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Test 1 Flashcards

1
Q

What are piping systems classified by?

A

1) service provided - heating, cooling, oil supply, condensate return
2) medium conveyed - steam, hot water, chilled water, refrigerant, oil, gas, condensate, chemicals, etc.
3) pressure class - low, medium or high pressure. Varies on medium conveyed.
4) temperature class - low, medium or high temperature
* 5) piping arrangement - one-pipe, two-pipe, direct or reverse return, series or parallel flow, etc.
6) hydraulics - gravity or forced flow (pump), open or closed
* 7) piping material - steel, copper, plastic, no metallic, etc.

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2
Q

Who installs HVAC piping systems?

A

Plumber installs, HVAC contractor carries the price

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3
Q

How do most piping systems maintain the flow of liquid? What is this called?

A

Using pumps or compressors. This is called a forced system.

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4
Q

What is an open system?

A

In an open system the fluids surface is exposed to the atmosphere. Flow may be by gravity or by pumping.

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5
Q

What is a closed system?

A

In a closed system the fluid is not in contact with the atmosphere. The flow must be by pumping.

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6
Q

What are most HVAC systems in relation to open or closed systems and what do they include?

A

Most HVAC systems are closed systems with:

  • direct return-imbalanced water flow
  • reverse return-balanced water flow ( cost more with more piping)
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7
Q

What is the most common fluid in HVAC systems? Why?

A

Water. It’s:

  • chemically stable, non-toxic and economical
  • has a density of 62.4 lbs per cubic foot
  • has a specific heat of 1 -> 1 BTU will raise the temperature of 1 lb of water by 1°F
    • stores and transfers more heat than air
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8
Q

What are common mediums in piping?

A
  • water
  • steam
  • refrigerant
  • fuel
  • etc.
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9
Q

What is the basic purpose of piping?

A

Pipes are used to transport fluids to and from system components, like heat exchanging equipment using (pumps) to transfer the fluids thermal energy.

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10
Q

Define hydronic.

A

The flow of fluid in a piping system.

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11
Q

What is the first step in hydronic heating?

A

The boiler system uses conduction to quickly and efficiently heat the water using a specific fuel.

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12
Q

What is the second step in hydronic heating?

A

The hot water being pumped through the building heats the concrete, tile, or other type of flooring through conduction and/or radiates heat into the room.

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13
Q

What is the third (and final) step in hydronic heating?

A

The flooring surfaces then radiates the heat they gained from the water into the room as well, if using in-floor.

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14
Q

Define conduction. What affects this ability?

A

The movement of heat through objects physically, from warmer to colder. Density affects this, which is why liquids are more conductive than gases.
*Hx in the boiler

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15
Q

Define convection.

A

This occurs when fluids or gases transfer heat while being circulated. *Traditional heating systems that use forced air are perfect examples.

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16
Q

Define radiation.

A

Thermal radiation is heat that travels in invisible waves through empty space. It cannot be blown by the wind or moved. It is absorbed by the person or object in the path of the energy and is a more effective way to transfer heat.
*near classroom windows

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17
Q

What will always be part of the cooling system.

A

Ventilation, cooling, humidification, dehumidification and filtration.

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18
Q

What is hydronic heating mainly used as? What is it used to overcome?

A

A split system - separate heating and cooling systems. It’s to overcome radiant heat loss. Warm to cold.

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19
Q

Define a boiler.

A

A closed vessel in which water or other fluid is heated. Can be gas, electric, or propane.

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20
Q

Define a connector heater.

A

A heater which operates by air convection currents circulating through the body of the appliance (uses a fan).

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21
Q

Define a radiator.

A

A heat exchanger designed to transfer thermal energy from one medium to another for the purpose heating. Can be a baseboard of RAD version.

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22
Q

What are the 4 boiler options?

A

Typical boiler, tankless hydronic water heater, combined hot water and heating systems boiler, and geothermal heat pump.

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23
Q

Explain a typical boiler.

