Can't say about your Rheem, but I set the lockout on my Carrier at 25°F and there haven't yet been any problems in three years.

Your tech is full of sh%t and just making an excuse.

What was actually reset? Why? A reset means something tripped. Not normal. There is an underlying issue that caused the trip.

Your heat pump is designed to run at low ambient temps (long run times). The lock-out temp should be at the economic balance point of the home.

Good luck.

The tech said it was a L21 (Lockout - Low Pressure Control Trip). However, when he put the gauges on, the pressures read normal.

I don't know it this had anything to do with it, but the outside temperature yesterday (during service call) was about 65 - 70. However, just a few days ago, the temperature was down in the single digits. I had heat from the Heat Pump before the cold snap, so the the L21 had to happen within the past week.

All he did was cycle power to reset the system.

Does your system use 410A refrigerant or R22 refrigerant? Is this the 16 Seer Rheem condenser? If it is the 410A system, then the tech needs to make sure the pressures are exact, according to the charging chart inside the unit. It is harder to charge when it is cold outside, but can be done. Tell them to recheck the charge.

I only have a 13 SEER unit (RPNL-JEZ), and it uses 410A refrigerant. The tech did consult the charging chart inside the unit, and I believe it was within a couple of PSI. I could see the gauges but was too far away to read the chart myself.

My balance point seems to be around 20 degrees, so I guess my real questions is, am I putting undo stress or damaging the compressor by having the lockout set below 40 degrees like the tech said, or is having it set to 25 or even 20 degrees fine?

I'm out of Augusta, Ga, so temps do not get quite as low as where you are at. Recommended condenser cut out is usually between 35 and 40 outdoor temp. I would definitely not go below 32.

I have a horribly set up duct system with a tempstar 13 seer and have had no problems with even a 15 degree cutout temp. I am in central Missouri and the heat pump starts to have fairly long run times around 20. If it is windy or really close to 15 it will have to kick in one stage of strips every now and then. I have switched it back and forth between 15 and 20 and think 15 works better here. I just hate to have it cycling between one and two stages of strips if I can keep from it. I plan to add LEDS to my t-stat so it is easy to see if or when it is staging strips and if one or both are on. I need to get my ductwork all set up right and sealed before I think about all of this.

The only problem is countryboymo is that you have a heat pump with electric heat strips and david2850 has a heat pump with a gas furnace for back up. The heat pump can run while the heat strips run at the same time, but the furnace and the heat pump can not run at the same time unless he has high temp cut outs in the supply plenum. But you are right about your heat pump. Also, you can buy a thermostat that has the aux LEDs for pretty cheap instead of rigging up some LED lights.

"The tech did consult the charging chart inside the unit, and I believe it was within a couple of PSI. I could see the gauges but was too far away to read the chart myself."

The proper way to charge a system is by measuring and adjusting "superheat" and "subcooling". These measurements not only require gages but temperatures of the liquid and vapor refrigerant lines. Next time the tech comes out, ask him for your superheat and subcooling temperatures.

"My balance point seems to be around 20 degrees, so I guess my real questions is, am I putting undo stress or damaging the compressor by having the lockout set below 40 degrees like the tech said, or is having it set to 25 or even 20 degrees fine?"

You are fine running your heat pump at 25F and below. As I stated before, your tech is full of sh%t and just making an excuse for his ignorance. I run my heat pump all the time at these temps (I have to as the heat pump is my primary source of heat). The lower the ambient temp, the cheaper the heat pump costs to run, but the less btu's it puts out along with lower temps out of the supply registers.

You need to figure out your economic balance point for the switchover from heat pump to gas furnace. What is your delivered price for electricity (in cents per kw-hr)? Delivered price = generation + distribution + transmission. What is your delivered price for natural gas (in $ per ccf or $ per therm)? Provide the pricing and I'll work the numbers for you.

Take care.

I am sorry Tlewis I forgot that he is using a gas furnace which I know changes things a bit. My visionpro T-stat does everything I need other then tell which stage of aux. is running but it does indicate that an auxiliary stage is on. It would be nice to have an indicator that I could turn on or off if I got tired of the lights off the wall bracket. I would use flat faced LEDS and bond them into holes in the bracket. I don't want to pay a fortune for a Tstat with lights when this one does everything I need other than have a few indicators. ô¿ô

UPDATE

The service manager was out on Thursday and rechecked the system, apologized for the erroneous information the service technician told me, and returned my un-cashed check. He told me that Rheem does not recommend any specific compressor lockout temperature setting, but their company policy is usually to set it to 30 or 35 degrees as a matter of comfort. As long as I don't mess with certain other settings, I can set the compressor lockout temperature to whatever I'm comfortable with. For the record, I current have it set to 15º.

Since resetting the system, it's already been down to 20º and the heat pump was able to keep up without needing backup heat. The temperature at the register was about 86 to 88 degrees and the thermostat was set to 70º.

In a weird side note, maybe it's just my imagination, but the heat pump seems to have a slightly longer rest cycle when the thermostat is set at 70º vs. 69º.

As for why the heat pump stopped working in the first place, he wasn't sure, but a lower pressure lockout is something usually associated with cooling, not heating. Since the system was installed about 5 months ago (during the summer), he suspected that error was an old error that happened during the install.

As for calculating costs, the gas company uses a fairly simple formula so it's pretty easy to calculate the total cost per therm used (about $1.44 at the moment). However, the electric company uses a tiered rate structure, so the price per KWH varies depending on monthly usage. Based on my calculations for my particular set of circumstances (geographical location, type of windows, amount of insulation, etc.), it costs less than $2.00 per day to operate the heat pump, even on the coldest of days. ThatÂs less than half of what it would have cost me using natural gas alone.

Thanks for everyone's replies.

My Trane with dual-fuel control is set to lockout the compressor and switch to the backup gas furnace at 28 deg. Trane rep agreed with this setting. I assume that the lower the setting, the more often the unit must defrost.

I have a HP with gas back-up in Michigan. I did Heating Cost Calcs that looked at the COf using the discounted DTE winter rates (5.5 c/Kw). The COF decreases at low temperature... But even at 15 F the theoretical cost of the heat pump is about half natural gas... Even using the full rates(10 c/Kw) it is about a break-even at 15 F... If you are comfortable and the unit keeps up, a HP should be the most cost effective.

How do I lower the lockout temp on an electric Seer 1600 Rheem heatpump, it is set at 40* and our temps get down to 10 or colder, seems like auxillary heat strip was on a lot because my last electric bill was $350.00. I asked the installer and they won't do it , he said WA has a rule that mobile homes have to be set at 40* but stick built can be set to 0* if they wanted to be. I bought a heat pump to lower my bills, not have hughe heat bills like that, can someone help? I have a honeywell THX 9321 thermostat . Thank you

This thread is over 4 yrs old.

I suggest you start your own rather than piggy backing on this one.

IMO