Tekmar Outdoor Reset or Internal Temperature Sensors for 14 Unit Apartment Building

nziegler · April 2022

Hello,

I've searched for posts regarding Tekmar outdoor reset vs internal temperature sensors, and all seemed to be focused on single-family homes, so hoping to get some feedback on its use in an apartment building.

I live in a 14 unit condo building (4 stories, brick) that has steam radiators with a central boiler. Currently there is one thermostat on the top floor in our central hallway that controls the furnace. It works but isn’t great. Either the furnace doesn't turn on when the units are chilly or it runs continuously for the entire "home" cycles. We are considering either putting remote sensors in a few units and letting an average temp trigger the furnace or a Tekmar with outdoor reset to control everything.

If anyone has experience with either system in an apartment building, I would like to hear how it has worked.

Thank You

EBEBRATT-Ed · April 2022

You will find it difficult or impossible to keep everyone happy.

Before you do the control thing it would be best to have the system serviced and cleaned and air vents installed/adjusted and balanced.

You can add all the controls you want, but if the system doesn't work well controls won't fix it.

Once you have the system running as good as it can, then add some controls.

I would use and outdoor air lockout to shut the boiler down at 55 degrees (adjustable) and the thermostats (maybe 4) to call the boiler on on an average temperature

mattmia2 · April 2022

Is it 1 or 2 pipe? Individual controls like TRVs at each radiator could possibly work here. Isn't this application like Heattimer's whole business? TRVs and steam are challenging but I'm not seeing 14 tenants agreeing on a single temp even if there was some way to balance it which there isn't because of varying gains and losses with changes in things like weather, occupancy and usage, and sunlight.

EdTheHeaterMan · April 2022

Is the "central furnace" a boiler that makes steam or hot water? Outdoor reset will not work with steam. It will work with a hot water boiler.

I have had experience with several multi-tenant buildings that have a common boiler with a single thermostat. The most cost efficient job I remember was a large 3 story Victorian home that was converted to a bed and breakfast. I installed individual thermostatic radiator valves on most of the radiators in the building and installed the thermostat in the coldest room in the building. This would cause the rest of the rooms to overheat if all the radiator valves were open. Each tenant or guest could adjust the valve on the radiator to a number that was comfortable for them. Once the room was comfortable the thermostatic valve would close, without the need for any electricity or wiring, and allow the hot water to circulate to other rooms.

If the coldest room ever was hot enough to satisfy the thermostat, the boiler would shut down. (this never happened before the TRVs were installed.) On one project, the owner saved over 1500 gallons of fuel oil, that first year of operation, after the TRV install. That savings paid for the entire job in 2 heating seasons.

I added ODR in the following years and there was even more savings.

If you have Steam Heat you can use TRVs designed for steam radiators. They go on the air vents if you have a one pipe steam system. Read page 20 of this text I used to use for teaching Hydronics. http://media.blueridgecompany.com/documents/ZoningMadeEasy.pdf

Mr.Ed

Steamhead · April 2022

@nziegler , this is the Tekmar control you need:

https://www.watts.com/products/hvac-hot-water-solutions/controls/boiler-mixing-controls/279/279

We have several buildings using this control, as well as its predecessor the 269. As long as the systems are in good shape, as @EBEBRATT-Ed says, the 279 will do what you want.

Tekmar Outdoor Reset or Internal Temperature Sensors for 14 Unit Apartment Building

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