HVAC question - Page 3

Posted by John Grabowski on October 19, 2009, 7:10 am

> I have a 2600 sq ft 4 level split home in Canada. It was built in
> 1985. This past spring we replaced our very non-effecient furnace with a
> Tempstar 95% effecient gas furnace. It really is wonderful as the old
> furnace would cause the house to feel sort of drafty and basement was
> always cold etc... Now I have this furnace that I love to bits BUT now
> since it has gotten colder outside these past two weeks, we have kept the
> doors and windows closed and now have a high humidity problem inside the
> home IE: fogged up windows (triple pane)...air basically feels
> clammy...bought a humidistat and the house is sitting at around 50%
> humidity.... we use bathroom fans in the shower, and have a fan over the
> stove when cooking that we use all the time...we keep lids on pots on the
> stove etc...We have no children and only the two of us in this home so no
> long lingering showers by kids or anyone else....
> I don't want to have to buy a dehumidifier over this new furnace..
> sort of defeats the idea of trying to be energy effecient... Thinking of
> trying to duct in an outside air source to feed the furnace?
> Thoughts? Thanks... Jim

*If the unit is the type that I am thinking of you should have two PVC pipes
coming off of it. One is for fresh air and the other is exhaust. The
exhaust pipe must be pitched (Sloped downwards slightly) towards the outside
so that condensation will drain outside and not into the unit. Check to see
if that is so. Also if your unit is not pulling air in directly from the
outside it would be a good idea to bring fresh air into the room.

Posted by Steve N. on October 19, 2009, 8:25 pm

> *If the unit is the type that I am thinking of you should have two PVC
> pipes coming off of it. One is for fresh air and the other is exhaust.
> The exhaust pipe must be pitched (Sloped downwards slightly) towards the
> outside so that condensation will drain outside and not into the unit.
> Check to see if that is so. Also if your unit is not pulling air in
> directly from the outside it would be a good idea to bring fresh air into
> the room.

On a typical condensing furnace, the PVC vent piping will slope slightly
UPWARD toward the outside,
so that the condensate in the vent will drain back thru the furnace
condensate handling system. See page 14 of the
installation instructions here for a typical system:
http://icpindexing.mqgroup.com/documents/086477/44001105007.pdf
8. All exhaust vent piping from the furnace to termination

MUST slope upwards. A minimum of 1/4? per foot (6.4mm

per 304.8 mm) of run is required to properly return

condensate to the furnace drain system

Posted by John Grabowski on October 20, 2009, 7:44 am

>> *If the unit is the type that I am thinking of you should have two PVC
>> pipes coming off of it. One is for fresh air and the other is exhaust.
>> The exhaust pipe must be pitched (Sloped downwards slightly) towards the
>> outside so that condensation will drain outside and not into the unit.
>> Check to see if that is so. Also if your unit is not pulling air in
>> directly from the outside it would be a good idea to bring fresh air into
>> the room.

> On a typical condensing furnace, the PVC vent piping will slope slightly
> UPWARD toward the outside,
> so that the condensate in the vent will drain back thru the furnace
> condensate handling system. See page 14 of the
> installation instructions here for a typical system:
> http://icpindexing.mqgroup.com/documents/086477/44001105007.pdf
> 8. All exhaust vent piping from the furnace to termination
> MUST slope upwards. A minimum of 1/4? per foot (6.4mm
> per 304.8 mm) of run is required to properly return
> condensate to the furnace drain system

*OOPS. You're right. I shouldn't respond to these things before coffee.

Posted by Lefty on October 19, 2009, 7:20 am

> Hello,
> I have a 2600 sq ft 4 level split home in Canada. It was built in
> 1985. This past spring we replaced our very non-effecient furnace with a
> Tempstar 95% effecient gas furnace. It really is wonderful as the old
> furnace would cause the house to feel sort of drafty and basement was
> always cold etc... Now I have this furnace that I love to bits BUT now
> since it has gotten colder outside these past two weeks, we have kept the
> doors and windows closed and now have a high humidity problem inside the
> home IE: fogged up windows (triple pane)...air basically feels
> clammy...bought a humidistat and the house is sitting at around 50%
> humidity.... we use bathroom fans in the shower, and have a fan over the
> stove when cooking that we use all the time...we keep lids on pots on the
> stove etc...We have no children and only the two of us in this home so no
> long lingering showers by kids or anyone else....
> I don't want to have to buy a dehumidifier over this new furnace..
> sort of defeats the idea of trying to be energy effecient... Thinking of
> trying to duct in an outside air source to feed the furnace?
> Thoughts? Thanks... Jim

Something does'nt add up about this post..........................
Are you saying the house was likely drier at this time last year, and this
problem is brand new?
The furnace you have now *makes* water, so to speak, but it should'nt
*contribute* to a high humidity level in the house. It should heat and dry
the air like any furnace would. The discharge air may be slightly cooler
than the air from your old one, but other wise it's pretty much apples to
apples. I would check to make sure that the furnace is not an internal
leaker, and the drain system is actually disposing of the water in a fashion
where it leaves the house. If there are no issues found with the furnace,
then I would look elsewhere for a humidity problem, if you indeed have one.
I would think that you are going to need a humidifier soon, like everyone
else, not a dehumidifier.

HTH, Lefty

Posted by ransley on October 19, 2009, 7:38 am

> Hello,
> =A0 =A0 =A0 =A0 I have a 2600 sq ft 4 level split home in Canada. It was =

built in

> 1985. This past spring we replaced our very non-effecient furnace with a
> Tempstar 95% effecient gas furnace. It really is wonderful as the old
> furnace would cause the house to feel sort of drafty and basement was alw=

ays

> cold etc... Now I have this furnace that I love to bits BUT now since it =

has

> gotten colder outside these past two weeks, we have kept the doors and
> windows closed and now have a high humidity problem inside the home IE:
> fogged up windows (triple pane)...air basically feels clammy...bought a
> humidistat and the house is sitting at around 50% humidity.... we use
> bathroom fans in the shower, and have a fan over the stove when cooking t=

hat

> we use all the time...we keep lids on pots on the stove etc...We have no
> children and only the two of us in this home so no long lingering showers=

> kids or anyone else....
> =A0 =A0 =A0 =A0I don't want to have to buy a dehumidifier over this new f=

urnace..

> sort of defeats the idea of trying to be energy effecient... Thinking of
> trying to duct in an outside air source to feed the furnace?
> =A0 =A0Thoughts? Thanks... Jim

In fall for the first month of heating system operation I have the
same problem and so do many with tight homes. The house has to dry out
a bit. Get air to circulate, leave a few windows cracked open. Does
your home have a house wrap like Tyvek, I bet condensation goes away
in a month, open windows will help.

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