With the temp at 0 degrees the other night, the heat pump wasn’t keeping up. It has two strip heaters as backup, but only one was energized. One heater ohms 10 and the other 25.The heaters are connected to a relay with one coil and 4 contacts labeled M1, M2, M3, M4. The best I can tell both, heaters should be on, right? I have heard the term sequencer by Hvac guys. What makes them sequence? Appreciate any incite.
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Greetings Karl, Welcome to Breaktime.
This post, in response to your question, will bump the thread through the 'recent discussion' listing again which will increase it's viewing.
Perhaps it will catch someone's attention that can help you with advice.
Cheers
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"I heard the term "sequencer" by HVAC guys. What makes them sequence?"
Hi Karl. Just so you know, I'm a carpenter by trade, not an HVAC guy...whom I'm sure could give you a better answer than me. When referring to strip heaters, I believe you are referring to the same type of heating elements found in a regular electric furnace, right?
Well, if so, those elements each have a relay switch; called a sequencer relay. What it does is this:
When the thermostat calls for heat, 24 volt current flows through the filament of the first relay. After several seconds, the heat created by the current , causes the bimetal switch in the relay to expand, thus switching on 240 volt current to its heating element. At the same time, this relay then allows 24 volt current to pass on to the next sequencer relay in the series, which then turns on the 240 volt curent to its heating element...and so on and so on.
To protect the household current against overload, each sequencer relay has a delayed reaction....switching on its element several seconds after the previous one.
The amount of sequencer relays that "fire-on" is determined by how much heat is called for by the thermostat. For example, if the heat setting is reached with say 3 relays firing and heating up their elements, then relay No. 4 or 5 automatically does not get turned on.
Also, each element has not only a relay, but also a limit switch, which would shut down the heating element if the element was overheating. As far as to how to properly wire this system up, I really couldn't say...sorry.
I hope this gives you some insight. Hopefully someone better schooled than me in furnaces can help you out more.
Davo