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Heath
Heath, HVAC Technician
Category: HVAC
Satisfied Customers: 1034
Experience:  11 yrs. comm.resid. service, Type III Cert.
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Armstrong Air-Ultra 80 Oil Furnace, model LBR80C84/95D16-1A furnace

Customer Question

Armstrong Air-Ultra 80 Oil Furnace, model LBR80C84/95D16-1A
furnace would not do anything found the control transformer was not working (open secondary coil). There are 5 terminals on secondary of the transformer but only 2 were used. 4 wires total going to the transformer. Was able to obtain a generic 120 VAC to 24 VAC transformer. When it was installed all the furnace would do was to start the blower when the power was apllied. The blower continued to run and nothing else happened. The circuit looks like it is doing just what it sould. Main power goes to the relay, secondary goes to the relay and the relay contact closes starting the blower. I can not understand how anything else can happen. There most be some function of the relay or the blower that I am not aware of. I worked 35 years as a factory electrician in a foundry and I have seen a lot of furnaces but I don't know what is going on here.
Submitted: 4 years ago.
Category: HVAC
Expert:  Heath replied 4 years ago.
Chat Conversation Started
Heath :

Hello my name is XXXXX XXXXX will be my pleasure to assist you. By blower do you mean the furnace blower or the blower in the gun itself?

Customer :

furnace blower

Heath :

Okay if you turned the power off to change the transformer if maybe going through a prepurge cycle where the blower will run for 90 seconds before trying to ignite the furnace. Let it go through the 90 second prepurge and see if it will try to reignite

Customer :

ran the blower for 4 minutes and it kept running

Heath :

Okay if you go to the thermostat is the fan switch set to auto or on?

Customer :

thermostat was off

Heath :

Is there a white knob sticking out of the fan limit?

Customer :

I am working with my son over the phone , so there will be some delay sorry no white nob

Heath :

Is this a honeywell fan limit with a silver cover over it/ If so pop the cover off and try turning the dial by hand to see if the fan shuts down when the dial is truned down.

Customer :

the switch did not stop the blower, having him run it for 90 seconds and try it again

Customer :

after 90 seconds blower still running

Heath :

Something is wrong in the wiring do the thermostat wiores connect directly to the transformer?

Customer :

the termostat wires (2 only) go to the primary control

Customer :

the furnace was running with this arrangement

Customer :

the original arrangement there was only 2 wires on the secondary of the transformer and they went dirrectly to the relay

Customer :

I said the original arrangement , it still that way I have not changed any of the wiring

Heath :

Just the two wires from the transformer to the relay

Customer :

yes there were only 2 wires on secondary

Heath :

They go to the relay?

Heath :

Switch the wires from the secondary side of the transformer to the relay swap them put one to the other.

Customer :

yes I can trace them very easily

Heath :

The ones you hooked up swap them

Heath :

The ones on the secondary side.

Customer :

we swapped the wires last night but I'm not sure if we ran it for 90 seconds in both con figurations we are switching them now

Heath :

okay

Customer :

my son switched the wires and the fan is still running after 2 min. with no burner attempt

Heath :

I will have to opt out I can picture the thing or find the schemtic sorry.

Customer :

I'm going to try to get some dinner but I will keep an eye on the screen as best I can might be some delay

Heath, HVAC Technician
Category: HVAC
Satisfied Customers: 1034
Experience: 11 yrs. comm.resid. service, Type III Cert.
Heath and 4 other HVAC Specialists are ready to help you
Expert:  Billy replied 4 years ago.
I think there is some confusion as to the connections....I need you to take the thermostat off the wall and tell me what wires you have on what terminals...then we can go from there
Customer: replied 4 years ago.

red wire on Rh terminal , white on the W terminal on the thermostat

on the primary control red to T , white to 3/T

Expert:  Billy replied 4 years ago.
So this unit is heat only...no ac?
Customer: replied 4 years ago.
no ac
Expert:  Billy replied 4 years ago.

The transformer you replaced....are you referring to the oil primary control that has T and T and F and F?

Customer: replied 4 years ago.
the transf. we replaced has a blk & wh wire for the primary on the secondary it had 5 terminals Y,G,W,R & C the only ones used were the G and C terminals. The transformer for the 24 VAC control voltage
Expert:  Billy replied 4 years ago.

Here is the confusion....

On the furnace we have T and T which start the burner...furnace heats up...a heat switch makes contact and the blower kicks on.

 

On the thermostat Rh is 24v from one of the T's...and the W on the thermostat is the return back from the thermostat to the other T.

 

You say you have a added transformer..but it works as a fan center for blower only. But you do not have G hooked up at the thermostat.....so the question is.....does the G wire go to a summer or blower switch?

The fan center is installed for when ac is added to a oil burner. Then a wire also runs from R on fan center to Rc on thermostat...and a wire to Y which turns on outdoor ac unit....and G which turns on circulation fan only.

Customer: replied 4 years ago.

the furnace has no AC with it, at the start nothing would come on , trouble shooting I discovered there was no 24 VAC coming from the control transformer ,(open secondary winding). orginal transf. had a blk. and wh. leads for the primary and 5 terminals on the secondary, primary wired to incoming 120VAC, secondary from terminals G and C went directly to the relay that controls the fan that blows heat thur the house. contacts on this relay NO blk. 120VAC feed to blk to the fan, NC blue from the fan and limit switch to blue to the fan. I did not find a transf. like the orginal, I used a generic transf. that is 120VAC and 24VAC out. Because the original had just 2 wires in and 2 wires out I thought this would do the job.

