If you have a Heat Pump and A Z-Wave thermostat that has an EHEAT setting then you can save your heat pump and maintain good temperature control by using the PLEG plugin to automatically change your thermostat from EHEAT to Auto as follows:
PLEG Input: OutsideTemp Bound to the Weather Underground temperature for your location.
Add an Action to the above conditions to set your thermostat in the appropriate mode.
Note: For those that already have protection of your Heat Pump, if you do not have a thermostat that automatically goes into EHEAT mode
(i.e. one with an external temperature measurement) then you will still have a large temp variation between ambient temp and setpoint temp before the aux heat is enabled. Turning on EHEAT will treat the Aux heat as primary heat and will cause it to come on immediately when the normal heat would normally be turned on.
Hi Richard,
As I do not have a thermostat connected to the Heat Pump (Water Air HP with curves management system based on outside temperature), I use the “Remote control” from the Energy Provider. They can switch off/on my Heat Pump remotely when there is too much energy used in my area. So I’ve installed a Fibaro to pilot my Heat pump. The problem is, as I have a lot of inertia (heating tubes from the floor), I’m still waiting for the “Forecast” Option from Weather Underground plugin. I mean now, at 6AM I see the weather information from the plugin, and for example, if "Overcast, or Rain, or… I switch off the Heat Pump. Because in my house I’ve enough passive solar energy (south oriented house with a lot of big windows). Then I switch again on when temperature goes below a defined limit. But If I can play with forecast, it will be better, any news from Weather plugin to handle forecasts?
The weather underground problem is suffering from two much discussion by committee … With no way to know when/what constitutes agreement.
A heat pump’s efficiency and safe operating limits are based on the actual conditions when it’s running.
If you a heatpump is running and the outside air temp drops … it can return liquid back to the compressor.
I do not interact with the safe operating limits, this is not an hardware shutdown, all safety operations of the pump are still alive, I’m just interacting with a “dry” contact in the unit…
I think you may be a little off here. The emergency heat setting of your heat pump uses only the aux heat and in most cases that aux heat is electric which is more expensive than the heatpump to heat your house.
If you have a gas furnace as backup then what your saying can make sense but the balance point will probably be a little liower than 40.
What are you trying to accomplish when you “save” your heat pump?
Heatpumps are made to run in the cold and every one I’ve seen has a accumlator to stop the liquid flood back you mention.
[quote=“willf650, post:5, topic:178668”]I think you may be a little off here. The emergency heat setting of your heat pump uses only the aux heat and in most cases that aux heat is electric which is more expensive than the heatpump to heat your house.
If you have a gas furnace as backup then what your saying can make sense but the balance point will probably be a little liower than 40.
What are you trying to accomplish when you “save” your heat pump?
Heatpumps are made to run in the cold and every one I’ve seen has a accumlator to stop the liquid flood back you mention.[/quote]
For my part, interracting with my Heat pump saves me around 1’000 kWh per year, for the last 3 years, that’s something like 3 X 250W photovolta?cs modules, if you consider that’s nothing, it’s up to you…
I see mention of a setpoint of 40deg and the statement that a compressor will be damaged by liquid flood back. That can be the case with a straight AC but air to air heat pumps have an accumulator to prevent that.
It’s not the fact that it’s not worth it but the fact that if you are using electric strips as a backup that the most effiecent point to switch over should be under 40 deg. If it is 40 deg than I would think their is something wrong with your heat pump. If you have a gas furnace that would change things. All systems won’t be the same but your ideal temp should be a little closer to freezing.
Maybe I came off a little coarse in my first post.
If you disagree or your system is most effiecent to switch over at 40 degrees disregard this. For a standard heatpump damage should not occur at cold temperatures and the ideal change over point would probably be lower than 40.
Just to backup what he said, I just had mine replaced (20 year old unit) with a new super efficient one and the point that it becomes less efficient at well under freezing. My HVAC guy even stated it was around 20-25 degrees.
My outdoor unit will not even kick on, and that is with a $20 thermostat (looking for a vera compatible replacement now).
Having said that, I know my older unit never made it to freezing, so it has a lot to do with the age of the unit.
[quote=“willf650, post:7, topic:178668”]I was talking in general to both of you.
I see mention of a setpoint of 40deg and the statement that a compressor will be damaged by liquid flood back. That can be the case with a straight AC but air to air heat pumps have an accumulator to prevent that.
It’s not the fact that it’s not worth it but the fact that if you are using electric strips as a backup that the most effiecent point to switch over should be under 40 deg. If it is 40 deg than I would think their is something wrong with your heat pump. If you have a gas furnace that would change things. All systems won’t be the same but your ideal temp should be a little closer to freezing.
Maybe I came off a little coarse in my first post.
If you disagree or your system is most effiecent to switch over at 40 degrees disregard this. For a standard heatpump damage should not occur at cold temperatures and the ideal change over point would probably be lower than 40.[/quote]
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