Heat Pump stages

[tismon]

We recently had a Rheem three-stage heat pump installed for our house, and I have always been interested in installing solar on our home and we currently have a 8750W peak portable generator with house inlet for emergencies. In the back of my mind, I was thinking that there has to be a way to lock out the higher power stages in the heat pump to only allow it to use the 30-40% stage. This way, there would at least be some cooling/heating if I had to run solely on generator/solar.

Has anyone gone down this road before with a heat pump?

Thank you

 

[Ampster]

Has anyone gone down this road before with a heat pump?

I am not sure I know the difference between a 3 stage heat pump and an inverter driven heat pump.
I just installed an LG heat pump with three zones and I use temperature and or zones to control how much mine consumes.

 

[tismon]

I am not sure I know the difference between a 3 stage heat pump and an inverter driven heat pump.
I just installed an LG heat pump with three zones and I use temperature and or zones to control how much mine consumes.

Pretty similar. Rheem and Ruud are the only ones that have a 3 stage. Otherwise it's just a 2 stage and a full variable system.
Technically, the 3 stage also has an inverter compressor like a variable system. It just locks in the compressor speeds to three different levels and simplifies some of the hardware/controls.

We only have one zone technically. I would micromanage the thermostat for power consumption if needed, but I am hoping to find a way to just lock out the high power consuming stages to then not have to worry about it.

 

[Supervstech]

We recently had a Rheem three-stage heat pump installed for our house, and I have always been interested in installing solar on our home and we currently have a 8750W peak portable generator with house inlet for emergencies. In the back of my mind, I was thinking that there has to be a way to lock out the higher power stages in the heat pump to only allow it to use the 30-40% stage. This way, there would at least be some cooling/heating if I had to run solely on generator/solar.

Has anyone gone down this road before with a heat pump?

Thank you

What model unit do you have?
Often the less expensive units use time algorithm to determine what stage is needed. Some can be hardwired with Y1, Y2, etc…

 

[Supervstech]

Pretty similar. Rheem and Ruud are the only ones that have a 3 stage. Otherwise it's just a 2 stage and a full variable system.
Technically, the 3 stage also has an inverter compressor like a variable system. It just locks in the compressor speeds to three different levels and simplifies some of the hardware/controls.

We only have one zone technically. I would micromanage the thermostat for power consumption if needed, but I am hoping to find a way to just lock out the high power consuming stages to then not have to worry about it.

I’m guessing it’s similar to the 5 stage inverters everybody else uses. I’ve requested data sheets from my online source, and will have he skinny for you on this soon.

 

[tismon]

What model unit do you have?
Often the less expensive units use time algorithm to determine what stage is needed. Some can be hardwired with Y1, Y2, etc…

The Rheem 3 ton RP17.

Find product information, documents, videos, and installation assistance for the Rheem Classic Plus Series: Three-Stage (RP17)

Find product information, documents, videos, and installation assistance for the Rheem Classic Plus Series: Three-Stage (RP17)

www.rheem.com

 

[OffGridInTheCity]

We recently had a Rheem three-stage heat pump installed for our house, and I have always been interested in installing solar on our home and we currently have a 8750W peak portable generator with house inlet for emergencies. In the back of my mind, I was thinking that there has to be a way to lock out the higher power stages in the heat pump to only allow it to use the 30-40% stage. This way, there would at least be some cooling/heating if I had to run solely on generator/solar.

Has anyone gone down this road before with a heat pump?

Thank you

I'd think about it differently - e.g. setup your solar system w/battery so it's capable of running it and use your generator as support to the solar system to charge the batteries. In this way, even if your generator peak is less that the max you need, it can still charge the batteries so that generator charging + PV = overall continuous operation for those days when PV is weak.

3 yrs ago I converted to a Lennox high-efficiency 4ton heat-pump for my 2600sq foot home so I could heat/cool on solar. The outdoor unit tops out at 18a@240v = 4,320w per it's label. The indoor blower, UV is about 600w. I have clocked it at 5500w-6000w at full-bore overload at 110F ambient trying to cool the house. Heating doesn't stress it as much - ~ 5500w absolute max. I run it on an AIMS 12,000w inverter from solar and use my Honda eu3000is to charge my batteries as the emergency backup . Even thought the generator only produces 1/3-1/2 of what's needed for the heat-pump, the generator + PV is enough since the heat-pump won't max out all 24hrs in a day.

 

[Supervstech]

Are you using eco net controls, or a standard thermostat?

 

[newbostonconst]

From the manual...

Standard Thermostat wiring....



R is usually Power
C is usually Common
Guessing Pin 1 is stage one on
Guessing Pin 2 is stage two on
And Guessing stage one and stage two on turns on stage three.

I would try disconnecting the wire on terminal 2 at the thermostat and see if it runs with just stage one only.

 

[Supervstech]

From the manual...
View attachment 100719
Standard Thermostat wiring....

View attachment 100718

R is usually Power
C is usually Common
Guessing Pin 1 is stage one on
Guessing Pin 2 is stage two on
And Guessing stage one and stage two on turns on stage three.

I would try disconnecting the wire on terminal 2 at the thermostat and see if it runs with just stage one only.

