Soft start needed for new heat pump?

Ghcoupons

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Hello. In our new home we have a 20 SEER heat pump. It has a variable Speed compressor that operates from 30-100% depending on the need. Would I benefit from adding a soft start system to this unit?

I ask because i would like to reduce energy usage before adding solar. I’ve done a lot (led’s, extra insulation, etc,) and am now looking at the smaller items that may help reduce a solar array size in the future.

thank you.
 

Ampster

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Would I benefit from adding a soft start system to this unit?
If it is variable speed it is most likely inverter driven and probably has very little surge. My new refrigerator is inverter driven internally and I can run it off a very small120 volt inverter. You can check the label and see if it shows LRA (locked rotor amps)
 

Bob B

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Hello. In our new home we have a 20 SEER heat pump. It has a variable Speed compressor that operates from 30-100% depending on the need. Would I benefit from adding a soft start system to this unit?

I ask because i would like to reduce energy usage before adding solar. I’ve done a lot (led’s, extra insulation, etc,) and am now looking at the smaller items that may help reduce a solar array size in the future.

thank you.
I'm jealous .... A secondary benefit of the high seer heat pumps is that they have very low surge currents.

You can probably look at the unit specifications to find that info .... but I doubt very seriously if you need to be concerned about it.
 

DThames

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A soft start is meant to spread the start over a longer period of time, reducing peak current (not reducing required work). The actual work of starting the load is roughly the same if it starts in 1 second, 5 seconds, or 10 seconds.
 

Ghcoupons

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If it is variable speed it is most likely inverter driven and probably has very little surge. My new refrigerator is inverter driven internally and I can run it off a very small120 volt inverter. You can check the label and see if it shows LRA (locked rotor amps)
Awesome, I will look for the LRA. Thank you.
 

Ghcoupons

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If it is variable speed it is most likely inverter driven and probably has very little surge. My new refrigerator is inverter driven internally and I can run it off a very small120 volt inverter. You can check the label and see if it shows LRA (locked rotor amps)
The ownerscmanual says it has an lra of 35 or 50 depending on the model.
 

DThames

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Are you planning to be able to run the heat pump in a 'grid down' situation or just looking for overall power savings options? Starting a 240v motor with even 35amp LR load will take a large inverter.
 

Ghcoupons

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Are you planning to be able to run the heat pump in a 'grid down' situation or just looking for overall power savings options? Starting a 240v motor with even 35amp LR load will take a large inverter.
I am currently working on reducing usage. We just finished an ICF house. I tried to build it as efficient as I could afford. I’m investigating items like a soft start kit that may not only reduce usage, but allow for a smaller array when that time comes. A SSK and water heater timer come to mind, but our heat pump seems efficient as it’s gonna get and our marathon water heater doesn’t have much stand by loss, so I suspect a timer would be not significantly helpful. We currently use Around 900-950 kWh a month. It’s significantly better than our last house but I’d like to get it lower if possible.
in a grid down situation, I suspect fans and even a a window AC would be a better cooling option than the heat pump. Thank you.
 

Hedges

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I'm surprised a heat pump with VFD would quote locked rotor amps. Maybe that is of the motor (if connected to 3-phase), but I would expect the heat pump to very soft start.

"reduce energy usage before adding solar"
Starting surge is insignificant in energy usage. Soft start won't reduce energy usage. It only matters for use with a generator or inverter.
A pair of my Sunny Island (120 each, 120/240V from the pair) would have no trouble driving 240V at 50A. Can pretty much put that out continuously.
If you want solar + battery backup, just select equipment that can deliver the power needed.

Of course, likely in summer you can produce enough power from PV for A/C, but not in winter for heating. Unless very efficient house and lots of PV panels.
 

Ampster

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I'm surprised a heat pump with VFD would quote locked rotor amps.
Yes, that is why I suggested he look to confirm the absence of LRA to confirm it was indeed a VFD. Essentially there is no LRA for a VFD.
Like an earlier poster I am envious of his system because of its efficiency. My next home will have a VFD heat pump with a variable speed zone fans.
 

Ghcoupons

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I'm surprised a heat pump with VFD would quote locked rotor amps. Maybe that is of the motor (if connected to 3-phase), but I would expect the heat pump to very soft start.

"reduce energy usage before adding solar"
Starting surge is insignificant in energy usage. Soft start won't reduce energy usage. It only matters for use with a generator or inverter.
A pair of my Sunny Island (120 each, 120/240V from the pair) would have no trouble driving 240V at 50A. Can pretty much put that out continuously.
If you want solar + battery backup, just select equipment that can deliver the power needed.

