Inspecting Furnaces

Check, Identify and Describe a Furnace

According to the InterNACHI Residential Standards of Practice, a house examination is a non-invasive, visual examination of a domestic house that is developed to identify observed product defects within specific parts of that house. Part of the house assessment includes the inspection, identification and description of the heating system.

The inspector is required to examine the heating systems utilizing regular operating controls, and describe the energy source and heating method. The inspector's report shall explain and determine, in composed format, the checked heating system and will determine material problems observed.

In order to perform an examination according to the Standards of Practice, an inspector needs to apply the understanding of exactly what s/he comprehends about the various kinds of domestic heating systems. To totally examine and determine a particular heating unit, explain its heating technique, and recognize any material defects observed, an inspector needs to have the ability to describe and discuss with his/her customer:

• the heating system;
• its heating technique;
•  its type or identification;
• how the heating system runs;
• the best ways to preserve it; and
• the typical problems that might be discovered.

The inspector must have the ability to completely analyze a heating system, comprehend how a specific heating unit runs, and examine and reason regarding its obvious condition. An inspector must likewise be able to validate his/her observations, opinions and recommendations that were written in the examination report.

Heater Fundamentals

Let's focus on the principles of a particular heating unit called a heating system. There are many ways to examine, determine and describe the various types of heating systems that may be discovered at a home using non-invasive, visual-only evaluation methods. It depends on the inspector's judgment regarding how detailed the assessment and report will certainly be. For instance, the inspector is not required to determine the ability or BTU of the inspected heating unit, but many inspectors record that in-depth info in their reports.

The American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) specifies a heater as a "full heating system for transferring heat from fuel being burned to the air supplied to a heating unit." Another definition of a heater is "a self-enclosed, fuel-burning device for heating air by transfer of combustion through metal straight to the air." Taking these two meanings into factor to consider, there are two fundamental characteristics of a heating system:

1. There is a fuel made use of to produce combustion; and
2. Heat is transferred to the interior air. Note that air-- not water or steam-- is used as the medium to communicate the heat. This particular identifies warm-air heating unit from other types of heating unit.

Let's take a look at determining and describing some warm-air heating unit called heating systems.

A lot of modern heaters are frequently described as main heating systems. The heater is typically centralized within the structure. The heater is utilized as the major, central warm-air heating system. The heat of the heater is required (or rises) through a system of ducts or pipelines to other locations or rooms in the structure. The heating system does not necessarily have to be centrally located within the structure if the furnace is a forced warm-air system.

Heaters that have no distribution ducts or pipelines are used in some heating applications. They are restricted in the size of the area that they can warm. They are set up within the space or location to be warmed and have no method to disperse the heat to other places.

Recognition and Description of Furnaces

There are several methods to identify and describe a heating system making use of non-invasive, visual-only evaluation methods, as needed by the InterNACHI Standards of Practice. Heaters can be recognized and explained by:

• fuel type;
• distribution;
• airflow;
• gravity or required;
•  effectiveness; and
•  ignition.

Fuel Type

One way to determine and describe a heater is based on the type of fuel utilized to produce heat. Based on fuel type, one can classify a heating system as:

1.gas-fired;
2.oil-fired;
3. coal;
4. wood;
5.multi-fuel; or
6. electrical.

Nonrenewable fuel sources are utilized to produce combustion in the first 5 types. The last one utilizes electrical power. Whether electrical energy can be considered a fuel is trivial right here, given that an electric heating system functions in the exact same way as the other fossil-burning heating systems. The electric heating system heats air and disperses it. According to the Standards, an inspector is needed to explain the energy source in their report.

Distribution

The inspector is likewise required to describe the heating method. One method to do that is to recognize the technique of how the air is dispersed throughout your home. Heaters can be identified and described (or categorized) by the way the air is distributed. There are 2 broad categories:

1. gravity warm-air heating systems; and
2. required warm-air furnaces.

The gravity warm-air heating systems rely mostly on gravity for circulating the heated air. Warm air is lighter than cool air and will certainly rise and move through ducts or pipes. After launching its heat, the air ends up being cooler and heavier. The air falls the structure through return signs up to the furnace where it is warmed again, and the cycle continues. The very earliest types of heaters were gravity-type heaters. In some cases they had a blower fan set up to move the heated air. They have mostly been changed by contemporary, forced warm-air furnaces.

Air flow

Required warm-air heaters can be identified and described by how the air flows through the heating device in relation to the warm-air outlet and the return-air inlet places on the heating system. There are 3 types of forced warm-air heating systems connected to airflow:

1. upflow (highboy or lowboy);.
2. downflow; and.
3. horizontal.

Heater producers frequently make use of the terms "upflow," "downflow" and "horizontal" in their literature that explains their items, including their advertising materials, and in their installation and operation handbooks.

Upflow Highboy.