A

Low/mid/high efficiency. Gas, propane, oil, biomass. Size depends on demand.

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24
Q

Explain tankless hydronic water heaters.

A

Smaller than traditional tankless water heaters, the are specifically designed for higher gpm.

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25
Q

Explain combined hot water and heating systems boiler.

A

Used for both radiant hydronic heating and domestic hot water for plumbing fixtures.

26
Q

Explain geothermal heat pump.

A

Can preheat the water by using the natural warmth found several feet below the soil. This reduces the amount of natural gas, electricity, or oil that your boiler will need to heat the water.

27
Q

Explain under floor radiant loops.

A

Series of tubes (PEX-a) are installed below the floor and/or within the floor as required to radiate heat through the floor structure.

28
Q

Explain baseboard heaters/radiators.

A

Hydronic baseboard units and radiators can be much easier to install. They should be located along the exterior walls and windows. No furniture can be located beside these units. In classrooms in high school/elementary.

29
Q

Explain connector units (cabinet unit heaters).

A

Usually located in vestibules and stairways. Anywhere you may want to distribute the heat in a special way.

30
Q

Explain a solar water heater.

A

Will not provide enough heated water by itself, therefore it works with your boiler. A panel on the roof heats a liquid that runs through tubes inside a water storage tank. this creates water that is naturally pre-heated and requires less energy from the boiler to bring to the right temp.

31
Q

Explain a circulator pump. what is the most common type?

A

It’s used to take hot water from the boiler, and then pass/pump it through the pipe system to the heating devices. the most common hydronic pump is a centrifugal type, It works by the fluid entering the pump impeller along or near to the rotating axis and is accelerated by the impeller (*typ. made of brass), creating a vacuum and pushing the fluid out.

32
Q

Why are expansion tanks installed?

A

to provide high and low limits on the pressure. high pressure will damage piping, change velocity etc. low pressure may allow air into the system.

33
Q

What is the most common type of expansion tank? how do they work?

A

closed tanks. they are constructed with the water surface obstructed, separated by a rubber diaphragm creating an air cushion. usually used with an air vent control.

34
Q

What happens when air gets into an expansion tank system?

A
  • air in heating system pipes, baseboards, radiators, etc. makes a gurgling noise and leads to loss of heat transfer.
  • Air will eat the pump impeller - use an air vent controller.
35
Q

What are some basic instruments used for the performance of a hydronics system?

A

Pressure gauge, thermometer (1 on supply, 1 on return side), temperature instruments are usually installed in thermal wells to separate the instruments from direct contact with the fluid.

36
Q

What are the types of valves?

A

gate valves, globe valves, ball and butterfly valves.

37
Q

What is a gate valve for?

A

to isolate flow.

38
Q

What is a globe valve for?

A

to isolate and regulate flow.

39
Q

What is a ball and butterfly valve for?

A

to regulate flow, although can be used for short term isolation.

40
Q

What are some outdoor uses for radiant heating?

A

snow melt (sidewalks, driveways, parking ramps, etc.), roofs (protect from ice dams and future leaks due to buildup), heated pools.

41
Q

Explain boiler operation.

A
  1. Room thermostat senses the temperature drop and switches on. The hot water circulator starts. If zone valves are installed on supply side, each is controlled by an individual thermostat, the zone valve opens. If no zone valves are installed each thermostat controls one or more hot water circulators.
  2. Hot water leaves boiler passing the air vent controller and expansion tank and enters the heating distribution piping.
  3. hot water then passes through baseboards or rads or wall convectors.
  4. Hot water passes through more distribution piping as it returns to heating boiler.
  5. Boiler temperature drops as cooler water returns temperature sensor (aquastat) inserted into the boiler water and connected to heating boiler primary control switch feels the temp drop and tells burners to operate.
  6. gas fired boilers open a gas valve and feed this fuel from an incoming LPG or natural gas line to the burner where it is ignited.
  7. Hot gasses from burning fuel pass through burner tubes heating the metal, sending heat back into the heating water through heat exchanger.
  8. Hot gasses are collected at top of boiler and sent out through exhaust flue or vent. Combustion make up air is either used from the room or an intake pipe is provided.
  9. Thermostat senses temperature rise and opens switch, turning the circulator pump off and boiler shuts down.
42
Q

What is a zone valve? What does it do? Why is it used?

