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Move or remove Johnson control A419 temp sensor and replace with setback thermostat for more control

Todd_33 Member Posts: 62
'Low. I've got a 9 unit building where I occupy a store front/office. Older steam boiler with Johnson a419 controller with temp sensor in centrally located apartment with the sensor roughly 75 ft or less to the a419. The A419 is set for 76 degrees with 1 degree differential. The problem is that in my space which has 3 outside walls the temp swings are great. Last night it was 30ish degrees out and my space was 65 degrees when I came in. Boiler kicked in twice in 6 hours ( I think )and my space got up to 77 degrees. My temp is staying steady around 76. Outside temp today mid 40s.

I'm thinking that since my space has 2 more outside walls and more temp fluctuation than the "control" apartment it might make more sense to have the sensor with me in my space. If I do that I'd like swap the A419 and remote sensor for a standard digital thermostat with daytime, evening and weekend setback control. That way I could also fiddle with various thermostat temp settings in conjunction with radiator venting (in my space) in order to balance the building's overall temp.

There is an outside temp sensor but that hasn't worked for a while so I just make sure it allows heating.

My question, can I just clip the wiring from where it goes into the A419 and splice it to the proposed setback thermostat without other alterations? It would only be about 30 feet from the burner. Second question is as to the wisdom of my strategy. Hoping to replace boiler in next year or 2 if that makes any difference.
Thanks, Todd


  • nicholas bonham-carter
    nicholas bonham-carter Member Posts: 8,578

    If the outdoor sensor is kaput, then the rest of the control is probably not working as well. Replace the control with a honeywell visionpro with remote sensor in the apartment to begin with. That way you can have the control, and the sensor is in a typical apartment. There may also be the Ecobee stat which can have 2 sensors, for averaging the temperature.
    When your building was new, the radiators would have been sized for each room, and assuming that has not changed, you should have an even temperature throughout the whole system. Your goal should be to restore the system to its once perfect state of operation.
    Make sure you have plenty of main venting, and don't use setbacks which are less than 24 hours in duration, or you may burn extra fuel just regaining the temperature. Ideally, the steam should arrive at all the radiators at the same time, as a result of the main vents allowing the steam to fill the mains first, and then the radiator vents will control the escape of air from the radiators, letting steam in all at the same time.
    Low pressure will ironically speed up the steam flow, so check your pressure, and keep it below 2psi, for basic functionality, and 6 ounces for economy, (requires a vaporstat)--NBC
  • John Mills_5
    John Mills_5 Member Posts: 952
    Along those lines, the newest Vision Pro has a remote control option. Looks like a TV remote. If you put the VP in the apartment where the controller was and had the remote in your store, you could have the remote read and set the temp during the day when you are there and the apartment Vision Pro take over at night when tenants are home. That does give them control of temp at night which may or may not be good but at least during the day, the temp in your store will be what you want and not reading their apartment.
  • Todd_33
    Todd_33 Member Posts: 62
    That's a pretty good idea. I really like the idea of the remote. - I'll look in to the VP line. Thanks for the suggestions. Not sure what I'll do at this point.