Manufacturer data plates details

GOODMAN® furnace or other GOODMAN® HVAC equipment
Serial number first 4 digits tell manufactured year and date. I.E.
Serial number is 9704011000. 97 is manufactured year and 04 is manufactured month.


LENNOX® furnace or other LENNOX® HVAC equipment 
Style 1:  5601D 08696 (or 5601D08696)
01 is year and D is month. D represents April. Stating from A represented Jan.

Style 2:  C89274AAC
First A is month and second A is year. First A is Jan and second A is 1980

Style 3:  15A67 JA098
15 is day, A is month and 67 is year.

Style 4:  4140720328
03 is year and 28 is week.


YORK® furnace or other manufactured YORK® HVAC unit
Style 1:  W0K5896070  (Oct. 2004 and later)
W is manufactured plant. 2nd digit and 4th digit combination represents year. I.E. 05. K represents September.

Style 2:  WAKM011379  (1971 - Oct. 2004)
W is manufactured plant. A is month, Jan. K is year, 1980 or 2001. M is type of item.

Field Excise #1: 44 Madelon Drive, Nepean, Ottawa

House Description
1. Built in 2010 by Richcraft.
2. Furnace is installed in 2010 and input capacity is 69000BTU/H
3. Air conditioner is installed in 2013 and input is 24000BTU/H

Limitations:
1. No access to concealed area
2. No access to roof view due to snow
3. Not able to crawl into attic due to possible damage. Used flashlight to view attic

General:
1. Roof missing gutter to help water move from roof to ground
2. Gas meter located in the front and has 1 3/4 inch black steel gas pipe into house
3. High efficiency furnace has air intake and exhaust outlet in good location
4. There are 3 washrooms, every washroom has vent. The powder room in the first floor has vent located at the ceiling of entrance hobby. The other two washrooms have vent located in 2nd floor.
5. Garage door works both with and without electricity power. Garage also has water facet and electricity outlet.
6. There are two outdoor electricity outlets, the front door one has Arc Fault Circuit Interrupter (AFCI) and can be reset with backdoor one
7. There are three washroom electricity outlets. All have AFCI and can be rest in the powder room
8. Kitchen has three 20A outlets with AFCI. (The differences between 15A outlet and 20A outlet is the 20A outlet has T shape of the neutral slot)
9. Electricity service box has no sign of double-tabbing.
10. Furnace starts and stops without flame deflection.

Issues
1. Roof missing gutter to help water move from roof to ground
2. Bathroom needs re-caulking

Heating:
1. Gas met has no sign of rust, mechanical damage. Gas is not shut off and locked. No ice built up and is not undersized. Easily accessible. No sign of leakage.
2. Gas pipe is black steel to both furnace and tankless water heater. No sign of leaks. Adequate support for 1 3/4 inch pipe every less than 10 feet and 3/4 inch every less than 8 feet. No sign of missing shut-off valve. No plastic pipe exposed above-grade. No piping in chimney and duct system observed. Copper tubing has proper label.
3. Furnace takes combustion air directly via PVC piping from outside.
4. Cabinet shows no sign of rust, mechanical damage and missing component. Air intake is not obstructed. No sign of scorching.
5. Power switch is in the same room with furnace and looks like a electricity switch.
6. There are two covers of the cabinet. Remove screws will remove cover. The cover for blower fan has a switch that will shut blower fan off if cover is removed.
7. Data plate showed input capacity is 69000BTU/H
8. It is induced-fan system. There are three burners and all of them are mono-port
9. Can't remove heat shield. No sign of missing, rust and scorched.
10. There is no pilot. It is electronic ignition.
11. No sign of fan switch. Electronic switch.
12. There is condensate line going to drainage pipe. No neutralizer is observed.
13. There is pressure differential switch that will shut down furnace if induced fan is not working.
14. It is sealed combustion
15. 3 inch PVC. Supported every 3 feet and has 1/4 inch slope down to furnace.
16. Unable to look at heat ex-changer.
17. Direct drive blower fan. Blower shows no sign of dirt, noise, rust and poorly secured. No fan belt and is balanced.
18. Normal furnace filter. No electronic air cleaner. Air filter is not dirty and not installed backwards. It is proper size and not loose.
19. No humidifier is installed.
20. Supply and return ducts. No sign of disconnected ducts. No sign of dirt, obstructed, collapsed and damaged ducts. No sign of leaky joints, excessive long runs. No sign of weak airflow and rust. No sign of pipes in ducts.
21. Everything looks reasonable to me.