Of course, likely in summer you can produce enough power from PV for A/C, but not in winter for heating. Unless very efficient house and lots of PV panels.
Thank you for your reply. I do want solar and battery back up eventually. My goal with this house, our last house, was to go into retirement in 10-12 years with a low maintenance house that doesn’t cost an arm and a leg to run when my income becomes more fixed. I think we’ve built a very efficient house, but of course you can always change something. I’m not wealthy but I can work so I spent the last year building my best version of an efficient home that didn’t break the bank, and we did a good job with that. 1600 sq ft, Nudura ICF, Marathon water heater, the heat pump being discussed, all LED, Tier 3 appliances, wood burning stove and high R value attic insulation are a few of the highlights. building a house while working full time sucks but it was “fun” to see the fruits of our labor unfold. Now I’m trying to get our electricity usage down more without going too extreme In our day to day lives. Soft start kits, water heater timers, clothesline, etc. It is my thinking, and please correct me if I’m wrong, that this will allow for a smaller, slightly more affordable system when we do take that plunge.
 
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Ghcoupons

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Yes, that is why I suggested he look to confirm the absence of LRA to confirm it was indeed a VFD. Essentially there is no LRA for a VFD.
Like an earlier poster I am envious of his system because of its efficiency. My next home will have a VFD heat pump with a variable speed zone fans.
It seems to work well so far. Its only a 2 ton unit for the whole house and what shocked me the most, aside from the price, is how quiet it is. It’s near our bedroom window and you can’t hear it run. The ICF walls help of course, but even outside, you can barely hear the fan.
 

RCinFLA

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There are two speed compressors, with associated air handler two speed operation.. They are not VFD.

Starter capacitor boost with soft starters do work well but I have never tried to put one on a two stage compressor.

I believe the two stage compressors just has some valves on the compressing head that bypasses some of the gas. This is in addition to any reversing valves for reverse cycle heat pump. It reduces head pressure requiring less work from compressor motor and produces less gas flow. Reduction is about 30-40%. I am not sure if they do anything to compressor motor. Normally if you lighten load to single phase induction motor it mostly just reduces power factor. Real power is less but VA apparent power current does not reduce much. Since residential U.S. utilities charge for real power and they don't charge for poor power factor, the compressor motor may not have any electrical modification to improve power factor. You have a bit less battery average consumption but if nothing is done to improve the degraded power factor you still have near full power peak currents on a battery power inverter with associated inverter and battery cable losses. Startup surge level would be uneffected.

I have a MicroAir EasyStart 368 on my 240vac 4.5 ton central. It took startup surge from 200 amps to 77 amps allowing my inverter to deliver the required startup surge current. A softstarter by itself does extend startup time but softstarter with start boost capacitor does not significantly change the startup time. It remains in the 400 to 500 millisecond range.
 

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DThames

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I am currently working on reducing usage. We just finished an ICF house. I tried to build it as efficient as I could afford. I’m investigating items like a soft start kit that may not only reduce usage, but allow for a smaller array when that time comes. A SSK and water heater timer come to mind, but our heat pump seems efficient as it’s gonna get and our marathon water heater doesn’t have much stand by loss, so I suspect a timer would be not significantly helpful. We currently use Around 900-950 kWh a month. It’s significantly better than our last house but I’d like to get it lower if possible.
in a grid down situation, I suspect fans and even a a window AC would be a better cooling option than the heat pump. Thank you.
Have you checked your local grid tie laws/rules? Do you get full credit for any extra power produced?
 

Hedges

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My goal with this house, our last house, was to go into retirement in 10-12 years with a low maintenance house that doesn’t cost an arm and a leg to run when my income becomes more fixed.
Deals on PV equipment keep appearing, and we're amazed at how cheap it has become. Maybe prices will come down further, maybe not. Partly, technology development and mass production drove cost reduction, partly economic disruption that left excess capacity. But even when the latter happened (2008/2009) and PV at utility scale got down to $2/watt, volume manufacturing and competition has since driven the cost down to $0.50/watt.

For that, you can buy PV panels and grid-tie inverters. Including balance of system, easy to stay under $1/watt (e.g. 7500W grid-tie system for $3750). At that cost, you can make your own power for $0.05/kWh (cost amortized over 10 years), or break even with $0.20/kWh utility bills in 2.5 years and free after that.

PV panels should last 25 to 40 years. Inverters should last 10 to 20 years.

Of course, utility rules get changed to take away the benefits (make you return as a profitable customer) by either not letting you bank/use power for free, or otherwise giving small credit for power produced, charging large price for power drawn from grid. Batteries are one way to avoid being subject to utility rate games. People are buying battery systems even when they cost more per kWh than just buying power from the utility. Eventually they should be cheaper, but today only when bought through grey-market channels as individual cells and assembled DIY.

Batteries may last 18 months (deeply cycled sealed lead-acid) to 10 years expected from lithium, in some cases 20.

