HVAC Hydronic Heating Systems 4

Question 1

What type of pipe fitting is used on hydronic systems to allow thermal expansion without stressing the pipe or boiler connections?

Accepted Answer

Expansion loop or offset

Answer

Expansion loops, offsets, or expansion joints are built into hydronic piping runs to absorb the linear expansion of pipes as they heat up, preventing stress on fittings and equipment.

Question 2

What is the purpose of a dielectric union in a hydronic system?

Accepted Answer

To prevent galvanic corrosion between dissimilar metals

Answer

Dielectric unions contain an insulating bushing that electrically isolates dissimilar metals (such as copper and steel), preventing the galvanic corrosion that occurs when different metals contact each other in water.

Question 3

A technician reads 22 psi static pressure at the boiler on a cold system. After firing the boiler, pressure rises to 28 psi. This indicates:

Accepted Answer

Normal system operation with thermal expansion

Answer

A 6 psi rise from cold fill pressure to operating pressure as water heats is typical and indicates normal thermal expansion being managed by a properly functioning expansion tank.

Question 4

What glycol concentration is typically recommended for hydronic antifreeze protection to -20°F?

Accepted Answer

50% propylene glycol

Answer

A 50% propylene glycol solution provides freeze protection to approximately -26°F and burst protection to well below -60°F, making it suitable for -20°F protection with a safety margin.

Question 5

Which instrument is used to measure the flow rate through a hydronic circuit during balancing?

Accepted Answer

Flow meter or ultrasonic flow meter

Answer

Flow meters, including ultrasonic clamp-on models or inline turbine types, measure the actual water flow rate in GPM needed to verify and balance hydronic circuits.

HVAC Practice Test

HVAC Practice Test

HVAC Hydronic Heating Systems 4