a dual walled flue for the entire run). The other units are forced vent (via 120VAC blower) and most likely require a dual wall stainless 4" vent. I know of several friends that opted to go Noritz in the past few years and have been very happy.

    Bosch Aquastar 1600H (117,000 BTU, up to 4.3 GPM flow rate, and 0.6 GPM turn on)
    Noritz 2007 Tankless Heater line. Main Noritz website is located here. While their N-063S (MSRP $999) would be totally adequate (180,000 BTU, up to 7.1 GPM flow rate, and 0.5 GPM turn on), I might splurge for the N-0751M (MSRP $1249) only because it comes with a digital remote control and if going with a computerized tankless heater why not get the cool display. The N-0751M has a more than adequate 199,000 BTU, up to 9.8 GPM flow rate, and 0.5 GPM turn on.
    Takagi TK-3 (199,000 BTU, up to 7.0 GPM flow rate, and 0.5 GPM turn on). This particular unit has an air intake like the direct vent Noritz units (example: N-0751M-DV). Takagi has other units that aren't direct vent but without a listing of their turn on flow rate which in the past was always 0.75 GPM it feels easier to choose Noritz at least until Takagi updates their web information.
    I should also note that compared to the competition Bosch copper heat exchangers are made of larger diameter copper tubing with thicker walls. The larger diameter promotes slower water flow (less erosion) and the thicker piping means the pipes will last longer.

    Lastly, you may have noticed Home Depot now carrying Paloma tankless water heaters. They have a $699 (118,000 BTU) and $999 (199,000 BTU) models with 0.6 GPM turn on. It appears Rheem carries these same heaters but rebadged with the Rheem brand name. Paloma's product selector page is located here.

    To help slow global warming (reduce CO2 emissions), reduce energy consumption, save on operational energy costs, eliminate landfill waste (from tanker heater disposal every 10 years), and NEVER run out of hot water, everyone should be upgrading to tankless water heaters if at all possible. Europe mainly utilitzes tankless water heaters for the past century having always been concerned about conserving (costly) energy.

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