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Honeywell Thermostat Anticipator???

I am enjoying your books Dan, I am also learning alot about my old/new system/boiler setup. I have a question about my plain old dial honeywell thermostat. In your books you write about using an amp meter to check the amperage of the system to them somehow set the anticipator to this setting. can you explain how and where to check the amperage, an how this number is used to set the anticipator? I'll tell you what the thermostat is doing. The room temp is usaully much lower tahn the etting temp before the burner lites off. sometimes 2 to 4 degrees different. the burner shuts off at the correct setting when you turn up the dial. it's just when you call for more later on that the difference occurs. i have had mant thermostats on this system and this one is difficult to setup. can antone provide any advise. thanks for your help


  • Mark

    If you have the T86 round type, remove the stat from its sub-base and use a milliamp type meter across the 2 stat wires. This will light the burner & tell you the fractional current the relay or gas valve requires.
    On your stat(in your hand), should be an adjustable scale with a pointer to allow you to set the same # you got on your meter.
    Provided the stat is level & calibrated properly as that is another issue.

  • Fred HarwoodFred Harwood Member Posts: 193

    The T87 is the best simple thermostat for steam, I think. And its anticipator allows you to set the boiler for two to three cycles per hour (on to on again). First, use an ampmeter to set the slide to the indicated amps. Then observe for a day or so. Slide the anticipator lever down to decrease the number of observed cycles per hour to two. Nudge it down over several days, if necessary. You'll be amazed how it stabilizes the house, provided your mains and rads are properly vented.
  • mel rowemel rowe Member Posts: 324

    Constantly learning good info just by monitoring this site. I have often wondered about the anticipator setting on my T87 stat. It seemed that it only resulted in two outcomes-- early shutoff if it was too low, or extended run time when I pushed it to higher setting. At the higher setting my boiler cycle usually is about 80-90 minutes long. Do I understand correctly that I may be able to get more cycles per hour by carefully nudging it lower and monitoring the results over several days?
  • scrookscrook Member Posts: 598

    Yes, nudging it lower will result in shorter runs before the T-stat opens.

    Start by measuring the current thru the thermostat when the T-stat is calling for heat, (2 amp AC range on a DVM should be good -- disconnect a wire and insert the ammeter between it and the T-stat) or read the stated current on the label of the boiler control the T-stat wires attach to (oil burner ignition primary, aquastat, control relay, 24V gas valve, etc.) and adjust gradually up/down from there.
  • Fred HarwoodFred Harwood Member Posts: 193
    More Cycles per Hour

    Yep. You can set the T87's anticipator for that magical two cycles per hour, provided that you get heat to every radiator on each cycle, which is a function of venting, and venting is key. With adequate venting (more is better), your burner will run least. With proper cycle time via the anticipator, you overshoot least.
  • Anticipator works like this

    First measure the amperage draw of the primary control, gas valve etc.

    You do this by placing the amp meter in series with the 24 volt wiring in the circuit any place will do just find the easiest place to disconnect a wire.

    Lets say you measure .45 then set the anticipator to .45 and observe your cycles. If you want longer cycles then move from .45 to .5 this will put less false heat (from anticipator) therefore longer cycles, therefore less cycles per hour. Most thermostats have an arrow pointing toward "longer".

    The key as someone else pointed out is to make sure all the radiators get steam before the system shuts off.

    Also make sure your pressuretrol is set to shut off below 2 pounds pressure.
  • Aniciprtor Help

    Thanks Everyone I have have a much better idea how this works now. The radiators are all getting even steam, so i don't want to change any venting settings, pressuretrol is at .5, works very well at this setting.
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