What is the difference between a a 90% furnace with a sealed combustion system and a typical 90% furnace?
A) sealed combustion units use household vented air for combustion.
B) sealed combustion units may use PVC pipe for venting material.
C) sealed combustion units do not produce any combustion products
D) sealed combustion units require combustion air to be piped in from the outside.
D
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Which material is commonly used as Class II vapor retarder (VR) in stud walls?
What will be an ideal response?
The swift fox is often mistaken for the red fox because it may have quite a bit of red hair
a. True b. False Indicate whether the statement is true or false
Which of the following can be used as directional control valves?
A. check B. pilot C. spool D. all of the above
In the greenhouse effect what type of radiation is re-emitted by the earth's surface and is absorbed and reflected by greenhouse gas molecules in the atmosphere warming the earth's surface and lower atmosphere?
A. Ultraviolet B. Infrared C. Gama D. Nuclear