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TEST water heaters in the 20-litre class
Wet heat home comfort on board
This test of Water Heaters for Yachts has There are wide differences bet-
been carried out by the independent
Norwegian Boating Magazine ween water heaters. In the best
BÅTMAGASINET, the leading motor- one, the temperature of the hot
boat magazine in Scandinavia. The
article is written and photographed by water fell by only 3,9 degrees
Jan Harry Svendsen and reported in over 12 hours of cooling.
issue nr. 7 of BÅTMAGASINET,
June/July 2004. This article is reprinted The worst of them lost more than
without any changes or comments by
Indel Marine Italy, producer of Isotemp
20 degrees and cost the most.
Water Heaters. The translation from
Norwegian language to English has
been made by authorised translator
Sprakservice, Member of Swedish
Association of Professional Translators.
TEST water heaters in the 20-litre class
he difference between a warm, pleas- COOLANT AS HEAT SOURCE drawback of this solution is that the tank is
ant shower and a cold shower that Most of the water heaters in the test have heavy. It weighs as much as 23 kilograms.
makes you shiver is no more than 1,35 the same basic design idea. An insulated tank
degrees an hour. While the Isotemp Basic has is connected to the boat's freshwater system ISOTEMP GOOD,
a heat loss of only 0,33 degrees an hour over and the engine cooling system. The engine WEBASTO DISAPPOINTING
12 hours, the Sigmar Thermoinox loses as coolant is conveyed through a heat exchang- The ATI BB 2212 had the highest tem-
much as 1,68 degrees. However, the Sigmar er inside the tank and heats up the water. perature after one hour of heating using the
is not the overall loser in the test. It redeems Most of the tanks are additionally supplied heat exchanger, 68,8 degrees. That's more
itself by having a slightly higher tempera- with a heating element which makes it possi- than 20 degrees warmer than the Mobitherm
ture after the heating cycle has ended than ble to heat up water from the shore power MWH-020 and the QL Water-Heater, with
the Webasto, which does not manage to sup- supply. 48,2 and 48,5 degrees respectively. The pic-
ply a drop of water over 40 degrees after a Vetus has chosen a different solution, ture changes when we have left the water
cooling period of 12 hours. with two tanks one inside the other. The heaters standing for twelve hours without
freshwater is in the inner tank,, while the en- heating. Then the Vetus provides the hottest
gine coolant circulates in the outer tank. The water at 55,2 degrees, while the Webasto
TO ENSURE THAT the test results were repeatable, and that the tanks operated in identical
conditions, they were tested on the bench. Here the tank of the Vetus is connected.
20L does not manage to supply water a valve it is possible to choose to add cold
warmer than 39,9 degrees. The limit for a water to the hot water drained from the
comfortable shower temperature is around heater. Better use is made of the hot water
40 degrees. in this way.
What is of greatest interest, however, is Another advantage is that using this
how many litres of water over 40 degrees valve it is possible to adjust how hot water
the heaters manage to supply after 12 hours the heater is to deliver. This reduces the dan-
of cooling. ger of burns, particularly if there are young
Here the Isotemp Basic is in a class of its children on board.
own. From its 24 litre tank it supplies as
much as 23 litres of water at a temperature CHECK OUTPUT
above 40 degrees. The Vetus is also good All the water heaters in the test, with the
THE TANKS were taken apart so that we
with 17 litres from a 20 litre tank. The exception of the Vetus, were equipped with a could study their construction.
Isotemp Slim 20 and Quick Nautic Boiler heating element as standard. Connecting the
deliver 15 litres. The Sigmar Thermionox hot-water tank to the boat's shore power sys-
and the ATI BB 2212 are disappointing, tem ensures that there is also hot water when SAFETY THERMOSTAT FAILED
with nine and eight litres respectively. Both the boat is moored. With a built-in thermostat, All the heating elements are equipped with a
have a capacity of 22 litres. By far the worst the efficiency of the hot-water tank is like at thermostat, and in the vast majority of cases
is the Webasto. It does not manage to deliv- home. Most of the tanks in the test have heat- these are adjustable. The exception is the
er so much as a drop of water above 40 de- ing elements that deliver around 800 Watts. Isotemp, which has a thermostat fixed at 75
grees after 12 hours. The exception is the ATI, which has a 1,500 degrees. For the water heaters from Sigmar,
Watt element. It is basically a good one, but Mobitherm, QL and Webasto the temperature
MIXER VALVE IS USEFUL the drawback is that most shore power sys- was a few degrees above the value at which
Part of the secret behind the good re- tems have many users connected to the same the thermostat was set, while the rest of the
sults achieved by the Isotemp is the mixer outlet. Too high a wattage in the element may tanks were a few degrees below the set tem-
valve. Both the Isotemp Slim 20 and the therefore lead to the fuse in the shore power perature.
