What temperatures are normal in this area of my furnace?


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Old 11-17-14, 05:43 PM
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What temperatures are normal in this area of my furnace?

Please see the attached picture and pay attention to the "temperature dial" in the inset

With the current settings the gas burner cycles like this

-limit temperature 200F
-at that temperature the burner shuts off and the furnace is cooling off to around 150F in about 35 seconds
From there the burner starts again and it the temperature goes up in about 1min

The temperatures in the circled area are the highest in the area but stable. I am not sure how hot these should normally be. I just fixed a problem with the control module and in the process I think I played too much with the fan/load control switch. I am trying to guess if everything is back to normal
 
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Old 11-17-14, 06:52 PM
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If your furnace is hitting the high heat point of 200° and shutting down the burner then it sounds like you have an air movement problem. Possibly a dirty filter, fan running too slow, too many registers closed off.
 
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Old 11-17-14, 07:35 PM
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Thanks PJMax

Should I understand that the burner should never shut off before the set temperature (set on the thermostat is reached) ?


I don't quite get it... then what is the point of the whole thing. I thought that the burner going on and off saves gas and makes sure the furnace does not burn more gas than the system is able to send into the house at an optimal temperature

Right now the limit point is set under 200 because I did not know what is right. I have seen some youtube videos that show the limit set to 200. I might have to adjust the on and off temperature for the fan but I never understood that the limit point should be reached.
Check this video out
https://www.youtube.com/watch?v=QpHfFdk04u0
 
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Old 11-17-14, 07:49 PM
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Is there a particular reason why you are adjusting the fan/limit switch ? Normally they are set when the furnace is built and there is no need to change the adjustments.

If the limit control did not shut the burner off at or around 200° the heat exchanger would have a melt down. Under normal furnace operation the furnace should not reach 200°. If it does it means you are not moving enough air thru the heat exchanger.

When the furnace is installed.... the heating fan speed is set to move the required amount of air thru the furnace to keep the heat rise constant. If the fan speed has been changed, if the A/C coil is clogged, if the filter is clogged, etc. .... the air movement is reduced and the furnace overheats.
 
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Old 11-17-14, 08:08 PM
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I had lots of problems with it
This is a This is about an old UltraMax Olsen HCS2 81AD gas furnace .
It used to vibrate heavily and I somehow managed to clean the dirt that was inside the fan motor and now it does not vibrate anymore.

It also got to the point where it did not work anymore. It was doing like in this movie
https://www.youtube.com/watch?v=-D7vcKfUujM We tried to fix it and we came to the conclusion that the main gas valve was not getting its 25V to open. We suspect it is the controller. Since then we run a wire from the relay to the 25V of the gas valve and now the burner turns on and it seems ok. I have ordered a new controller, I will get it Thursday. I am now monitoring the furnace closely

Here is the wiring diagram. So now it is back to almost normal excepting this overheating

 
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Old 11-17-14, 08:37 PM
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In that video you have a pilot problem. The spark lights the pilot and the pilot lights the main burner. If the pilot is not a full sized flame.... the main valve won't open and it will keep trying to re-ignite.
 
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Old 11-17-14, 08:46 PM
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I already ordered a new one:
http://www.amazon.com/Honeywell-S861..._eetyp_p_img_1

I hope to survive till Thurday when I am going to get it.
Till then I am going to watch the furnace every minute till it brings the temperature to what we need

How do I solve the airflow/cooling problem!!??
I was told on other sites that I need to clean the AC coil and there is a secondary coil below the burners and above the fun. I was told that I need to remove the fan ..will that be difficult ??
 
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Old 11-17-14, 08:51 PM
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Yes... it can be a real challenge to clean the A/C coils. I'm not familiar with your unit so I don't know how difficult the blower removal will be.

I take it that there is very little air coming out of the registers ?
 
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Old 11-17-14, 09:00 PM
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That is not true. A lot of air comes out of the registers. I just don't know what is normal to be.
Donwstairs in one of the registers it is actually quite a lot of air coming out. Something like when you remove the cap from an air bed, the camping ones

Now if I think twice upstairs the air flow is weaker, I am not sure if we did something or it is unchanged...I can not say.

However if you put a piece of paper in front of them it is moving. The living has two ..the airflow is strong enough to move the curtains lightly and the leaves of two plants that sit above 1,5ft
 
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Old 11-17-14, 09:10 PM
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A friend of mine who helped me with all these played with this lever



The picture that you see is taken from the side that is opposite to the side where the burners are
So as you look at the burners on your left side above the solder you see this, just above the line where the furnace joins the tin

The yellow arrow indicates a zoom in. That lever has two positions, winter and summer. I put it back to winter but that did not change much
 
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Old 11-18-14, 04:27 AM
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Hmm ...I had a second look at what is going on with my registers and I realized that in fact downstairs out of 4 vents only one has a decent and very strong air flow. It is the strongest in the whole house. That means that there is something blocking the air ducts and I need to see what.
Initially I suspected that is must be the secondary exchanger as someone suggested
I will have to see what is going on when I get back home...
 
 

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