HydroFreezeblock is used in closed loop systems to prevent the freezing that is exposed to low temperature enviorments, such as snow melt systems. If Glycol is required in a system, we reccomend that the concentration of glycol be be above 20% and and no more than 50% . Below a concentration of 20% glycol becomes a nuetrient for the growth of bacteria, which can infect the system and cause biological growth and metal loss. Once this develpes, it is very difficult to remove. A glycol above 50% makes the water viscous and and will cause damage to system components, pumps, and other moving parts. Also, Glycol concentrations cause systems to loose some heat transfer ability and actually decreases the system efficiency.  The average life of propalyne glycol is up to 9-10 years.

HydroShield has little to no negative effects on seals, elastomers, or other construction materials commonly found in HVAC systems. However, we do not recommend its use in systems containing galvanized steel unless etching of the zinc, or magnesium-based coatings.

• Anti foaming agents added to comply with most boiler manufactures requiements. 

• Specially designed package of industrial corrosion inhibitors to protect metals.

• Polypropylene glycol is non-toxic.

• Available in full concentration or premixed with dionized water.

Note: We reccomend using demineralized water to dilute glycol. 

Boiler Derating Formula when using Propylene glycol: 

Derating the boiler for capacity when glycol is introduced is not necessary as long as the pumping rate is increased and accounting is made for the additional pressure drop in the system.

The basic equation used for this is:
qw = 500*Q*(ρ/ρw)*Cp*ΔT (Ref: 2016 ASHRAE Systems Handbook page 13.24 Equation 21)

Where:
qw= Total heat transfer rate BTU/h
Q = flow rate, gpm
ρ= fluid density, lb./ft^3
ρw = density of water at 60 Deg F, lb./ft^3 Cp = specific heat of fluid Btu/lb. Deg F.
ΔT = temperature increase or decrease Deg F.

Example:
Assuming 30% Propylene Glycol and using data from the 2013 ASHRAE Handbook of Fundamentals Chapter 31. ρ= fluid density, lb./ft^3 = 62.18 at 170 Deg F.
Cp = specific heat of fluid Btu/lb. Deg F = .957 at 170 Deg F.
Assuming flow remains constant, (62.18/62.37)*.957 = .954
So the output of the boiler would be 95.4% after the addition of glycol.
Compensation for this can be made accordingly with an increase in pumping rate.