Question regarding my Amana Propane furnace

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I have an Amana AMH95 (Model # AMH950703BX).
Installed in January 2007.

Just a quick question regarding its operation.

If we go away for the weekend, I set the thermostat at 55 degrees.
When I return home, I raise the setting to 68 degrees.
The furnace will kick on.

But, it doesn't run constantly until it has reached 68 degrees.
Meaning it will run for a while, then kick off for a few minutes or so, then kick back on.

So, my question is this:

When the furnace is trying to get to the set temperature, should it run constantly until it gets to the set temperature or is it normal for the unit to cycle on/off occasionally as it is trying to reach the desired temperature?

Thanks.
mike
 

Jadnashua

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Many, not all, heating plants have a max run-timer in them. They'll shut down for a few minutes and won't allow 100% max output it it exceeds a certain time to prevent overheating of the components. It could be normal. You'd have to read the manual on yours.
 

MaintenanceMan

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Does everything shut off or does the blower stay running and then the burners shut off periodically?

Everything shutting off sounds like it could be the anticipator in the T-stat set wrong (if you have a non-digital t-stat) or maybe a furnace that is short cycling due to being oversized.
 

Jimbo

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Depending on where the thermostat is located, for example if it gets some direct draft from a supply register, it may see set-point temp before the room temp actually equalizes
 

hj

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furnace

The fan switch will turn the blower on when the temperature rises and shut it off when it drops below a certain point. Normally the start point is fairly high so it only blows warm air once the unit is hot. BUT, if the turn on point is fairly low, the blower will start almost immediately, but then the incoming cold air will cool it down to the point where the blower shuts off until the heat can build up again. This process will continue with longer and longer cycle times until the unit finally gets hot enough to overcome the cooling of the fresh air, or the air warms up enough so that it does not cause the cooling effect.
 

MaintenanceMan

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The fan switch will turn the blower on when the temperature rises and shut it off when it drops below a certain point. Normally the start point is fairly high so it only blows warm air once the unit is hot. BUT, if the turn on point is fairly low, the blower will start almost immediately, but then the incoming cold air will cool it down to the point where the blower shuts off until the heat can build up again. This process will continue with longer and longer cycle times until the unit finally gets hot enough to overcome the cooling of the fresh air, or the air warms up enough so that it does not cause the cooling effect.

I don't believe that's the problem with this particular furnace. I believe he has a 95% AFUE furnace that has a circuit board and thermal limits and not a fan switch/limit. I, of course, could be wrong.
 
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follow up....

I came home from work today.
Wife had already turned up the thermostat to the usual 68 degrees. She said the temperature on the thermostat when she came home read 62 degrees. (I turned the thermostat down to 55 degrees when I left the hose this morning).
I checked the thermostat. It read 66 degrees.
I ran downstairs to check the furnace.
It was off. completely off.....no blower....no nothing....and it hadn't yet reached the 68 degrees setting.
It kicked back on a few minutes later and then went to 68 degrees.

SO.....the furnace couldn't go from 62 degrees to 68 degrees without shutting down at least once.

so.....since everyone says this is not proper operation (that is, the furnace should run constantly until it reaches the set temperature), I will be calling the installer tomorrow.

i'll keep you posted.

UGH!
 

Jadnashua

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Do you have the manuals? They should have left them with you. If not, you can probably get them online. Have you read them?

Almost all heating devices have a max runtime, and, if called for heat that takes longer than that max, will shut down for a period. The length of that period depends on the design. It could be anywhere from a couple of minutes to 10-15 minutes.

You could have problems, but, as said earlier, it could be entirely normal.

The blower typically comes on when there is heat, so it would not stay on forever during the mandatory cool-down. Before you spend money on something that could be working properly, I highly suggest you actually read the manual. I know that is an anathma to many people, but hey...it's your money...you do what you want.

There are other reasons to short-cycle, and they've been discussed as well. If your thermostat is in the direct path of an air vent or some other draft, sitting maybe in the sun, or under a high-powered lamp, any or all of those could affect its ability to actually regulate the volume properly.
 
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Do you have the manuals? They should have left them with you. If not, you can probably get them online. Have you read them?

Almost all heating devices have a max runtime, and, if called for heat that takes longer than that max, will shut down for a period. The length of that period depends on the design. It could be anywhere from a couple of minutes to 10-15 minutes.

You could have problems, but, as said earlier, it could be entirely normal.

The blower typically comes on when there is heat, so it would not stay on forever during the mandatory cool-down. Before you spend money on something that could be working properly, I highly suggest you actually read the manual. I know that is an anathma to many people, but hey...it's your money...you do what you want.

There are other reasons to short-cycle, and they've been discussed as well. If your thermostat is in the direct path of an air vent or some other draft, sitting maybe in the sun, or under a high-powered lamp, any or all of those could affect its ability to actually regulate the volume properly.



I do have the manuals at home. I did review them when I first had the furnace installed. I will look over them tonight.
I tried calling Amana, but they said they only provide techincal support to installers/technicians. :confused: I may try to call them again today and hopefully get someone else on the phone to see if this is normal operation.

The thermostat is in the hallway on the main floor (it's a ranch).
It is not near a lamp nor in the sun.

