HVAC Hydronic Heating Systems 5

Question 1

What is the typical pH range recommended for water in a closed hydronic heating system?

Accepted Answer

7.0 to 8.5

Answer

A slightly alkaline pH of 7.0 to 8.5 helps protect ferrous metals from corrosion while remaining compatible with copper, gaskets, and other system materials.

Question 2

A condensing boiler in a hydronic system achieves its highest efficiency when return water temperature is below what threshold?

Accepted Answer

120°F

Answer

Condensing boilers extract latent heat from flue gases when return water is below approximately 120°F, causing water vapor in the exhaust to condense and release additional BTUs.

Question 3

What type of valve is used at each terminal unit in a hydronic system to allow the system to be balanced by limiting flow through high-flow circuits?

Accepted Answer

Globe valve or circuit setter

Answer

Globe valves and circuit setters (calibrated balancing valves) provide precise throttling and are used to balance hydronic systems by restricting flow through over-supplied circuits.

Question 4

In a two-pipe direct-return hydronic system, why is balancing more difficult compared to a reverse-return system?

Accepted Answer

Terminal units closest to the pump have shorter circuits and naturally receive more flow

Answer

In a direct-return system, units closest to the pump have the least resistance, so they receive disproportionately high flow and must be throttled back to balance the system.

Question 5

What safety device is required on every hydronic boiler to prevent catastrophic failure from excessive pressure?

Accepted Answer

Pressure relief valve

Answer

A pressure relief valve (PRV) is a mandatory safety device that opens automatically to discharge water if system pressure exceeds the rated limit, preventing boiler explosion.

HVAC Practice Test

HVAC Practice Test

HVAC Hydronic Heating Systems 5