Best Of

1. Reconnected the thermostat to SR501
2. Put low voltage wires from 5 and 6N/0 on SR501 at one end and put the other end to the primary control TT.
3. I had to join the two wires removed from the L4006B Aquastat to turn on the circulator…if not connected circulator wouldn't go on.
4. I set thermostat and room temp increased and water temperature on boiler was 100 degrees and it started at 50 degrees since it was off. I took some temperatures at radiators and range was 118 degrees to 103 degrees. I turned off the thermostat at that point.
5. I guess the gauge on boiler may not be accurate.
6. If the heat was left on would the burner have gone off when the differential temp was met?…high limit of Aquastat L4006A was 180 degrees…I read may be a 10 degree differential factory set?…and when would it turn on again?
7. Circulator goes on as expected and even heat distributed throughout the house…I can see how this is more efficient now.
8. Will do some more testing and get some thermostat wire to make connection from SR501 to TT terminals at Primary Control to replace the temporary hookup.
9. I know you said the burner would not operate without a jumper at the TT on Primary Control. The thermostat would be on or off depending on call for heat,room temp..etc…and I tested all of that and agree…but if a jumper was there the burner would go on all the time. Just wondering where would the thermostat come in wth that setup…that jumper was always there with the coil in use making hot water from the boiler…it would seem that this jumper would override the thermostat.
10. Seems like the bugs are being worked out here. Thanks for all your help and not only that I understand alot of this information now and how it all works thanks to your guidance!

Weil McLain charges too much. and that WM part number does not have the electrode for the sparker. It is for standing pilot burner only. This one looks a lot like yours https://www.supplyhouse.com/Baso-Gas-Products-Y90AA-3223-1-4-Inlet-Fitting-w-023-Orifice-Natural-Gas. It has a .023 orifice

Will keep looking for .020

Here is a .021 orifice https://www.controlsincgas.com/Product-Name/Y90AA3221

Sorry, your post was very clear; I missed the key word.

I don't think the pilot assembly is a Weil-McLain part; probably Honeywell and I don't know where to find the orifice size. And I don't think they sell the orifice by itself, but I've never looked for one so I may be wrong. You might have to buy the entire pilot assembly.

Interesting question.
The cistern is the house where I grew up was set up for cloths washing and such. A deeper ground well provided for drinking water. Both retired well before my time.