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Guidance on types of coolant for liquid DELTAs


The recommended coolant is a mixture of water, anti-freeze and corrosion inhibitors and should meet the performance specification of BS 6580 “Specification for corrosion inhibiting, engine coolant concentrate (“antifreeze”)” or the equivalent national standard.

The coolant must provide:

  • Corrosion protection, scale inhibitors (against hard water); all year and summer coolant.
  • Frost protection if there is any risk of the coolant freezing. Note that heat-exchangers located external to a building usually require anti-freeze protection.


Do not mix antifreeze or corrosion inhibitors of different types or from different manufacturer’s. In unfavorable conditions this causes an increase in corrosion.



Use pure or de-mineralized water. Do not use water as the only coolant. Coolant must contain corrosion inhibitors.


Corrosion and scale inhibitors types vary according to the local region’s water mineral content (phosphates, calcium, magnesium,..).  The inhibitors are optimized to prevent harmful chemical reactions with these minerals.  The use of de-mineralized water avoids these additional reactions.


Other contaminants in the water may cause blockages, erosion from solid particles, biological growth or accelerated corrosion.



Type:                     Mono-ethylene Glycol (see also corrosion inhibitors).

Concentration:  Sufficient to prevent freezing (for the minimum external temperature)


Corrosion inside ducting caused by wrong coolant

Wrong coolant has caused corrosion to the aluminum which has then led to leakage of coolant

AVID Controls