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I'm swapping out a defunct Hot Dawg shop heater with a similar Beacon Morris model. The new unit is 40,000 BTU as opposed to (I think) 35k on the old one. The Hot Dawg was vented through the roof with double wall 3 inch vent. The new unit has a 4 inch outlet from the furnace. My question is can I reduce the vent from 4" to 3" as it leaves the heater? My total run is about 4'. Basically the vent leaves the furnace and elbows up through the roof. Thanks!
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Only way to tell is to ask the manufacturer.
Their answer would probably depend on total flue length.
Matt
If trees could scream, would we be so cavalier about cutting them down? We might, if they screamed all the time, for no good reason.
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It does probably depend on flue length, but they (BM) have an email CS address, asking them would be a good idea.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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What does the manual say? Generally, you cannot reduce the size of a vent on an appliance but RTFM.
Blackhat
Bad experiences come from poor decisions. So do good stories.
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[quote pid='7579376' dateline='1516403730']
Ok guys, you forced my hand and I read the manual
. Not surprisingly it says I can't reduce the size. I has hoping with such a short run (albeit with 2 elbows) I could get away without climbing on my snow covered roof and enlarging the hole, replacing the flange etc.. I'm not an HVAC guy by any means but I would think it would be a matter of maximum allowable back preasure on the exhaust side. Thanks for setting me straight.
[/quote]
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If your roof flashing is tall enough, maybe you can just trim a little around the existing one to allow a 4" vent (and new storm collar)?
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
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(01-20-2018, 12:10 PM)fredhargis Wrote: If your roof flashing is tall enough, maybe you can just trim a little around the existing one to allow a 4" vent (and new storm collar)?
That is plan "A". Although I bought a new flange, just in case plan A doesn't work out.
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Make sure the hole is large enough to meet all clearance to combustibles!
Matt
If trees could scream, would we be so cavalier about cutting them down? We might, if they screamed all the time, for no good reason.
-Jack Handy
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(01-19-2018, 06:15 PM)ed kerns Wrote: I'm swapping out a defunct Hot Dawg shop heater with a similar Beacon Morris model. The new unit is 40,000 BTU as opposed to (I think) 35k on the old one. The Hot Dawg was vented through the roof with double wall 3 inch vent. The new unit has a 4 inch outlet from the furnace. My question is can I reduce the vent from 4" to 3" as it leaves the heater? My total run is about 4'. Basically the vent leaves the furnace and elbows up through the roof. Thanks!
Hey guys, Just an update and (I hope) a final question. The furnace is installed and seems to be functioning normally. At the initial start up however, after all hookups, and the first few times I powered up the unit, I got nothing but a quiet electrical buzz- like it was coming from the transformer. Also the LED would blink in a pattern the manual said indicated normal operation. So I'd shut everything down, recheck my connections, scratch my head a little and power it back up. I probably did this 4 or 5 times over the course of an hour. I wiggled a few wires, but never found an obviously bad connection. Then the final time, the blower kicked on as soon as I flipped the breaker and everything works as it should. I hate fixing stuff when I don't know what I did, cause someday it will probably break again. Obviously I'm a rookie at this. Is there anything inherent in a brand new heater that would require it to cycle on/off a few times before firing? I did purge the air from the gas line as much as possible before powering the unit. Thanks for any insights!
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How long did you wait after you first powered it up? It may have had to go through some diagnostics/set up procedures before ti fired. BTW, I just installed a Sterling GG heater (owned by the same parent co. as the BM you have) and the transformer in it hums audibly as well. I'm not happy about it (my last one didn't have that hum) but's it's not unusual for a transformer to do that. The last one was installed about 6 years ago (different shop) and they may have had a higher quality transformer back then.
I started with absolutely nothing. Now, thanks to years of hard work, careful planning, and perseverance, I find I still have most of it left.