Isotemp Basic have this as standard. Using system blowing. All the thermostats are additionally
DRAIN: The tank of the Vetus is drained SMALL SLEEVE COUPLING: The tank is drained
by unscrewing a plastic lid. This solution via the small sleeve coupling. Not only does this
will result in waste-water when the tank take a long time, it is also difficult to attach a hose
has to be drained. to the sleeve coupling.
SAFETY THERMOSTAT: The Isotemp is
the only water heater in the test with a
safety thermostat that works on boiling
dry. The blue "box" is the safety ther-
mostat, while the operating thermostat THERMOSTAT: All the water heaters in MIXER VALVE: The tanks from Isotemp have a mi-
is the white "box". the test with the exception of the xer valve as standard. The temperature of the wa-
Isotemp have an adjustable thermostat. ter to be supplied by the heater is set here. Cold
However, the safety thermostat failed on water is mixed in with the hot water to attain the
all the thermostats. correct temperature.
equipped with a safety thermostat. This is in- six bar. The deviations between specified and heavy. Vetus charge no less than NOK
tended to trip if the water heater is switched on opening pressure and actual opening pres- 3.855 for their tank and if you want a heating
and there is no water in the tank (boiling dry) sure were minimal for these tanks. element the price rises to NOK 4.617. The
or if the ordinary operating thermostat fails. Quick Nautic Boiler offers a lot for the mon-
Only the Isotemp had a system that worked the SAME MAKE ey. With a guide price of NOK 2.350 it is the
way it was meant to. After just under five min- We have brought together nine different most inexpensive tank in the test. The 20-litre
utes the safety thermostat tripped on both the tanks in this test. But four of these tanks are tank nevertheless delivers 15 litres of hot wa-
Slim 20 and Basic. The element in the Vetus of the same make. Sigmar has produced the ter, and in material selection it is superior to
and ATI short-circuited and blew the fuse on tanks for Mobitherm, QL and Webasto. the other tanks in the test. Stainless steel
the shore power side. On the other water However, there are some differences be- (AISI 316) is used in the tank, heating coil
heaters the operating thermostat took over the tween the tanks. The Thermionox has a tank and in the casing around the tank. Despite
job of the safety thermostat and switched on capacity of 22 litres, while the Webasto, QL low price, good performance and quality ma-
and off with an empty tank. and Mobitherm have 20-litre tanks. terials, the tank of the Quick comes third be-
Webasto for its part has its own heat ex- cause the safety thermostat did not trip in the
POOR CONNECTING OPTIONS changer for the connection of external heat, boiling-dry test. The Quick is therefore beat-
A combined one-way valve and safety for example a Webasto heater. en by the Isotemp Slim 20. Its performance is
valve is fitted on all the tanks. This valve The QL and Mobitherm, on the other the same as that of the Quick with regard to
has several functions, including preventing hand, are completely identical tanks, which hot water, but the Slim 20 has a mixer ther-
hot water from running out of the tank. In our test results also show to be the case. mostat as standard and has a safety thermo-
addition, the valve is used when the water They track each other with regard to both stat that works. The drawback is the price.
heater is to be drained. The drawback with the number of litres above 40 degrees the The Isotemp costs nearly NOK 1.000 more
most of the valves is that the diameter of the tank can deliver and the temperature after than the Quick.
drain coupling is too small. This makes it heating has ended. The heat loss is also Modest performance and a high price
difficult to attach a hose to the valve, and at identical for the two tanks. It might be should make the tanks from both QL and
the same time it takes too long to drain the thought that identical tanks would cost the Mobitherm uninteresting. The Isotemp
tank. A welcome exception is the Vetus, same. They do not. The QL costs NOK Slim 20, for example, is cheaper to buy than
which has a valve with a decent connection 3.125, while the Mobitherm carries a price the Mobitherm MWH-20.
