Hi, I have a Gas Boiler (25-30 yrs. old) connected to a Honeywell Aquastat L8148J relay and a circulating pump. My problem is the gas valve doesn't open consistently. The pilot stays on and circulating pump works normally (whenever the room temp. is below the thermostat setting, the pump is running). Sometimes the valve will open for 1/2 a heating cycle and then close and sometimes it will work properly for 1-2 days. The gas valve appears to be connected to the millivolt circuit of the aquastat (connectors B1 and B2 in Figure #13) ... http://customer.honeywell.com/Techli...0s/60-2278.pdf . The B1 connector appears to be elevated from the circuit board by a metal connector with a screw on the end of it. (I can only see the connection from the side view b/c the aquastat is about 2 inches from the wall, facing the wall.) I have disconnected the wire from B1 an reconnected it to the screw, that works sometimes but for a short period (usually no more than a couple heating cycles). I have tried making the wire touch different parts of the B1 connector and sometimes that will work well for a day or so, but then it stops working even though the wire is touching the connector. I have replaced the wire going from B1 to the gas valve and still it does not work consistently. Sometimes if I push in on the B1 connection towards the immersion well, the valve will open and burner will fire....but not all the time. Sometimes if I turn the thermostat down and then back up again, that works for a cycle or 2, but doesn't always work.

Please let me know what you think and if there is anything else I can do to troubleshoot.

Also, if it is the aquastat, is it simple to replace? Would the boiler have to be drained to do so?

Any advice would be appreciated.

Thanks!

 

As I recall, this terminal is a 1/4" male spade with a push on female. Get some 16 or 18 ga. stranded wire rated at at least 90ºC & use it to connect a new female crimp on connector & run the new wire from the control to the gas valve. You can probably find this wire at Radio Shack or similar store. I prefer to use tin coated wire but uncoated will be ok.

 

Thanks. I have cleaned the B1 terminal using contact cleaner and replaced the wire running from B1 to the control valve. The wire is tightly screwed onto the female connector at the B1 terminal. But the same problem still exists. The push on connector and terminal at B1 look like they are in good shape and are making good contact. One thing that seems to help is pressing the B1 terminal into the board. Most of the time when this is done, the gas valve opens. As a temporary fix, I have used a zip-tie to firmly apply pressure to the B1 terminal. that seems to work for a few heating cycles. Once it reaches a cycle where the valve doesn't open...I have to turn the thermostat down, wait about 1 minute, turn the thermostat back up to temperature above the room temp., switch the aquastat to manual (gas valve opens right away) and leave it in that position for a few minutes, then switch the aquastat to auto...and it runs good for a few cycles. I think the aquastat board is shot...do you have any other suggestions?

 

It seems I'm getting a lot of 8148 problems of late for some reason. I think you have a bad solder joint somewhere on the circuit board of the aquastat. Repair is usually easy if you have the skills & can find the bad joint, otherwise, I agree, it's time for a new aquastat.