No…

1 and 2 are communication conductors to the smart thermostat econet. Like a serial connection to the system.

 

[Supervstech]

Y1 and Y2 are first and second stage, but there isn’t a Y terminal for 3rd stage, so it must be an algorithm.

 

[newbostonconst]

The manual states it can have a normal therm hooked up so I think the logic I stated above might be close.

pin 1 on and pin 2 off = stage 1
pin 1 off and pin 2 on = stage 2
pin 1 on and pin 2 on = stage 3
pin 1 off and pin 2 off = unit not running.

 

[Supervstech]

The manual states it can have a normal therm hooked up so I think the logic I stated above might be close.

pin 1 on and pin 2 off = stage 1
pin 1 off and pin 2 on = stage 2
pin 1 on and pin 2 on = stage 3
pin 1 off and pin 2 off = unit not running.

Incorrect.
The 4 pin wiring is serial communication to the econet smart communicating thermostat.

The RCYGW etc connections are for standard thermostat control.

 

[OzSolar]

A friend and I are playing around with the same thing at his house. He has an everyday single stage heat pump with emergency heat, AKA strips.

In laymen's terms here's what we think we found for his heating modes.

Heat Pump - Heat pump runs downs to around 32f
Auxiliary - Heat pump and strips come on somewhere around 32f
Emergency - No heat pump, unit goes straight to strips around 32f

We did did some testing and found that with a little bit of reprogramming we could disable to strips and make it think it was a heat pump only. Common wisdom seems to be that heat pumps don't work below ~28f-32f but what we found at his house is that his nothing specials older HP still put out usable heat down to the mid teens of air temp.

Of course it ran almost continuously but we proved that he keep his house warm when the power was out with an 8000 watt 240v generator. We regularly get to the 30f temps in the winter but rarely get below 15f so he now how a much more useable set up than before.

edit to fix typo.

 

[tismon]

I'd think about it differently - e.g. setup your solar system w/battery so it's capable of running it and use your generator as support to the solar system to charge the batteries. In this way, even if your generator peak is less that the max you need, it can still charge the batteries so that generator charging + PV = overall continuous operation for those days when PV is weak.

3 yrs ago I converted to a Lennox high-efficiency 4ton heat-pump for my 2600sq foot home so I could heat/cool on solar. The outdoor unit tops out at 18a@240v = 4,320w per it's label. The indoor blower, UV is about 600w. I have clocked it at 5500w-6000w at full-bore overload at 110F ambient trying to cool the house. Heating doesn't stress it as much - ~ 5500w absolute max. I run it on an AIMS 12,000w inverter from solar and use my Honda eu3000is to charge my batteries as the emergency backup . Even thought the generator only produces 1/3-1/2 of what's needed for the heat-pump, the generator + PV is enough since the heat-pump won't max out all 24hrs in a day.

I haven't pushed this unit to the limit yet to know what it really draws. I've got a Sense monitor, but I want to check it during a 100F+ day and <10F day for full system draw when it turns on/off just in case Sense isn't detecting every aspect of it.

With a well, septic, all electric heat pump and water heater, and a full size deep freeze (surprisingly not that much consumption), a 10kW system wouldn't keep up enough to run everything without restriction. And from the one energysage quote that we got, a 9-10kW array is about all will fit on our roof on the south side (trees everywhere else).

So what my mini-goal would be is a system that could handle my well (2.5-3kW startup surge), fridge/freezers, and a tuned-down heat pump in case of emergencies outside of normal grid offsetting. Completely being able to be off-grid/sell back to the grid would be the stretch goal.

 

[tismon]

Are you using eco net controls, or a standard thermostat?

Econet. With a 3 stage + strips, my 2nd gen Nest couldn't handle it. Plus the Econet has a LOT of system information.

 

[tismon]

A friend and I are playing around with the same thing at his house. He has an everyday signal stage heat pump with emergency heat, AKA strips.

In laymen's terms here's what we think we found for heating modes.

Heat Pump - Heat pump runs downs to around 32f
Auxiliary - Heat pump and strips come on somewhere around 32f
Emergency - No heat pump, unit goes straight to strips around 32f

We did did some testing and found that with a little bit of reprogramming we could disable to strips and make it think it was a heat pump only. Common wisdom seems to be that heat pumps don't work below ~28f-32f but what we found at his house is that his nothing specials older HP still put out usable heat down to the mid teens of air temp.

Of course it ran almost continuously but we proved that he keep his house warm when the power was out with an 8000 watt 240v generator. We regularly get to the 30f temps in the winter but rarely get below 15f so he now how a much more useable set up than before.

Bingo. That's exactly my goal. Thank you for adding your experiences with this.
Would you mind sharing what the setting were? Setting the temp cutoff to stop heat pump only I assume is a given, but was there more?

 

[OzSolar]

Bingo. That's exactly my goal. Thank you for adding your experiences with this.
Would you mind sharing what the setting were? Setting the temp cutoff to stop heat pump only I assume is a given, but was there more?

I don't recall exactly other than we basically just told the thermostat that it was only hooked up to a heat pump. In a perfect world your HP thermostat would have an outdoor temp sensor and you could program the switchover temp.

In this case he had to be alert to change the settings manually or his strips would never kick on. Not the best solution but it worked.