for a hose on the safety valve. The draw- tag of NOK 3.750. Mobitherm thus charges Both the Sigmar Thermoinox and the
back with the Vetus solution is that they NOK 600 more than QL for exactly the ATI BB2212 have a capacity of 22 litres.
have chosen to have a separate unit to drain same tank (1 8,5 NOK). However, they do not manage to deliver
the tank. This is done by unscrewing a more than nine and eight litres of water re-
small plastic lid. This solution is not ideal, ISOTEMP BEST spectively at a temperature above
and will cause waste-water in the boat. This test provides ample proof that expensive 40 degrees. The only tank worse than these
All the tanks with the exception of the is not always best. The Webasto 20 L is the is the Webasto 20 L, which does not pro-
Isotemp and Quick have safety valves that most expensive and worst tank in the test. vide a drop of water warmer than
open at a pressure of four bar. The manufac- The Isotemp Basic is the best. With its tank 40 degrees. The price is also very high, so
turer's information was in good agreement capacity of 24 litres, it delivers 23 litres of you need to have a very good reason to
with our test results during our pressure water at a temperature above 40 degrees after choose the Webasto tank.
test. However, it is poor when the ATI and a cooling period of 12 hours. The Basic costs
Webasto valves already start to ooze at NOK 3.350, but a mixer valve comes as stan-
three bar. dard. Vetus is also a tank with good perfor-
Both the Isotemp and the Quick have mance. No less than 17 litres from its 20-litre
valves that do not open until a pressure of tank is good, but the tank is both expensive
Isotemp Basic 24 Price: NOK 3.350 inn
The ISOTEMP BASIC has good la-
The Isotemp Basic is the
show winner in the test. It supplies
various a lot of hot water in relation to
hoses are its size and has low heat loss.
to be con- The water heater is well put
nected. together in all its details, and
has a high level of equipment.
A mixer valve, for example, is
The Isotemp Basic has a tank capa- acid-proof steel (AISI 316). A casing, THE CONSTRUCTION makes no temperature at 55.8 degrees. This is
city of 24 litres. It can be mounted ho- made of non-magnetic stainless steel compromises. The heat exchanger relatively modest, when the tempera-
rizontally and vertically, but in that (AISI 304) protects the tank's insulati- goes in several loops, and the hea- ture of the water that circulated
ting element is angled downwards
case with the connection points fa- on. The insulation is of polyurethane for optimum output.
through the heat exchanger had a
cing down. The water heater has very foam. temperature of
strong feet that are spot-welded to a The thermostat of the heating ele- The Isotemp Basic has low heat 70 degrees. However, the capacity of
strap that goes round the tank. Mixer ment is not adjustable, but is pro- loss. After 12 hours the total heat loss the water heater is impressive. After
thermostat and heating element are grammed to trip at 75 degrees. The was only 3.9 degrees. That gives an 12 hours of cooling, the tank delivers
standard. safety thermostat works as intended average heat loss per hour of only as much as 23 litres of water at a
Both the tank and the heat ex- on boiling dry, and trips quickly. It has 0.33 degrees. After one hour of engi- temperature above 40 degrees.
changer are made of high-grade to be reset manually. ne running we measured the water
The Isotemp Slim 20 is a good
Isotemp Slim 20 Price: NOK 3.265
hot-water tank. Its modest di-
mensions mean that it also
CONNECTION is straightforward, fits into tight spaces.
thanks to good labelling of the va- The water heater has a high
rious con- level of equipment and has
THE CONSTRUCTION of the
Slim 20 L is identical to the
Basic. Here too the heating ele-
ment is angled down, but be-
cause the tank is smaller the
heating coil has fewer loops.
