[grarrsmi]

Hey guys,
I have a furnace that I have been having problems. I will tell you all the issues I have been having but don't know all the part names so bare with me.
Let me start by telling you I live in Michigan where it gets cold and the furnace is in my cottage up north. It only runs when I am there. I do not keep the cottage at a minimum temp like some do. So earlier in the winter I ran it with no problem, shut it down when I left than when I went back up to turn it back on it would try to start but wouldn't. Found the water in all the hoses, drain and where some water sits froze. I got it all thawed out and than ran fine. So when I left, I drained all the water out of furnace so I don't have that problem again.

Go back up there last night and the furnace fan would start, igniter would lite up in the site glass than as soon as it tries to light the propane it shuts off with a 3 light blinking code. I understand that means its a closed pressure switch.

Can taking the water out have an effect on the starting and also where can I get parts?

Thanks in advance.

 

[user_12345a]

You mean open pressure switch?

 

[grarrsmi]

Yes sorry

 

[roughneck]

This is a condensing furnace I assume? If so not a good idea to leave it off in freezing conditions. Huge amounts of damage can result to the equipment. Also, condensing furnaces usually have a minimum return temp of somewhere between 50-60*.
What does that code mean?

 

[ben's plumbing]

3 code is pressure switch ..not working properly..check all tubing ckeck trap assy. check ports where tubing connects too for blockage and restriction of vaccum...

 

[grarrsmi]

I would say its a condensing furnace. Why do you say it does a lot of damage? The code is a stuck open pressure switch. I am just trying to get my ducks in a row before I go back up there. Want to try some things before I call someone that cost lots of money.

 

[roughneck]

I would say its a condensing furnace. Why do you say it does a lot of damage? The code is a stuck open pressure switch. I am just trying to get my ducks in a row before I go back up there. Want to try some things before I call someone that cost lots of money.

Because condensing furnaces, well, condense. They form condensation in the secondary heat exchanger. Turn it off and allow it to freeze and the heat exchanger can crack from ice formation, along with all the tubing and sensors associated with that side of the system.
Run it too cold and the flue gasses will start to condense in the primary heat exchanger and cause it to rot out.
No way to dry it out without dismantling the furnace or leave it sit for a long period of time so the condensate evaporates.

 

[grarrsmi]

Ok so i understand that this unit should not be turned off. I would like to get it running. I went there the last 2 days to test some things. Still getting a 3 light code and tries to lite. 1 time had it going for about 30 seconds than shut back down but all other times it spits a flame out than shuts down. Lines are all clear including inlet, outlet, rubber hoses and no freezing lines. Pressure switch closes and opens. Gas valve clicks. Clean filter.
Now what to do? Is it possible the propane line regulator is bad? Any suggestions for the next move?

 

[yuri]

If it actually fires gas in and lights occasionally then the pressure switch is working. It proves there is enough air for safe combustion at startup.

However once you get a flame you get flue gases/smoke and they have a mass/volume to them. This will cause the exhaust fan/ventor to have to work harder. I suspect you are then getting the pressure switch tripping because the amount of vacuum you have decreases due to the gases. It probably is at the tripping point at startup. Add some flue gases and it trips. You may have a cracked heat exchanger or plastic collector box the inducer attaches to or other venting problems. Need to put a manometer inline with the switch to check the vacuum. May have other problems as mentioned B4. Not much we can do from here.

How old is it? If it is getting older it may not be worth throwing a lot of repair $$ in as it may have some serious damage or corrosion to the heat exchanger etc.

Sorry.

 

[grarrsmi]

I think it is about 6-8 years old. Is that the only way left to check it? If that fails the test the start looking for new furnace?

