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Central Heating Review - Undersize Boiler20
April 2006 Central Heating Review – Name of Premises Removed Dear Mr xxxxxx I have completed the review of
your central heating system and have pleasure in submitting, for your
consideration, the following information and comments. Background History (Name of Premises Removed
)is a traditional brick built detached 4 bedroom house. The property was
converted into two flats, each with its own independent central heating system
and boiler. Upon re-conversion to a single dwelling the central heating pipework
was joined together to make one system and the upstairs boiler decommissioned.
In effect the system now requires the downstairs boiler to serve all the heating
requirements of a large house when it was originally required to serve a
substantially smaller system. The boiler runs practically
continuously and the radiators do not heat up sufficiently. The boiler has also
recently suffered intermittent faults such as the pilot light failing. The property has poor insulation,
there is no double-glazing and the existing windows and doors are draughty. The
loft insulation is thin and/or non-existent. The trustees of the property have
recently decided to fit double-glazing and better loft insulation. I understand
they are also considering having the boiler de-scaled and the system power
flushed to aid circulation and efficiency. Boiler The boiler is situated in the
kitchen on the ground floor. It is a Potterton Kingfisher make, floor-standing,
conventional gas boiler. The maximum output is 13 Kilowatts
with a required input of 18 Kilowatts giving a maximum efficiency rating of
around 72%. Radiators/Heat Loss Calculation The existing radiators are a mix
of styles, mostly fed by 10mm microbore pipework. None heat up to full capacity
and the radiator in the bathroom does not work at all. There are no thermostatic
radiator valves fitted to the system. A heat loss survey was conducted
on all rooms using Barlo Rad-Calcs Softwear. The heat loss calculation considers
the size and use of the room, the thermal insulation capabilities of the walls,
floor, windows and ceiling and the required temperature to calculate the
subsequent heat loss and the size of radiator required to service that room. The
calculation and temperature requirements were carried out to British Standard/EN
442. The results were :-
A second set of calculations was
made to compensate for the effect of the planned Double-Glazing and additional
Insulation. The results were that the Double-Glazing would decrease the heat
loss by 2.3 Kilowatts and the Insulation by 1.4 Kilowatts. Boiler Power The boiler is incapable of serving
the heat requirements of the house at present even considering that the total
radiator output is below the standard required. The existing radiator capacities
total 16.6 Kilowatts. Therefore the total output of the existing radiators is in
excess of the maximum boiler capacity of 13 Kilowatts; in addition an extra 1.5
Kilowatts are required for hot water. This means the existing boiler is under
capacity by 5.1 Kilowatts. In other words to serve the
existing system the boiler should have an output of over 18 Kilowatts i.e. 39%
larger than the existing output. The existing boiler is inefficient
by modern standards. It has an efficiency of 72%. This
means that for every £100 of gas used £72 worth is used for heating and the
remaining £28 is immediately lost. Modern condensing boilers can have
efficiency ratings in excess of 96%. If one were fitted to the premises the
annual saving on an annual gas bill of £1500 would be £360. The savings made
would probably pay for the installation within a few years. The existing boiler is running at
maximum capacity and understandably suffers from intermittent faults. Radiators Some of the radiators are too
large for their situation and some too small. They are not individually
controlled. Generally the over capacity is upstairs (Beds 2,3 & 4) and the under capacity downstairs (Dining,
Hall and Study). One option would be to re-size the
radiators to suit the heat loss for each room; this would entail either buying
and fitting new radiators or moving the existing radiators around, or a
combination of both. This would be expensive and without a boiler upgrade would
be ineffective because of the extra load being placed on an already overworked
boiler. A more cost-effective option would
be to control the over capacity upstairs by use of Thermostatic Radiator Valves.
This option would make sense as the upstairs will benefit the most from the
double-glazing and insulation and therefore the upstairs heating requirement
would be less. This would provide two advantages, firstly it would make more
efficient use of energy and secondly the reduced heating drawn by the upstairs
would be diverted to the under-capacity areas downstairs resulting in a more
balanced system. De-scale of Boiler and Powerflushing If a boiler replacement is not
considered viable at present due to the expense of the other work planned then a
de-scale and powerflush would almost certainly improve the existing boilers
efficiency and the current system circulation problems. The water supply is
acknowledged as being hard - Thames Water Report a hardness of 20.2 on the
Clarke Scale for the property. The boiler and system is likely to be heavily
scaled as a result. I would recommend that a pre
flushing agent be introduced directly to the system 14 days before flushing in
order that the agent can circulate at heat to aid the cleaning process. On the
day of the Powerflush an acidic flushing and de-scaleing agent can be used to
complete the process. Once cleansed a scale and rust inhibitor should be
introduced to the system to prevent further problems. I am able to offer this service,
if required, using the Kamco Hyperjet Power Flush System. Due to the size of the
property and the fact that microbore pipework is present extra chemicals will be
required which unfortunately increases the cost. However I am still able to keep
the cost to less than £300. Conclusions and Recommendations My recommendations are In the short term the system
should be made more efficient to cope with the overworked boiler situation by
fitting Thermostatic Radiator Valves to the bedroom radiators and by de-scaleing
the boiler and Power Flushing the radiators and pipework. This work should relieve the
stress being placed on the boiler which would probably see it through another
winter if it is serviced in the autumn but after that serious consideration
should be given to replacing the boiler with a modern condensing unit.
My estimate for this work is enclosed. Yours sincerely Martin
Ball
Update March 2007- The trustees of the property upgraded the insulation and paid for two powerflushes (not by me) and the system still does not perform. It will only be cured by a new boiler of sufficient capacity for the system. |