Any HVAC experts in here?

XXVoid MainXX
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XXVoid MainXX
Edited Date/Time 10/4/2015 4:30pm
The fan isn't kicking on in my electrimicated furnace when the fan is set to "auto" on the thermosticat. If I turn the fan to "on" it works and I will get heat until the selected tempermature is reached, but of course the fan continues to run in the "on" position. I notice when I set it to auto and increase the desired tempermature a couple of degrees I do feel the duct above the heater get a bit warm, but the fan doesn't kick on. I assume there is a thermal safety gadget in there to keep it from getting too hot without the fan blowing. Ideas on how to troubleshoot? I took a picture of the schematics posted on the side of the heater if that will help. I'm decent with flipping breakers and using a multimeter, etc. I assume there is some sort of thermal relay that should detect the heat and turn on the blower, but am not sure. Here's the schematic:



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XXVoid MainXX
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XXVoid MainXX 10/12/2014 9:07am
10/12/2014 9:07am Edited Date/Time 10/12/2014 9:07am
A little more investimigation makes me think I should look toward the limit switches?
Old-Man
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Old-Man 10/12/2014 9:15am
10/12/2014 9:15am
I'm no HVAC guy by any means but I had a similar problem couple winters ago.
I had just changed the filter and the fan wasn't turning on...Come to find out I put the cover back on wrong and the safety switch wasn't engaged. I pulled the cover back off then put it back on correctly and it worked fine.



XXVoid MainXX
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XXVoid MainXX 10/12/2014 9:30am
10/12/2014 9:30am Edited Date/Time 10/12/2014 10:16am
Thanks! Mine actually works with the cover off or on (no cover switch), and the fan does work, but just not in auto mode. Now I'm thinking it could also be a sequencer, but I think most likely the limit switch. They both look easy to trouble-shoot. Going to check them now, hope I don't let the smoke out!
borg
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borg 10/12/2014 11:00am
10/12/2014 11:00am
I think you are looking in the right direction Void. Anything with coils (relays) and or contacts (relays, limit switches) are prime suspects. The symbols in the motor relay are confusing as they are the symbols normally used for capacitors but are clearly contacts. One normally open and the other normally closed. The sequencers are black boxes but it would be sequencer 1 that controls the blower motor I believe.

The Shop

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XXVoid MainXX
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XXVoid MainXX 10/12/2014 11:04am
10/12/2014 11:04am
So here's what I found out so far and I am not sure if it means anything at all, but I checked the limit switches. With power off and cool they all show closed. I hooked up my meter and turned power on and called for heat and the heater coils heat up and the top 2 limit switches click and let 240v through. The bottom limit switch doesn't seem to do anything. Again, not sure if that means the bottom one is bad or if it's not getting enough heat to make it work. Thoughts? It looks like if it does switch properly it would supply power to sequencer #2.
Foghorn
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Foghorn 10/12/2014 11:06am
10/12/2014 11:06am Edited Date/Time 10/12/2014 11:10am
It's a series circuit so relatively easy to check your limit switches and other components for continuity with a multi-meter.
500guy
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500guy 10/12/2014 11:33am
10/12/2014 11:33am
Does the Fan work in Auto with The A/C on ? if it does then it's a Heater issue, if it doesn't maybe it's the Auto side of the thermostat ?

XXVoid MainXX
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XXVoid MainXX 10/12/2014 11:50am
10/12/2014 11:50am Edited Date/Time 10/12/2014 11:54am
Okay, so I might have more pieces of the puzzle. I noticed all 3 limit switches are the same part number so I just swapped the bottom one with the middle one. I turned the power on and the fan starts running. I turned the call for heat down and it shut off. It seems to be working properly now but I have to think that the middle limit switch is now suspect. But what is the purpose of that middle one if everything seems to be working? Also I made an incorrect statement previously. When cold the limit switches are closed and allow voltage through. When hot they are open. I ohmed the two out that I pulled out and they seemed to have continuity until I pushed the back of them in and they both seemed to behave exactly alike. Maybe the switches weren't the problem at all any maybe I just jiggled something in there futzing with it and make it start working? Smile
Old-Man
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Old-Man 10/12/2014 11:54am
10/12/2014 11:54am
Does the furnace run properly all the way though the cycle? (Fan keeps blowing after the flames shut down)
and though the AC cycle as well?
XXVoid MainXX
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XXVoid MainXX 10/12/2014 11:55am
10/12/2014 11:55am Edited Date/Time 10/12/2014 11:56am
It's electric so no flames (hopefully) but I guess the only way to tell that would be to check the voltage and the appropriate places to see if what you are asking is true. I'm not exactly sure how to check, but I *think* it's working properly now.
XXVoid MainXX
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XXVoid MainXX 10/12/2014 12:54pm
10/12/2014 12:54pm
So I punched the part number (HQ1056848TD) from my limit switches into google and only 2 hits came up, out of stock in both places. But, the second link yields a little extra info about them:

