The whistling noise may be from an improper air intake shutter control adjustment. For a Natural Gas Unit the air shutter control should only be open about 1/4 " . Also, when checking that, look to see if it's clogged with dust and lint. If so, vacuum it out using a crevice tool on the hose of your vacuum.
Vent-free Gas Appliances should be cleaned and serviced at least once a year. Usually in the Fall before firing it up for the heating season. Twice if you have house pets. Especially one's that shed a lot.
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The whistling noise may be from an improper air intake shutter control adjustment. For a Natural Gas Unit the air shutter control should only be open about 1/4 " . Also, when checking that, look to see if it's clogged with dust and lint. If so, vacuum it out using a crevice tool on the hose of your vacuum.
Vent-free Gas Appliances should be cleaned and serviced at least once a year. Usually in the Fall before firing it up for the heating season. Twice if you have house pets. Especially one's that shed a lot.