The thermostat has only 2 wires red from terminal Rh goes to T on primary controler white from terminal W goes to 3/T on the primary controler. The furnace was running when it stop and had run for at least 2 years. I did not add anything or change anything. All I did was replace the transformer as described above. Now when I turn on the power the fan starts and continues to run and nothing else happens. The way the wiring is I don,t understand what is not happening or what sould happen to get to function correctly.

 

Expert:  Billy replied 4 years ago.
Ok...the G terminal on the transformer relay...where does it come from?

I hope I am not confusing the issue...but the furnace should run simply from the T and T terminals...nothing else is needed. The fan turns on when the heat exchanger heats up. The only reason for having the transformer relay is if you wanted to run the fan continuous without running heat.
Customer: replied 4 years ago.
G terminal on the transf. goes to the coil on relay and terminal C on the transf. goes to the other side of the coil on the relay. My son scanned the schematic form the Insallation Instruction into his computer and Emailed to me, if I had an email address I could email it to you.
Expert:  Billy replied 4 years ago.

You can attach using the small tree icon at the top of the dialog box.

Customer: replied 4 years ago.

Attachments are only available to registered users.

Register Here
Expert:  Billy replied 4 years ago.
I am sorry but the graphic did not attach. Do you have the part schematic or furnace schematic. Also....if you unattach the G wire...and turn the thermostat to heat and up..what happens?
Customer: replied 4 years ago.
I am not located where the furnace is now and no one is there to do what you ask

Attachments are only available to registered users.

Register Here
Expert:  Billy replied 4 years ago.

 

Is the schematic from the furnace or from the part?

You see the only reason I am still perplexed is the control with T and T where the thermostat wires are attached has its own transformer inside. This is responsible for the furnace operation. Then the fan/ limit kicks on the blower when heat builds up.

Thus if there is no fan switch or ac...there is no need for the transformer with the G and C since the only function of that control is turn on the blower manually instead of with heat build up.

That makes the new transformer redundant and doing nothing if there is not a fan switch.

 

If furnace only...T and T on the primary control is all that is needed.

Customer: replied 4 years ago.

Attachments are only available to registered users.

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Attachments are only available to registered users.

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tried again to attach that file with the schematic and it was in the book that came with the furnace , my son just got home ,he is going to pull off the wire from the G terminal and try the furnace
Expert:  Billy replied 4 years ago.
What was result of G wire pulled?
Customer: replied 4 years ago.

When I pulled off the G wire the blower did not come on but the furnace didn't start. Apparently when someone wired this furnace the transformer was no good or they destroyed it some how and that allowed them to start the furnace. I attempted to start the furnace with G disconnected. Nothing happened , 120VAC on L1 , 24VAC across T and T/3, on the primary controller, I pulled the oil nozzle igniter assemble and cleaned it looked good, while investagating I discovered that as I lifted the cover,( where the cad cell and the connections for the igniter are mounted). the green light on the primary contoller would come, it just dawned on me now it was probably the cad cell picking up the flourescent light hanging in the panel, the question is what do I do (check) next to see why it won't start when there is 24 VAC coming from thermostat and 120VAC coming from the fan limit switch

Expert:  Billy replied 4 years ago.

 

Unhook the cad cell wire from F (either one)....then see if unit starts...if you have 24 v between T and T.....then you should be able to directly jump T and T which bypasses the thermostat. Also just in case.....hold the oil primary reset button down for 30 seconds in case in hard lock out. Unhooking the cad cell makes the primary think it is ok (dark) but then you only have so much time to either jump F and F together or reattach cad cell wire and hope cad cell is ok.

Customer: replied 4 years ago.
thank you for your help I will have to try that tomorrow I'm not at the furnace now, sorry for all the delays , the computer I contacted you on is in my home and the furnace is in my sons home , I tried contacting you with my sons computer but it didn't get me where I needed to be, were you able to down load the schematic, if you are going to be on I'll get back to you tomorrow, thanks again
Expert:  Billy replied 4 years ago.

I was not able to see the diagram. There must be a glitch. However I am very familiar with the oil furnace wiring and operation and am confident we can make headway. Lets run the test I mentioned and then go from there.

 

Thanks for your patience!

 

 

Customer: replied 4 years ago.
The cad cell was picking up the ambient light light causing the green (flame on) light to come on. I covered and uncovered the cad cell and the light responded as it should. But the furnace still didn't start , there was still 24VAC on terminals T and T/3 and I thought that was all that was necessary but I better jumper it to be sure. Lo and behold the furnace started right up I let it run for a few minutes then pulled the jumper. My son is replacing the new electronic thermostat with the old one he replaced and see how that works. The wire is small solid wire and very easily broken. It may just be the wire. Thank You for all the help. I think we can take it from here. I will accept and if I have another problem I hope I get you again.
Expert:  Billy replied 4 years ago.

That is excellent news...I am very glad you were persistent and stuck with it. Well done!

 

 

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