A

Its basically an electronic ball valve (controls flow) used to provide spaces into multiple zones and t-stats. improves efficiency and occupant comfort. a controller needs to be installed with the zone valves to control their actions.
* each zone may have their own circ. pump to reduce main pump size.

43
Q

Explain water balancing.

A

All hydronic systems require balancing. In a balanced system every heat exchanger (radiator/baseboard/convector/zone) gets just enough hot water to allow it to heat up fully as per manufacturer recommendation at current pressure and flow rate (GPM).

44
Q

Where is a circuit balancing valve (CBV) installed and why?

A

Installed at each branch to the heat exchanger to provide precision flow measurement, pump throttling, and temperature measurement capabilities.

45
Q

Define union.

A

A union is used on threaded pipe joints to facilitate disconnecting the pipes for maintenance or repair.

46
Q

Define strainers.

A

Installed to prevent foreign materials from damaging pumps and control valves. They contain a perforated basket to entrain larger objects.

47
Q

What does every building require in regards to ventilation?

A

They require exhaust from washrooms and ventilation/outdoor air as per ASHRAE.

48
Q

What is the best way to incorporate ventilation and exhaust?

A

Using packaged ERV units. They incorporate DX cooling and gas heat exchangers/electric to make a “packaged unit”.

49
Q

How does a packaged ERV normally work?

A

Exhausted air is taken from the space, it passes over a plate heat exchanger or wheel taking the sensible + latent heat and uses it to precondition the incoming outdoor air.

50
Q

What are the 4 system types?

A

1) Series main
2) One-pipe main
3) Two-pipe direct return
* 4) Two-pipe direct return
* Lindsay’s go-to

51
Q

Explain a series main.

A

All of the units are in series, one loop is formed. The entire water supply flows through each terminal unit then returns back to the boiler. Considered a simple arrangement system.

52
Q

What are the disadvantages of a series main?

A

To maintain any terminal unit, you need to shutdown the system.
The # of units is limited because the water temperature decreases as it gives up heat at each unit. The far unit(s) may not provide adequate heat to the space.

53
Q

Explain a one-pipe main.

A

Each terminal unit is connected by a supply and return branch to the main. By putting valves in the branch lines, each unit can be controlled and serviced.

54
Q

What is a disadvantage of the one-pipe main?

A

Like a series loop, the far units may not get enough heat to heat the room.

55
Q

Where is a venturi tee fitting used?

A

Only used on one-pipe main system types.

56
Q

Explain a venturi tee fitting?

A

It can do flow restriction to force water up or down depending on branch requirements. Always installed on return side. If not installed, water wouldn’t flow through the supply side and would continue through the main. Sometimes called diverter tees because they force the flow of water.

57
Q

Explain two-pipe direct return.

A

Generally good for large systems, consists of 2 mains. One for supply and one for returns. Costs more than one-pipe, but it allows each unit to be separately controlled and serviced because the supply temperature to each unit is the same.

58
Q

Why is the two-pipe direct return system called direct return?

A

Because the return main is routed to bring the water back to the source by the shortest path.

59
Q

Explain two-pipe reverse return.

A

Similar to two-pipe direct return, but the supply and return mains are equal in length and size. *The first terminal is the last terminal returned and vise-versa, making it easy to balance flow rates. *Don’t need CBV’s (it’s naturally balanced).

60
Q

What is water pipe sizing based on?

A

The basis of flow, velocity, and friction losses through the pipes, fittings, and equipment.

61
Q

What is the flow of water in pipes based on?

A

The material of the pipe, the smoothness of the interior surface, the types of fittings in the pipe, and velocity of the water.

BED (1 decks)

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