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I was standing on the corner of Varick and Watts St when the first plane flew over my head. It struck me what a mechanical sound it was and then I noticed the plane was much lower in the sky than planes typically are. I didn't think much more of it. Not more than 4 or 5 seconds later I heard the crash and looked up and saw the hole in the tower with smoke pouring out of it. There was instant panic around me and a prayer circle seemed to spontaneously form. The Lord's Prayer filled the moment and was interrupted by police shouting unintelligibly into radios. The second plane hit and everyone on the street scattered. No more prayers. No more police. Some people abandoned their cars and ran. I ran into my small 5-unit apartment house to find my friends. They all ran outside to see, then came back in to turn on the news. What was happening?
The scene on the street was indescribable. I was 32 years old and I was terrified. It changed the course of my life. Terror leaves a lasting scar.
Meanwhile, my wife (now ex) and coworkers were advised by security to stay in their building across the street from the towers. No one knew what to tell them to do. When the towers came down they all felt it and heard it but didn't see it. It created more panic. Change of plan. They were hastily told to exit the building and find their ways home. To get everyone out, they were ushered quickly toward large loading dock doors. The doors, now pressed closed with a hill of debris, wouldn't not open. They were trapped in the building surrounded by loud sounds and only emergency lighting.
Finally, we made contact by landline and made a plan to stop trying to stay connected and focus on getting out of Manhattan and get to Staten Island, where I still have family, by boat. When I got across the harbor hours later, a story all its own, she was already there with some of her coworkers and we were both fine.
The day was unimaginable and I am triggered by the concept of all the "Never Forget" stuff we encounter this time of year because if I could, I most certainly would forget. I'd be better off.

so total load is 70K?

One rule of thumb is the low temperature load should not be more than @10% of the boiler capacity. That is to prevent the boiler from extended cold run times as it will see the radiant return temperature. At design the radiant may be returning 95F to the boiler (SWT 105-10 delta) If the boiler is keeping up or gaining on the loads that radiant return temperature blends with the boiler operating temperature, so that RWT is a moving target. You could calculate that number knowing flows and temperatures. You want to assure the oil boiler return is above 130 within 10 minutes or so of run time.

If the buffer tank is hot and any call for heat comes on, it will just pull from the buffer tank. The boiler and its circ will just run when the tank aquastat drops low enough to call. I'd guess you would run the buffer 140 or so + the 25° diff, so up to 165. That may be cutting it close to assure warm enough return to the oil boiler, worse case you run it 150- 175. Calculate that, or sit and observe for an hour or so.

Do so until you reach thermal equilibrium. That being when the boiler is no longer adding heat to the system, SWT and RWT are staying put. Heat input and heat output are perfectly matched at this point.

The hotter you run the boiler the less efficient, but the hotter the buffer tank, the longer the drawdown time. So tradeoffs there. Obviously a non condensing boiler has a min imum return temperature requirement, 130 seems to be the industry agreed number.

Any addition heat input, mod con, heat pump, solar, etc, just ties into the headers off the buffer tank. You could have a multi, multi fueled system, selecting the most efficient heat input device at any point in time.

More info and formulas here.

It was a cheap way of wiring a 2 story, 2 zone house.

14/3 Romex from the boiler to the first floor thermostat.

14/2 Romex from the first floor thermostat to the second floor thermostat.

White is Common and connects to the Line side of each thermostat, and R on Zone 1. (You might need to make a splice in the fist floor Gem box if there's not 2 Common posts on the thermostat.)

Red connects to the Load side of the first floor thermostat, and W on Zone 1 in the Zone Panel.

Black connects to the Load side of the second floor thermostat, and W on Zone 2 in the Zone Panel. (Black must be sliced through in the first floor Gem Box.)

The reason only one R is needed at the Zone Panel is because both zones share a what?... Beuller? Beuller? A "Common" feed.

**This ONLY works the way described if you're using a Low voltage circuit with Line voltage thermostats. And these Line Volt thermostats are obviously battery powered for switching because 24 volts isn't going to cut it.

If this is somehow still a Line Volt circuit with a "Zone relay", then there should be a couple of additional transformers somewhere.

Old Radiator Ratings

If you're replacing a steam boiler, there's only one right way to size that boiler, and that's to measure the radiators. If you're replacing a hot-water boiler, you'll do a heat-loss calculation on the building as it is today, but it also pays to measure the radiation to see if you can reduce the water's temperature and save fuel. The challenge, though, is that it's often difficult to find the ratings for many of those old radiators and convectors, and that's why Dan Holohan compiled E.D.R.: Ratings for Every Darn Radiator (and Convector) You'll Probably Ever See.

Dan collected a ton of heating books and heating-manufacturers' literature from the past. E.D.R. is 272 pages of nothing but radiator and convector ratings and if that old unit is out there in the field, it's probably also in this book. This is a terrific resource for any heating professional who wants to get it right the first time.