1. Blower fan started as expected.
2. Thermostat's location is close to direct sunshine. It is not poor location but location is not ideal. No sign of loose but some dirt observed. Adjustment and calibration is proper. No anticipator.
3. Yes. There is purge cycle. It is electronic ignition. Flames look stable and in correct color.
4. About 30secs. House fan comes on. Flame pattern didn't change after house fan comes on.
5. No draft hood
6. Supply and return. Proper insulation is installed. Supply registers and return grills are in good location.

Structure Inspection Section#1 Footings and Foundations Quiz#4

You should have finished Study Session 3 and Quick Quiz 3 before starting this Study Session. This Study Session covers causes, implications and inspection strategy for differential cracks as well as some common corrective actions.

The estimated completion time is one hour.

Objectives
At the end of this study session, you should be able to:

• List nine implications of differential cracks.
• Define the maximum lot slope.
• Describe in two sentences cut and fill lots.
• Define in two sentences how crack size can be misleading.
• Describe three planes of differential movement that result in cracks.
• Describe in one sentence pyramid cracks.
• Describe in one sentence V-shaped cracks
• List four things you may recommend to clients with respect to cracks.
• List six structural repair strategies.

In your own words, explain what a cut-and-fill lot is and what implications this might have on building settlement.

A cut-and-fill lot is a side-hill lot where some of the hill is cut away to allow part of the house to fit into the hillside. The excavated material is often used to fill in the lower part of the slope and create a level pad for the rest of the home. Part of the house sits in the cut area and part of the home sits on the filled area. The filled area is disturbed soil and is more likely to settle.

It is a good idea to inspect the neighbourhood as you are arriving at an inspection. What kinds of things should you look for and how can they help you in your inspection?

1. Look for structural problems in other homes in the neighbourhood. 
2. Check the general topography. 
3. Houses on side-hill lots may be subject to cut-and-fill type settlement problems. 
4. Houses near the bottom of slopes may experience flooding problems. 
5. The general age of the neighbourhood is useful information.
6. Older neighbourhoods provide a more reliable test of time. 
7. You also may know about specific problems such as expansive or weak soils, high water tables, underground streams or reclaimed land.

There are a number of clues that might indicate to you that a crack is active. List as many as you can.

1. Opened patches
2. Cracks with no paint in the cracks (if paint is in the crack and the paint is old, the crack existed before the paint was applied)
3. A lack of dirt and debris in the crack (old cracks are often largely filled with dirt and debris)
4. Sharp corners on cracks (old cracks are often worn and rounded)

What is underpinning and in what situation would it be used?

Underpinning is re-supporting footings from below. This can include new foundations and footings, helical anchors, or piles. Underpinning is used in situations where differential settlement has to be stopped. Before underpinning, there should be some confidence that the soil below the building can support the underpinnings.

If you identify a foundation crack, is it possible to determine the rate of movement at the time of the inspection?

No

In general, which crack would be more serious?

A crack that has moved in two different planes

Structure Inspection Section#1 Footings and Foundations Quiz#3

You should have finished Study Sessions 1 and 2 and Quick Quiz 2 before starting this Study Session. This Study Session lists some common foundation problems and includes the first part of our foundation cracks discussion.

The estimated completion time is 30 minutes.

Objectives
At the end of this study session, you should be able to:

• List twelve common foundation problems.
• List four types of cracks.
• Describe in one sentence the cause and implication of shrinkage cracks.
• List four characteristics of shrinkage cracks.
• Define control point.
• Distinguish between uniform and differential settlement in two sentences.
• List eight causes of differential settlement.
• List two reasons soil bearing capacity may change after the house is built.
• List five soil problems that can cause differential settlement. 

Describe a typical shrinkage crack.

Shrinkage cracks are rarely more than 1/8 inch wide and typically do not involve displacement of the concrete on either side of the crack. Shrinkage cracks usually show up within the first year of the life of a home. Shrinkage cracks do not extend through the footings or up into the structure above. Shrinkage cracks may occur at stress concentration points such as window openings.

Explain the difference between uniform settlement and differential settlement.

