Converting a single zone of 5 rooms to behave as 5 individual zones

rfriedman

I have a 2-pipe hydronic heating system with cast iron radiators in each of 5 rooms. All rooms were connected to a single zone with the thermostat in the hall. The heat distribution was uneven and could not meet the demands of the individual rooms, some of which were unoccupied for extended periods of time.

As you can see from the images, I have cast iron radiators with 1” angle valves. I replaced the original frozen valves with Danfoss Thermostatic angle valve bodies, although I did not use their temperature sensors and actuators.

I fitted 24 VDC NC thermal actuators to the valves along with Wi-Fi Relays. These actuators were intended for radiant heating manifolds.

I installed a smart circulation pump that would automatically adjust flow based on the flow demand and assembled a circulation pump relay module (see image) that had one Wi-Fi Relay for each radiator valve. They are all wired to the same circulation pump. So, when all relays were off the pump turned off.

Each room required:

1 Wi-Fi temperature sensor,

1 Angle Valve with 30mm X 1.5 adapter

1 Thermostatic Actuator

1 Wi-Fi relay

1 Power Supply (24 VDC)

The Relay module required:

5 Wi-Fi Relays

1 Power Supply

The control of all these devices was through a free Shelly Cloud application. I could monitor and change the settings from my cell phone.

Each room has a virtual thermostat that communicates with: the rooms temperature sensor, the relay on the radiator actuator, and the relay in the circulation pump module.

Conclusion:

I am pleased with this project. It’s simple, uses only two types of electronic devices, so my inventory of spare parts is small. I have converted a single zone to a multi-zone system with individual room temperature control at low cost, and perhaps saved fuel by not over heating unoccupied rooms

Concerns:

I wonder if I have introduced short cycling and wonder what period constitutes a short cycle. I invite comments and feedback.

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EBEBRATT-Ed

I guess if your saving fuel your saving fuel

I like to see a boiler run for at least 15-20 min. That is not always possible.

The correct size boiler will reduce short cycling. A buffer tank would help. A Mod Con boiler that modulates would help.

Ironman

I believe thermal actuators would have worked just as well, but I get it: some folks like electronic gadgets.

hot_rod

what type of boiler? How does it match the radiator size, btu wise?

10 minutes is the minimum tun time, as a rule of thumb. On a large high mass boiler even longer to get it hot.

The short cycling and also low return would be a bigger issue with a conventional boilet