Heating and Cooling

May 12, 2017

The heating and cooling use hot or chilled water-glycol mixture to transport heat or cold to four air handlers, located in the kitchen-dining room, bridge and each cabin.

Each air handler has its own digital cabin control and controlling unit and is completely independent from the central air conditioning unit, that is, there is no direct electrical or electronic connection.  The water-glycol temperature sensor on each controlling unit determines whether heating or cooling is currently being available.

Each digital cabin control can be individually programmed.

The most practical way to heat a boat is using a diesel fuel heater, since diesel fuel is or should always be available.
When the sea temperature is above 8 to 10 degrees you can use the reverse cycle of the air conditioning compressor.

The hot water generated by the heater is also used to warm the fresh water used in the bathrooms and kitchen through a heat exchanger (boiler).  This gives you a large quantity of hot water without having to use the generator or shore power.  The boiler can also heat the warm water with 220 V AC electricity.

The cooling is done with a conventional compressor that cools the water.

The Webasto heater operates on diesel fuel and 12 V DC, the compressor, air handlers and water-glycol circulating pump operate on 220 V AC.  This is not a problem when cooling the boat since to run the compressor the generator must also be running.  When heating the catamaran unfortunately the generator has to be running for the air handlers and the water circulating pump.  When not using all air handlers at full blast it may be possible to run them and the circulating pump off the inverter and batteries, thus providing a few moments of heat in absolute peace and quiet.

The heater outputs 9.1 KW when running at full blast, which means it uses a little less than 1 liter of diesel fuel an hour.

I chose to use a water-glycol mixture as opposed to a direct expansion system for various reasons. The most important is that I have to be able to heat the cat also in cold weather, with outside temperatures below zero Centigrade (and that is when you really need heating).  With low sea water temperatures the reverse cycle heating becomes very inefficient, practically not working anymore below a temperature of 8 degrees Centigrade and an additional way of heating has to be provided.  To send to four air handlers compressed gas requires an involved plumbing system made of copper pipes, with  at least 6 T junctions and eight ball valves, where very connection is a potential leak of refrigerant, leak that goes straight into the living quarters.  A water-glycol leak is easier to fix and the leaked water-glycol mixture easy to replace.


Kitchen - Dining Room

Total area app. 12.7 m^2, app. 25.5 m^3.


Total area app. 12.7 m^2, app. 25.5 m^3.

Main Cabin and Bathroom

Total area app. 12.83 m^2, app. 25.7 m^3.

Guest Cabin and Bathroom

Total area app. 12.83 m^2, app. 25.7 m^3.


To convert from Btu's to kW-hours multiply with 2.93 x 10 ^ -4.
To convert from kW-h to Btu's  multiply with 3414.



Heating the Catamaran 

Make sure that the water-glycol circuit valves are set for heating.  See below for instructions.

The LEDs besides the heater switch indicating that 12V DC and 220V AC are present must both be on.  
The breaker for the 12V DC is located in the branch circuit box above the port tank.
The breaker for the 220V AC is located in the main AC panel on the bridge.

Turn on the heater switch.  The LED beside the switch must come on and stay on.  If the LED starts blinking there is a problem.  See below for the error codes.

Turn on the requested air handlers and set the desired temperature and fan speed.

To heat the catamaran with the air conditioning compressor (when all the valves are set to cooling) change the air conditioning compressor control from cold to hot.  See below.

Programming the Cabin Controls (Thermostats)

Refer to the Webasto manual 2 for further instructions.

Changing from Heat to Cold

Before changing the position of any valve make sure that you know what you are doing and that you are closing or opening the right valve.  Failure to do so may over pressurize the system and cause a catastrophical failure.

Close the water valve at the Webasto water heater.

Always leave the two ball valves near the air handlers open.

Always leave the valves that connect the water heater (bolier) to the Webasto open, even when running the air conditioning.

Changing from Cold to Heat

Before changing the position of any valve make sure that you know what you are doing and that you are closing or opening the right valve.  Failure to do so may over pressurize the system and cause a catastrophical failure.

Open the water valve at the Webasto water heater.

Always leave the two ball valves near the air handlers open.

Changing the Air Conditioning Control from Cold to Heat

To change air conditioning control from cold to hot or from hot to cold press the F key and proceed to the F function.  Then press the hot or cold buttons to go to the desired value.

F01 cool cycle only
F02 hot cycle only
F03 automatic cooling or heating

To memorize the change press immediately the F key again.


Webasto Error Codes

The LED beside the heater switch indicates errors when blinking.  During normal operation the LED must be on and steady.
Refer to the Webasto manual  for complete instructions.

To indicate an error the LED flashes quickly 5 times, followed by a number of longer flashes.  The number of longer flashes indicate the nature of the problem.