In uniform settlement, the entire house moves and no cracking develops. With differential settlement, one part of the house moves relative to another. This typically results in cracking.

Make a list of typical causes of differential settlement.

1. footings that are missing, undersized or deteriorated
2. soil below the building that is disturbed, weak, expansive, eroding, or heaving due to frost
3. increased loads due to snow and ice
4. building additions.

Name four causes of cracks in foundation walls

1. Shrinkage
2. Differential settling
3. Heaving
4. Horizontal forces

What causes a shrinkage crack?

Shrinkage cracks are typically caused by natural curing of concrete

What is the main implication of a shrinkage crack?

The implications of shrinkage cracks may be leakage, but not structural problems. 

Structure Inspection Section#1 Footings and Foundations Quiz#2

You should have finished Study Session 1 and Quick Quiz 1 before starting this Study Session. This Study Session includes an Introduction to Structure inspections and the functions, types and materials of footings and foundations.

The estimated completion time is one and a half hours.

Objectives
At the end of this Study Session, you should be able to:

• List two functions of footings and foundations.
• Define dead loads and live loads in one sentence each.
• List seven common soil types in order of strength.
• Describe in one sentence how frost can affect foundations.
• List three common foundation configurations.
• List three common slab-on-grade arrangements.
• Describe in one sentence each the following: 1) spread footings, 2) pad footings, 3) pilasters, 4) piles, 5) piers, 6) grade beams.

Explain the difference between a full structural review and a performance-based inspection.

A structural review includes an analysis of the design. A home inspection is a field review based on the test of time and evidence of performance or non-performance of the system. A full structural review would typically include reviewing calculations or checking codes to ensure proper sizing and arrangement of components.

Explain the difference between a live load and a dead load. Give examples.

Live loads vary, such as people, wind, and snow. Dead loads are relatively fixed, such as building materials.

List three common foundation configurations and footing types

Common foundation configurations include basements, crawl spaces, and slab-on-grade. 
Common foundation types include spread footings, pad footings, piles, and piers.

There are several different materials that a foundation might be made of. List as many as you can.

Foundation materials include concrete, concrete block, cinder block, brick, clay tile, stone and wood

What is the difference between a pilaster and a pier?

A pilaster is a thickening of a foundation wall to accommodate the concentrated load of a beam or column. A pier is a stand-alone structural member that can be thought of as a column sunk into the ground.

What is the difference between a strip footing and a pad footing and where would each be used?

A strip footing or spread footing is used under a foundation wall. A pad footing is used under a column. Pad footings distribute concentrated loads. Strip footings handle more evenly distributed loads.

What is the function of a footing? - a foundation?

Footings transfer the live and dead loads of the building to the soil over a large enough area so that neither the soil nor the building will move. In areas where frost occurs, footings prevent frost from moving the building. Foundations transfer loads from the building to the footings. Foundations may also act as retaining walls, resisting lateral soil pressure, for example.

Why is it critical to document how the crawl space was inspected?

Your client has to understand the limitations of your inspection. Crawl spaces can be troublesome. If you couldn?t get a good look, your client should understand that there is a greater risk of unforeseen problems

When a foundation is supported on piles, are the piles typically visible for inspection?

No

As long as the footing is below the frost line, it is not a problem to let the temperature in the basement to go below freezing.

False. 

If the building is not heated, the frost line will be lowered. If the depth of frost is two feet, for example, it may be expected to be two feet below the basement floor if the home is not heated.

Structure Inspection Section#1 Footings and Foundations Quiz#1

This Study Session outlines the scope of footings and foundations inspections as set out in the ASHI®/CAHI Standards of Practice (note: ASHI® stands for the American Society of Home Inspectors; CAHI stands for the Canadian Association of Home Inspectors).

The estimated completion time is 30 minutes.

Objectives
At the end of this Study Session, you should be able to:

• List six structural elements that must be observed in a standard inspection.
• List six structural elements that must be described in a report.
• Describe in one sentence when probing is required.
• Describe in one sentence when attics or crawlspaces should be entered.

According to the ASHI Standards of Practice, an inspector must inspect all structural components. Two components are listed. What are they?

Foundation and Framing

According to the ASHI Standards of Practice, which structural elements must be described in your report?

1. Foundation
2. Floor structure
3. Wall structure
4. Ceiling structure
5. Roof structure.

Under what conditions are you not required to inspect crawl spaces?