http://surpluscityliquidators.com/view_product/24182/

If I punch "LIMIT SWITCH:L175-40F" into google I get a bunch of switches I bet would work in their place. For example, this little guy:

http://www.amazon.com/dp/B00IDFED0C/ref=asc_df_B00IDFED0C3351253

Cygnus
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Cygnus 10/12/2014 2:37pm
10/12/2014 2:37pm
Electric furnace? Get a fire place. Problem solved. I turned my 12k furnace off a few years ago. $ 500 a month was crazy for heat.
Cygnus
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Cygnus 10/12/2014 2:40pm
10/12/2014 2:40pm
I have a fire going now. It went from summer to winter here. I miss fall.
XXVoid MainXX
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XXVoid MainXX 10/12/2014 5:19pm
10/12/2014 5:19pm Edited Date/Time 10/12/2014 5:20pm
Doing more research the lights are starting to come on. I don't think there is any way that the limit switches could have been the problem. So, now I'm not sure why it started working. The limit switches should only turn power off to the heating elements if it gets too hot, because fan is not blowing, or low air flow because of clogged filter etc.
XXVoid MainXX
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XXVoid MainXX 10/12/2014 5:46pm
10/12/2014 5:46pm
500guy wrote:
Does the Fan work in Auto with The A/C on ? if it does then it's a Heater issue, if it doesn't maybe it's the Auto...
Does the Fan work in Auto with The A/C on ? if it does then it's a Heater issue, if it doesn't maybe it's the Auto side of the thermostat ?

Now that you mention it I recall at the beginning of the year when I first went to turn on my AC the fan wasn't working. I called my AC guy and when I went to show him what it was doing the sun of a buck worked just fine. So, I do believe it's common for both AC and heat and it seems to be intermittent.
markit
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markit 10/12/2014 8:25pm
10/12/2014 8:25pm Edited Date/Time 10/12/2014 8:31pm
Replace the fan relay and the Sequencer it;s one of the two. The heat part of the fan works on a time delay, the sequencer is a time delay switch. So if your getting 24v to the coil the contacts will (if working correctly should) close on delay. The high limits are ok, there in case the fan does not come on and cycle the heat strips (limit) to keep the unit from overheating.
SEEMEFIRST
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SEEMEFIRST 10/12/2014 10:55pm
10/12/2014 10:55pm Edited Date/Time 10/12/2014 10:57pm
Mine was a bad motor starter (Capacitor). It would work sometimes, and not others. Once summer hit, it quit altogether.

But this guy ^^^ seems to know what goes where, when.

Pit Row

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XXVoid MainXX
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XXVoid MainXX 10/13/2014 6:31am
10/13/2014 6:31am
Okay, I'll get the part numbers off the relay and sequencers and start shopping. Thanks!
markit
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markit 10/13/2014 9:35pm
10/13/2014 9:35pm
SEEMEFIRST wrote:
Mine was a bad motor starter (Capacitor). It would work sometimes, and not others. Once summer hit, it quit altogether. But this guy ^^^ seems to...
Mine was a bad motor starter (Capacitor). It would work sometimes, and not others. Once summer hit, it quit altogether.

But this guy ^^^ seems to know what goes where, when.
A bad cap will reduce motor torque anyone time the motion r is on cool and heat settings
lostboy819
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lostboy819 10/13/2014 9:44pm
10/13/2014 9:44pm Edited Date/Time 10/13/2014 9:45pm
XXVoid MainXX wrote:
I'm way too lazy for a fire place. Smile
Pellet stove is the answer, dump 40 lbs of pellets in it and you are good to go. I run mine off and on and a bag will last several days at $4 a bag and there is no heat loss up a chimney or hauling or cutting wood. I rarley run it at night but fire it up in the morning and its warm in 15-20 mins. It cut our gas bill by 60% in the winter. Still run the furnace but it is set to come on at 62 degrees.
markit
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markit 10/13/2014 9:53pm
10/13/2014 9:53pm
SEEMEFIRST wrote:
Mine was a bad motor starter (Capacitor). It would work sometimes, and not others. Once summer hit, it quit altogether. But this guy ^^^ seems to...
Mine was a bad motor starter (Capacitor). It would work sometimes, and not others. Once summer hit, it quit altogether.

