Furnace anticipator

[Rmack1]

I had the control board on my furnace replaced, which fixed it, but before that I tried a new thermostat.

The new one, like the old, had an adjustable anticipator. This is a little dial on the inside of the thermostat that adjusts the amps, or something. The manual said to set the thermostat anticiptor to .7 amps, which I did.

The thing is; my furnace now goes on and off several times sometimes before settling down and running. I tried adjusting the anticipator .05 amps at a time, like the manual says, to .8 and .6, but all settings seem to produce a stutter before the furnace decides to stay on.

Should I just try further settings on the anticipator?

[Rmack1]

dougrainer wrote:
Sorry, you have another problem and it is NOT the Anticipator. Doug

Well, the furnace wouldn't come on at all until we put in a new control board. It's a DynaSoar fan 50+.

Except for the only occasional on and off before staying on, it seems to be working fine.

[Rmack1]

enblethen wrote:
What is make and model of thermostat?

It is a White Rogers model 100

[enblethen]

What is make and model of thermostat?

[dougrainer]

Sorry, you have another problem and it is NOT the Anticipator. Doug

[Rmack1]

SoundGuy wrote:

Rmack1 wrote:
Well, Doug, the problem is not temp control, but the fact that the furnace was popping on and off, less than a second, a few times before staying on. I was worried that this would screw something up.

This would seem to me to be a pretty good indication you have an issue with the furnace itself, particularly if it's worked properly up 'til now, in which case fudging the thermo anticipator would hardly be the correct solution.

It seemed to help, though. Before it was false-starting, if you will, four or five times before staying on. Now, it only does one false start before staying on sometimes.

I'm thinking of trying a higher setting yet, to see if it goes away completely.

[SoundGuy]

Rmack1 wrote:
Well, Doug, the problem is not temp control, but the fact that the furnace was popping on and off, less than a second, a few times before staying on. I was worried that this would screw something up.

This would seem to me to be a pretty good indication you have an issue with the furnace itself, particularly if it's worked properly up 'til now, in which case fudging the thermo anticipator would hardly be the correct solution.

[enblethen]

I did not see what the make and model of your replacement thermostat.
Some have jumpers to be set for type of furnace. Whether it is gas or electric.
If anything you would move stat toward 1.0 and not down. This will give larger temperature swing.

[Rmack1]

dougrainer wrote:
The SIMPLE way to "fix" this type problem---You like 70 degrees in the RV but it seems the RV gets to 71/72. Just set the tstat at 68 degrees and forget attempting to adjust the Anticipator. Sorry, but this type problem is NOT a problem. Just people trying to waste their time obsessing over something. In 38 years as a tech, I have NEVER had to or had a customer state he seemed to have a problem with the furnace that required the anticipator be adjusted. Also, since the majority of Wall RV tstats are electronic, that stops this type problem and has for over 25 years. Doug

Well, Doug, the problem is not temp control, but the fact that the furnace was popping on and off, less than a second, a few times before staying on. I was worried that this would screw something up.

I set the anticipator to 8, and that seemed to work. However, in the middle of the night, I still heard a second or so of blowing and it would shut off for a couple of seconds, then come on and stay on. Not every time but once in a while.

I was thinking of upping the anticiptor a half amp or so, to see if it eliminated the on and off phenomenon.

[dougrainer]

The SIMPLE way to "fix" this type problem---You like 70 degrees in the RV but it seems the RV gets to 71/72. Just set the tstat at 68 degrees and forget attempting to adjust the Anticipator. Sorry, but this type problem is NOT a problem. Just people trying to waste their time obsessing over something. In 38 years as a tech, I have NEVER had to or had a customer state he seemed to have a problem with the furnace that required the anticipator be adjusted. Also, since the majority of Wall RV tstats are electronic, that stops this type problem and has for over 25 years. Doug

[SoundGuy]

red31 wrote:
Once the anticipator was set I saw no reason not to use the mechanical stat, no need for a fancy digital one when the mechanical one worked so well sans batteries.

I've never seen a stock bi-metal thermo able to control furnace temp to within 1/2 degree F as does pretty well any garden variety digital thermo such as that Honeywell I referred to. Replacing a stock bi-metal thermo with a digital version that costs perhaps $40 in a trailer that costs $25,000 is hardly going to break the bank and a mod most would consider a worthwhile upgrade. 😉

[red31]

Once the anticipator was set I saw no reason not to use the mechanical stat, no need for a fancy digital one when the mechanical one worked so well sans batteries.

The poor placement of the stat in a PU trailer was easily solved by FREE anticipator adjustment. Very common factory stat works great.

[SoundGuy]

dougrainer wrote:
A Furnace Anticipator is just a simple way to TURN THE BURNER OFF before the RV reaches the set temp.

BTW, some electronic Tstat control systems CAN and do have an anticipator adjustment.

The Honeywell RTH5100B digital thermostat I used to replace the stock bi-metal thermo is a common choice for many RV owners - relatively inexpensive, offers both HEAT & COOL functions, has a back lit screen so it's easy to see, and controls temps really well even though it's anticipator value is preset and is not adjustable. I see no reason for anything fancier for most RV applications.

[time2roll]

+1 for going digital.

[Chris_Bryant]

The way I was taught was measure the cutrrent flowing through the thermostat and start it at that figure. The older time delay relay models ran about 1 amp while running. Haven't measured a newer fan control board model.