1. Readily not accessible
2. Dangers
3. May damage property

Under what conditions would you not enter the attic? Give some examples?
1. Dangerous
2. May damage property
3. Not readily accessible
4. Insulation covers the ceiling joists or bottom truss chords

You are required to probe structural elements where deterioration is suspected. When would probing not be required?

Probing is not required where it would damage any finished surface or where no deterioration is visible.

Do the Standards require you to explain how you inspected the crawlspace or attic?

Yes

Do the Standards require you to inspect a foundation footing?

No. You are not required to inspect a foundation footing because it's usually not visible.

If the client is able to produce building drawings, are you required to look at the drawings to see if the foundation footing size is correct for your area?

No. You are not required to do a design review. Nor are you required to determine the strength, adequacy, effectiveness or efficiency of any system. You are also not required to perform any engineering services.

Heating I Section#1 Furnace - Gas and Oil Quiz#3

This study session deals with the combustion process and equipment in a gas furnace.

The estimated completion time for this study session is ninety minutes.

Objectives
At the end of this study session, you should be able to:

• Write the theoretical combustion equation for natural gas.
• Determine the amount of combustion air required for a gas appliance, given its input capacity in BTU/hr.
• List and describe the two most common types of gas burners.
• Describe, in one sentence, the function of the gas valve, pilot light and thermocouple, on a residential furnace.
• List nine conditions that may be found with gas combustion equipment.

A 80,000 BTU/hr furnace and a 40,000 BTU/hr water heater are in an open unfinished basement. How much combustion air is required? How much dilution air is required?

Standard answers:

We need 15 cubic feet of air for every cubic foot of gas burned, for each of combustion and dilution air. One cubic foot of gas contains 1,000 BTUs. The total firing rate of the 2 appliances is (80,000 + 40,000)=120,000 BTU/hr. This means we burn gas at a rate of 120 cubic feet per hour, or (120/60 minutes) 2 cubic feet per minute. This means we need (15cubic feet of air/ cubic foot of gas x 2 cubic feet of gas/minute) 30 cubic feet of air per minute(CFM) for combustion air, and 30 CFM for dilution air.

My answer:

Typically, 10 cubic feet of are is required for a perfect combustion of 1 cubic feet of gas, which is equal to 1000BTUs. 5 cubic feet of access air is needed for perfect combustion. In conclusion, for 80, 000BTUs, 15 multiple 80 = 1200 cubic feet of air is needed for combustion, for 40, 000BTUs, 15 multiple 40 = 600 cubic feet of air is needed for combustion. In total, 1200 + 600 cubic feet air is needed for combustion. At least same amout of air is needed for dilution, so another 1800 cubic feet of air is needed for dilution

An 80,000 BTY/hr input natural draft furnace with a draft hood is enclosed in a closet. How big should the 

combustion air intake be? How big should the dilution air opening be?

Standard answers:

Each opening should be 80 square inches.

My answer:

80, 000 BTU/hr = 80 cubic feet of gas per hour which required 1200 cubic feet of air per hour = 20 cubic feet per min

The combustion air intake has to be able to at least take in 20 cubic feet per min. 

The same as dilution air, which has to at least take in 20 cubic feet per min. 

Describe briefly how the pilot light and thermocouple work to ensure safety.

Standard answers:

The pilot flame heats the thermocouple, which senses the flame, allowing the gas valve to open. If the flame goes out, the gas valve is automatically closed.

My answer:

The automatic safety control is the thermocouple. The thermocouple has a very special job. It sits in the pilot flame and senses whether the pilot is on or not. If the pilot is on, the thermocouple allows the electrical current to flow through to the gas valve so that when the thermostat calls for heat and closes its part of the circuit, the gas valve can open. If the thermocouple doesn't sense a pilot flame (because the pilot is out or the thermocouple is defective), the thermocouple will open the circuit and won't let electricity flow through to open the gas valve, even when the thermostat does call for heat. 

Explain the path the gas and primary air take through a ribbon burner. You should start at the gas valve.

Standard answers:

The gas travels through the manifold to the orifice. As it passes through the orifice it mixes with the primary air at the shutter, then the combination air/gas travels down the burner where it is burned.

