Hi Monica, I installed several of these combination units in Riverdale (Bronx) on a 27 story building and in the “Sovern” around 57th and sutton place. I think it is 56 strories high
What you need to find out is if these are cast Iron or steel fin tube or copper fin type AND if your building is willing to allow for a drain down this time of year.
One of my condo accounts will not allow a drain down until the temperature is above 55 degrees.
If you live in a co-op Or rental most lightly the building will replace this if a Condo it is up to the board of directors to call the shot.
For example in the CO-OP I work in I am the building plumber as I work directly for the building not the individual stock holder Unless the stock holder gets board permission for me to do other types of replacements like complete bathroom modernization etc.
You should try the Water source supply (718 549 6132) and ask for Eric Or Try Solco plumbing Supply on 18th street and Tell them Sylvan says “HEY”
Your very Lucky as we in NYC have EVERYTHING anyone can ever hope for in plumbing and heating