The Isotemp Slim 20 has a tank ca- Both the tank and heat exchanger on boiling dry, and trips quickly. It capacity of the water heater is ap-
pacity of 20 litres. It can be mounted are made of high-quality acid-proof has to be reset manually. proved. After 12 hours of cooling,
horizontally and vertically, but in that steel (AISI 316). A casing protects The Isotemp Slim 20 has an ave- the tank delivers 15 litres of water at
case with the connection points fa- the insulation. The insulation is of rage heat loss; after 12 hours the to- a temperature above 40 degrees.
cing down. The water heater has polyurethane foam. tal heat loss was 12.1 degrees. It
strong feet that are spot-welded to a The thermostat of the heating ele- provides an average heat loss of
strap that goes round the tank. Mixer ment is not adjustable, but is pro- one degree per hour. After running
thermostat and heating element are grammed to trip at 75 degrees. The for one hour we measured the water
standard. safety thermostat works as intended temperature at 62.7 degrees. The
The Quick Nautic Boiler is a
good hot-water tank.
Quick Nautic Boiler Price: NOK 2.350
The tank is reasonably pri-
ced, but is costly in choice
of material. It has useful ca-
pacity and an efficient heat
exchanger. A disappoint-
ment is the safety thermos-
tat, which does not work as
THE HEATING COIL is strong
and well dimensioned. The wa-
ter heater ought to have had
rather better insulation.
The Quick Nautic Boiler has a tank The QUICK has a clear front, with good The safety thermostat is integrated The Quick Nautic Boiler has relati-
capacity of 20 litres and can be labelling. The fact that the text is cast into the thermostat housing which sits vely high heat loss; after 12 hours the
mounted horizontally and vertically. into the plate means that problems on the outside the tank. This works po- total heat loss was 15,6 degrees. This
with glued-on slips are avoided.
The water heater has simple feet orly because the sensor is too far gives an average heat loss per hour of
welded to a strap that goes round the of steel (AISI 316), protects the tan- away from the heating element. 1,3 degrees. After one hour of engine
tank. Heating element is standard k's insulation, which is made of poly- During our test the water heater knoc- running, we measured the water tem-
equipment. urethane foam. ked against the operating thermostat perature at 64,3 degrees. The capaci-
Both the tank and the heat ex- The thermostat of the heating ele- on boiling dry. In other words, the safe- ty of the water heater is approved.
changer are made of acid-proof steel ment is adjustable in the ty thermostat did not work as inten- After 12 hours of cooling the tank deli-
(AISI 316). A casing, also of acid-pro- 20-80 degree range. ded. vers 15 litres of water at a temperature
above 40 degrees.
THE LABELLING of the connecti-
Price: NOK 3.855
Vetus supplies a tank with
solid performance. Its capa-
city is very good and it has
on points is useful. However, the
distinctive low heat loss. However, the
design of tank is too expensive; with
the tank an electric heating element it
makes costs NOK 4.617. Its design
correct also makes the tank heavy.
DOUBLE: The Vetus has an
inner and an outer tank, with
the engine coolant circulating
The Vetus has a tank capacity of outer tank in which the engine coo- in safety thermostat is intended to in the outer tank. Its design
20 litres and can be mounted hori- lant circulates. The inner tank is protect against boiling dry, but the makes the tank heavy.
zontally and vertically. The water he- made of non-magnetic stainless steel element short-circuited before the
ater has strong feet screwed into the (AISI 304). The outer tank is made of thermostat tripped. perature at 63 degrees. The capacity
tank itself. A heating element is not steel. The design of the tank makes it The Vetus has a low water loss; af- of the water heater is very good. After
standard, despite the high price of very heavy. The insulation is poly- ter twelve hours the total water loss 12 hours of cooling the tank delivers
the water heater. urethane foam with a casing of vinyl, was 7.8 degrees. This results in an 17 litres of water at a temperature
The design of the Vetus differs ra- but there is polystyrene at each end. average water loss per hour of above 40 degrees.
dically from the other tanks in the The heating element is adjustable 0.65 degrees. After an hour of engine
test. There is an inner tank and an in the 40 to 80 degree range. A built- running we measured the water tem-
QL Water Heater Price: NOK 3.125 CONCLUSION
The QL Water Heater is a
THE CONNECTION POINTS are simple hot-water tank. The
belled. heating loop is U-shaped
The insu- and therefore makes poor
lation is use of the coolant. Only
un-protec- 12 litres of hot water above
ted. 40 degrees is also on the
low side. The tank is identi-
cal to the Mobitherm MWH-
The QL Water Heater has a tank ca- with any protective casing. THE CONSTRUCTION of the tank is butes to the water in the water heater
pacity of 20 litres and can be moun- The thermostat of the heating ele- simple, and the material is acid-pro- having the lowest temperature, toget-
ted horizontally and vertically. The ment is adjustable; the temperature of steel (AISI 316). The heat ex- her with the Mobitherm, after one
water heater has simple feet that are range is from 30 to changer is very rudimentary, as the hour of engine running. The tempera-
test results also show.
