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wiring the new T87

DaveDave Posts: 1,405Member
the t87k and t87n are troubled thermostats. do you think this is honeywells purposeful attempt to make the t87 round thermostats obsolete. if so why then would they make non mercury round thermostats to begin with. if not, then why are there so many problems with this thermostat, and why hasnt honeywell done anything yet to correct the problems or at least address the subject. they must know that these thermostats are not compatible with cad cell relays alone. they must also know that these thermostats have function problems as well. sometimes they work at +/- 2 degrees sometimes they have to be turned all the way up to call for heat. just looking for some answers, if you have any i would appreciate them. thanks. allen leo
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Comments

  • rjmrjm Posts: 60Member
    electronic T87

    What is the correct way to wire a mercuryfree t87 to a steam blr. Iknow you have to add a 24vac transformer.But not exactly sure how to wire it.
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  • DaveDave Posts: 1,405Member
    honeywell t87k and t87n non mercury thermostat

    do yourself a favor; stop using the t87k and t87n. if you are using these thermostats, there is somethings you have to know about them first. the t87k is a heat only thermostat and cannot be used with cooling applications.
    the t87n is a heat/cool thermostat and cannot be used on heat only applications.
    neither of these thermostats work with a typical cad cell relay set up. in order to use it with a cad cell relay you would have to add a 24volt transformer and an r8222 power to power isolation relay or you will end up burning out the new transformer. its not worth it. the cost for the additional transformer and relay is too much.
    the other thing that i have noticed about these thermostats is that they are very inaccurate, even when set up to a switching relay that will power them with 24 volts from the tt contacts.
    my company has stopped using these thermostats because they have become cost ineffective and the source of many callbacks.
    we are using the honeywell focus pro 5000 thermostat now. it is a digital non-programmable thermostat that can be used for many different heating and cooling applications and they cost only about six dollars more than the honeywell t87k and are cheaper than the t87n.
    with what you save on the transformer, relay, and possible callbacks, it is well worth converting to.
    the honeywell focus pro thermostat is battery operated, so that means no need for a separate transformer, but can still be used with relays that have contacts powered by 24volts.
    i hope this helps you out.
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  • carolcarol Posts: 397Member


    I second the motion to go to the TH5000. Cool stat.
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  • carolcarol Posts: 397Member


    I'll see what the product specialist has to say. Stay tuned.
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  • carolcarol Posts: 397Member


    The Honeywell product specialist has emailed back with a thanks for the feedback. I asked for a specific response--I'll let you know if I get anything more.
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  • SinghSingh Posts: 58Member
    T87

    I recently installed two new T87, for baseboard. I set the dip switches for hot water and they go into a Taco SR506.
    I had the Tsat cranked at 80 (testing and purging new zones) However I noticed
    zone would go off eventhough not satisfied after a period of time. By observing the indicator lights for that zone on the Taco relay.
    Then after a few minutes would come back on. Both Tstat did this.
    Is this normal for this tstat to take a break?

    TIA
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  • allenleoallenleo Posts: 26Member
    tanks carol

    i look forward to any insight that they can provide.
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  • carolcarol Posts: 397Member


    The stat wants to run until set point is reached. My guess is that something is causing power to be cut intermittently.
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  • carolcarol Posts: 397Member


    Here's the word from Honeywell:

    Subject: T87K and T87N Field Applications

    We have recently received some customer feedback that the T87N and T87K Round thermostats are not calling for heat. We expect this to be regionally isolated due to the types and age of the equipment that are more commonly found in that region.

    These no heat call issues are showing up when the thermostat is connected to dirty AC power, DC power, Carlin controls, or when there is an abused use of range stops.

    Below is a summary of the investigation results and how to address the situations. These issues to date have been isolated to the Northeast region of the U.S.

    NO CALL FOR HEAT FINDINGS: DIRTY AC POWER, LARGE DC POWER, CARLIN CONTROLS

    The Round technology requires that the AC power cross the zero point and then rise with part of the normal AC sign wave. The presence of (or lack of) this wave-shape tells the thermostat that it is installed and to ‘wake up’. If the power has a large enough DC power signal or has a severely distorted AC signal, the thermostat may not ‘wake up’. Possible causes of dirty power are primary controls (such as gas valves) beginning to fail or actual DC applications such as millivolt applications.

    FIELD ACTION:
    The occurrence of extremely dirty or large DC power is rare so typically no field action is required.

    Applications with dirty AC power, if the source of the dirty power cannot be identified and corrected, the FocusPRO TH5110 should be used. The TH5110 is very universal and can be setup for heat only (including normally open, normally closed or power to open and power to close zone valves), cool only or heating and cooling applications. It will also operate 750 mV applications.

    When installing on Carlin controls if the result is no call for heat, switch the R and W wires at the thermostat.

    NO CALL FOR HEAT FINDINGS: RANGE STOPS
    If range stops are installed and the thermostat setpoint is forced beyond the range stop limits, the setpoint will be pushed to and stuck beyond the limits. A large amount of torque is required to break past the range stop limits.

    FIELD ACTION:
    When operating the thermostat with the optional range stop accessory installed, do not force the dial setpoint past the range stop limits.

    If you have any further questions, or are experiencing additional issues with these products, please contact Honeywell Customer Care or the Thermostat Product Management team.

    Thank you.


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  • qmodelingqmodeling Posts: 2Member
    T87K Thermostats not working

    I have an NTI boiler supplying six zones of radiant heat and an indirect domestic hot water loop.  I'm using a Taco controller for all the zones. I using T87K thermostats bought from Home Depot.  They simply don't call for heat.  To bring up the system and purge the lines I simply tied the R and W together and the Taco controller sensed the need for heat and turned on the boiler.  I was able to get the system operating an bring up the building to a comfortable 70 degrees, but no matter what I did I couldn't get the T87K to work.  Friend of mine said maybe they were a bad batch from Home Depot.  I bought another set from a quality electrical supply house, these came in a box not the plastic packaging found at Home Depot.  Same result they simply don't work.  I tried using a digital thermostat a friend had and it worked fine.  So I assume the T87K don't work on systems like the one I have?  Any suggestions or should I just bite the bullet and pick up some digital thermostats?
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  • qmodelingqmodeling Posts: 2Member
    T87K Thermostats not working

    I have an NTI boiler supplying six zones of radiant heat and an indirect domestic hot water loop.  I'm using a Taco controller for all the zones. I using T87K thermostats bought from Home Depot.  They simply don't call for heat.  To bring up the system and purge the lines I simply tied the R and W together and the Taco controller sensed the need for heat and turned on the boiler.  I was able to get the system operating an bring up the building to a comfortable 70 degrees, but no matter what I did I couldn't get the T87K to work.  Friend of mine said maybe they were a bad batch from Home Depot.  I bought another set from a quality electrical supply house, these came in a box not the plastic packaging found at Home Depot.  Same result they simply don't work.  I tried using a digital thermostat a friend had and it worked fine.  So I assume the T87K don't work on systems like the one I have?  Any suggestions or should I just bite the bullet and pick up some digital thermostats?
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