Compliance with NYC heating laws & resident comfort: send heat all day, or only when code requires?

dschwarz

We have a high rise multifamily coop apartment building with 2-pipe steam heat (district steam; NO BOILER.) 1960s brick building, minimal insulation, decent dual pane windows. Our goal is to lower overall steam usage and maintain or improve resident comfort.

NYC code says:

From 6am-10pm we must maintain a minimum indoor temperature of 68F when it is below 55F outside.

From 10pm-6am we must maintain a minimum indoor temperature of 62F regardless of outdoor temperature.

We have an outdoor thermometer and thermometers in 25% of our units sending indoor temps back to the central controller. We have our setpoint temperatures MUCH higher than code requires; our setpoint is 75F during the day and 74F at night.

When outdoor temperatures are hovering at or above 55F during the daytime, we send no heat, so indoor temperatures will tend to drop during the day. Then we send heat starting at 10pm.

This doesn't seem optimal for resident comfort. I think we ought to send heat when indoor temp drops below setpoint, regardless of what the outdoor temperature is. That way, residents have a predictable temperature all day and night, and the system doesn't have to work as hard to "catch up" at 10pm nightly. (Note, with district steam, we get steam instantly on demand; there's no boiler to fire.)

My hope is that if we maintain constant indoor temperatures all day and night, we could lower our setpoints to something like 72F or 73F and save on steam usage.

My concern is that we will be using a lot more steam to maintain temps during the day, and the steam usage will not be offset by less steam use overnight.

What do you think? We do not have good heat loss measurements for our apartments; I think the only way we'll find out what works is to try it experimentally and measure results.

GGross

If you have it set up according to the requirements currently you may reach out to some long standing residents to find out if they have any issues with the current set up before you make a change.

dschwarz

Oh, our residents reach out to us OFTEN. With 420 units, we have people running electric resistance heaters during the day and night (even though our setpoints are high!) and other people opening windows to cool down their apartments. We'll never satisfy everyone, my goal is to find a happy medium where most people don't feel the need to run electric heat or open windows so much.

ARobertson13

dschwarz, The first thing that you should do is identify the apartments on each side of your building that have the highest heat load. These are the units that you must legally satisfy. Place your thermometers [I assume wireless] in these units. This change will give you a better guide for providing heat. The second thing is to change your controller or the way it operates. The more you rely on timing or outdoor temperature to supply steam, the less comfortable your residents will be. That is assuming your system is reasonably balanced. I had this issue in my Coop and had to build a controller. I intend to cover this in another discussion.

EBEBRATT-Ed

@dschwarz I agree it will be trial and error. You will probably never get it perfect but holding a more steady temperature will reduce complaints and maybe reduce fuel usage…..no guarantee.

To large of a temp set back can be counterproductive.

ARobertson13

@dschartz, You should also get a data logger if you do not have one to measure the time the steam actuator turns the steam on, the out door temperature and the mains temperature of the end of the longest mains run. Then place data loggers in the coldest apartments. I assume you are in Manhattan so they would be in apartments on the Eastern, Southern and Western windowed apartments. This is because of the effect of sunlight. This arrangement will allow you to measure any improvements in your system. Example: comparing a daylong period with an average temperature of 45 F to another period later in the year with the same average temperature. [the sunlight and wind which can found from the weather service]

JUGHNE

Are there separate electric meters for each unit?

dschwarz

We have temp sensors throughout the building on all risers. It's a 20fl building and we have 5 temp sensors per riser, so 1/4 of the apartments on the North, South, East, and West sides are all being logged. We had PEPCO install a Delta Controls control system and have access to logged data via enteliWEB.

I think we may have some balance issues particularly on the lowest floors, trying to get reliable info on that using our sensors.

The building electrical system is master metered with no submetering, so that won't help us determine which apartments are running heaters and when. I can see them on the data charts; anytime the system is not sending steam for hours and the apartment temp is WELL above our setpoint, that's a sure sign they're running a heater.

Likewise if an apartment is continually below our setpoint, even when sending heat, we know they have windows open.

If I had full access to the sensor data I could write some Python code using heuristics to detect heater-on and window-open scenarios. I don't have that yet.