spot-welded to a strap that goes 80 degrees. The safety mechanism ture is only
round the tank. does not work as intended on boiling The QL Water Heater has low wa- 48.5 degrees. After 12 hours of coo-
Both the tank and the heat ex- dry; the sensor is located too far ter loss; after 12 hours the total water ling the tank delivered 12 litres of wa-
changer are made of acid-proof steel away from the heating element. The loss was 5.9 degrees. This gives a ter at a temperature above
(AISI 316). The insulation is of poly- result is that the water heater knocks total heat loss per hour of 0.49 degre- 40 degrees.
urethane foam, but is not equipped against the operating thermostat. es. An inefficient heating coil contri-
Mobitherm MWH-020 Price: NOK 3.750
The QL Water Heater is a
simple hot-water tank. The
heat coil is U-shaped and
thus makes poor use of the
coolant. Only 12 litres of hot
water above 40 degrees is
on the low side. The tank is
identical to the QL Water
The Mobitherm has a capacity of USEFUL labelling of the connection SIMPLE CONSTRUCTION, and the ves an average heat loss per hour of
20 litres, and can be mounted hori- points on the tank. material is acid-proof AISI 316 steel. 0,44 degrees. An inefficient heat coil
The insulation is unprotected. The test shows that the heat ex- contributes to the water in the water
zontally and vertically. The water he-
changer is rudimentary. The tank is
ater has simple feet spot-welded to a The thermostat of the heating ele- heater having the lowest temperatu-
identical to the QL.
strap that goes round the tank. ment is adjustable; the temperature re, together with the QL, after one
Both the tank and heat exchanger hour of engine running. The tempe-
range is from 30 to 80 degrees. that the water heater knocks against
are made of high-quality acid-proof rature is only 48,2 degrees. After 12
The safety thermostat does not the operating thermostat.
steel (AISI 316). The insulation is of hours of cooling the tank delivered
work as intended on boiling dry; the The Mobitherm Cal 020 has low
12 litres of water at a temperature
polyurethane foam, but is not equip- sensor is located too far away from heat loss; after 12 hours the total
above 40 degrees.
ped with any protective casing. the heating element. The result is heat loss was 5,3 degrees. This gi-
The Sigmar Thermoinox is a
Sigmar Thermoinox Price: 2.575
simple water heater. The
choice of material is good,
but the insulation can be
improved. A heat loss of
more than 20 degrees over
12 hours is scandalous.
Its capacity is also very
poor. The water heater only
managed to deliver nine li-
tres of hot water from its
tank of 22 litres.
The Sigmar Thermoinox has capa- POOR insulation on the Sigmar SIMPLE TANK. The heat coil is a sim- 20,1 degrees. This gives an average
city of 22 litres, and can be mounted Thermoinox, but the connection ple U, and the water heater has high heat loss per hour of 1,68 degrees.
horizontally and vertically. The water points are well labelled. heat loss. After one hour of engine running the
heater has simple feet that are spot- not equipped with any protective ca- the operating thermostat. Here too water heater delivers water at a tem-
welded to a strap that goes round the sing. the sensor for the thermostat is loca- perature of 60,6 degrees. The capa-
tank. The thermostat of the heating ele- ted too far away from the heating ele- city is, however, lamentable.
Both the tank and the heat ex- ment is adjustable from 30 to ment. The water heater only manages to
changer are made of acid-proof steel 80 degrees. The safety thermostat The Sigmar Thermoinox has the deliver nine litres of water above
(AISI 316). The insulation is polyuret- does not work as intended on boiling highest heat loss in the test. After 40 degrees.
hane foam, but the water heater is dry. The water heater knocks against 12 hours the total heat loss was
ATI BB 2212 Price: NOK 2.530
The ATI BB 2212 is a hot-wa-
ter tank with an unusual
choice of materials. Instead
of acid-proof steel, the insi-
de of the steel tank has been
enamelled. A plus point for a
powerful heat exchanger,
but the capacity of the tank
exchanger for optimum utili-
sation of the engine coolant.
