Is there any HVAC techs here?

[MACKIN]

I've been having this pain in the ass issue with my furnace driving me completely NUTS!!


I know enough to be dangerous and fix my own furnaces. This particular one is my home hot air furnace. I'm having a issue with the Blower. Unfortunately it is a solid state timer control with a separate high limit control not the mechanical fan control high limit switch which is super easy to diagnose.

The thermostat calls for heat burner will fire, heat up the exchanger then the blower will come on in 2-3 minutes run ,thermostat will no longer call for heat ,burner shuts down ,fan runs for an additional 5 mins or so and shut down.

Sounds right so whats the problem?

Well like this, it's a intermediate problem. It will run fine for awhile (maybe 24 hrs) and then the furnace will fire heat up and shut down on the high limit and never will the blower run! It will continue to do this until I manually turn on the blower at the thermostat. And fiddle with the temp at the thermostat until the burner quits firing.

Obvious fix is to replace the timer. Did so and it's STILL doing it!!!

What I did at this point is change the blower speed from med high to high to see if there is a issue with that speed ,med hi.

Let me back up here for one min. When ever I go to manual fan setting on the T-stat the blower immediately starts even before I changed the speed. So IMO there is nothing wrong with the blower motor. Also when I switch to COOL or AC the blower also fires which that is high speed anyway.

Ok so where I'm at at the moment (blower is wired high speed) is now the T-stat calls for heat ,burner fires ,blower starts as it should and runs then after I guess a normal cycle shuts down and the furnace is still running as the T-stat is still calling for heat! From what I can tell so far it does NOT shut down off the high limit but T-stat not calling for heat.

I adjust temp on T-stat so it wont call for heat burner shuts down but fan never runs to cool off the exchanger! I have to manually switch over the fan at the T-stat to cool off the exchanger!

WTF is going on? IMO the blower should NOT shut down until the burner shuts down and it runs it's normal timed cycle!

Do you think I have a defective NEW timer? Or what?

There is no way it's timed to shut down on a predetermined cycle as there is no way of knowing the length of time the T-stat will call for heat. The timer has to be set or timed AFTER the burner shuts down then t runs for a predetermined length of time to cool exchanger. Man I wish it had a mechanical high limit fan control.

The furnace is pretty old (19 years) but I burn wood so maybe I run a tank of fuel through it every year so there is no real hours on it. Parts are a bit of a issue. I'm not gonna replace the furnace because of this either!

Heres a link to what the timer looks like. Timer was bought at a local supply house not E-bay.

http://www.ebay.com/itm/New-ICP-Hei...-HQ-Control-Board-HQ-1005229-WA-/190632576194



HELP!!!!

 

[MACKIN]

I'm assuming the adjustment pot is for turn on not turn off. So I have not touched that

150/200 seconds is a short period of time that is why I assume that. If that is what it represents, timed seconds?




I also found that this is the recommended replacement. What I have is exactly what is pictured in the link above post.

http://www.patriot-supply.com/products/showitem.cfm/25576

 

[blk smoke lb7]

I just had a problem similar to this and replaced all the parts in my furnace and come to find out it was the thermostate F'n with me never had a problem after that.It was even a Honeywell t stat which are suposed to be better

 

[MACKIN]

Ya know I thought that also. I have one of those seven day programmable ones and don't really use it as someone is home all day anyway. Only use it if we go away which is far and few between lately.

I was gonna try that think I might at this point. Mine is a Honeywell also

The reason I thought it might be it is sometimes ,of course it's when I'm having issues,is when I turn the T-stat down in temp it seems like it doesn't. Of course if it kicks out on the high limit not sure IF the T-stat is effective as it might have to cycle through the high limit shut off.

This is where my limits of HVAC come into play.

When you say similar can you describe?

 

[MACKIN]

That's it no HVAC techs here?

 

[KEVINL]

Sounds like possibly a thermostat issue does the unit actually have a control board or just a delay relay for the fan.

You could take the green wire from the t stat and connect it to the white for heat If it works normally the thermostat may be at fault.

If you have a Make and model # I could probably be of more help

 

[TheBac]

As silly as this sounds, when was the last time you changed out the batteries in your thermostat? I have a Honeywell programmable, and I forgot to change the batts out one year (I usually do at DST changes) and my furnace just wouldnt work right that winter til I did.

