Anyone have a manual for Ackomatic Gas Boiler Model C21W5S

Joseph_4

Hey out there,

Anyone have a manual for  Ackomatic Gas Boiler Model C21W5S

Thanks

Joe

Tim McElwain

I do not have

a manual but I am sure I can help you if you have a question concerning the boiler.  Ask a way and we will see if we can assist you. Some pictures are a big help.

Joseph_4

Question is regarding the milivolt gas valve

Ok Tim, thanks for looking at my question. I'll elaborate. There is a really old millivolt gas valve on this boiler. From pictures in  your Manual on Millivolt systems, it looks to me like a vs8279 or vs 8195.The customer said the boiler was on as recent as last week. There appears to be 2 pilot tubes coming out out of this gas valve. I lit the pilot and jumped the 2 terminals which would open the main gas valve and the boiler doesn't come on. I'd like to know if I can replace the gas valve with a vs820, only I wanted to read up on the function of the 2 pilot tubes. I checked with my meter the 2 terminals coming from the powerpile while they are connected to the gas valve and got 631 milivolts (dc). I was told that should be enough to open the main gas valve and it doesn't that's why I figured I'd try and see if gas valve change fixes problem.

Thanks

Joe

Tim McElwain

Before you change

the gas valve disconnect the small tubing running to the pilot at the gas valve then try and see if it comes on, if it does you have a plugged bleed tube from the gas valve, pull the pilot and clean that tube, it usually gets plugged right at the end of the tubing at the pilot.



If that does not work make sure you have gone through the entire Powerpile troubleshooting procedure that is on the HeatingHelp website from me. It is found



at "RESOURCES"/"LIBRARY" then Tim McElwains Closet.



Yes the VS820 gas valve will replace that valve and you can just eliminate the small bleed tubing.

Joseph_4

why does a plugged bleed tube not allow valve to come on?

Tim,

 Could you explain to me more on the function of the 2nd pilot tubing. Why if its plugged does it not allow main valve to open?

Thanks

Joe

Tim McElwain

The bleed tube

is required as that is an external bleed type diaphragm gas valve. How the valve works is when there is no call for heat there is gas on top and on the bottom of the diaphragm the gas valve is not powered (no call for heat). There is inside the valve an electromagnet that is powered by the call for heat it closes an internal pressure port and opens an external bleed port, the gas bleeds off the top of the diaphragm, now the gas pressure underneath the diaphragm is greater than pressure above and the diaphragm lifts. The seat is attached to the diaphragm and gas passes to the outlet to the burners. If the bleed tubing becomes clogged the gas can not bleed off and the valve will not open.



When the thermostat is satisfied power to the electromagnet ceases, the bleed port closes and the pressure port opens (this is accomplished by an armature in the gas valve) now gas is allowed back on top of the diaphragm and when the pressure is equal the weight of the seat and the spring attached to the seat will close it off waiting for the next call for heat,



These valves are no longer made. Modern valves the bleed is now an internal bleed type diaphragm valve which bleeds into the outlet of the gas valve, it is also a pressure sensing port sensing downstream demand caused by the orifices on the manifold. This is turn operates a built in servo regulator in the gas valve which remotely keeps pressure at the preset point. The regulator controls pressure the orifices control flow..

Joseph_4

Thanks for the explanation Tim

Thanks for the explanation Tim. I went back to job, and unscrewed that bleed pilot tubing as you described and valve still did not open. I replaced valve and they are up and running.

Thanks for the help

Joe