F  00  Only 5 quick flashes, no long flashes. The electronic unit has locked up.  See below on how to reset it. 
F  01  No start-up (after 2 start-up attempts)
F  02  Flame extinguished

Webasto Blue Cool Chiller Unit Error Codes

The error codes are displayed directly on the digital display and will be followed by a system halt (except for <bA11>.  Whenever any of these codes appear the system is stopped for approx. 60 seconds and then a restart is attempted.  If for more than 30 minutes the same malfunction occurs, the system will be stopped completely and the error code will become steady.  No more resets will be attempted and the user will have to reset the system by pushing the <On/Off> switch or by temporarily cutting out the AC supply to the system.

AAA   Low voltage cut out.  Default setting 195 V.
A01    Compressor lacks cooling water or cooling fluid.  Is the sea valve of the compressor open?



Check the level of the  water glycol 25% mixture in the expansion tank located near the air handler of the guest cabin. The tank must be about half full.

The impulse pump that pumps the fuel from the day tank to the heater cannot be opened to be cleaned.  When not used for a lengthy period of time (say six months) it is possible that the plunger inside gets stuck and the pump will not work.  The only solution is a new pump.  To avoid this problem periodically (say every month or so) turn on the heater for a few minutes.  


Resetting the Webasto Electronic Control Unit

The procedures described below must be performed only if you know what you are doing and are familiar with working with live electricity.

When the LED beside the heater switch quickly flashes 5 times, followed by no long flashes, the Webasto electronic control unit has locked up.

To reset it leave it blinking and open the 12V DC box besides the Webasto heater unit.  Momentarily disconnect the red wire coming from the heater.  After reconnecting the red wire the electronic contol unit should be operational again.

Priming the Webasto Heater

The Webasto heater has a small impulse pump that supplies the diesel fuel to the unit through a flexible plastic hose with an inside diameter of 2mm.  To fill the small hose with fuel it is advisable to manually operate the pump since turning on the unit too many times may cause the electronic control unit to lock up.

To manually operate the pump open the 12 V DC box besides the Webasto heater unit.  The pump is connected to the heater with two wires, a blue one and a brown, with a four circuit terminal block.  Momentarily disconnect the brown wire going to the heater unit and quickly touch the brown wire going to the pump to the positive 12V DC (red) supply.  A "tick" will be heard from the pump and the fuel will advance a few centimeters in the plastic hose.  Continue to connect and disconnect the 12 V DC supply until the fuel reaches the heater.  Reconnect the wire and start the unit in the usual way.

Cleaning the Webasto Heater

The flame chamber of the Webasto heater has to be cleaned and checked every year or so.  It is not necessary to detach the unit.

Webasto 2

Make sure that there is no water below, in the bilge.  You are going to drop something.
Detach the exhaust.
Loosen the big clamp, so that the burner unit turns.
Detach black box with the electronics, on the left.  Otherwise the wires are too short.
Remove the two screws that attach the burner.  Turn unit to have access to the screw behind.
Separate the two units.
Detach the two nuts inside.
Detach the screw that holds the fuel pipe.

Clean everything

Webasto 3

The thermo couple (gray wires) and the igniter (brown yellow wires) must be cleaned only with paper and WD40.  Under no circumstances scrape or scratch them with tools or sand paper.

The small hole between the wires supplies the air to start the flame.  Should it get clogged the burner will not start.

Put together everything.  Don't forget the big O-ring.




May 8

AC compressor problems, due to the clogged water strainer.  Strainer was clogged even though no dirt was visible from the outside.  Cleaning the strainer put things back to normal.



Webasto 90ST D Heater

The Webasto water heater uses diesel fuel and runs on 12 V DC.

The diesel fuel is pumped with a small impulse pump that runs on 12 V DC. 

Webasto 1

The diesel fuel must NOT contain any water, otherwise the combustion chamber will suffer irreparable damage, as shown on the picture on the right..

Unfortunately the small impulse pump cannot pump the necessary fuel directly from the main fuel tank.  So a heater day tank had to be installed above the port fuel tank, which can be filled with the main fuel pump.  Care must be taken that the condensation that forms in the tank does not contaminate the fuel.

The heater wires are connected to the power supply and controls through the 12V DC box located near the unit with the following wires connected to the left 8 place terminal block (from top to bottom):

White Connected to a LED and indicates status of unit.
Black When connected to 12 V DC turns on the unit.
Red + 12 V DC 
Brown - 12 V DC

Two more wires from the heater must be connected to the diesel impulse pump also through the 12V DC box located near the unit with the following wires connected to the right 8 place terminal block (from top to bottom):

Brown Connected to the impulse pump
Blue Connected to the impulse pump

The picture below shows how the Webasto wires are connected.  From left to right:

brown - blue
green - green
gray -gray                   thermocouple
yellow - brown            igniter                                
violet - violet

big connector:
yellow red         single wire, diagnostic (usually not connected)

brown - blue        diesel fuel pump


Webasto closeup


Purchased September 2006.

By January 2011 the unit had worked for 951 hours, with 331 startups.

