Vacuum line for pressure switch pulling atmosphere

3636 Views 5 Replies 2 Participants Last post by yuri, Feb 12, 2016

juels98

Discussion Starter · Feb 12, 2016

Hi,

I'll try and keep this brief unless someone requests more information. I moved in to a house that has an apparently 2004 Gibson High Efficiency (92+?) direct vent furnace that started acting up 2 months in to the cold MN winter. The issue it was having is it'd go through its sequence, heat up the ignition element, seem like the gas valve would open and 3 seconds later would close, the ignition element would stop glowing and the furnace would try again. Eventually it would fire and work fine.

1. Now there was a PVC pipe next to the furnace bringing in the fresh air, but it wasn't connected directly to the furnace's provided opening right in to the hot box. I hooked it up-- that seemed to help (firing became more predictable)

2. THE MAIN QUESTION. After the tech left (who took the money but lacked the skill... more on that if you're interested

) I started looking around and noticed this. There are 3 1/4" vacuum tubes that hook up to the pressure switch. There's 3 of those hoses (1 pressure switch). One hose hooks up to the fire box where the burners are (probably pulls vacuum there), one that hooks up to what the install manual calls the "header box" not sure what that is. The 3rd one, I noticed, was tucked behind the pressure switch simply sucking atmosphere vacuum. I tinker with cars a bit-- there you don't want the vacuum line to be just hanging not connected. So, I plugged up that line.

Furnace seems to be working fine for 2 days now. So I wonder, is there any scenario where that would be a correct install to have the vacuum line sucking unplugged, or did someone mess up? I think my main issue was probably resolved more by bringing in the fresh air directly, but who knows. BTW, there wasn't any codes on the board.

Thanks for your help!

Julian

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yuri

· #2 · Feb 12, 2016

Normally those three lines go to:

1) burner box

2) collector box which is what the exhaust fan/inducer attaches to

3) VERY important, it goes to a port on the gas valve. Usually there is a barbed fitting on the side of the valve and the hose goes there. It is supposed to modulate the gas valve pressure if the intake pipe starts to plug with snow or debris. The vacuum in the burner box sucks on the gas valve diaphram and the pressure switch at the same time. Not all furnaces do it that way but if they have a closed burner box they should. If the burners are wide open when you remove the front door then there is no box to hook it up to.

Sounds to me like the previous tech(s) did not know what they were doing and decided to cheat by disconnecting it. That can be dangerous as the switch is getting the wrong vacuum and the gas valve should modulate the pressure for safe and proper combustion.

After 5 posts you can attach pics here. Intro yourself on the home page and get 5 posts. Then post pics of the hoses and burner area.

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juels98

Discussion Starter · #3 · Feb 12, 2016

Hi Yuri,

Thanks for the reply. Speak russian? :wink2: Me too

Anyway, you're right-- I misspoke- The one vacuum line does connect to the gas valve, burner box, and collector box. I guess there's 4, because the one I spoke about was in fact unplugged and sucking atmosphere-- So would you say I did good by plugging it up?

On a different note-- is it possible that now that the vacuum is correct, the furnace would blow hotter air?

Thanks!
Julian

yuri said:
Normally those three lines go to:

1) burner box

2) collector box which is what the exhaust fan/inducer attaches to

3) VERY important, it goes to a port on the gas valve. Usually there is a barbed fitting on the side of the valve and the hose goes there. It is supposed to modulate the gas valve pressure if the intake pipe starts to plug with snow or debris. The vacuum in the burner box sucks on the gas valve diaphram and the pressure switch at the same time. Not all furnaces do it that way but if they have a closed burner box they should. If the burners are wide open when you remove the front door then there is no box to hook it up to.

Sounds to me like the previous tech(s) did not know what they were doing and decided to cheat by disconnecting it. That can be dangerous as the switch is getting the wrong vacuum and the gas valve should modulate the pressure for safe and proper combustion.

After 5 posts you can attach pics here. Intro yourself on the home page and get 5 posts. Then post pics of the hoses and burner area.

Go Advanced>Manage attachments

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yuri

· #4 · Feb 12, 2016 (Edited)

A bit of Ukrainian and Slovak.

Actually I am related to Yuri Dolgorukiy, Grand Prince of Kiev:biggrin2:

IMO that line should not be open to atmosphere. I see very few Gibsons or Nordynes as they are not popular where I am. Post the full model # and pics and maybe someone here who is familiar with them can tell you where it goes. And you should try find a manual for it online with pics. Does not sound safe the way it is now and makes no sense to me.

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juels98

Discussion Starter · #5 · Feb 12, 2016

Yuri Dolgorukiy vodka is very good :devil3:

The model number of Gibson is KG6RC 100C - 16B. I do have a manual for it, but none of the diagrams show what I have for some reason.

Thank you,

Julian

yuri said:
A bit of Ukrainian and Slovak.

Actually I am related to Yuri Dolgorukiy, Grand Prince of Kiev:biggrin2:

IMO that line should not be open to atmosphere. I see very few Gibson or Nordynes as they are not popular where I am. Post the full model # and pics and maybe someone here who is familiar with them can tell you where it goes. And you should try find a manual for it online with pics. Does not sound safe the way it is now and makes no sense to me.