On a normal upflow highboy heating system, the warm-air outlet is situated at the top of the heater, so warm air discharges out of the top. The return-air inlet is located at the bottom or sides of the heating system. A cooling unit is commonly included to the top of an upflow heater. A typical upflow highboy heater stands no greater than 6 feet and can occupy a floor space of 6 square feet (2 feet x 3 feet).

Upflow Lowboy.

An upflow lowboy heating system is developed for low clearances. Both the warm-air outlet and return-air inlet are located at the top of the heating system. The lowboy is commonly set up in a basement where a lot of the ductwork is above the heating unit. This compact heating unit usually stands no greater than 4 feet. It is generally longer from front to back than either the upflow highboy or downflow furnaces.

Downflow.

A downflow furnace is likewise described as a counterflow heating system or a downdraft heater. Warm air discharges from all-time low of a downflow heater, and the return-air inlet lies at the top. The downflow heating system is set up normally when most of the duct or pipeline distribution system is listed below the heating system. The ducts may be embedded in a concrete floor piece or suspended in a crawlspace below the heating device. The downflow heater is similar in measurement to the upflow, however the warm-air outlet is located at the bottom instead of the top.

Horizontal.

A horizontal heater is designed primarily for installations with low, limited area, such as a crawlspace or attic. A common horizontal heater has to do with 2 feet wide by 2 feet tall, and 5 feet long.

Gravity Warm-Air Furnace.

A gravity warm-air heating system utilizes the reality that warm air is lighter than cool air, and warm air rises. In a gravity warm-air heating system, warm air might rise through ducts or pipes. After releasing its heat, the air ends up being cooler and heavier. The air drops down the structure through return signs up to the heater, where it is warmed once more. The air is circulated through your house in this way.

The extremely earliest kinds of heaters were gravity warm-air heating systems. They were popular from very first half of the 19th century to the early 1970s. Occasionally they had a blower fan installed to move the heated air. But the primary way the air moved through the home depended on how gravity impacted the different weights of warm and cool air. Gravity warm-air heaters were in some cases called "octopus" furnaces because of its appearance with all of the pipes coming out of the centrally situated heating device. The majority of these gravity furnaces are outdated and at the end of their life expectancy.

A gravity warm-air heater can be described in among the following 3 methods:.

1. a gravity warm-air heater without a fan;.
2. a gravity warm-air heating system with an essential fan; or.
3. a gravity warm-air heater with a booster fan.

A gravity warm-air furnace without a fan relies completely on gravity and the different weights of air to circulate the air through your house. The air flow rate is sluggish. The air circulation and distribution of heated air is not reliable. It is all however impossible to successfully control the heat supplied to individual rooms of the house. Occasionally an integral fan is installed in the distribution ducts or pipes to reduce the internal resistance to airflow and boost air movement.

A booster fan is set up to do the exact same, however does not interfere with air circulation when it is not in use. A booster fan may be a belt-driven fan device, resting on the floor and connected to the outside of the heating device.

Floor and space heaters run using the exact same principles of gravity and air weights, as do the gravity warm-air heating systems. They vary by the method a floor or area heater is created to supply heated air to a particular space or area, and do not distribute air throughout the home.
Warm Air Rises

When a certain amount of air is heated up, it expands and uses up more area. In other words, hot air is less dense than cold air. Any element that is less dense than the fluid (gas or liquid) of its environments will certainly drift. Hot air floats on cold air because it is less dense, just as a piece of wood floats since it is less thick than water. Warm air is frequently explained as weighing less than cool air.

Gas Furnaces

There are a variety of methods to describe various types domestic gas furnaces. Gas furnaces can be categorized by:

1. the instructions of the air flowing through the heating system;
2. the heating performance of the device; and
3. the type of ignition system set up on the unit.

Air flow in Gas Furnaces

One way to determine and describe a gas furnace is by the direction of the air flowing through the heating device, or the location of the warm-air outlet and the return-air inlet on the heating system. Gas furnaces can be called upflow, downflow (counterflow), highboy, lowboy, and horizontal circulation. Air can flow up through the heater (upflow), down through the heater (downflow), or across the furnace (horizontal). The plan of the heating system need to not considerably influence its operation, or your inspection.

BTU

Gas furnaces can be classified by their various capacities. A furnace capacity can be explained by BTU output. The BTU is identified by exactly what is required by the heating device for the structure, which is the duration of heat the unit has to produce to replace heat loss and offer the occupants an excellent convenience level.

AFUE

Furnaces can be recognized and described by heating efficiency. The energy performance of a gas heating system is determined by its annual fuel usage efficiency (AFUE). The higher the score, the more reliable the heating system. The united state government has actually established a minimum rating for heating systems of 78 %. Mid-efficiency heating systems have AFUE ratings from 78 to 82 %. High-efficiency heating systems have AFUE scores from 88 to 97 %. Old, standing-pilot gas furnaces have AFUE ratings from 60 to 65 %. Gravity warm-air furnaces may have effectiveness lower than 60 %.