Power 12 V, 83 W (7 A)
9.1 KW (31,000 BTU)


Webasto heater Webasto Thermo 90 S

Serial No. 00 0019 02 1173

1 Webasto impulse pump 12 Volt Ident-Nr. 85106B

Contec Webasto Alba
Webasto International

The following manuals provided by the manufacturer is also part of this section:

Webasto Thermo 90S Manual
Webasto Accessories Manuals


Webasto Blue Cool Chiller Unit

The chiller units runs on 220 V.

The unit has its own digital control and is completely separate from either the Webasto heater or air handlers.


Webasto chiller unit Webasto # WBCL005207

Serial No. ??

1 Digital chiller contol Webasto # WBCL000827  

Contec Webasto Alba

The following manual provided by the manufacturer is also part of this section:

Webasto Blue Cool Premium Manual


Air Handlers and Cabin Controls

There are two 3.5 KW (12,000 BTU) Webasto chilled water air handlers and two 4.7 KW (16,000 BTU) Webasto chilled water air handlers complete with digital cabin controls and controlling unit.

Each air handler has hose barbs that connect to a rubber hose with an ID of 15 mm.

They all operate with 220 V and 50/60 Hz.  The 3.5 KW ones consume 0.2 A, the 4.7 KW ones 0.8 A.

The air handlers are programmed from the corresponding cabin control.  The procedure is straight out of the eighties and cumbersome, to say the least.  On top of that the manual explains the procedure very poorly.  The following instruction must be revised.

To access the hidden parameters do the following:

On then bring the minimum temperature to 15 deg.
On then off, then for 3 seconds press sun and cold at the same time
Press F, then advance from one parameter to the other
Change param,eter by pressing either sun or cold

Each air handler control box has a fuse.

Purchased September 2006.


3.5 KW air handlers Webasto # WBCL000747 Serial No. 26032278
Serial No. 26032416


4.7 KW air handlers Webasto # WBCL000748 Serial No. 26032882
Serial No. 26032945


Digital Cabin Controls, 2004 series Webasto # WBCL000373  

Contec Webasto Alba

The following manual provided by the manufacturer is also part of this section:

Webasto Air Handlers and Cabin Controls Manual


Hoses and Valves

The equipment is connected with insulated, flexible hose.

The main trunk line has a ID of  20 mm, while the air handlers are connected with hoses of an ID of  15 mm .

Each air handler has two ball valves to be able to shut them off.  Unless performing maintenance on the air handlers, leave the valves always open.

Each air handler also requires a reinforced flexible hose to connect the condensation drain pan to an overboard discharge.

The refrigerant must be a mixture of 25% glycol and 75% water.


20 mm ID water hose with insulation  Webasto # WBCL002003  


15 mm ID water hose with insulation Webasto # WBCL002002  

Contec Webasto Alba


Water Expansion Tanks

The water expansion tanks are located near the air handlers in the cabins.


 Expansion tanks Webasto # WBCL002030  


Contec Webasto Alba


Magnetic Water Circulation Pumps

The heating - cooling water glycol mixture is circulated through the system with a magnetic drive pump.

The pump employs a magnetic coupling to eliminate the seal on the impeller shaft.

The pump must not be run dry since dry running causes abnormal heat in the bearing, resulting in a broken pump.  The motor is equipped with a thermal overload protector that automatically stops the motor when it is over heated and starts again when the temperature decreases to the set value.  The pump is not self priming.

Voltage  220 V
Frequency 50 - 60 Hz
210 - 300 W
RPM 2860 - 3380
Max. capacity 86 - 97 l/min
Max head 6.7 - 9.7 m


 IWAKI magnetic drive pump MD series Webasto # WBCL001107 Serial No. 

IWAKI Co., Ltd.
Contec Webasto Alba


Fresh Water Heater

In this picture the hoses for heating the water with the hot water generated by the Webasto heater have not yet been connected to the two yellow in and outlets.

The hot water generated by the Webasto heater is also used to heat the fresh water through a heat exchanger coil in an electric water heater.  The water heater can also be used with the Webasto heater even when the cat is being cooled by the air conditioning equipment.  See the procedures above.

Voltage 220 V
750 W
Capacity 50 Liters
Pressure relief valve 7 bar
Heat exchanger max. 2 bar

Purchased February 2007 through Contec srl.


 Isotemp basic water heater Type 50HXC Serial No. 0006103653

Contec Webasto Alba
Indel Marine

The following manuals provided by the manufacturer is also part of this section:

Indel Marine boiler Manual


Air Supply Grilles

The air supply grilles have a teak frame and are completely closeable.


 Air supply grilles Webasto # WBCL004005  

Contec Webasto Alba


Remote Control Wires

The remote control wires to the heating panel on the bridge for the heating and cooling system consists of a cable with 9 black wires numbered from 1 to 9 and one yellow-green wire.

The wires have the following functions:

Yellow - Green -12 V
#1 +12V after relays
#2 Webasto start (Webasto black)
#3 Webasto LED (Webasto white)
#4 + 12V after main breaker




Boat Heat Terry Johnson, Pacific Fishing November 2002


cat_30 heating.htm