Page 436 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

Balancing a secondary circulation system
Large secondary circulation systems should contain bronze lockshield valves on
every return leg of the hot water secondary circuit. These should be fitted as
close to the appliances as possible and are used to balance the system so that
the flow rates to each leg are such that:
● heat loss through the circuit is kept to a minimum
● the temperature of each leg is constant
● the temperature of the return at the cylinder is not less than 50°C.
Correct balancing is achieved by opening the valves on the longest circuits and
then successively closing the lockshield valves a little at a time, working towards
the cylinder until the flow rates through each circuit are equal. The flow rate
should be balanced so that all of the circuits achieve the same temperature at
the same time. This is especially important with those systems that operate
through a time clock.

Dealing with defects found during commissioning
Commissioning is the part of the installation where the system is filled and run
for the first time. It is now that we see if it works as designed. Occasionally,
problems will be discovered when the system is fully up and running, such as
those described below.

Systems that do not meet correct installation requirements
This can take several forms, as follows.
● Systems that do not meet the design specification: problems such as
incorrect flow rates and pressures are quite difficult to deal with. If the
system has been calculated correctly and the correct equipment has been
specified and installed to the manufacturer’s instructions, then problems
of this nature should not occur. However, if the pipe sizes are too small in
any part of the system, then flow rate and pressure problems will develop
almost immediately downstream of where the mistake has been made.
In this instance, the drawings should be checked and confirmation with
the design engineer sought that the pipe sizes used are correct before any
action is taken. It may also be the case that too many fittings or incorrect
valves have been used, causing pipework restrictions.
● Another cause of flow rate and pressure deficiency is the incorrect set-up
of equipment such as boosting pumps and accumulators. In this instance,
the manufacturer’s data should be consulted and set-up procedures followed
according to the installation instructions. It is here that mistakes are often
made. If problems persist, then the manufacturer’s technical support should
be contacted for advice. In a very few cases, the equipment specified is at
fault and will not meet the design specification. If this is the case, then the
equipment must be replaced.
● Poor installation techniques: installation is the point where the design is
transferred from the drawing to the building. Poor installation techniques
account for problems such as noise. Incorrectly clipped pipework can often

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