3. Water connections:
3.1 Fittings and hoses:
Use only fittings and accessories made of non-corrosive material such as
brass or stainless steel. Avoid plastic fittings on the water heater depending on the heat. For the engine
cooling water connections, use heat resistant (100°C / 210°F) reinforced rubber hoses, resistant to anti-
freeze and pressure proved for 5 bar (70 psi). For the fresh water, cold in and hot out, use heat resistant
fresh water hoses (food industry quality). They shall be rated min. 8 bar (115 psi) and heat resistant.
Seal the threaded connections with e.g. Loctite 577 or Bondline T777.
3.2 Engine connections (see diagram, fig. 2):
The water heater is meant for use on fresh water
cooled engines. Some sea water cooled engines, having a thermostat temperature control and possible
hot water hose connections, could also be used, if the working temperature is enough, 65 - 85°C / 150 -
185°F. The flow of cooling water from the engine through the water heater must be at least 2 litres/min. If
the boat has two engines, connect the water heater to one engine only. If two water heaters are to be
mounted, connect them in parallel.
Connection to the engine shall be done with min. 16 mm / 5/8” hoses and adaptors to avoid restrictions.
See the instructions in the engine operators manual, regarding hose connection points.
On some smaller engines, 10-15 Hp, it may be necessary to reduce the flow with a restrictor to keep the
engines cooling capacity an a correct level.
3.3 Freshwater connections (see diagram, fig. 2):
The water heater is fed with fresh water from
the electrical fresh water pump connected to the fresh water tank. Max pressure for the pump 3 bar (42
psi). A multi chamber pump creates less pressure peaks and gives a smooth flow. The hot water outlet,
which also vents the water heater, should be connected to a mixer tap at the sink and/or basin outlet, to
mix cold water with hot to avoid scalding. If the water heater is equipped with a thermostat mixer valve a
suitable temperature between 38 and 65°C / 100 and 150 °F can bee chosen with the thermostat mixer
valve.
Mount a waste water hose on the safety valve outlet, 10 mm / 3/8”, it must always have a free outlet, to a
lower point. There must be no valves or skin fittings, fitted to the waste water hose. A small quantity of
water may be expended via the safety valve during the heating up period.
3:4 Electrical connection:
All internal connections are made in the factory. The mains power supply
cable is fitted with an international plug (EU plug), which should be fitted to a correctly installed socket.
This socket shall be connected to a on board mounted double fuse unit including an earth leak switch. All
”high-voltage” installations on board, must be carried out in a proper way to fulfill valid regulations. The
Isotemp Slim water heater is designed to meet EU regulations in this field. When leaving the boat for
longer periods, it is recommended to pull out the cable connector from the socket. This should be done
even if the shore power system is shut off, as there can be a potential difference in the electrical system,
between the earth from shore and the sea-water earth of the boat. This can seriously damage the heater
element or the water heater.
4. Start up/Test:
Start the engine and check the circulation of the cooling water. Secure the hoses after
checking. Compensate with anti-freeze in the header tank on a fresh water cooled engine, for the
additional volume in hoses and heat exchanger. Fill up the water heater with fresh water by starting the
fresh water pump, leaving the hot water tap open to air the system. Check there are no water leaks and
finally connect the power cable when the water heater is full. Check that the safety valve outlet is free to
allow water to escape.
Note: the water expands during warm up, a small quantity may come out through the safety valve.
5. Maintenance:
5:1 Winter drain:
When there is a risk of freezing temperatures, the water heater must be drained.
This is done by pulling the lever on the safety valve to its open position. Take off the hot water hose and/
or open the air bleeder screw on the mixer valve, to allow air coming into the tank. It is a small stainless
steel M5 screw.
The water heater can be left safely on board over winter after it has been drained.
