How to best operate our (multifamily, 2-pipe, Vari-Vac) steam system?

dschwarz · September 19

I am on the board of a 420 apartment midcentury high rise multifamily coop in Manhattan. We are trying to reduce our heating expenses while keeping residents comfortable.

Our building has a 2-pipe Vari-Vac steam heating system (on district steam; we have no boiler on site). Brick building, minimal insulation, double-pane windows from the late 1990s.

For each steam heat riser, we have equipped adjacent rooms on 25% of the floors with wireless thermometers transmitting indoor temps to a central controller. The central controller uses these readings to determine if heat should be sent to each riser.

None of the radiators have TRVs. Residents typically respond to overheating by opening a window.

We have implemented the following setpoints for the system.

6AM-8AM - morning boost - 76F setpoint

8AM-10PM - normal operation - 75F setpoint

10PM-6AM - nighttime setback - 74F setpoint

These temperatures seem ridiculously high to me. But if we, for example, lower the nighttime setpoint below 74F, we get flooded with complaints from residents.

I'd like to get us down to reasonable daytime and nighttime temperatures. What is generally reasonable and expected? Is the setpoint programming (with a morning boost and nighttime setback) best practice?

What else can we do to save on heating? Different people have recommended that we:

Increase our wireless thermostat count to at least 10 per riser (50% of floors covered)
Install TRVs

The above recommendations seem to be at cross purposes with each other.

Thanks for your help.

EdTheHeaterMan · September 19

Just a little psychology might work.

I can make a suggestion to lower the set points one degree at a time. Leave that new setpoint for two weeks or so. You won't get as many complaints and you would by lowering the temperatures all at once to 68°

After 2 to 3 weeks of one degree lower temperature, and answering those fewer complaints with "minor adjustments" with a wrench and a screwdriver visit to the complaining residents' apartments and telling them that the (placebo) adjustment should take care of the problem. (Don't use the word Placebo when describing the adjustment!). After 2 to 3 weeks, drop the temperatures another degree. After you do this for 3 to 5 degrees, you will end up with some unhappy residents, and you will still have some open window tenants, but when you average it out over the 420 apartments you will get the lower cost you are trying to accomplish, you can't please all the people all the time.

Finally a letter explaining that the fuel savings at the new settings is $$$$ per month. and that if anyone wants the old settings restored, they can pay the full amount of that savings themselves, since the other tenants are enjoying the lower operating cost and the accompanying fee reduction (or not needing an increase). It is not fair that one individual's additional cost for comfort be carried by everyone else. If one person wants the Co op to pay more for that one person's comfort, then that one person needs to cough up the additional $$$$. They can [pay for the inconvienencd of the res to the tenants that need to poen windows for their higher temperature.

Also you need the maintenance superintendent and their staff to understand the purpose of the procedure. To lower costs so you can afford to pay them. And that any resident that they need to visit is the “only one” that has a problem and there are no other complaints. If the staff lets the cat out of the bag, then the procedure won’t work as well.

There is another approach that someone was trying to market that used an electronically controlled blanket or covers over the radiators that may solve the problem. I wonder if that system is available yet?

Perhaps @Erin Holohan Haskell might be able to find the article that was posted by her faterh a few years back about this idea. I think the guy who invented the idea was going for a patent and was going to market the product to NYC to building owners (or co op boards). like yours.

HeatingHelp.com · September 20

Here you go: https://heatinghelp.com/systems-help-center/invisible-tenants/

It was called the Cozy and is now called Kelvin and is a product of Radiator Labs in NYC. @Garrett_Modeste and @RadiatorLabs may be able to help you.

dschwarz · September 20

I like the psychological approach. We might just try starting off this heating season with setpoints 2F lower across the board.

… but I have a feeling that some people's complaints about the heat may be valid?

Theory: we have through-wall air conditioners in each unit, no insulation in the walls, and it's possible that they are reacting to drafty conditions.

Re: Kelvin radiator cozys. We had initial discussions with Kelvin. Their cozys offer the most dramatic results when used with a one-pipe system. Our two-pipe vari-vac is inherently more efficient, so there are less gains to be had.

Their analysis projected a 16% reduction in heating costs and elimination of Local Law 97 carbon penalties through 2034. Which is pretty good! And their networked solution MIGHT integrate with our central controls.

BUT: Installation of cozys over our baseboard radiators would be intrusive - residents would lose some floor space. A tricky problem to solve: Cozys need a 110V outlet for power, which we only have near 1/3 of radiators.

Compare that to TRVs, which may offer us a 10% energy savings at considerably lower cost with a less intrusive installation.

But a dumb TRV installation will still conflict with the wireless thermostats, and I don't know if commercial grade smart TRVs exist that can be integrated with the central control system (which uses BACnet/LoRaWAN). Anyone have experience with this?

mattmia2 · September 21

It is probably more that the system isn't balanced and that different people like their homes at different temps.

You say baseboard. What type of emitters do you have? Doing a heat loss analysis and a radiation survey to see how well things match might be the first step.

If you can control the pressure you can then install orifice plates in the supply to each radiator to balance it then people can use the radiator valves to modulate the heat.

I'm not sure exactly what the vari vac means so it might not be possible to regulate the steam pressure differential.

When you figure this out you will have to figure some people will want their apartment at 62 and others at 75. It will have to be able to supply the 75 but be able to be throttled for the 62. Trvs could also provide the lower temps where desired but they will perform poorly if the system isn't balanced first. There are 24vac heads for trvs but I'm not sure how you'd control them.

dschwarz · September 21

I agree it is likely the system isn't balanced. Also true that different people like their homes at different temps. But 75F doesn't seem like a happy medium for anyone.

The steam radiators in our building I have also heard called convectors. They are metal tubes surrounded by many metal fins. I will ask about a heat loss analysis and radiation survey.

Vari-vac systems are two pipe steam heat with vacuum pumps to adjust the pressure of the system in a range, it can pull vacuum and reduce radiator temperature to 133F or increase pressure for radiator temp up to 220F. According to product literature, it already has adjustable orifices built in.

I think we'll benefit from consulting with vari-vac system experts. I'm going to call G.S. Dunham.

mattmia2 · September 21

A convertor is an element like a car radiator horizontally in a usually steel cabinet. The cabinet creates draft through the element and produces much more output than if the element were in free space.

Your goal shouldn't be to make the building all the same temp but to adjust the needles or stops in the valves so if the valves are all fully open the system is balanced and then have the tenants that want it cooler partially close the valves to make their apartment cooler. I'm not sure how you control that with one thermostat, you really need to read multiple set points based on preference

dschwarz · September 21

We have wireless thermometers on each riser - on 25% of the floors. These send back current in-room temps to the central control system. We have 5 thermometers per riser. If 2 on the riser are below setpoint, heat is called for on that riser. Subsequently, if only 1 on the riser is below setpoint, heat is stopped on that riser.

How to best operate our (multifamily, 2-pipe, Vari-Vac) steam system?

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