This information compiled by Roger Berke and is a work in progress.

If you have photos / information, I would appreciate corrections or additions.
 

Aqua-Hot Models

431/12 - Prior to serial 94180	AHE-100-00S	AHE-100-04S	AHE-600-D04
431/12 - After serial 98571	AHE-100-01S	AHE-600-D01
411/12	AHE-100-02S	AHE-600-D02
AHE-101-000	AHE-100-03S	AHE-600-D03

• 3 zones + engine circulation pump PLX-809-200
• 1650 watt electric element ELX-2E7-540
• Mixing valve  PLX-4A8-180  - Rebuild kit PLX-4A8-18R
• Radiator Cap - PLX-102-229 or with lever PLX-102-229-L
• Terminal Block 
• Fuse Block  ELX-BB6-10A
• Relay  ELX-W1A-486
• Relay Socket  ELX-SR3-805
• Coolant Check Valve  PLX-2A1-300

• 3 zones + engine circulation pump PLX-809-200
• 1650 watt electric element ELX-2E7-540
• Mixing valve  PLX-4A8-180  - Rebuild kit PLX-4A8-18R
• Radiator Cap - PLX-102-229 or with lever PLX-102-229-L
• Terminal Block 
• Fuse Block  ELX-BB6-10A
• Relay  ELX-W1A-486
• Relay Socket  ELX-SR3-805
• Coolant Check Valve  PLX-2A1-300

   There were mid model changes. See more information for thermostat and mechanical connection details.

This model was produced until mid 1998 through serial 98571. Replaced by model below, "After Serial 98571".   The 24-volt version of this model is 431/24

   Exactly like 431/12 with the following changes

• 1 zone pump and NO engine circulation pump

      Webasto removed in this photo

   This model was produced until mid 1998

   Thanks to Michael Pierce for photo

   Exactly like 431 prior to serial number 98571 with the following changes

• Pumps are slightly different (replace with same part number as 431 above)
• Engine preheat hoses, fuel hoses, water connections go through bulkhead fittings.

 This model was produced until mid 1999 and was replaced by the AHE-101-000.  The 24-volt version of this model is 431/24

Looks Like 431/12 after 98571 above

   Exactly like 431 prior to serial number 98571 with the following changes

• No check valve on fuel return line

Looks Like 431/12 after 98571 above

  Exactly like AHE-101-000 with the following changes

  This model was produced until mid 2000 and was replaced by the AHE-100-01S.

  Exactly like AHE-100-00S except has 6 thermostats and dual elements

  Dual electric thermostats (one set for each electric element)

• Uses two -  Electric Control (Red Dot) ELE-010-198
• Uses two - Electric High Limit (White Dot) ELE-254-010
• Dual 2000 watt 120 volt elements.

Looks Like 431/12 after 98571 above

  Exactly like model AHE-100-00S with the following changes

 This model was produced until mid 2001 and was replaced by the AHE-100-02S.

Looks Like 431/12 after 98571 above

   Exactly like model AHE-100-01S with the following changes

   This model was produced until mid 2002 and was replaced by the AHE-100-03S.

   This model is a MAJOR redesign of AHE-100-02S

• Electronic Control Board! - First Aqua-Hot Model with Electronic Control Board
• Uses propylene glycol coolant
• Float switch (Plastic) replace with Brass float - ELE-800-002 or liquid sensor ELE-200-001-HYD
• On this model the entire drain valve is plastic.  Replace with Drain Valve Kit
• Pumps are different on this model.  Uses the PLE-100-821 pump
• Uses one control thermostat instead of the two in the previous models.  ELE-800-100
• There is high limit thermostat for Diesel and a high limit for electric.  They are the same ELE-HLT-322
• Mixing valve is changed.  PLX-09P-100

   This model was produced until mid 2005 and was replaced by the AHE-100-04S.

Looks like AHE-100-03S above

   Exactly like AHE-100-03S except

• On this model there is a short brass nipple, then the rest of the drain valve is plastic.  Replace with Drain Valve Kit

   This model was produced until mid 2007 and was replaced by the AHE-600D.

    Exactly like AHE-100-04S except

• White powder coated case
• Pumps are mounted to case with Nylatch fittings
• Drain valve is completely brass

Looks like AHE-600-DE1 above

    Exactly like AHE-600-DE1 except

• No radiator cap (uses zero pressure system)
• Has interlock switch (will not allow operation with cover off)
• Solid steel fuel lines (no rubber hoses)
• Redesigned combustion chamber - first Low Emission Model in this series
• Mounts in coach in "tray"

   This model is a redesign of AHE-600-DE2  

• Check valves are now horizontal between the pump and the boiler tank.
• Mixing valve moved into case right next to boiler tank. Access through front / side.
• A/C high limit thermostat - ELE-HLT-425
• Dual Diesel high limit thermostats - ELE-HLT-425
• Cover for thermostats much larger
• A/C power connection / location different
• Check valves are horizontal between the zone pump and the boiler tank
• Uses 'Liquid Sensor' - no mechanical float switch - ELX-800-003 - Liquid Sensor

Hydro Hot Models

HHE-500-03M

• Open zone pumps (no plastic cover)

• Engine preheat pump is PLX-CM3-P71 - Pump, Circulation, w/Bracket, Engine Preheat, 12 VDC - List price $1,081.75.