Unfortunately the tank has
The ATI has capacity of 22 litres and THE CONNECTIONS on the tank of the ling dry, because the heating ele- high heat loss and poor capa-
ATI ought to have been labelled better. city.
can be mounted horizontally and ver- ment short-circuits. The ATI is the
tically. The water heater has simple The ATI is the only tank in the test to only tank in the test to have a zinc one hour of heating. We measured
use 3/8 inch couplings on the inlet and
feet that must be screwed onto the outlet of the fresh-water side.
anode fitted as standard on the hea- the temperature as being as high as
straps that go round the tank. ting element. 68.8 degrees. A decent heat ex-
The tank is made of steel, but the sistant aluminium protects the insula- The ATI has high heat loss. After changer with as many as 16 loops is
surface is enamelled and heat-tre- tion. 12 hours the total heat loss was responsible for the good result.
ated at 860 degrees. The heat ex- The thermostat of the heating ele- 19.2 degrees. This gives an average Unfortunately the capacity of the tank
changer is made of copper and the ment is adjustable in the range from heat loss of 1.6 degrees per hour. On is not good. It only manages to deli-
insulation is made of polyurethane. 0 to 70 degrees. The safety thermos- the other hand, the water heater has ver eight litres of water above
A casing of anodised, sea-water-re- tat does not work as intended on boi- the highest water temperature after 40 degrees.
Webasto 20 L Price: NOK 4.340
The Webasto 20 L is the big
surprise in the test. It might
THE WEBASTO'S tank has many
connection be thought that the name
points would oblige. It evidently
with good does not do so in this case.
labelling. The capacity of the tank is
below criticism; it does not
manage to deliver a drop of
water above 40 degrees. In
addition, its price is far too
The Webasto has a capacity of In addition to the heat exchanger OWN HEAT COIL for use together The Webasto 20 L has relatively
20 litres and can be mounted hori- which is connected to the engine co- with boat heaters. The high location high heat loss. After 12 hours the to-
zontally and vertically. The water he- oling system, the water heater has of the heat exchanger that circulates tal heat loss is 17,3 degrees. This gi-
the engine coolant contributes to
ater has simple feet spot-welded to its own heat exchanger for the con- the poor test result. ves an average heat loss per hour of
straps that go round the tank. nection of external heat, for example 1,44 degrees. The water temperatu-
Both the tank and the heat ex- Webasto boat heaters. as intended on boiling dry. The water re after one hour of engine running
changer are made of acid-proof ste- The thermostat of the heating ele- heater knocks against the operating is 57,2 degrees. It is disappointing
el (AISI 316). The insulation is made ment is adjustable; the temperature thermostat. This happens because that the tank does not deliver water
of polyurethane foam, but it is not range is from 30 to 80 degrees. the sensor of the thermostat is located above 40 degrees after 12 hours of
equipped with any protective casing. The safety thermostat does not work too far away from the element. cooling.
TEST water heaters in the 20-litre class
simulates a natural cycle as found on a board with a pressure increase of 0.1 bar.
How we performed leisure craft. The temperature was measured. Measurements were performed when the
the test The circulation of the engine coolant was then
started up again to equalise the temperature
valve started to ooze water and when there
was full opening.
he test was performed in the heavy lab- drop which the one litre of cold water had The test was performed in March and
oratory of the Department of Maritime brought about. The circulation this time was April 2004.
