Gas boiler multizone apartment systems need heat turned off, hot water kept on

You need a boiler management control system. Tekmar and Heattimer are just 2 that come to mind off the top of my heat. There are tons of these available.

The information given so far is insufficient to answer the question asked.

1. We know this
   1. there is more than one boiler
   2. some are HB Smith that are old from 1971
   3. some of them are Weil McLain that are newer
   4. these boilers produce space heating and domestic hot water
   5. most of the boilers have 2 aquastats.
2. We don't know this
   1. how many boilers there are
   2. if the boilers are in the same building or if the boilers are in separate buildings: like one boiler per building.
   3. what size boilers they are
   4. are the boilers manifolded together as one large system or if there are separate systems
   5. how the boilers make hot water
      1. indirect tanks
      2. heat exchanger coils with storage tank(s)
      3. tankless coils inside the boilers
      4. or some other potable hot water source that is heated by the boiler(s)
   6. what existing controls are on the boilers
   7. what controls the hot water temperature
   8. what controls the room temperatures in the apartments
   9. if there is even a problem with apartments over heating in the summer as a result of the hot water operation

But without that additional information, we can all answer this with the experience we have all had on similar buildings. I remember shutting down a 220,000 BTU boiler for the winter that was only used to generate heat that goes into a shell and tube heat exchanger that fed a 2000 gallon domestic hot water tank that was covered with 3 inches of asbestos insulation with a plaster coating that was in pristine condition. the reason for shutting the boiler off for the winter was that no one lived in the building in the winter and the entire building was drained of water to prevent freezing water damage.

But that info won't help in this case.

EDIT:

The more info we have, the lower the cost of the solution to the problem: For example @pedmec solution is a complete control system for thousands of dollars. @EBEBRATT-Ed solution is to repair something that is already there. That has to be less expensive.

And since some of those boilers are from 1971, I believe that this situation has come up at least 54 times over the last half century. But that is just a guess

I thought he has 5 boilers in one building. but the more I thought about it, I believe there are many buildings with individual boilers in each building. Why would you have several boilers manifolded together and have 1971 boilers in the same system as boilers that are only a few years old? Makes no sense. that is when I thought of separate buildings. BUT… I am only guessing like you.

@4343 needs to offer more details.

I wonder if that is a new member that replaces @4321 from the other building down the parking lot of the apartment "systems" 🤣