Older Gas Valve Question

Dan_58

I have a pre-1960 gravity warm air natural gas furnace that was converted from coal. It has a Minneapolis-Honeywell thermostat/electric gas valve/limit switch system. When the thermostat calls for more heat, the valve (V155A) will not open automatically. If you press the electrical contacts in the valve, the valve will open. The valve closes by itself after a normal period of running and also closes when you lower the thermostat dial but will not cycle on again without the contacts on the valve being pressed. Through all this, the pilot remains on and has never gone off. Is the motor on the valve starting to go or is something else a probable cause? Are there replacement valves or rebuilt motors available? (it's labeled 20 volts.) Thank you for your help.
Sincerely,
Dan

bob_46

Series 10

Dan, You have a series 10 MH control system. Series 10 is a three wire system. The thermostat was 3 wire the high limit was 3 wire and the gas valve was three wire. The systems were color coded red, blue, white. The thermostat has two contacts one for a starting circuit the other for a holding circuit. Are you still using a series 10 thermostat? If you are there is a problem with the red wire or the starting contacts inn the valve or dirty contacts in the thermostat, you clean them by draging a dollar bill through them. If you are using a two wire thermostat it should be connected to the B(blue) and W(white) terminals remove the wire from the R(red) and tape it up.

Unknown

The V-155

is a motorized valve and needs annual oiling be inserted into the small cups on the valve. The oil to use was called FINOL oil and Honeywell sold it. I am not sure if it is around anymore. I still have a can that I keep for a couple of Series 10 jobs I maintain.

That valve can be replaced by a 24 volt gas valve. The replacement should however be done by a Pro as it requires some small changes in wiring and pilot application.

Dan_58

Thanks Bob and Tim for the replies. I believe the thermostat is the original series 10 3 wire unit (it looks like the one pictured in the 1949 Minneapolis-Honeywell guidebook.) I passed an index card between the contacts without seeing an improvement and I don't see any signs of carbon near the contacts although they are quite dark. I placed a drop of light electric motor oil in each oil tube. The contacts ride on a cam which appears to have a flat spot. Is this how the holding and starting circuits operate? The motor feels slightly warm to the touch. Can I tell the condition of the 20 volt motor trying to measure the current it draws? Thanks again.
Dan

Mark Custis

I need to retire

I got this, NP.

bob_46

Old

Dan, With the "A" cock in the OFF position remove the thermostat wires from R,W and B terminals on the valve. Place a jumper from R to W nothing should happen. Momentairily short B to the R-W jumper the valve should open and stay open as long as R-W are jumped. If not you need a new valve....bob

Unknown

Here is the checkout

directly from the Honeywell Manual on V-155.

If The Valve Fails To Operate Properly:

1.First check the pilot light to make sure it is lighted.

2.Connect a meter across the terminals of the basement line switch to check the voltage supply.

3.If an electric switch type of pilot safety is used, connect the two terminals "W" and "Y" of the valve with a piece of bare copper wire. Then, if the valve operates with the thermostat and limit control calling for heat, the trouble is with the Pilot Safety. See separate instructions packed with Pilot Safety.


4.With a piece of bare copper wire short circuit the red, white and blue terminals of the valve where the thermostat wires connect. Refer to diagram below. Failure of the' valve to operate indicates either lack of current supply or trouble with the valve itself.


5.If the valve operates properly, remove the wire used to short circuit the red, white and blue terminals and short circuit the red, white and blue terminals on the valve side of the Series 10 Limit Control (if used). This is a test of the 3-wire cable between the Series 10 Limit Control and the valve. Failure of the valve to operate indicates a break in this section on the cable, or loose connections at the valve or Limit Control.


6.Remove the previous short, and short circuit the red, white and blue terminals on the thermostat side of the Series 10 Limit Control. This is a test of the Limit Control itself. The indicator of the Limit Control for this test should be set well above the boiler pressure or temperature. Failure of the valve to operate indicates poor contacts, an open circuit within the Limit Control, or that it is out of adjustment.

7.Remove the previous short, and place a piece of wire across the red, white and blue terminal posts on the thermostat. This is a test of the cable between the Series 10 Limit Control and the thermostat, and also of the connections to the thermostat at the thermostat side of the control. Failure of the valve to operate indicates an open circuit in one of these connections or a break in this length of cable.


8.Remove the previous short and move the thermostat indicator well above room temperature. Failure of the valve to operate indicates poor thermostat contacts, or that the thermostat is out of adjustment.


9.If the thermostat or Limit Control (if of open contact type) is not contacting properly, clean the contacts by pulling a piece of hard finish writing paper (not newspaper) between the contact points. Be sure that no paper shreds remain between the contact points.


10. If valve does not operate normally and appears sluggish in its action, work Minneapolis-Honeywell Regulator oil into both front and rear motor bearings.

Dan_58

Thanks for the replies. I'll work my way through the test steps.