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Troubleshooting
Chimney
Fires are a Problem. To reduce the
risk of a chimney fire you need to;-
- choose an appropriate fuel for your
appliance and burn it as efficiently as possible.
- keep the chimney warm.
- inspect and clean the flues and
chimney at regular intervals.
Damp/unseasoned logs can very quickly
create a fire hazard in any chimney – particularly if they
are burned slowly in a closed stove. The frequent use of household
("bituminous") coal in a closed stove can likewise
generate high volumes of soot. Therefore make a special effort
to season your firewood thoroughly before you burn it. (To see
a useful technique for doing this click here). If you burn solid fuel, avoid household coal.
You'll find smokeless fuels are far more satisfactory.
A warm chimney is far less prone to
fouling up than a cold one. Therefore chimneys contained within
the body of the house work best and those on the end of a building
- particularly when fully exposed to the weather - have a built-in
disadavantage. In the latter case, it may be possible to boost
flue-temperatures by lining the flue with a low-mass flexible
liner back-filled with an insulating filler material. (Click
here for a discussion of internal/external chimney
placement)
You should sweep your chimney 'as often
as is necessary'. There is no fixed rule about this since much
will depend upon the frequency of use, type of appliance, type
of fuels used - etc. If in doubt, call the sweep in sooner rather
than later and consult him on his findings. If your useage pattern
is fairly consistent it should become fairly easy to judge the
intervals at which cleaning is necessary.
Deflector
plate - frequent replacement necessary. Deflector
plates are generally made from cast iron or mild-steel. These
materials have a high melting point but they are in the hottest
part of the fire and should be considered as a 'sacrificial'
component. How long a deflector plate lasts depends partly on
the overall design of the stove and partly on your manner of
running the stove. If a deflector burns out at short intervals
you should take this as a warning to mend yuour ways! Either
you are burning a fuel with a long flame that actually causes
the deflector plate to become red hot for long periods, or you
are simply over-running the stove. Either way you are almost
certainly losing much of your heat straight up the chimney thereby
incurring excessive fuel costs.
A central heating stove does far more
work than a 'dry' stove that is simply heating one room so it
is unsurprising that deflector plates tend to burn out much faster
in boilered stoves. All the more reason to choose your fuel carefully
when you want to keep a battery of radiators hot for hours at
a stretch. Smokeless fuel is by far the best choice in this situation.
You should aim to create a fire with plenty of heart in it and
even, radiant output. This means keeping the airflow through
the stove under tight control and not over-running the stove.
If you're burning wood only, click here to see the right approach and here to see the wrong approach. If you're burning
solid fuel or a 'mixture' of solid fuel and wood click here to
see the right approach and here to see the wrong approach.
Door glass
has cracked. Why? Modern door glasses
are made of single-piece ceramic glass which is far more stable
than the strips used in early stoves. Nevertheless, glass is
funny stuff and sometimes contains invisible stresses that can
cause it to crack for no apparent reason. Therefore the occasional
crack is to be expected. However if you have frequent problems
the most likely cause is that you are over-tightening the glass
into the door-frame. Cast iron and glass expand and contract
at different rates. When you fit a new glass, renew its compressible
gasket at the same time and take care not to over-tighten the
attachment bolts. They shouldn't be much more than finger-tight.
Door seals
- gumming up problems. It is unlikely that your door-seals are the
only things gumming up! The glass is probably blacking up as
well – and perhaps other fire-box components. The use of
damp/unseasoned wood is the most obvious cause, coupled perhaps
with a tendency to go in for long, slow burns. Take this as a
warning that you are almost certainly building up flammable deposits
in the chimney – and the prospect of an unpleasant chimney
fire. If you must run your stove on a low setting for long periods
the use of bone-dry wood becomes absolutely critical and even
then, some judgement is needed to ensure you don't under-run
your stove with the consequences illustrated here.
Enamel is chipped.
Enamel is only ever applied to stoves assembled from cast-iron
panels. The process involves re-heating the panels to a high
temperature, sprinkling them with pigmented glass dust which
melts to form the high-gloss coat we are familiar with –
then cooling the panels slowly under controlled conditions. From
this you will gather that it simply is not possible to 'touch
up' chipped enamel with some matching heat-proof paint, though
you might manage to make the chip slightly less conspicuous.
The only final answer is to replace the entire affected panel.
Firebricks
- frequent replacement necessary
In the last few years most stove manufacturers have changed over
from the old-style refrectory fire-bricks (heavy and brittle)
to the new, lightweight insulating firebricks which resemble
a light-coloured chipboard. The new material is more durable
than the older but is softer. Like deflector-plates these lining
materials should be regarded as sacrificial and will need to
be replaced from time to time. And like deflector plates you
can shorten the life of your fire-bricks very considerably by
running your stove too hard.
Fracture
- a stove panel has cracked. Why?
