Cold Air Return HVAC & moving heat

[EL DRIFTO]

there seem to be many threads about circulating heat using your existing hvac system so i guess i'll make my own too.

while the wife was at work i tried to light the furnace & reuseable air filter on fire with no sucess.
i tried it with the fan running too, it cleaned out all the deeply embedded dust, but no ignition.
the only combustible material in my hvac furnace is wire, not the filter.

although convection is the obvious goal, it gets hot downstairs & can't feel it upstairs for hours.
my stove is in the unfinished basement, concrete walls & floor.
with steady use, the hvac fan seems less neccessary.
i'd say the house feels warmer in the morning, with the stove, without the fan all night, than it did before with the gas fur fan running all night.
but when i haven't been home all day, it's 67 upstairs...
the day i got the stove, it took 6 hours for heat to get upstairs, something had to change.

my first attempt was rerouting the cold air return to the two joist spaces directly above the stove.
this resulted in very low outlet temps, very drafty feeling with the hvac fan on high @ 67...
not to mention the electricity & noise.

i used an additional hvac thermostat, set on ac, to come on when the top of the hvac furnace reaches 91+.
it's in series with the existing hvac htr thermostat upstairs.
only the fan comes on, no gas heat & this way the fan stops "helping" once the upstairs gets over 72, which it does.

i may have knocked a % off of the 120" code min space between stove & cold air return here...
my master hvac friend mentioned keeping intake temps below 100 for the fan motor's sake.
so i located a thermometer in the cold air return, it hasn't gotten over 92 @ 500.
i have a metal screen over my modified hvac inlet, i can touch all but an inch or two of the hvac tin.
i throughly cleaned out the reused vent sections before i rerouted them.
the huge all metal encased hvac furnace used to get really hot on gas, i can't imagine a fire hazard.
i contemplated if it would do more than smoke damage the house if i threw in a cup of gasoline, match & fan on...

it seems to be working now, with the two thermostats in series.
the fan shuts off mostly since it's fed off the existing hvac programable thermostat upstairs.
if the upstairs is set to heat & on, then the basement ac thermostat only comes on if the stove is hot, or intermittantly.
literally on top of the hvac furnace is my add on ac thermostat location.
depending on the heat coming off the stove, it may run for 2 minutes on & 5 off, or continuously.

the proof is in the fact that i used to come down stairs & was hit in the face by the heat.
now it's the same temp down stairs & stairway.
furthermore, i had the bedroom end of the house vents shut off since the stove is under them.
but after my most recent cold air location change, the bedrooms above the stove were the only cold ones until i opened their vents back up
although i haven't experienced COLD yet, this season has the fan running from 5-10 pm every night.
then it doesnt need to run over night obviously, or the next morning, or all day with no one home...

while staying @ home this weekend, i noticed it's performance is seamless.
the fan may only run 20% of the time since the basement ac thermostat cycles off.
it's interesting how the fan will keep cycling, even during cool down, fully automatic.
not to mention my mate & a consistant thermostat setting upstairs was not possable before.

one of my main concerns is people running their fans continuously.
waste of elec compared to the btus that gas hvac system is meant for, drafty too.
without any kwh eq installed, i do think my fan system is just as eff electrically.
the old system used to run fan all night to heat, my fan stops & system keeps heating all night, good heat too.
but it's running 5 - 10 pm everynight.

 

[laynes69]

Thats a nice way to fall asleep in a home and never wake up. It may work, but I would never do something like that. If you need the heat spread out in the home, buy a wood furnace and go that route. You could get negative pressures on the stove and pull co2 from the firebox distributing it through the home. I don't recommend this at all.

 

[EL DRIFTO]

good to know.
i have a co detector.
the only draft problems i have encountered are with the home's ex fans since they're the only thing changing air pressure in my house vs outside, like the chimney is.
& it would do that regaurdless of a closed loop circulating system inside the house.
the old cold air return vents are wide open to the basement still, so even if the basement door gets closed, no pres changes, i've checked.

the whole idea that co would kill everyone in the house, if a back draft formed, in the basemen,t with a fan
quicker than without a fan is debateable.

i've experimented with incoming air for the chimney draft.
the only window open that helps is one in the basement.
i had it @ a 1/4", it only needs < 1/6", it's a big window.
i've checked & i can turn on the bath ex fan & kit stove ex fan, no probs.
but the basement bath ex fan has cause back draft, with the stove hot once.
again this problem would exist if my all inside the house, closed loop system were on or not.
not sure if it would set the co detector off any slower or not, maybe i'll get another.

 

[daleeper]

Thats a nice way to fall asleep in a home and never wake up. It may work, but I would never do something like that. If you need the heat spread out in the home, buy a wood furnace and go that route. You could get negative pressures on the stove and pull co2 from the firebox distributing it through the home. I don't recommend this at all.

I am not wanting to argue this, but am asking, because I want to know the answer. With these newer epa stoves, how is the risk of CO being distributed in the house any higher with a wood stove (installed like this with the cold air return) than with your furnace, or the newer epa listed fireplaces that have the option of being hooked up for house distribution? It would seem to me that any one of these systems would be just as likely to have a failure and distribute CO as a well maintained wood stove, yet the codes allow the wood furnace and fireplace to operate, yet the wood stove ductwork as described here is violating code. What part of this installation is more risky than a wood furnace, or any type of furnace that has a heat exchanger leak?