My answer:

primary air goes through shutter and then mixed with gas flow

gas started at gas valve, then go through manifold, then pass gas orifice, then mixed with air and go into burner. 

List 3 reasons that a furnace may short cycle. After each one, note if the reason is a minor maintenance item or a major concern.

Standard answers:

Thermostat problem, defective high limit switch, cycling on high limit switch, (which is working correctly) due to poor air flow causing overheating or a failed heat exchanger.

My answers:

1. A thermostat is defective or has an inappropriate anticipator setting. Minor maintenance. 

2. A fan limit switch that is defective or not set properly. Minor maintenance.

3. Cycling on high temprature limit switch due to 

- A crack in the furnace heat exchanger allowing hot products of combustion to enter the house-air side of the furnace and trip the high limit switch every time the furnace come on

- most of the supply registers are closed. 

- the furnace is too large for the ductwork

- the ductwork is collapsed or obstructed. 

- the air condition coil is plugged, restricting airflow.

List 6 conditions you'll find on gas combustion equipment.

Standard answers:

rust, scorching, inoperative, delayed ignition, short cycling, poor flame color or pattern, flame wavers when house fan comes on, dirt or soot, gas odor or leak.

My answers:

1. Inoperative

2. Scorching

3. Poor flame color or pattern

4. Flame wavers when house fan comes on

5. Rust

6. Dirt or soot

7. Delayed ignition

8. Gas odor or leak

9. Short cycling

What are the three normal combustion products of natural gas?

Standard answers:

water vapour, carbon dioxide and heat

My answers:

Carbon Dioxide, water and heat.

What is meant by "spillage" on a gas furnace?

Standard answers:

Spillage (backdrafting) is when the combustion products flow out of the furnace into the room through the burner or draft hood, rather than up the vent. This is a life threatening situation.

My answers:

Spillage is also known as backdraft. This is also implied lack of dilution air. This means that combustion products can't go up the chimney or vents, but are dumped back into the room.

Incomplete combustion of natural gas produces:

nitrogen dioxide

carbon dioxide

ozone

carbon monoxide

sulphur dioxide

Standard answers:

carbon monoxide

Scorching is noted on the inside of the burner access door. This is generally a result of:

overfiring

underfiring

lack of combustion air

faulty high limit switch

chimney obstruction

Standard answers:

faulty high limit switch

The flame wavers over one burner in a gas furnace when the blower comes on. What is the likely cause of this?

the heat exchanger has failed

the gas valve is faulty

the blower motor is running too slow

airflow across the heat exchanger is insufficient

the vent is partially blocked

Standard answers:

the heat exchanger has failed

Heating I Section#1 Furnace - Gas and Oil Quiz#2

This study session deals with the methods of heat transfer and gas piping and meters.

The estimated completion time for this study session is sixty minutes.

Objectives
At the end of this study session, you should be able to:

• List and describe the three methods of heat transfer.
• List the seven major components of a gas furnace.
• List nine possible problems you may find with gas piping.
• List eight possible problems you may find with gas meters

List 5 gas meter conditions you should watch for.

1. Rust

2. Mechanical damage

3. Gas shut off or locked

4. Ice build-up

5. Undersized

6. Poor access

7. Leaks

8. Poor location

List 5 of the components of a gas furnace.

1. Fuel system (steel piping or copper)

2. Combustion air delivery system

3. Burner, including gas valve, pilot and maybe pressure regulator

4. heat exchanger

5. Controls

6. Venting system

7. Distribution system

List 6 gas piping conditions you should watch for.

1. Leaks

2. Inappropriate materials

3. Inadequate support

4. Rusting

5. No drip leg

6. Missing shut-off valve

7. Improper connections

8. Plastic pipes exposed above grade

9. Piping in chimneys or duct system

10. Copper tubing not properly labeled. 

One half inch diameter black steel piping should be supported every _____ feet, unless it is rising vertically, in which case it must be supported every _____

6 feet, and at every floor when rising vertically.

My answers:

1 1/4 to 2 1/2 inch piping should be supported every 10 feet. 

1/2 inch diameter piping or less should be supported every 6 feet

3/4 inch and 1 inch piping should be supported every 8 feet

What is the purpose of the drip leg?

To collect dirt, separating it from the gas before it gets to the gas valve.

