Page
15
of
16
17.
Gas
rating
of
Magiglo
Flueless
Appliances
Magiglo’s
Flueless
Gas
Appliances
are
all
gas
input
rated
in
the
factory
and
undergo
further
line
tests
for
combustion,
sooting
and
visual
performance.
For
Installers
who
wish
to
gas
input
rate
appliances
we
need
to
establish
tolerances
for
pass
and
fail.
Manufacturers
Tolerances
The
Heat
Input
on
appliances
can
be
expressed
as
either
a
Nett
or
a
Gross
figure.
When
the
installer
is
gas
rating
from
the
meter
they
will
be
using
gross
heat
input
which
is
10%
higher
than
Nett.
This
conversion
has
to
be
taken
into
account
if
the
manufacturer
has
quoted
a
nett
figure.
The
manufacturer
also
has
to
account
for
production
tolerances
on
pipes,
injectors,
valves
etc
and
is
allowed
a
further
+/
‐
5%
tolerance
on
the
maximum
rate.
Burn
Down
Cold
appliances
generally
allow
a
greater
rate
of
gas
to
pass
through
them
and
once
the
appliance
warms
the
gas
density
alters
and
causes
the
rate
to
reduce
to
the
figure
stated.
This
is
known
as
Burn
Down.
Manufacturers
carrying
out
their
technical
tests
allow
appliances
to
be
fully
warm
and
burn
down
before
taking
readings
and
this
is
typically
after
1
hour.
Some
appliance
manufacturers
quote
a
‘cold’
figure
for
the
gas
rate
so
that
installers
can
measure
this
immediately.
Installer
Tolerances
It
is
important
to
take
a
gas
rate
test
over
a
reasonable
period
of
time
so
that
the
capacity
of
the
meter
is
used.
On
low
Input
appliances
such
as
our
flueless
this
is
even
more
critical
because
uncertainties
can
creep
in.
It
is
worth
measuring
over
a
5
minute
period
to
make
sure.
It
is
also
important
to
get
your
inlet
pressure
to
20mBar.
In
a
gas
appliance
factory
compensation
is
also
made
for
variations
in
•
%
Saturation
of
Gas
•
Variation
in
Calorific
Value
•
Variation
in
Gas
Density
•
Gas
Temperature
•
Gas
Pressure
•
Atmospheric
Pressure
•
Meter
Calibration
•
Stopwatch
Calibration.
In
the
home
it
is
not
possible
to
correct
for
these
therefore
an
uncertainty
factor
needs
to
be
built
into
all
measurements.
Currently
Gas
Safe™
(formerly
CORGI)
does
not
quote
a
figure
on
this
uncertainty
but
the
measured
gas
rate
could
vary
by
+/
‐
5%.
Conclusion
In
adding
all
the
variables
together,
•
an
appliance
quoting
Gross
Heat
Input
could
be
anything
from
+/
‐
10%
of
the
quoted
heat
input
•
an
appliance
quoting
Nett
Heat
Input
could
be
anything
from
0%
to
+20%
of
the
quoted
figure
when
measured
as
a
Gross
figure.
•
If
the
appliance
is
cold
anything
up
to
a
further
10%
error
could
be
expected
and
we
don’t
quote
these
figures
because
they
change
rapidly.
The
figures
shown
below
are
hot
figures.
Model
Heat
Input
Quoted
Minimum
(Gross) Maximum
(Gross)
Cu
Ft
Per
Hour
Environ,
Esteem
2.5kW
Nett
2.5kW
Gross
3.0kW
Gross
8.49
Ambience
4121
3.5kW
Nett
3.5kW
Gross
4.2kW
Gross
11.67
Acumen
/
Elan
4111
4.2kW
Nett
4.2kW
Gross
5.3kW
Gross
14.85