 

[laynes69]

Woodfurnaces shouldn't have returns in the basement or rooms where they are located to risk negative pressure on the appliance. The jacket is also sealed around the firebox to prevent the pull of air thats needed for the primary, or secondary combustion. With that setup its like having an oversized shopvac pulling combustion air from the stove. The big thing is the sealed chamber around the firebox thats not effecting the draft of the furnace or fireplace around it. If a furnace has a leak in the exchanger, it shouldn't be operated period. Yes it can happen in a woodfurnace, but it also happens in central furnaces. Its something I wouldn't even attempt to try. A woodfurnace thats installed properly is much safer and more efficient at heat distribution. Not to mention excessive temperatures across that central furnace can damage components.

 

[EL DRIFTO]

your stove is hot
& this forum has been priceless
i've only had the internet for a year & a half, but i found this forum after my purchase
i'm in the learning curve still

it's not illegal for a 16 yr old girl to get into an automatic 300+ hp car,
it would also be immoral for my wife to tend the stove @ the end of the night, but not illegal
in my world, my co problems & hot water heater may be having it out now that i've abandoned the gaser

i've heard of this problem in an apartment once
twice a summer the co detector would go off
i would come downstairs to smell co & notice the hot water heater running when the detector went off
come to find out my house is insulated well enough that if my wife turned on the cooktop fan on high,
it would down draft the furnace & h2o heater flue, with every window shut & the ac on of course
after the second time, i concluded to shut the ac off, run the furnace for 30 seconds in the middle of summer
the furnace would jet start the flue really hot & the already running water heater would draft fine, from there on
then i'd turn the ac back on, which you shouldn't do for three minutes of course, laid the detector on the clothes dryer & put the batteries back in later

keep in mind that the window beside my stove is always cracked
during the week end, i turned the upstairs bath ex fan on & the kit ex fan was on high
then i went down stairs, shut that window, left the hvac fan on & OPENED THE DOOR
the 30 had a serious draft going, although it wasn't loaded & had no smoke shooting out when i just cracked the door open
there wasn't anywhere for the stove blast to go up the chimney fast enough once i whipped the door open though
so that massive wake of hot air when you first open the door didn't rush up the chimney
it flowed into the room and quickly disappeared into the fan....hahhaahahhahaah
& looked like a seriously bad idea to not shut the fan off when ever you open the door, which i do btw
if you notice in the picture, the furnace switch is @ code distance & clears the door by 1/2", open
but regaurdless leaving the door open @ that point would of chernoble anyway
i dont drink & my wife doesn't touch the stove
an additional co detector upstairs is a great idea since the one above the furnace may not be as sensitive with the return air suction @ the leak...
although literally the thermostat shuts the fan off 10pm every night

so now that my gas furnace isn't running @ night or at all,
the water heater had the same back draft problem that only occured in the summer b4, this morning
house is closed except for window next to stove & stove has been running fine all night, no serious draft in the stove next morning though...
i run into the bathroom for a coffee emergency, crank on the ex fan timer for 5 minutes, get in the shower 2 minutes later
well, although the stove is working fine, now the ******* water heater fires up
stove has no issues, but the water heater flue is back drafting from the bath ex fan & i can smell it when i come downstairs
i guess i'll hear that it's the stove now, although it certainly didn't smell or look like stove co
i just put my co detector back in operation this morning after your post...thanx again

i guess i'll find out if i have to plumb the stove inlet outside after i get rid of the water gaser, which would take the house pres problems out of the equation except when you open the door of course
now i've really got to get rid of the water heater & it's continuous draft sucking cold air up the water heater into oblivion, cooling the water or heated by the pilot
my house is air tight, i haven't searched by i can't imagine people not plagued with ex fan problem
the clothes dryer being a huge one
i dont know if your furnace has a seperate outside air inlet or fan driven ex, but your furnace would have the same co problems, just not near the cold air return, if you switched on enough ex fans in an air tight house
i'm having a gas flue draft problem before i have a stove draft problem, in my house @ a lower pressure difference
the window opening size i currently have OKd, next to the stove, that's aparently not enough window opening for the water heater pilot light flue draft

i happen to have the window covered in plastic except for small opening & can meter the air coming in pretty well

 

[EL DRIFTO]

update:

come to find out, the low speed hvac fan circuit is turned on by a furnace thermostat switch, in the exchanger @ 120v AC

the high speed fan circuit is turned on by a contactor/relay by 24v AC/transformer, totally different speed, switch & circuit, same fan DUH

so when i turned the old LP furnace back on, the fan didn't come on automatically
the limit switch that should detect overheat in the exchanger, & shut off the gas DIDN'T work either SO...
the exchanger got hot enough to burn all the lint off it & the A coil
smoke pouring out of the vents, when i finally turned the fan on manually, in less than 2 min after startup
pretty interesting how my error & a bad limit switch combined for a tasty afternoon
i've always assumed furnace overheat switches wouldn't fail in the "stuck on" fashion, but i guess the warranty is over so who cares how the limit switch is designed !
wonder what the 85,000 btu would of done if i hadn't been baby sitting it like my stove ?!?!
would of been more CO than my stove chimney full blast, into my vents, once the exchanger let go
certainly worth posting

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update EDIT:
after some real winter time, (it's 4F degrees here with 17mph steady wind),
the stove boost works great with the LP furnace running normal
the furnace seems to be running as though it were 50F, very little
the supply vents get pretty warm