Module 18 Water Heaters and Combination Systems
What is the maximum pressure a boiler can produce
150 Psig
A properly functioning pilot-stat coil should close the pilot-stat valve when the reading on the milli volt meter reads?
2-5 Milli-volts
What is the minimum size and type of water heater recommended for a combination system?
40 gallon
What is the maximum allowable velocity of fluid in supply and return lines less than 2 in?
4ft per sec to 140 3ft per sec to140
What is the allowable maximum total length of supply and return piping?
50ft
What is the allowable clearance to combustibles for single wall vent installed on gas fire water heater
6 Inch
What is the minimum allowable clearance to combustibles from a gas-fire water heater?
6 Inches
May all types of water heaters be installed in a bathroom, What Clause covers this type of installation?
7.26.1
May combustion air openings be in the same room as the draft hood? What code clause covers this situation
7.26.2
On a power-vented water heater, when does the exhaust fan start?
Before the burner comes on
How is store water Heated indirectly?
By the Heat Exchanger and coils heated in the tank
What controls fluid flow between heating units in a combination system?
Circulating Pump
How does Indirect water heaters maintain water?
Circulating convection flow of water through the system
What type of system stores large amounts of hot water for intermittent use
Circulation System
May a draft hood be altered? What code clause covers this situation?
Clause 8.23.3
Water in the combustion chamber is usually a sign of what?
Condensation
What is the purpose of an open circuit test?
Detect faulty Thermocouple
The most common type of water heater used in residential and low demand commercial applications is?
Direct Fired Storage Heater
What type of water heater is most commonly used for residential and low demand commercial installations?
Direct Fired Water Heaters
What causes a rod and tube aquastat to operate
Dropping of water temperature 15F Below
When installing gas-fired water heaters, who is responsible for following code requirements?
Gas Technician
Define what Direct Fired means?
Heat from the gas flame is in direct contact with the Tank or Pipe
What is a dedicate water heater system used for?
Hydronic radiant heating
A negative pressure in the vent may be caused by ?
Improper termination of vent To many bends and blockage
Hot water storage tank connected to a coil located in boiler.The water in the heating coils is heated by steam produced by the boiler
Indirect Heaters
A cause of negative pressure in a building is ?
Lack of make up Air
Insulated butt splices are recommended for what type of connections?
Low voltage devices
What is the most accurate way of testing gas Manifold pressure?
Manometer
How is lime formed inside a water heater?
Mineral build up
Ferrous metals are acceptable for potable water applications?
No
Hot water piping runs should be as long as possible?
No
Is is acceptable to use steel pipe as relief valve discharge piping?
No
It is acceptable to install a relief valve discharge piping in areas that may freeze?
No
May chemicals be used in a combination system?
No
What is the minimum frequency of a combination system pump cycle?
Once every 24 Hours
If manifold pressure is correct and clocked input is incorrect, what could be the problem?
Orifice Size
Why should you not solder a fitting directly onto the cold water inlet of a water heater?
Plastic drip inside the water inlet could melt
What must be used to test a combination system?
Potable Water
How may fluid flow through combination system components be controlled
Pressure bypass valve or shunt pump
State the rule of thumb pump sizing formula?
Pump should be 15 pm per 10,000 Btu/h Input of the water heater 1ft of friction loss per 40ft of pipe run
If the thermostat on the control unit is more than 20F off setpoint, what should you do?
Recalibrate it
If a control unit is sticking in the on position, what should be done?
Rotate the dial on and off a few times If still sticks, replace it!
The Canadian plumbing code specifies two areas that most concern a Gas Technician, what are they?
Shut off Valves Relief Valves
What device is installed in the flue of a residential water heater to improve heat transfer to the water?
Spiral Baffle
What acts as the heat exchanger in a direct-fired water heater?
The Flue Tube
How should three-way valves be sized?
To match the flow requirements of the heating unit supplied by the system
Explain the purpose of a Flammable Vapour Sensor?
To prevent flammable vapor to enter in burner
A storage-type heater may be used in a fan-coil combination system?
True
Is Carbon Monoxide is tasteless and odourless ?
True
Loose wiring causes increased resistance?
True
The heating output of an air handler should exceed the calculated space heating loss of a building?
True
Name three types of automatic controls that can be used on instantaneous water heaters?
-Water pump Drop sensor -Water flow sensor -Aquastat in water heater
At what slope should horizontal venting be run?
1''-3 Ft