I suggest avoiding use of batteries for now unless you need them. Maybe a small battery-backup system if keeping phone/internet going during outages is desirable. I have a relatively small battery bank as part of a system that lets my grid-tie PV supply the house including A/C during the day. It isn't particularly cost-effective, more of a luxury/toy just because I could. If there is a suitable "hybrid" inverter which works batteries-optional and is grid-tie, that might be best. Of course, in 10 years who knows what battery chemistry will be competitive; the inverter may not have a charge profile which is compatible.

Installing PV panels on the roof today with any quality grid-tie inverter could be the way to go (assuming suitable net-metering rates). In the future, you might replace the inverter with a battery-based system go get around unfavorable rate changes. But you will probably have already enjoyed years of free power.
 

DThames

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Just FYI, we use about 1100kwh per month. We are now producing about 1400kwh per month. We get full credit from the power company. The extra pays for our connection service fee of $22 per month. Total DIY install cost was $13000 (ground mounted). No battery. Total electrical bill since June 2019.....power company owes us $218 right now. Total electric and 3 years from retirement, yes that looks pretty good. I am working on an emergency system that is not connected to our main PV system.
 

Ampster

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correct me if I’m wrong, that this will allow for a smaller, slightly more affordable system when we do take that plunge.
Congratulations on your efforts. The size of a system may have to do with the Net Energy Metering plan your utility provides. You may want to oversize because no matter how good the NEM plan is today, it will most likely get eroded as time periods change and fixed charges creep into the rate structure. The good new is that costs continue to come down. I just saw a generic Tesla proposal for $2.00 per Watt in California.
 

Ghcoupons

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Have you checked your local grid tie laws/rules? Do you get full credit for any extra power produced?
Yes, it’s pretty straightforward. They buy wholesale. They encouraged me not to look at it as a revenue source and shoot for but not go over 95-100% of the power we need. That is my goal anyways. A small or non existent power bill would be great, but self sufficiency is more my main goal.
 

Ghcoupons

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Deals on PV equipment keep appearing, and we're amazed at how cheap it has become. Maybe prices will come down further, maybe not. Partly, technology development and mass production drove cost reduction, partly economic disruption that left excess capacity. But even when the latter happened (2008/2009) and PV at utility scale got down to $2/watt, volume manufacturing and competition has since driven the cost down to $0.50/watt.

For that, you can buy PV panels and grid-tie inverters. Including balance of system, easy to stay under $1/watt (e.g. 7500W grid-tie system for $3750). At that cost, you can make your own power for $0.05/kWh (cost amortized over 10 years), or break even with $0.20/kWh utility bills in 2.5 years and free after that.

PV panels should last 25 to 40 years. Inverters should last 10 to 20 years.

Of course, utility rules get changed to take away the benefits (make you return as a profitable customer) by either not letting you bank/use power for free, or otherwise giving small credit for power produced, charging large price for power drawn from grid. Batteries are one way to avoid being subject to utility rate games. People are buying battery systems even when they cost more per kWh than just buying power from the utility. Eventually they should be cheaper, but today only when bought through grey-market channels as individual cells and assembled DIY.

Batteries may last 18 months (deeply cycled sealed lead-acid) to 10 years expected from lithium, in some cases 20.

I suggest avoiding use of batteries for now unless you need them. Maybe a small battery-backup system if keeping phone/internet going during outages is desirable. I have a relatively small battery bank as part of a system that lets my grid-tie PV supply the house including A/C during the day. It isn't particularly cost-effective, more of a luxury/toy just because I could. If there is a suitable "hybrid" inverter which works batteries-optional and is grid-tie, that might be best. Of course, in 10 years who knows what battery chemistry will be competitive; the inverter may not have a charge profile which is compatible.

Installing PV panels on the roof today with any quality grid-tie inverter could be the way to go (assuming suitable net-metering rates). In the future, you might replace the inverter with a battery-based system go get around unfavorable rate changes. But you will probably have already enjoyed years of free power.
I looked into solar about 12 years ago and man was it sticker shock. The prices have come way down. Right now, batteries aren’t on the table, but I want the future option. Battery technology, in my painfully uninformed opinion, still seems like it’s in its infancy. It’s shaky and expensive And I feel best to hold off. A grid tied system that will allow me access to The power when the grid is down, even just when the sun is shining is my goal, with the hope to add batteries sometime in the future. I have just enough knowledge to be dangerous when it comes to solar DIY, but I pretty handy so I’m trying to Learn more. I get the impression, and please correct me if I’m wrong, but diy solar isn’t that complicated, but you do need to do it correctly or risk a hair raising situation. Lol.
 

Ghcoupons

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Just FYI, we use about 1100kwh per month. We are now producing about 1400kwh per month. We get full credit from the power company. The extra pays for our connection service fee of $22 per month. Total DIY install cost was $13000 (ground mounted). No battery. Total electrical bill since June 2019.....power company owes us $218 right now. Total electric and 3 years from retirement, yes that looks pretty good. I am working on an emergency system that is not connected to our main PV system.
How many panels is your system? Sounds like you’re set for retirement!
 
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