The large grill (where the air returns to the furnace) is in the ceiling above it.
Do you think that could affect it? Are the thermostats that sensitive?

Is there a chance I need a new thermostat? The thermostat I am using is a Honeywell programmable type. It is the same one that was on the old furnace.

Thanks.
mike
 

MaintenanceMan

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By your description your t-stat is most likely in an ideal spot. It certainly could be a malfunction in the t-stat, but really all anyone can do here is pull at strings and theorize. Your HVAC guy should be able to line it out. It's gonna take some time with a voltmeter and some observation to figure this out.
 
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I just called Amana.....

they said the furnace should stay on continuously, especially when it is only going from 62 to 68 degrees.
They said it may cycle if the difference is larger, say going from 55 to 68.
 

Jadnashua

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WIthout knowing the heating requirements of the house, and the outside conditions, there is no way, IMHO, they can say that. The manual will say how long the thing will stay on at any one call for heat...that is a definite, whether your situation would reach that maximum is another thing entirely. If the heater is marginal, and the house isn't well insulated, will all play into how long it takes to recover. That amount of time it will stay on SHOULD be in the manual. If it stays on that long then shuts off for the specified time then automatically continues, it IS working as designed. Now, whether that is great for you is another issue entirely.

Many electronic thermostats indicate when they are actually calling for heat. WHen the system is off, regardless of what the temperature readout is, does it indicate it is calling for heat? If it isn't, the furnace is just doing what it is told. Does the thermostat have backup batteries? ARe they fresh? Are the leads' connections tight?
 

Hube

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Mike; You say the furnace will only run for a while then shut off for a few minutes. (Just how long is a while?... 3 minutes, 5 minutes ,15 minutes?The furnace burner, whether it's oil or gas, when called upon for heat by the T stat, should remain ON until the Tstat set point is reached. If the burner does shut off before reaching the set point, it usually indicates a tripping of the "hi-limit " control.(a safety feature). This tripping is generally caused by LACK of air flow due to a dirty filter or too LOW a fan speed, or other restrictions in the duct system. Usually, if it is the hi-limit tripping ,the burner will shut down for approx 4-6 minutes while the fan may still continue to operate normally.

Check the filter.
Make sure dampers/registers are mainly open.
IF, your furnace has an adjustable hi-limit, what is it set at?
 
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I installed a new thermostat (Honeywell Focus Pro 600 #TH6110D1005) last night, but before I did I ran the furnace on the old Honeywell stat to see what happened...
Here's what happened:

Got home.
Stat read 63 degree house temp.
Set the heat at 73 degrees and furnace fired up.
Took about 9 minutes to get to 64 degrees.
Approximately 20 minutes later, with the temp at 66 degrees, furnace shut off.
Blower ran for approximately 2:30 then the furnace was completely off.
Furnace fired up approximately 2 minutes later.
Furnace ran for approximately 29 minutes then turned off. Temp was 71 degrees.
Blower ran for approximately 2 minutes then furnace was completely off.
Furnace fired up about 1 minute 15 seconds later.
Furnace ran for approximately 10 minutes and then turned off. Temp at 71 degrees.
Blower ran for approximately 2 mim 30 seconds then furnace was completely off.
Furnace fired back up approximately 1 minute later.
73 degrees obtained some time later. (lost track of how long it ran to get from 71 degrees to 73.)

Each time the furnace shut down, I went downstairs and checked the peephole on the furnace to see if the little red light was blinking any codes. It wasn't.

So I then changed the stat and hopefully that will fix it. If not, then the installer will be coming out.

anyone have any thoughts on my problem??

thanks.
mike
 

Ian Gills

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Having just spent the last week working on my furnance, it could be anything. A high limit switch, bad air flow, a cracked heat exchanger (unlikely but dangerous), a dirty blower or filter, a worn gas valve (unlikely), the ignitor locking out, a vent damper going wrong, a dirty electrical connection, a bad or dirty flame sensor or simply nothing at all. So getting the installer out is a good call and, as I have found out, cheaper than going through all of the above both in time and parts.

My problem is short-cycling as well. My gas valve clicks every 15 minutes or so when the furnace is on. It does not shut off. You just see the flames turn down and then go back up again. I have tried everything to fix it and have given up. It doesn't do it much in the evening, but I can always hear it when it is cold in the morning from my bedroom. It annoys me so much it has started to wake me.

So I am going to buy a new furnance (it's 18 years old) and get someone else to install it. I don't like working with gas and propane, especially, would simply scare the bejesus out of me. Except gaswork for landlords of course.......:D

Only joking!
 
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Well, it seems to have been a thermostat problem, as my installer thought it was.

With his help, I installed a new thermostat.
Installed a Honeywell Focus Pro 6000 (TH6110D1005).

Since installing the thermostat, the furnace has run continuously until it reaches the set temperature.
Most times it has been from about 62 degrees to 68 degrees......runs non stop, no problems.
But I finally went a away for a weekend and gave the house a chance to cool down to 55 degrees.
Set the temp to 68 degrees when I got home and the furnace ran non-stop until it reached 68 degrees. Took the furnace about 45 minutes or so.

Problem solved. Excellent.
Thanks to everyone who helped.
 
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