Cast iron panels are inherently brittle. You should never fire
up a cold stove too fast or you run the risk of creating uneven
expansion – the single most common cause of fractures. Also
make sure the internal burnplates or firebrick linings are in
sound condition. If you study this section on Technique and create
burning conditions within your stove that deliver a steady, even
radiant output, your cast-iron stove should give many years of
trouble-free service. This assumes you have bought a branded
product assembled from top-quality casting. Cheap, imported stoves
of dubious origin are a different matter and are best avoided
for obvious reasons.
Fuel consumption
is excessive. You may simply be
over-running your stove. It is a common mistake to allow too
much air to enter the stove. The more air you let in, the more
heat you let out to the chimney. So aim at a balance and study
the general discussions on 'Technique' in this section.
Other factors include use of unseasoned
wood. The moisture content in logs has huge impact on the actual
amount of fuel you have to burn for a given output as is illustrated
here.
You may also be expecting too much
of your wood if you are trying to obtain sustained high-outputs
from a central-heating stove. The burning characteristics of
wood are not well suited to driving high-output boilers in modestly
proportioned domestic heating appliances. Switching to a smokeless
grade of fuel (Like Homefire or Phurnacite) may well solve your
problems.
Finally, take a hard look at your installation.
A deeply recessed stove is operating at a massive disadvantage
and may only be delivering a fraction of its output to the surrounding
air. A properly designed and insulated convector-box can overcome
this difficulty. To learn more click here.
Fumes coming
into the room. Any stove that has
been sprayed with a matt paint will produce fumes for a short
period while the volatiles are driven off. This is nothing to
worry about – simply open a window and air the room until
the process is completed.
You may also want to check that there
is no physical blockage in your stove - caused for instance by
a badly deformed deflector plate.
Solid fuel cookers - particularly when
run on household coal, can clog rapidly in the flue passages
around the oven(s) and should be cleaned at regular intervals.
But in the
vast majority of cases, the stove is blameless and the real culprit
is your chimney which if it is doing its job properly should
be generating enough 'suck' to remove all fumes. If it is not,
check the flue-connector between your stove and chimney first,
since this is often a bottle-neck that clogs up first.
If the problem persists even after
you have had the chimney inspected and swept, you may have more
serious design/structural problems. Click here for a general discussion on chimneys that may
help you trouble-shoot your problem.
Glass keeps
going black. Why? Most modern stove
designs offer an 'air-wash' or 'clean-burn' option that helps
to keep your glass clear. The best designs employ three techniques;-
- The air supply is pre-heated by
being passed through a duct in the head of the stove and is then
passed over a blade that causes it to spread out and wash the
internal surface of the glass.
- The door is double-glazed.
- The fire-box is lined with insulating
fire-bricks in the area of combustion.
The effect of these three techniques
is to boost temperatures to a level at which smokeless combustion
can take place.
If your glass keeps blacking over,
your stove may not be a clean-burn model or the clean-burn features
may be poorly implemented. High output boilers virtually obliterate
the benefits of a clean-burn design by keeping the combustion
temperature down at a level at which even the driest fuelwood
is likely to produce some smoke and tar.
The final and most frquent cause of
glass blacking up is use of damp/unseasoned wood – particularly
in conjunction with long, slow burns.
Glass - how to clean? You
can clean your stove glasses using steel wool dipped in water.
Alternatively, a Stanley blade in a plastic holder does the job
quickly and efficiently. It goes without saying that you should
not attempt to clean hot glass!
Grate bars
- frequent replacement necessary Grate
bars are cast at an extremely high temperature and contain various
additives including chromium to make them more durable. This
explains their high cost.
The best way to extend the life of
your grate bars is to riddle and de-ash at regular intervals.
That way the bars are cooled by the air-stream passing through
below.
If you let ash levels build up, the
cooling effect of the air is lost. In extreme cases you may even
'submerge' the bars in a bed of red-hot ash. At these elevated
temperatures they will distort and quickly burn out.
Some grades of anthracite generate
temperatures high enough to shorten the life of your grate bars.
Over-running your stove on almost any fuel will have the same
effect – a practice that's all too common when the stove
is a boiler model driving several radiators.
Cheap grate bars of dubious origin
will nearly always fail prematurely. Buy only branded spares
originating from your stove manufacturer.
[Footnote; the above text relates to
stoves being fired on solid fuel. If you are burning wood
only, you should be burning onto a bed of soft sand or ash -
see here
- and your grate (if your stove is equipped with one) should
last virtually forever.]
Heat output
to hot water is inadequate. The
rated output of a boiler is generally only met when the stove
is run at its rated output. Therefore if your stove is rated
at 4 kW and you run it closer to 2 kW the boiler capacity will
drop from 10,000 BThUs to just 5,000 BThUs. It may drop more
and it may drop less. Much depends on the design of the stove
– but also on the way you run it. Again, a common mistake
is to let too much air into the stove. This literally cools the
internal surfaces of the appliances and allows most of the heat
to rush up the chimney.
The burning characteristics of different
fuels can have a major bearing on boiler performance. A fuel
with a short flame and high radiant output does best. Smokeless
fuels and charcoal cannot be beaten, but once again, damp/unseasoned
wood is unsatisfactory.