BTU and Efficiency

BTU stands for British Thermal Unit. The BTU is a system of energy. It is roughly the amount of energy had to heat one pound of water 1 degree Fahrenheit. As soon as cubic foot of gas includes about 1,000 BTUs. A gas heater that fires at a rate of 100,000 BTUs per hour will certainly burn about 100 cubic feet of gas every hour.

On a gas heater, there need to be a data plate. On that plate there might be composed the input and output capacities. For example, the information plate may state, "Input 100,000 BTU per hour." And it might also state, "Output 80,000 BTU per hour." While this furnace is running, about 20 % of the heat created is lost through the exhaust gases. The ratio of the output to the input BTU is 80,000 ÷ 100,000 = 80 % efficiency. This is the "steady state effectiveness" of the furnace.

Steady state efficiency measures how effectively a heating system converts fuel to heat, when the furnace has actually warmed up and is running gradually. Nevertheless, furnaces cycle on and off as they maintain their desired temperature level. Furnaces normally do not run as efficiently as they launch and cool off. As a result, steady state performance is not as dependable an indicator of the overall efficiency of your heater.

AFUE and Efficiency

The AFUE is the most widely made use of procedure of a furnace's heating performance. It determines the duration of heat rendered to your home as compared to the quantity of fuel that should be provided to the heater. Thus, a furnace that has an 80 % AFUE rating converts 80 % of the fuel that is provided to heat. The other 20 % is lost and squandered.

Note that the AFUE refers just to the unit's fuel efficiency, not its electrical energy usage. The united state Department of Energy (DOE) figured out that all heating systems offered in the U.S. must have a minimum AFUE of 78 %, starting January 1, 1992. Mobile home heaters are required to have a minimum AFUE of 75 %.

The DOE's definition of AFUE is the procedure of seasonal or yearly performance of a furnace or boiler. It takes into account the cyclic on/off operation and associated energy losses of the heating device as it responds to modifications in the load, which, in turn, is affected by modifications in weather condition and owner controls.

Ignition Type

Gas heaters can be determined and described by the kind of ignition system on the furnace. The different types of ignition systems are:

1.standing-pilot;
2.intermittent-pilot or direct-spark; and
3.hot-surface ignition.

The older gas furnaces have a standing-pilot light that is always burning. Modern heaters with greater effectiveness ratings are slowly changing these older, conventional gas furnaces.

Standing-Pilot

Standing-pilot gas heaters provide a substantial variety of residential gas furnaces that are still in use today. A standing-pilot gas furnace is equipped with a naturally aspirating burner, a draft hood, a solenoid-operated main gas valve, a constantly operating pilot burner (standing- pilot), a thermocouple safety device, a 24-volt AC transformer, a heat exchanger, a blower and motor assembly, and several air filters. The standing-pilot is the major distinguishing characteristic of the low-efficiency traditional gas heating system.

Mid-Efficiency

A mid-efficiency gas furnace is geared up with naturally aspirating gas burner and a pilot burner. The pilot light differs a standing-pilot. It does not run continuously. The pilot light is shut down when the heating system is not in operation (when the thermostat is not requiring heat). The heat exchanger is more reliable than one inside a traditional heating system. There is no draft hood. There might be a little fan set up in the flue pipe to create an induced draft, so these heaters are occasionally described as induced-draft heating systems. A mid-efficiency gas furnace is likewise geared up with automatic controls, blower and motor assembly, venting, and air filtering. Some mid-efficiency heaters will certainly have a motorized damper set up in the exhaust flue pipe. A mid-efficiency furnace is about 20 % more energy-efficient than a conventional gas heating system. A mid-efficiency furnace has an AFUE score of 78 to 82 %. The intermittent-pilot is the main distinguishing characteristic.

High-Efficiency

High-efficiency gas heating systems have AFUE scores of 90 % and greater. A solid-state control board manages the ignition. There is no constant pilot burner. There are 2 or in some cases 3 heat exchangers set up inside a high-efficiency gas heater. Condensate is produced when heat is drawn out from the flue gases. The temperature of the flue gases is low enough to use a PVC pipe as the vent exhaust pipeline. There is no have to vent the exhaust gases up a chimney stack. There are 2 various kinds of high-efficiency heaters:
1. one with an intermittent-pilot or direct-spark; and
2. one with a hot-surface ignition system.
The production of extreme condensate is the major distinguishing characteristic.

The Best Techniques

There are lots of methods to identify and explain a furnace. According to the InterNACHI Standards of Practice, the inspector is required to examine the heating unit utilizing normal operating controls, and explain the energy source and heating method. The inspector's report will describe and recognize, in written format, the examined heating system, and will determine material problems observed.


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