Millivoltage Thansformer

bk14x32

I need a 750mV power supply th bench test control components for compatibility with Millivoltage systems. Also it is possible for the generator to meter test good without load yet not be able to power the system. Want to be able to disconnect the generator and see if the boiler will fire with power from the external supply. Honeywell did make a transformer with 750 mV as the secondary voltage but it has been discontinued. Anyone else make such a transformer? Does anyone have the Honeywell unit as NOS or a good used one? Any suggestions?

I believe Honeywell made such a transformer for use when doing a boiler replacement when the new unit does not have a standing pilot and the desire to use the millivoltage controle/thermostat exists or perhaps for the purpose I am presenting here.

Tim McElwain

No such thing I am aware of

because to the best of my knowledge millivoltage used on heating equipment is DC voltage produced by the pilot flame hitting the upper 1/2 to 3/8 of a 750 millivolt generator. Transformers are AC voltage.



If you are looking to bench test a powerpile system it will not work as they must be tested at the point of application. To answer the question I believe you are asking. Can the pilot be lit and the system not work  -  the answer is yes.



What I would suggest is you contact me by e-mail at gastc@cox.net as I have a complete manual on self generating systems and how to troubleshoot them which I sell. I am sure it will answer all your questions.

Steamhead

Right

and remember, the powerpile generator also serves as the flame detector, which would keep the gas valve from opening if the pilot goes out. So an external power supply would, in effect, bypass the safety feature built into the unit.



If I was going to do bench testing to see whether a certain control could be used with an existing system, I'd simply get a powerpile pilot assembly, set it up for propane, and hook it up to a tank, being careful to keep it from catching something on fire. This way I could test it using the same type of power supply in use on the existing unit.



What exactly do you have in mind here?

bk14x32

Reply to Steamhead

First of all I may be mistaken about seeing a Honeywell Transformer in my Tradeline Catalog (1999?) that had a secondary voltage of 750 mV. I have been interested in Millivoltage for years and I am relatively sure I saw this item beacuse it set me to thinking how the manufacturer intended the transformer to be used and how I could use it. If there was such a transformer I would never use it to power a mV system in a boiler with a standing pilot beacuse if the pilot was lost the gas valve would not close as it would continue to be powered by the transformer. I thought Honeywell produced the transformer for boiler replacements with electronic ignition when the mV controls were to be retained.

I want to test spill switches and rollout switches with my meter to see if they would work in a 750 mV system. Most manufactures consider mV obsolete and do not give mV electrical specifications( if mV compatible) as they once did. Your idea would work but be a bit less convient than a power supply on the bench.

You have probably worked on steam boilers with Millivolt systems. If the gas valve and thermostat are mV and the low water is the #1 switch the pressuretrol will work with any power.

Thank you for a workable suggestion.

Bobby K

bk14x32

Powerpile Pilot Assembly

Steamhead,

Please consider the following:

Honeywell has a small gas valve intended for fireplaces and space heaters the VS5820. This valve is set up for both a Thermopile and for quick drop-out a Thermocouple. If I plug the burner tapping and use the valve with a Q327 Pilot Burner with both the A and B brackets seems it would serve my purpose and be relatively safe. Plase comment.

Thank you,

bk14x32

Tim McElwain

I worked for Honeywell from 1994 to 1999

First of all I may be mistaken about seeing a Honeywell Transformer in my Tradeline Catalog (1999?) that had a secondary voltage of 750 mV.

I NEVER REMEMBER ANY SUCH TRANSFORMER, SIMPLE TRUTH A TRANSFORMER ONLY WORKS ON ALTERNATING CURRENT MILLIVOLTS AT DIRECT CURRENT IMPOSSIBLE!



I have been interested in Millivoltage for years and I am relatively sure I saw this item because it set me to thinking how the manufacturer intended the transformer to be used and how I could use it. If there was such a transformer I would never use it to power a mV system in a boiler with a standing pilot because if the pilot was lost the gas valve would not close as it would continue to be powered by the transformer. I thought Honeywell produced the transformer for boiler replacements with electronic ignition when the mV controls were to be retained.

THE HONEYWELL ELECTRIC IGNITION RETROFIT KITS WERE NOT DESIGNED TO REPLACE 750 MILLIVOLT SYSTEM. THEY WERE TO REPLACE STANDING PILOT THERMOCOUPLE OPERATED SYSTEMS WHICH WERE 24 VOLTS AC ALREADY.



I want to test spill switches and rollout switches with my meter to see if they would work in a 750 mV system. Most manufactures consider mV obsolete and do not give mV electrical specifications( if mV compatible) as they once did.

AL;L SWITCHES ARE COMPATIBLE WITH MILLIVOLTS AND THE ALLOWABLE MILLIVOLT DROP ACROSS ANY SWITCH IS 0 TO 10 MILLIVOLTS.THE ONLY SPECIAL SWITCH IS A MCDONNELL MILLER # 11 MV FOR SPECIFIC USE ON MILLIVOLTS AS IT HAS EITHER GOLD OR PLATINUM CONTACTS TO REDUCE THE POSSIBILITY OF PITTING DUE TO SURGING AFFECT ON STEAM SYSTEMS. THE ONLY OTHER EXCEPTION IS A MILLIVOLT RATED SAY TS86 THERMOSTAT WHICH HAD A FIXED ANTICIPATOR SO IT COULD HAVE A MILLIVOLT DROP BETWEEN 85 TO 125.



 Your idea would work but be a bit less convient than a power supply on the bench.

You have probably worked on steam boilers with Millivolt systems. If the gas valve and thermostat are mV and the low water is the #1 switch the pressuretrol will work with any power.

AGAIN YOU ARE SIMPLY TALKING ABOUT SWITCHES SO ANY SWITCH JUST ABOUT IS COMPATIBLE WITH POWERPILE.

Thank you for a workable suggestion.

Bobby K



BOBBY YOU NEED TO BE EDUCATED ON POWERPILE SYSTEMS SO I WOULD SUGGEST GETTING TO MY CLASS ON THE SUBJECT OR BUY MY MANUAL WHICH I EMAILED YOU ABOUT.

Tim McElwain

Answer is

if you know how to trouble shoot powerpile systems you do not need a bench setup. once you take your first three required readings in troubleshooting then chart them out with the powerpile charts you are on your way to finding any problems.

Tim McElwain

By the way the

purpose of the quick drop out thermocouple is a safety issue to prevent the possibility of Carbon Monoxide. The thermocouple drops out in 30 seconds when the oxygen level in the combustion zone drops below 18% normal is around 20 to 21%. That is its only function and it is designed to shut down the entire valve operation while the powerpile is the operating system only.

Steamhead

You could also

simply feed the test pilot directly from the propane tank, and feed low-pressure compressed air to the gas valve. This means you wouldn't need to plug the VS5820 or risk a discharge of gas.



But Tim says these switches will work fine on a powerpile system- so there shouldn't be a problem using them.