But this guy ^^^ seems to know what goes where, when.
Yea Lol Elect & hvac from 1980.... To long
oshow
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oshow 10/13/2014 11:15pm
10/13/2014 11:15pm
XXVoid MainXX wrote:
I'm way too lazy for a fire place. Smile
lostboy819 wrote:
Pellet stove is the answer, dump 40 lbs of pellets in it and you are good to go. I run mine off and on and a...
Pellet stove is the answer, dump 40 lbs of pellets in it and you are good to go. I run mine off and on and a bag will last several days at $4 a bag and there is no heat loss up a chimney or hauling or cutting wood. I rarley run it at night but fire it up in the morning and its warm in 15-20 mins. It cut our gas bill by 60% in the winter. Still run the furnace but it is set to come on at 62 degrees.
What kind of pellets do you burn?
CR250Rider
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CR250Rider 10/13/2014 11:55pm
10/13/2014 11:55pm
Have you followed the power on the white thermostat wire through sequencer2?
Have you measured the resistance on all the heating elements?

I like to just turn the device on and start following signal power until it stops.

you got this!
lostboy819
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lostboy819 10/14/2014 5:26am
10/14/2014 5:26am
XXVoid MainXX wrote:
I'm way too lazy for a fire place. Smile
lostboy819 wrote:
Pellet stove is the answer, dump 40 lbs of pellets in it and you are good to go. I run mine off and on and a...
Pellet stove is the answer, dump 40 lbs of pellets in it and you are good to go. I run mine off and on and a bag will last several days at $4 a bag and there is no heat loss up a chimney or hauling or cutting wood. I rarley run it at night but fire it up in the morning and its warm in 15-20 mins. It cut our gas bill by 60% in the winter. Still run the furnace but it is set to come on at 62 degrees.
oshow wrote:
What kind of pellets do you burn?
I buy what ever they have at my local lowes.I have burned several different brands and have not noticed any difference in how any of them burn.
markit
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markit 10/14/2014 8:37am
10/14/2014 8:37am
lostboy819 wrote:
Pellet stove is the answer, dump 40 lbs of pellets in it and you are good to go. I run mine off and on and a...
Pellet stove is the answer, dump 40 lbs of pellets in it and you are good to go. I run mine off and on and a bag will last several days at $4 a bag and there is no heat loss up a chimney or hauling or cutting wood. I rarley run it at night but fire it up in the morning and its warm in 15-20 mins. It cut our gas bill by 60% in the winter. Still run the furnace but it is set to come on at 62 degrees.
oshow wrote:
What kind of pellets do you burn?
lostboy819 wrote:
I buy what ever they have at my local lowes.I have burned several different brands and have not noticed any difference in how any of them...
I buy what ever they have at my local lowes.I have burned several different brands and have not noticed any difference in how any of them burn.
Sounds interesting, I have a wood burning stove in my camp. I'm going to give this a look see. Only thing is live in the LA swamps an any large stores are 45+ mi away.
markit
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markit 10/14/2014 8:48am
10/14/2014 8:48am
CR250Rider wrote:
Have you followed the power on the white thermostat wire through sequencer2? Have you measured the resistance on all the heating elements? I like to just...
Have you followed the power on the white thermostat wire through sequencer2?
Have you measured the resistance on all the heating elements?

I like to just turn the device on and start following signal power until it stops.

you got this!
I would never advise a non qualified person to live test a heating system. It would be better to ohm the system out with power off but this is still a more in depth method than i would be willing to advise to a non tech. The Fan relay and Sequencer is one of the most common calls on a electric heating system and also the no fan on heat with the heating elements clicking in and out on limit pre much puts a nail in it.
XXVoid MainXX
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XXVoid MainXX 10/14/2014 11:11am
10/14/2014 11:11am
Yeah, had already live tested it before any comments on the subject and of course it all checks out fine when it's working properly which it is now. It appears to be an intermittent issue. I figure I can order a sequencer and a blower relay and have them on hand for when one or both of them finally do go again and just replace them. They're not that expensive.
racin mason
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racin mason 10/14/2014 7:05pm
10/14/2014 7:05pm
Not trying to be a smartass here, but maybe that shit was only supposed to last 22 years......

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