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Honeywell RA89A buzzing

JaymeHart Member Posts: 10
Hi all,

We had some renovation done to our house, and a hot water loop was run off the gas boiler for a second zone in the kitchen. The thermostat for that zone runs into a Honeywell RA89A. Occasionally, the RA89A will buzz, and won't fire the boiler / circulate hot water to that kitchen zone radiator, and it gets stuck in that state (aka no heat) until I turn the thermostat off and back on again.

I *think* it generally happens when the main zone has already called for heat, and the boiler is already fired and working. Then it gets stuck in the buzzing state.

The main zone is single pipe steam, and running pretty well. (I used this site years ago to figure out how to optimize it at low pressure and high mains vent rate, so Thank You!)

Any thoughts on how to resolve this new zone issue would be helpful. A bad RA89A? Or a cheap Thermostat issue?



  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,576
    If that is a fan center, then it’s output in amps may be too low to operate the water loop circuits, and some modern thermostats combined.
    Maybe the installer of the loop should come back to have a look.—NBC
  • Jamie Hall
    Jamie Hall Member Posts: 22,077
    If you can, check the voltage across the relay coil when it is buzzing. The 24 volt transformer you have may not be able to put out enough voltage -- if so, you will need a bigger 24 volt transformer.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • JaymeHart
    JaymeHart Member Posts: 10
    Thanks. I will check the voltage on the relay when it happens again.

    NBC - what is a "fan center"? I don't know that term.
    EBEBRATT-Ed Member Posts: 14,472
    An RA89A is a switching relay with the transformer already built in. Is this relay new or old??

    It is usually rust or dirt on the relay coil that causes it to make noise if it's an older relay. De-energize the relay, check the wiring connections and clean between the relay coil and the magnetic part of the relay. Operate it a few time to see if it works better or replace it

    If it's a new relay it could be a wiring issue. With the thermostat turned down (not calling for heat) you should read 24 volts between T and T.

    You should have 120 volts between 1 and 2

    was this relay added during the renovation....under warrenty??
  • unclejohn
    unclejohn Member Posts: 1,833
    Probably a power stealing tstat.
  • HomerJSmith
    HomerJSmith Member Posts: 2,307
    uncle john is probably right, a nice new led display thermostat may be current robbing. I think that the relay box is only rated at .2A. A relay can more than gobble that up.

    However, funny thing, you might try switching the line coming in. If it is an extension cord it may be incorrectly connected to the L1 & L2 in the box or even incorrectly wired up in the receptical box on the wall.
    L1 to ground measured with a volt meter will be 115V and L2 less. Polarity is important in many electrical devices.

    Remove the wires on the back of the thermostat and connect them together and if the problem goes away, it's the thermostat or the wiring between the thermostat and relay.

    You can add an auxiliary transformer to the existing transformer in parallel to boost the current to the thermostat. THIS has to be done in a special way to prevent polarity differences between the two transformers, which could cause a failure in one or more transformers.

    Honeywell came out in the late '80' with a paper on how to connect their current robbing "magic stat" thermostat with an isolation relay, a copy of which I still have.