Monday, August 3, 2015

Replacing a Bosch Aquastar 125FX with a Bosch Therm 830ES

The older Bosch Aquastar model 125FX came in either Natural Gas (NG) or Liquid Propane (LP) and was 117,000 BTU and was a direct vent unit that was good for one major application at a time.  The 125FX had electronic ignition and was fan-assisted and took its combustion air from the room it was installed in.  The heater had a built-in fan so the heater could be vented right out the sidewall of the building.  The Aquastar 125FX had to be vented with 4" sealed stainless steel venting going a maximum of 15' out the sidewall of the building into the FXHood.  The FX Hood was a termination hood specifically designed for the 125FX and had a built-in flapper to keep cold air from penetrating the vent pipe and freezing the heater.  The Bosch Aquastar 125FX is discontinued now and has not been made for over 8 years or so.  One of the closest replacement models for the 125FX would be the new Bosch Therm 830ES.
Bosch Therm 830ES
The new Bosch 830ES comes in either Natural Gas (NG) or Liquid Propane (LP) and is 175,000 BTU which is slightly more BTUs than the older 125FX.  The Bosch 830ES needs a minimum of a 3/4" gas line and has 3/4" water connections also.  The 830ES is a sealed unit and takes its intake air from the outside using 3" PVC.  The unit is vented to the outside using 3" Stainless steel venting and this could be attached to the FX Hood that is already in place using a 3" to 4" increaser (Z-Flex Part #2SVSI0304).  The 830ES is digitally controlled and can go from 100 - 140 degrees F.  See below for more specifications and capacity.

Therm 830 ESSpecifications
ApplicationResidential or Commercial
Max Input (BTU)175,000
Min Input (BTU)19,900
Capacity at 35°F Rise (gpm)8.3
Capacity at 55°F Rise (gpm)5.3
Intelligent CascadingYes
Min Flow Rate0.5 gpm
Temp Range (°F)100 - 140
Temp Stability (°F)+/- 2
Default Temp (°F)122
Energy Factor.82
Thermal Efficiency82%
Installation OptionsIndoor or Outdoor (for outdoor, kit required)
Dimensions (w x h x d)17 7/8" x 31½" x 11¼"
Weight (lbs.)67
Inlet Connection¾" NPT
Outlet Connection¾" NPT
Gas Connection¾" NPT
Max Water Pressure150 psi
Min Water Pressure30 psi
Min NG Presure3.5" WC
Condensing Heat Exchangern/a
Venting OptionsStainless Steel
Vent Maximun Run61.25'
Energy Star RatedYes