Can I Connect Multiple Electric Heaters (with 24V Control Circuit) To A Single 24V Thermostat?
The short answer is YES, provided the wiring is setup correctlty.
If your building has a open-concept layout where multiple functions are combined into one larger area, having one thermostat control mutliple heaters may be ideal because you’re essentially heating one large space.
However, it is not recommended to connect more than one heater from different rooms to a single thermostat because the temperature in both rooms would be determined by the temperature of where the thermostat is located, which is not ideal. Doing so would defeat the advantages of creating the zone-based heating that electric heat is known for. With zone-based heating you heat each room independently, which maximizes individual comfort and minimizes the electric bill.
So how do you hook up multiple heaters to one thermostat?
IMPORTANT:
For Multiple 24V Controlled Heaters To Properly Work
On a Single 24V Thermostat There Are Several Challenges To Be Aware Of:
Level of Difficulty:
3 Phase Heaters: High Risk
1 Phase Heaters: Low Risk
Lets start with Single Phase as it is a simple 50/50 success rate.
Single Phase: Key Action For Success – All Transformer Phase’s Need To Match.
- The line voltage power feeding the heater has to be wired in Phase 1 (or L1) and Phase 2 (L2)
- The Transformer also must attach to these 2 phases from the line power.
When the transformer’s 24-volt pair of wires get to the thermostat location from heater one, the second pair of thermostat wires from heater 2 need to match the L1 and L2 phase of the first heater.
How to Match the Single Phase at the Thermostat Location.
Steps:
- Apply a volt meter to one thermostat wire from each heater.
- Both will need to read Zero Volts to ensure they are on the same phase.
- These two wires can be attached to each other without burning up the transformer.
- If you read any higher voltage you are out of phase and this is a dead short for the transformer.
Note: This dead short burns up the transformer very fast.
3 Phase: Control Wiring Multiple Heaters Together On One Thermostat
As you see in the single phase wiring explaination above, you have a 50/50 chance to get the wiring correct. With 3 phase we add another phase to complicate our options. Most heaters may be wired the same internally, but the installer may not have placed the feed wires L1,L2,L3 at the same location on each heater input, so at the thermostat location may never see zero volts, no matter what combination you try.
This is because the transformer is powered by only 2 of the 3 lines of power.
To rectify this, you must swap two of the legs on the main Circuit Breaker panel of the non-compliant heater so that you will now see zero volts at the thermostat location.
Single Phase Relationship
Three Phase Relationship