• Check valves are outside of the case.

• Has large radiator cap.  PLX-403-000

• Must use plastic float (PLX-01G-ML7) (or float sensor - ELE-200-001-HYD).

• NO drain valve

• Used the PLE-100-830 - Stir Pump. NOT AVAILABLE use PLE-100-830-HYD - Pump, Stir Kit - Cooper Standard Pump

• Uses ‘clip on’ Low Temperature Cutoff Thermostat - ELE-LTC-505

• Electric system uses ELX-228-1A1 - Relay, SPST, 12 VDC/30 Amp. Neutral wire is switched through relay and high limit. Upgrade kit available, here: ELE-630-002-HYD

HHE-500-04M

Click on photo for additional views

• Open zone pumps (no plastic cover)

• Engine preheat pump is PLX-CM3-P71 - Pump, Circulation, w/Bracket, Engine Preheat, 12 VDC - List price $1,081.75.

• Check valves are outside of the case.

• Has large radiator cap.  PLX-403-000

• Must use plastic float (PLX-01G-ML7) (or float sensor - ELE-200-001-HYD).

• NO drain valve

• NO stir pump

• Uses ‘clip on’ Low Temperature Cutoff Thermostat - ELE-LTC-505

• Electric system uses ELX-228-1A1 - Relay, SPST, 12 VDC/30 Amp. Neutral wire is switched through relay and high limit. Upgrade kit available, here: ELE-630-002-HYD

  Model HHE-x00-07x   Webasto 2010 - Uses ethylene glycol coolant

• Open zone pumps (no plastic cover)

• Engine preheat pump is PLX-CM3-P71 - Pump, Circulation, w/Bracket, Engine Preheat, 12 VDC - List price $1,081.75. Upgraded Cooper Standard pump is available.

• Check valves are directly over the circulation pumps.

• Has large radiator cap.  PLX-403-000

• Must use plastic float (PLX-01G-ML7) (or float sensor - ELE-200-001-HYD).

• NO drain valve.

• Used the PLE-100-830 - Stir Pump. NOT AVAILABLE use PLE-100-830-HYD - Pump, Stir Kit - Cooper Standard Pump

• Uses ‘clip on’ Low Temperature Cutoff Thermostat - ELE-LTC-505

• Electric system uses ELX-228-1A1 - Relay, SPST, 12 VDC/30 Amp. Neutral wire is switched through relay and high limit. Upgrade kit available, here: ELE-630-002-HYD

   This model is a MAJOR redesign of HHE-x00-07x

   Exactly like HHE-x00-07x except

• Zone pumps now have plastic covers over the moving parts
• Engine preheat pump is PLE-100-830 - Stir Pump. NOT AVAILABLE
• On this model the entire drain valve is plastic.  Replace with Drain Valve Kit or Brass Drain Valve Kit
• Uses ‘screw in’ Low Temperature Cutoff Thermostat.  ELE-000-606
• Use ELX-630-001 electric relay or ELE-630-002-FRU kit that already has the relay attached to a cover.

   Exactly like HHE-x00-08x except

• On this model there is a short brass nipple, then the rest of the drain valve is plastic.  Replace with Drain Valve Kit or Brass Drain Valve Kit

   Exactly like HHE-x00-09x except

• White powder coated case
• Pumps are mounted to case with Nylatch fittings
• Drain valve is completely brass

  This model is a major redesign of the Hydro-Hot series

   Exactly like AHE-450-DE1 except

• No radiator cap (uses zero pressure system)
• Has interlock switch (will not allow operation with cover off)
• Solid steel fuel lines (no rubber hoses)
• Redesigned combustion chamber - first Low Emission Model in this series
• Drain is on a rubber hose
• Mounts in coach in "tray"
• Redesigned A/C connector
• Check valves are horizontal between the zone pump and the boiler tank
• Uses 'Liquid Sensor' - no mechanical float switch - ELX-800-003 - Liquid Sensor
• Control thermostat - ELE-014-003
• A/C high limit thermostat - ELE-800-108
• Dual Diesel high limit thermostats - ELE-HLT-425
• Low Temperature cutoff thermostat - ELE-LTC-608

    More Photos

   Serial Numbers ???? - 100277

    Exactly like AHE-450-DE2 except

    More Photos

  Serial Numbers 110278 - 110278

    Exactly like AHE-450-DE3 except

• Zone pumps, stir pump and engine preheat pumps are the Cooper Standard pumps.

      More Photos

   Serial Numbers 110279 -

   Similar to AHE-450-DE4 except

• No engine preheat!
• No 'stir pump'
• Note: Cooper Standard Circulation Pumps
• Larger - 5.4 gallon boiler tank, a 32% increase of stored heat over 450 models.
• Rated at 1.25 gpm hot water

• Uses Beckett burner instead of the more common Webasto
• Nozzle - WPX-886-41A
• Fuel Filter - Should Be - Garber Filter FLE-120-100