 

[camomax]

Damn man, just saw this. Feel free to call me, and I'll walk ya through it. 614.315.6910

 

[MACKIN]

Tom not silly at all but that was the first thing I did was change the batteries. No luck


Matt appreciate it thing is the darn thing does it intermediately. So what I'll do is IF it does it at a reasonable time and day I'll take you up on your offer!


I think what I'm going to do is buy a new T-Stat without the bells and whistles or less bells and whistles and then give it a try. Also I might for $23 bucks buy the so called replacement timer.

http://www.patriot-supply.com/products/showitem.cfm/RHEEM_47_102686_81


Looks totally different but it is the replacement part . Perhaps it's new and improved. I paid $60 for the current one an this one is cheaper. First the T-stat. I hate throwing parts at things.

Winter is over but I still need to fix it. Thanks for the info if anyone else thinks of anything feel free to chime in

Thanks

 

[TheBac]

Call Matt first before throwing more money at possibles, Mac. Its tougher to explain the problem on a forum than it is to actually talk to someone.

 

[MACKIN]

I'm assuming that it needs to be screwing up to diagnose?

Heres what it did at 5 AM this morning. I don't leave it on at night as I don't trust it.

It was 64 degrees in the house T-stat set at 68 degrees. Threw the E-switch on ,burner fired 30 seconds or so the blower fired up. Ran for I don't know 15 20 mins burner shut down fan ran until timer kicked out which DID satisfy the proper cooling of heat exchanger ,in other words NORMAL.

Then about 1/2 hour or so burner fired again blower fan came on as it should. Then I don't know exactly when but burner continued to run but the blower fan shut down while the burner was still running!!!!! Not suppose to do that !!!!

Then burner shut down. I didn't check to see if it went out on the high limit but I don't believe so as I went and turned the T-stat down to 65 degrees and put the blower on manual to cool off the heat exchanger and the burner did NOT fire back up like it has done in the past when it goes out on the high limit. Cooled of the heat exchanger dumped the e-switch went to work.

So having this happen makes me rethink a T-Stat but back to a faulty Timer OR what drops line voltage from 110 to 24 volts that activates the timer. Funny thing is prior to changing the Timer and changing the timer it would run say for 24 hrs with out issue then act up. NOW since the timer has been changed EXCEPT for the first day it was changed (that day it ran fine for a day and a half with no issues) it seems that the very first run cycle it is fine and dandy and then on the second calling of heat it screws up if that makes any sense.

So I believe that why I need to do is when the Blower stops and the burner keeps running check the 24 volt side and see if the voltage drops out ??? I think anyway

Almost like something heats up temp wise and quits working. Like say a transformer?

Problem is I don't which pins are 24V on the timer.

I'm no exspurt . The flea Bay one (link) is the one I have . There is a diagram sort-of on the replacement one. Anyone have a clue? I assume the way it works is burner fires ,sends from transformer (?) 24v to timer ,timer (relay) switches at designated time to 110V to fire Blower. Then Burner drops out Timer has another timed event to drop 110V to blower. Sound right?

I don't believe it's the capacitor (blower fan speed control) or blower motor as it does it on med-high and high speed and the blower always starts manually also on the AC side.

Talking out loud

 

[MACKIN]

Is it C & R in this picture?


http://www.ebay.com/itm/New-ICP-Hei...-HQ-Control-Board-HQ-1005229-WA-/190632576194

Com and N O (normally open) 110V and what is G?

 

[tinman22]

G should be for the fan.
R usually denotes the 24 volt signal wire
W is usually for heat
G is for fan ( blower motor) control
Y is usually for AC condenser
C is common. for if a T stat uses 24 volt instead of battery power.

so if you take wires of stat and touch the R wire and the G wire. your blower should come on. but not the heat or ac. basically just be a fan

 

[MACKIN]

Have a friend of a friend who is a HVAC Tech stopping by tonight hopefully we can figure it out!! So I didn't bother messing with it last night and go figure didn't screw up once. I so hate intermediate issues.

Now you know what service departments go through when they say cannot repeat cannot duplicate issue to diagnose. PITA

Thanks for the assist feel free to add anything as it aint over till its fixed. I have my doubts.

 

[MACKIN]

He came he looked was stumped as I as it was operating normally,said timer was obvious place to start. Then while burner was running he pulled the t-stat wire off the control and burner kept running.

He tapped on some relay adjacent to the t-stat control and burner would quit. So he believes that this relay is was sticking and swapped it out. No idea what the relay is he explained it ,what it's suppose to do,made sence that it could be the issue.

We shall see, hope so!