 

[yuri]

You have a possibility of a VERY badly damaged furnace. If the secondary heat exchanger is cracked it is very difficult to get at and find a crack w/o removing the whole heat exchanger. If you want to pay a tech by the hour to look for damage and he is experienced enough to find it then it may be worthwhile. Kinda hard to find them. Not sure what to tell you other than it may be a very expensive operation and even if it is a cracked collector box the rest of the heat exchanger may be corroded and fail next year. Hard lesson to learn that you do not want to run those furnaces too cool or get water damage.

It may be a better idea to have a basic Goodman installed and start over. All depends how you want to spend your $$ and what you feel is good value for them. I don't have a good feeling about this furnace and would lean to replacing. It is past it's 5 yr parts warranty and you did get some good use out of it.

 

[grarrsmi]

Well lets just say I am not the one who put this furnace in. Bought the place from a buddy and told him what you guys are saying about putting this type of furnace in a cottage that it gets shut off. He is not happy because he had his heating and cooling friend put it in and his friend knew it would get shut off during the winter. Lesson learned and was just thinking about replacing it so I don't have to have anymore of these problems.
One thing I don't understand is that I would have a multi meter on the pressure switch from the second I start it and it would go closed (0) and stay that way but not start.
What am I missing?

 

[Ben25]

There is propane in the tank, right? Just checking.

 

[yuri]

The pressure switch must be open at start. The circuit board does a self check and checks to see it is open. Then the inducer starts and it closes and only then does it energize the igniter after a 30 second purge timer.

You may have a weak pressure switch. They are inexpensive and I would replace it.

americanhvacparts.com or supplyhouse.com

 

[beenthere]

May also just be that ice formed in the pressure switch and damaged the switch.

 

[kirby.j89]

What's the venting like? Total length of each run of vent pipe and how many elbows and 45's? Try taking the intake off of the furnace and see if it will run, this will tell you wether your not getting enough air or not expelling enough combustion gasses. Next I'd check that the inducer motor is running at its rated amperage or close, running amps should be on the side of the inducer. Then id take the pressure switch off and clean the ports with a small piece of wire and make sure it doesnt have condensation inside. If that passes I'd borrow or buy a manometer and tee it into the pressure switch and observe what is happeneing when the switch opens. And I can't suggest you do this as I don't know your technical aptitude... But I'd bypass the pressure switch and force the furnace to run for a minute until the blower comes on to make sure flame characteristics don't change or flame roll out or another safety trips... Also would suggest that the blower is slid out of the way to visually inspect the secondary to make sure frost hasn't damaged anywhere you can see...

This all depends on your level of skill of course.

Sent from my LG-D852 using Tapatalk

 

[grarrsmi]

The venting is fine. I compared that to the install instructions and it is getting plenty if venting and is all clear. Intake is just a short piece going to outside of furnace.

I would have to check inducer motor next time I go there but seems to be running very fast like normal.

As far as manometer, I would have to have a heating guy do it since I have no way of borrowing one.

I am very technical aptitude so I can just about do anything. How do you bypass the pressure switch? Put the 2 wires together?

If none of this works than I guess I will take apart to look for damage.

Attatched is a picture of the furnace inside if that will help at all.

 

[roughneck]

You cannot just start bypassing things. That will not solve anything.
You'll either need to invest in the proper tools or a professional tech.

 

[yuri]

Bypassing the pressure switch can be dangerous and techs only do it to see if the circuit will complete and allow the gas valve to open. Even bypassed you still need to know the vacuum across it. If you are interested I can help you buy a manometer and test it. If the pressure switch has a rating in "WC inches water column written on it we can test it. If not you have to get that info from the manufacturer.

If the vacuum drops when it fires you either have a inducer which is running too slow or a heat exchanger damaged from freezing. Usually inducers last at least 10 yrs and if you have not run it many hours then I doubt it is worn and slow.

You can buy a manometer for under $100 and it will cost you that or more to get a tech to drive out and do it for you plus the time he spends is extra.

 

[ben's plumbing]

that furnace was known for trap clogging.. remove the clear hose from base of exhaust pipe area and blow thru it.....see if its clogged there..