Hydronic Heating & Gas — Plumber (306A) Practice Questions

Free Hydronic Heating & Gas practice questions

1. 1.A hydronic heating system circulates what medium?

   • A.Air
   • B.Water (or water/glycol mixture) to transfer heat from boiler to radiators✓
   • C.Refrigerant
   • D.Steam only

   Why: Hydronic systems circulate heated water through pipes to radiators, fan coils, or in-floor tubing. Glycol is added for freeze protection in systems exposed to freezing temperatures.

2. 2.In-floor radiant heating tubing is typically made of:

   • A.Copper only
   • B.PEX (cross-linked polyethylene)✓
   • C.Cast iron
   • D.Steel

   Why: PEX is the standard for in-floor radiant: flexible, corrosion-resistant, handles thermal expansion, and long continuous runs minimize joints in the slab.

3. 3.A gas pipe leak test uses what medium?

   • A.Water
   • B.Air or nitrogen at specified pressure for specified duration✓
   • C.Oxygen
   • D.The gas itself

   Why: Gas piping is tested with air or inert gas (nitrogen) at the test pressure specified by code. NEVER use oxygen or the fuel gas itself for testing. Soap solution finds individual leaks.

4. 4.Black steel pipe for gas is joined by:

   • A.Solvent cement
   • B.Threading with approved pipe thread compound or PTFE tape rated for gas✓
   • C.Soldering
   • D.Compression fittings

   Why: Black steel gas pipe: threaded joints with gas-rated thread compound or yellow PTFE tape (gas rated). Regular Teflon tape (white) is NOT approved for gas. All joints must be accessible.

5. 5.A hydronic zone valve controls:

   • A.Gas flow
   • B.Water flow to individual heating zones for temperature control✓
   • C.Electrical power
   • D.Air flow

   Why: Zone valves open/close to allow or stop hot water flow to specific heating zones, controlled by individual thermostats. This provides room-by-room temperature control.

6. 6.CSST (Corrugated Stainless Steel Tubing) for gas requires:

   • A.No special grounding
   • B.Bonding to the electrical grounding system per manufacturer and code requirements✓
   • C.Only plastic fittings
   • D.Burial underground

   Why: CSST must be bonded to the building's electrical grounding system to protect against lightning-induced voltage that can puncture the thin stainless steel wall. Critical safety requirement.

7. 7.Glycol in a hydronic system requires the circulator pump to be:

   • A.Smaller
   • B.Sized larger because glycol is more viscous than water, increasing friction loss✓
   • C.The same size
   • D.Turned off

   Why: Glycol is thicker (more viscous) than water and has lower heat capacity. Pump must be sized for increased friction losses. System also needs more flow to carry the same amount of heat.

8. 8.The minimum clearance from a gas vent to a window or air intake is:

   • A.No clearance needed
   • B.As specified by code — typically 300mm-1800mm depending on vent type and appliance✓
   • C.Directly adjacent is fine
   • D.3 metres always

   Why: Clearances vary by vent type, appliance category, and BTU rating. Codes specify minimum distances to prevent flue gases from re-entering the building through windows or air intakes.

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