Poor chimney draught – and even
excessive chimney draught can upset boiler performance.
A poorly designed system may be 'robbing' heat due to lengthy
pipe-runs, or circulation may be poor. There is too, the possibility
that your boiler has been under-specified for the job it has
to do.
Thus there are several variables to
be examined and in practice a boiler that is actually defective
is so rare as to be almost the last thing to consider!
A useful reference point when outputs
are in dispute is to do a test-firing with a 'benchmark' fuel.
If your principle fuel is wood, try burning a quantity of really
dry ex-demolition timber. The results may well astound you! If
you burn mainly solid fuel, run a test with Homefire. This again
will enable you to compare the fuel you are burning against something
you can always refer back to.
Heat output
to room is inadequate All of the
above factors apply. However it is also worth checking that your
appliance is correctly specified for the job it has to do. And
be on-guard if it is recessed. In such cases a properly constructed
and insulated convector-box may clear up your problems. Click
here for more information.
Radiators
are hot but room with stove in it is underheated This most commonly arises when the stove is
an 'inset' model. These stoves are effectively buried in the
wall and deliver only a small fraction of their output to the
room they are installed in. Adding a radiator or increasing the
size of the one fitted should solve your problem.
Radiators
aren't heating up fully Click here for a discussion
of the issues likely to be relevant.
Soot problems.
Stove/flues keep clogging up. Check
your fuel first. Household ("bituminous") coal produces
large volumes of soot and the modest airflow through a closed
stove is simply inadequate to carry it clear of the chimney.
Slow-burning is another area to review
- especially if you are burning damp-unseasoned wood. All stove
installations need to be burned up brightly at regular intervals
to purge condensate and tars from the flue-ways.
Chimneys on the end of a building –
particularly those fully exposed to the weather – soot up
far more rapidly than a 'warm' chimney accomodated within the
main body of the house. Click here for a further discussion on this.
Stove is
difficult to light and smokes a lot. Click
here
for a discussion of the issues likely to be relevant.
Stove is
over-heating the room but radiators remain only lukewarm The most likely cause is that the stove has
the wrong output ratio for the job it is doing. Take a situation
where your sitting room needs 3 kW of heat and the rest of the
house needs 30,000 BThUs. If you now install a stove that delivers
5 kW of heat to the room and 30,000 BThUs to hot water, your
sitting-room will receive 2 kW more than it needs.
In the short-term your only option
is to attempt to 'spill' some of the excess heat from your sitting-room
to an adjacent area. In the longer term you should consider replacing
you stove with one correctly balanced to your needs.
Stove runs
out of control A stove that runs
out of control in average conditions obviously needs attention.
Most likely the door seals are worn and possibly one or more
damper-seals (if fitted). If the stove has been over-fired the
doors may be warped to the extent that they no longer close properly.
If the stove is new, a thermostat may
be malfunctioning or a damper sticking.
These are the obvious and cheapest
things to check 'on the ground'.
One other tip to consider if you're
burning wood only is to fill the base of your stove with a bucket
full of sand to a level around 25mm (1") above the grate
bars. This kills all air-movement through the heart of the fire
and creates a far more stable burning environment. (For a discussion
and illustration of the principles involved click here).
If you are in a very exposed location,
your chimney draught may exceed the values your stove is designed
for. A well-engineered stove built to tight tolerances is better
able to resist this problem than a leaky appliance with poorly
aligned door-hinges and crude air-valves – and thermostatically
controlled appliances are more vulnerable than stoves with robust
manual controls.
Often it is best to tackle extreme
draught problems at their source. Aerocowls have an excellent track-record for both taming
excessive draught and helping to eliminate down-draughts.
Stove won't
'stay in' for long periods See above.
This problem is related to the problems of a stove running out
of control.
Unpleasant
smells coming into the room from the stove A
cold chimney doesn't generate much draught so this problem is
most likely to arise when the fire is out. The smells are also
associated with moisture so anything you can do to dry out the
chimney and warm it up will help. Burning a small quantity of
smokeless fuel at low output may be beneficial and if you have
to leave the house unattended in wet weather for an extended
period you should fit a rain-cap. This won't afford much protection
though when rain is carried under the cap by strong winds. One
short-term expedient is to tie a plastic bag over the chimney
if it is accessible. But remember to remove it before lighting
up your next fire!
Water keeps boiling There
are several possible causes for this;-
- Airlock somewhere in the system.
- Insufficient rise in the pipes between
the appliance and the domestic hot water tank.
- Pipes too small in diameter.
- Pipe runs excessively long.
- Boiler over-specified for the job
it is doing.
In the first four cases, the time taken
to heat up a tank of cold water may be noticeably slow. You need
to call in a plumber – unless you have the competence to
tackle the issues yourself.
If the boiler is over-specified for
its job, one possible solution is to mask part of it off with
some insulating fire-brick using adhesive fire-cement. Another
possibility is to dissipate the excess heat through a towel-rail
or something similar. The third option of course is to replace
the boiler with one matching your needs – though this may
involve replacing the entire stove.
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