Why won't this work?

robert griggs

I had a no heat call tonite on a gas fired steam boiler with a milli-volt system. The problem was the thermostat. The customer told me that he had to put a T-87 on a few years ago because he was told a digital t-stat would not work on this system. I thought it should because doesn't it just complete the circuit when there is a call for heat?

I tried to put in a digital t-stat, but it would not work. I put in a new T-87 and everything worked fine, but I do not understand why the digital t-stat does not work on these systems. Anyone know why this is?

Thanks,
R. Griggs

jeff_25

stat

to usea digital stat it must be a battery operated stat with dry contacts no24 volts for stat jeff

Unknown

> I had a no heat call tonite on a gas fired steam

> boiler with a milli-volt system. The problem was

> the thermostat. The customer told me that he had

> to put a T-87 on a few years ago because he was

> told a digital t-stat would not work on this

> system. I thought it should because doesn't it

> just complete the circuit when there is a call

> for heat?

>

> I tried to put in a digital t-stat,

> but it would not work. I put in a new T-87 and

> everything worked fine, but I do not understand

> why the digital t-stat does not work on these

> systems. Anyone know why this is?

>

> Thanks, R.

> Griggs

Unknown

A TS-86 will work

a lot better. It is designed with fixed anticpator to work with Powerpile systems. The digital will not work as it needs power from a transformer.

There are some digital thermostats that can be used. I will look them up and post them tomorrow.

Bill from Honeywell can probably give you a list.

Just curious were did you set the anticipator on the T-87?

tim from Reed Wright

mv stats

There is another reason even a battery powered digital stat wont work. The contacts and circuits in stat have too much resistance and will drop your millivolts below operating range. Also the t87 will alot of the time give problems due to the same reason. Use a stat specified for mv current.

steve_6

millivolt systems

The only differance on a lot of the millivolt controls I've seen is that they have gold contacts for less resistance.

Unknown

If you are going to use a T-87

set the anticpator for about .35 to get about a 115 millivolt drop across the thermostat. That is equal to the drop for the fixed anticpator in the TS-86. There are other millivolt thermostats that drop a lot less if that is a concern.

Some gas companies replaced the TS-86 thermostats with a T-87 and set them to 1.2 for minimum resistance and longer cycles on some steam systems. I do not agree with that and find that using a TS-86 is the best way to go.

Unknown

Gold Contacts some even had

platinum. The McDonnel Miller # 11MV swich used on the #67G float type LWC was such. Most other switches on presuretrols, limits etc are fine as they have a pilot rating to accept Low voltage DC.

Unknown

I have an excellent Manual

available on Powerpile Systems and how to troubleshoot them. It has detailed procedures on taking readings and control resistances. If you are interested e-mail me.

BillW@honeywell

Millivolt programmable stat

As of early 2001, our new T8602D 2000 & 2018 programmables will work with 750mv systems, and 24 volt cooling (if installed). They must be new stats, and never connected to 24 volts, so you can't recycle one off another job. If you only want a non-programmable, try the TS86A.

Paul Pollets

Timmie

I hope you're able to collate all of your writings, troubleshooting and tables in one book. I'd buy it, for sure!! How about a video or CD? Your knowledge should be documented and available to all. It's worth alot.
Paul Pollets

To Learn More About This Contractor, Click Here to Visit Their Ad in "Find A Contractor"

Sizzle

Milivolt system

We been using White-Rodgers digital thermostat
1F80-261 on all our Viessmann ECD-XXX milivolts
installation without any problem by the way milivot
boiler are very popular here since 1998 ice storm.

Serge

Unknown

Too much material for one book

as it is I have 27 volumes of training manuals and over 50 Troubleshooting guides. I am not sure I could collate all that into one book. I am working on two new manuals right now on Integrated Boiler Controls and Integrated Furnace Controls.

Howard

I'd use RA832A

or a fan relay center near the bioler. KeepItSimpleSilly

Howard Hansen Service Technician Extraordinaire