My answer:

It is intended to catch foreign materials before it gets into gas valves, burners and etc. The first appliance downstream of the meter must have one and in some areas every appliance needs one.

Which methods of heat transfer are used by hydronic systems?

Radiation, and convection

Bonding the gas piping to the supply plumbing system means that:

any stray electrical current will not cause arcing, which could ignite the gas

Gas meters located below the drip line of a roof are particularly susceptible to:

ice build-up in winter

Warm air rising off the pavement on a hot day would be heat transfer by

convection

Our Standards require us to inspect gas meters.

False

Heating I Section#1 Furnace - Gas and Oil Quiz#1

This study session outlines the scope of the heating inspection as set out in the Standards of Practice of the American Society of Home Inspectors (ASHI ®). These Standards, as they apply to heating inspections, are defined in your reading.
It also includes a discussion of the evolution of residential heating.

This is a short study session. The estimated completion time is forty-five minutes.

Objectives
At the end of this study session, you should be able to:

• List the two components of the heating system that you must inspect.
• List the two things you must describe in your report.
• List six ways heat is generated, four ways heat is delivered, and seven safety controls.
• Define the BTU.

A BTU is defined as:
The amount of heat required to raise the temperature of 1 pound of water by 1 degree Fahrenheit.

Forced air systems use ______ and ______ to move air around the house.
ducts and fans

Hydronic systems use ______ and ______ to move water around the house.
pipes and pumps

List 4 reasons that a house may be uncomfortable even though the furnace is large enough.
1. Low air temperature from registers
2. Drafts
3. Distribution problems
4. Air too dry or humid
5. Cold floors or walls

List 5 ways that heat is generated.

1. Fossil fuels
2. Solar
3. Geo-thermal
4. Electricity
5. Coal
6. Heat pumps

To meet the Standards, your report must describe: (2 items)

1. Energy source of heating equipment

2. Distribution method by its distinguishing characteristics. 

Why are our heating systems grossly over-sized for most of the year?

They are sized for the coldest day.

Most residential heating systems are:

fixed output

The first heating system which did not require manual stoking was:

oil

The purpose of our heating inspection is to ensure that the system:

is safe and adequately sized

We are required to look at normal operating controls and automatic safety controls.

True

We should test automatic safety controls.

False

Inspector "Shall" and "Not required to"

Heating system
The inspector shall:
A. inspect:
(1) the installed heating equipment.
(2) the vent systems, flues, and chimneys.
B. describe
(1) the energy source
(2) the heating method by its distinguishing characteristics
The inspector is not required to:
A. inspect:
(1) the interiors or flues or chimneys which are not readily accessible.
(2) the heat exchanger.
(3) the humidifier or dehumidifier
(4) the electronic air filter
(5) the solar space heating system
B. determinate heat supply adequacy or distribution balance.
Structure system
The inspector shall:
A. inspect:
(1) the structural components including foundation and framing.
(2) by probing a representative number of structural components where deterioration is suspected or where clear indications of possible deterioration exist. Probing is NOT required when probing would damage any finished surface or where no deterioration is visible.
B. describe:
(1) The foundation and report the methods used to inspect the under-floor crawl space.
(2) the floor structure
(3) the wall structure
(4) the ceiling structure
(5) the roof structure and report the methods used to inspect the attic.
The inspector is not required to:
A. provide any engineering service or architectural service.
B. offer an opinion as to the adequacy of any structural system or component.

Heating I notes

1. Roughly 10 cubic feet of air are needed to burn every one cubic foot of gas, under perfect combustion circumstances. In reality, there is always more air provided than is required for perfect cumbustion. The excess air is typically about 5 cubic feet. Generally speaking, 15 feet of cubic air is provided for every cubic foot of gas burned.
2. A cubic foot of natural gas contains about 1000 BTUs, a furnace that fires at the rate of 120, 000BTUs per hour, would use 120 cubic feet of gas if it fired constantly for 60mins.
3. There is another 15 cubic feet of air required as draft air. So for a conventional gas furnace, roughly 30 cubic feet of air for every cubic foot of gas burned, that is 1000BTUs.
4. For every 1000 feet above sea level, the fire rate should be decreased by 4%. I.E. We have a furnace that has fire rate 138,000BTU/hour, and the location of the furnace is 5000 feet above sea level. The actual fire rate is 138,000 * 0.8 = 110,400BTU/hour