Thank you for the helpful info. Yes our condo only has 23 units, and only a main shut-off. I have a electric zone valve, that I am currently using manual control (only off or on) to regulate heat upstairs as the motor had burned out. I have asked a building associatation reguarding this problem; normally any heating problem is handled by the a contracted company in charge of the building maintananc, however this only covers problems with system, and nothing inside the units. And shuting it off for any non-critical reason or internal unit repairs requires a advance notice application to do so, at a cost of nearly $500. They have to called the contracted maintenance to shut off and reactivate it. (way too much hassle and cost to replace a zone valve.) Guess I’ll have to wait till spring and take my chances with luke warm water instead of scalding heat.
This could all be solved with ease if I could track down an old bell & gossett modumate model zone valve, but of course its discountinued and now where to be found.
Thanks all for the info, reallly appriciate it