Sciences at Vestfold University College interrupted after half an hour. The tank was
(HIVE) in Horten. A Fluke 54 II temperature then left standing for 12 hours to simulate a
gauge was used as measuring equipment. The night on board. Cold water was added to the
instrument was calibrated in a liquid bath at tank after 12 hours with a flow rate of four
IKM Laboratorier in Tananger. In addition, a litres a minute. The temperature was mea-
pressure gauge was used during the pressure sured for each 15 seconds, or for each litre
testing of the tanks. The pressure gauge is ac- drained from the tank.
curate to +/- 5 per cent. The test on the heating elements of the tanks
A test bench was used during the test. A hot was carried out by setting the thermostat to
water tank with a 3.000 Watt heating element max. The tank was then filled with water at a
delivers "coolant" at a temperature of 70 de- temperature of 20 degrees and then it was
grees. A circulating pump was used to circu- plugged in. The temperature as measured when
late the coolant through the heat exchanger in the thermostat tripped for the first time. The
the water heaters. The speed of the pumps test on the safety thermostat was carried out by
could be regulated, and they could be adjusted the tank being connected to the power source
so that the flow through the heat exchanger of WITHOUT there being water in the water
the tank was 3 litres a minute. The tanks were heater. The time before the safety thermostat
fitted and connected before each test. They tripped was then measured. Several of the tanks
were then filled with freshwater at a tempera- did not pass the test, and for these the test was
ture of 20 degrees before circulation of terminated after 30 minutes.
"coolant" was started. The circulation was in- The pressure test on the safety valve was
terrupted after an hour, when precisely one undertaken by filling the tanks with water and
litre of cold water (20 degrees) was added then adding compressed air. The compressed
through the freshwater inlet of the tank. This air was let into the tank by means of a valve,
MEASUREMENTS WATER HEATERS IN THE 20-LITRE CLASS
Water heater: Isotemp Isotemp Quick Vetus QL Mobitherm Sigmar ATI Webasto
Basic Slim 20 Nautic Boiler WH20A Water MWH-020 Thermoinox BB 2212 20L
1 hour engine running: 55,8° 62,7° 64,3° 63° 48,5° 48,2° 60,6° 68,6° 57,2°
12 h cooling: 51,9° 50,6° 48,7° 55,2° 42,6° 42,9° 40,5° 49,6° 39,9°
Heat loss: 3,9° 12,1° 15,6° 7,8° 5,9° 5,3° 20,1° 19,2° 17,3°
degrees per hour: 0,33° 1° 1,3° 0,65° 0,49° 0,44° 1,68° 1,6° 1,44°
No, litres water
above 40 degrees: 23 litres 15 litres 15 litres 17 litres 12 litres 12 litres 9 litres 8 litres 0 litres
Temp, with heating
element: 69,6° 67,2° 78,3° 66,2° 82,3° 82,8° 83,9° 62,5° 81,1°
Time before safety
thermostat trips: 4 min 50 sec 4 min 01 sec Element short-circuits Element short-circuits
after draining: 0,2 litres 0,4 litres 0,78 litres 2,65 litres 0,76 litres 0,1 litres 0,92 litres 3,65 litres 0,68 litres
Volume: 24 litres 20 litres 20 litres 20 litres 20 litres 20 litres 22 litres 22 litres 20 litres
Length: 480 mm 660 mm 505 mm 540 mm 387 mm 391 mm 538 mm 492 mm 401 mm
Width: 395 mm 287 mm 327 mm 406 mm 352 mm 351 mm 299 mm 318 mm 347 mm
Height: 400 mm 302 mm 313 mm 430 mm 395 mm 374 mm 299 mm 326 mm 384 mm
Weight: 11 kg 11,5 kg 10,9 kg 23 kg 9 kg 8 kg 11 kg 14 kg 9 kg
Heating element output: 750 watt 750 watt 500 watt 1.000 watt 800 watt 800 watt 800 watt 1,200 watt 800 watt
Opening of safety valve:
Oozing: 6 bar 5,6 bar 5,6 bar 4,2 bar 3,9 bar 3,6 bar 3,7 bar 3 bar 3,1 bar
Full opening: > 6 bar 6 bar 5,8 bar 4,4 bar 4,3 bar 4,4 bar 4,2 bar 4 bar 3,7 bar
Diameter of couplings:
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Heat exchanger: 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2 1/2
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Inlet cold water: 1/2 1/2 1/2 1/2 1/2 1/2 1/2 3/8 1/2
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Outlet hot water: 1/2 1/2 1/2 1/2 1/2 1/2 1/2 3/8 1/2
Price (1 8,5 NOK): 3,350 3,265 2,350 3,855 3,125 3,750 2,575 2,530 4,340
Indel Marine, I - 61019 S. Agata Feltria (PU) Italy - Phone +39 0541 848030 - www.indelmarine.com