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You may be able to get help from the supplier - when you buy a furnace online/yourself, the supplier is responsible for the warranty, the manufacturer will not deal with it.

Why was it fired up without first changing the orifices?

Should still identify what's shutting it down - pressure switch opening or proving flame.
 

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What size is the vent pipe? Is it ran to a masonary chimney, or a B vent chimney? Sounds like the unit is set to operate in single stage mode, not 2 stage. If it was set to operate in 2 stage mode, you wouldn't be able to measure the 9.7 to 10.3" pressure with it kicking out after 30 seconds of run time.

Is it possible that the installer increased manifold pressure in first stage to be at second stage pressure?

It may be tripping the secondary/auxiliary limit switch.
 
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Discussion Starter #24
It was never fired without orafices. It was fired up for a while with the wrong orafices (45 instead of 55). That caused a bit of soot build up. But its since been corrected.

It's not the flame sensor, since the unit will stay on when on lower propane pressure.

The techs used a multimeter on the pressure switch, but maybe it fluttered so fast they didnt catch it...

You may be able to get help from the supplier - when you buy a furnace online/yourself, the supplier is responsible for the warranty, the manufacturer will not deal with it.

Why was it fired up without first changing the orifices?

Should still identify what's shutting it down - pressure switch opening or proving flame.
 

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Discussion Starter #25
The pressure switch was checked with a multimeter. And I think one tech evn tried jumping it. The techs said the pressure was fine, but maybe it's fluttering so fast they didn't catch it.

The flame sensor works fine at low propane pressure.. I suppose higher propane pressure could be effecting it, but I'd be suprised.

Why would bypassing the thermostat help? If there was a problem with a bad connection, marginal ground, or call for heat interruption, why would the unit work properly when simply adjusting the gas valve pressure lower? Wouldn't these issues cause a problem regardless
Of the gas valve pressure setting?
It's unlikely to be the thermostat or wiring but it's best to start with the basics and rule out anything external that could cause problem.

The gas pressure can impact pressure in the heat exchanger as well as flame signal.

When you say flame current, I assume you mean whether the flame and gas pressure is steady when the burners are on
No - there's a flame sensing circuit and the current should be checked.

Meter is set to DC microamps and wired in series with the flame sensor.

While I suppose it could be a pressure switch issue, multiple techs said they checked that possiblity.
How was it checked?

Voltage drop across it needs to be monitored with a meter that responds fast.

If it's opening for a fraction of a second, pressure it's seeing needs to be checked.

If the pressure is normal and steady, the pressure switch is bad.
 

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Discussion Starter #26
I will throughly clean the soot, and combustion motor, just to be sure.

What is the model # again?

I Googled it and nothing matches.

If you ran it with incorrect orifices and it produced soot in the heat exchanger and secondary heat exchanger then they may be partly plugged.

If the manifold pressure is where it should be and you have a partly plugged heat exchanger then the sheer amount/volume of fumes could trip the pressure switch quickly.

A fluttering pressure switch can be hard to diagnose.

If you continue to run it with a lower manifold pressure you are seriously fouling it up/sooting and plugging it up. The damage may be done>> you have a partly plugged heat exchanger.

Reversed polarity will prevent it from running at all. Some newer units have a error code for that.
 

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Discussion Starter #28
The Hvac-talk.com website says something about "moving." I think the site is being moved and not accessible right now.

Consider going to the HVAC Talk forum. There are professionals there who may have run across this issue. And they will NOT tell you how to fix it but may come up with some suggestions.
 

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Discussion Starter #30
The vent pipe starts at 4 in I believe, then ramps up to 5 or 6 in pretty quickly. You can look at the photos I recently posted on this discussion.

It's ran to a B vent chimney. If the vent pipe or chimnet were the issue, then the pressure switch would be fluttering right?

The unit is definitely 2 stage. I've heard this unit actually starts in the second stage and then is SUPPOSED to drop down to the first stage. though I'm not sure it ever gets to switch stages due to the problems its having.

I thought maybe the 1st and 2nd stage pressure was off, but I've tried adjusting it. If I put the second stage pressure low, then it stays on, otherwise it just cycles every 30 seconds.

What size is the vent pipe? Is it ran to a masonary chimney, or a B vent chimney? Sounds like the unit is set to operate in single stage mode, not 2 stage. If it was set to operate in 2 stage mode, you wouldn't be able to measure the 9.7 to 10.3" pressure with it kicking out after 30 seconds of run time.

Is it possible that the installer increased manifold pressure in first stage to be at second stage pressure?

It may be tripping the secondary/auxiliary limit switch.
 

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I can pretty much tell by the location of the safety’s around the burner, but you have an up flow unit installed upside down.
You’ll likely need a new furnace. And another installation.
 

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Discussion Starter #33
The unit is convertable to a downflow. The manual it came with explains it can be converted to downflow and should work fine. Though I know its labeled upflow.

I can pretty much tell by the location of the safety’s around the burner, but you have an up flow unit installed upside down.
You’ll likely need a new furnace. And another installation.
 

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Yup, you have an up flow furnace rolled upside down in a downflow configuration. That furnace is unusable in your setup, and is a rather large fire risk. Rolled over the rollout and limit are ineffective.
Post the steps needed for conversation. I don’t see how that furnace would work like that.
 

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A GDS model is a downflow. D stands for Downflow.

H is for horizontal and M is upflow.

Model type determines which installation procedures must be
used. For GMS and GHS models, you must follow instructions for
Horizontal Left, Horizontal Right or Upflow installations only. GMS
and GHS models are not approved for Downflow installations.
 

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If that is the problem, is there any reason why wouldnt any of the 6 technicians have mentioned it?

Also would I need to replace the ac coil below the furnace as well? The AC was working fine.
Likely because the installer and techs you’ve had working on it sound like idiots. Firing the unit with the wrong nozzles. Jumping safety’s out. Missing the whole thing is upside down. Likely no permit pulled. Just stupidity all around.
But these are the things that happen when a customer buys their own equipment and then hires someone to install it. And why it shouldn’t be done. If you want to buy your own equipment it’s best to do the installation yourself. That way you can work on it when it breaks.
 
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