HVAC question

Page 1 of 2  

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

50% RH is "high"?
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@aol.com wrote:

Hi, Yes, for the Canadian winter temp.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
wrote:

I guess to me it is...I also have an indoor swimming pool in the back yard (not attached to house) and I keep the RH in that building to 30-35%...I park my BMW in the same building with no issues.... Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

They run computer rooms at 50%. I guess I am just more used to a higher number in a home. I just looked and it is 44% in here right now and my lips are cracking and my throat feels dry..
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@aol.com wrote:

Hi, R.H. is function of temperature. Computer room is for the machine not people. Too low humidity will cause static discharge and it is harmful to the machines. Here in winter, most of time at home we keep it around 25% when it gets real cold(like -30C)
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Tony Hwang wrote:

Here in SE Iowa our inside RH is currently 34% and outside it is 77%. In fact, if you want to take a look just point your browser to www.crsales.com/weather.htm and you will see my amateur weather station. I don't look at the inside RH that often and quite honestly I was surprised that it was that low.
Don
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Sun, 18 Oct 2009 21:54:32 -0400, snipped-for-privacy@aol.com wrote:

-snip-
50% is high to the Aprilaire folks-- I've been dicking around off and on for 2 weeks wondering why mine isn't kicking on. One year old humidifier-- new furnace install. Bought a new transformer. . . tested where I had it hooked up. Finally read the manual again. Max humidity is 45%. Mine is 47%.
*That's* why it has that 'test' setting.<g>
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jim wrote:

Hi, Fresh air intake is two ways, one for combustion for the furnace and one going into return air duct. Wonder if it is damper controlled and it is operational in your case. Too air tight home definitely needs outside fresh air in proper amount. My house is R2000 spec. We have damper controlled outside air intake. Yet I am running a power humidifier in the winter. I am in Calgary that is why. Our winter air is extremely dry.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

In winter, I sometimes have to run a humidifier to get the humidity up to 50%.
Outside combustion air is quite common on high efficiency units but I'm not sure it would lower the humidity level. Right now, the moist internal air is being used and going out the stack and infiltration is replacing it with the outside air. You may want to experiment a bit and crack a window open in the room with the furnace and close it off from the rest of the house.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

*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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

*OOPS. You're right. I shouldn't respond to these things before coffee.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

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.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Makes me wonder if the installers added a humidifier. If so, it may be set too high. Please call whoever installed the furnace, they are likely to know the details.
--
Christopher A. Young
Learn more about Jesus
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

What did you change in addition to the furnace? Windows? insulation? Did the furnace come with a humidifier?
The last would be my guess-- and it should have both an adjustment and an outside sensor.
What does the installer say?
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

It's possible the new furnace has a seperate intake where it pulls outside air in for combustion. The old one drew air directly from outside, so there was always a significant amount of fresh air being pulled into the house, at least into the basement. That would have lowered the humidity, but now that is gone.
I agree with others who have said 50% humidity isn't excessively high and it shouldn't make it feel clammy. It is the highest you would want it though, otherwise you risk condensation. You wouldn't want it that high when it's 15 outside, but by then with the furnace running more, it's likely the humidity will decrease.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
snipped-for-privacy@optonline.net wrote:

Sounds like an entirely reasonable answer.
And as the outside temperature drops the moisture content of the outside air also drops, which should lower the inside humidity.
I don't remember it has come up, if the furnace combustion is discharging into the house the humidity would be high. The probability is very low for a new install, but possible. A carbon monoxide detector is a good thing to use in any case.
--
bud--

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
On Mon, 19 Oct 2009 05:47:04 -0700, trader4 wrote:

Hmm. Ours has an intake and outlet to the outside world - but it also has a small shoebox-sized pump beside it, which collects moisture and pumps it into the waste water system for the house. I'm not sure if that pump is for extracting moisture that's in the air, or from the gas supply - but given the way it's floor mounted beside the furnace it looks like optional extra equipment, as otherwise surely it'd be built into the furnace...
If it *is* optional on furnaces and the OP doesn't have it, maybe they need it, whatever its exact function is...
(just idle speculation, not based on any knowledge of how furnaces work! :-)
cheers
Jules
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Site Timeline

Related Threads

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.