Mercury-Free Round Stat Issues

[Deleted User]

The gobbledegook w/ sine waves & dirty DC power sounds just like the geeks @ MH. Something along that line, only more unintelligible, is the line they fed me & a lot of others, about Fault Code 39 on their RM7895C1012 Primaries in 2002 & 03.

Many phone calls, e-mails, & refusing to pay for new controls (which flashed the same code) got someone's attention. They made a software change & Code 39 went away. Unfortunately, we are still dealing w/ those Primaries. And. Warranty? What's a warranty?

When is MH going to learn to address the deficiencies in their pieces w/o all the Bravo Sierra first?

I wouldn't want your job. But, you do it well. Regards.

BillW@honeywell

T87N&K issues from previous threads

This is the latest from the Honeywell labs testing returned products,the T87K & N mercury free round stats.

"The T87N&K technology requires that the AC power cross the zero point and then rise with part of the normal AC sine wave. The presence of(or lack of) this wave-shape tells the thermostat that it is installed and needs to "wake-up". If the power has a large enough DC power signal, or has a severely distorted AC signal, the stat may not "wake-up". Possible causes of "dirty" power are gas valves or oil primaries that are beginning to fail, or actual DC applications like using these stats on millivolt systems. They aren't intended for use with millivolt systems."

Field Action
The occurrence of extremely dirty or large DC power is rare, so no field action is required.

Applications with dirty AC power, if the source can't be identified and corrected, use the Focuspro 5000 series non-programmable. It is battery powered, can be set for heat or cool only, works with 750 Millivolts.

CARLIN OIL PRIMARIES
When installing with a Carlin Oil primary, and the result is no call for heat, simply reverse the R&W wires at the stat.

RANGE STOPS(no call for heat)
If the stat has the optional range stops installed, and the stat setpoint is forced beyond the range stop limits, the setpoint contact will be pushed to and stuck beyond the limits, and the stat will no longer function. A LARGE amount of torque is required to break the range stops.

allenleo

to bill w

bill i started the threads to try to get more info on the problems that my company has encountered with these thermostats. i suggested to my company that we change to the focus pro 5000 about three weeks ago because it seemed like the best suited replacement thermostat outside of the t87.


the reversing of the wires has been a myth and proved through many countless trial and errors with callbacks.


even when it is used with a switching relay, the thermostat has function problems.
this is just my opinion, but people are better off staying away from the t87k and n altogether. they should definitely use the fp 5000, it costs only about 6bucks more than the t87k and is as usable as the old mercury round ones. the only downside is that the batteries have to be watched and replaced from time to time.