The efficiency of a heat pump has to do when it's operating in heat pump mode and has nothing to do with heat strips. If the heat pump is working correctly and can produce enough heat from the outside temperature, then that would be the cheapest way to keep the home warm. If the outdoor temperature is above the design operating low temp for the equipment but inside isn't warm enough, then something's wrong.

A 10kw heat strip draws 10kw when it's on. It's electric resistance heat and all such devices produce the same amount of heat for the given amount of electricity, they all operate with the same "efficiency". It is what it is.

If the heat strips are coming on when the heat pump alone should be sufficient, the operation of the heat pump, its control system, or even the thermostat may all individually be possible culprits. Your call should be to the HVAC contractor, not to Lennox.

What thermostat do you have? Is it connected to an outdoor temperature sensor?

I am curious as to why you turned off the auxiliary heat lock out. Without knowing the outdoor temperature, the thermostat makes a guess as to when to turn on the auxiliary heat. The typical algorithm is to turn on the auxiliary when the room and set temperatures are greater than two degrees. This happens when coming out of a set back condition. The heat pump could be the most efficient in the world, but the thermostat decides when the auxiliary heat is needed.

The heat strips will also turn on in defrost mode.

Good point, on for defrost mode.

You’re not likely to go into defrost mode when the outdoor temperature is 62˚F. Aux will likely come on if there’s a temperature differential of 2˚F or more on the T-stat due to set backs or for any other reason. With a compressor lockout and Aux lockout you would have no heat until someone intervenes.

What happened to your DX system?

SR

mike_home, I have the Lennox iComfort S30 that is fully communicating with an outdoor sensor located in the outdoor compressor.

The ambient lockout range allows 3 modes of operation. When the exterior temperature is above the lockout range all heat will be produced by the heat pump only. When the outdoor temp enters the top of the lockout range (say 25 degrees) the system will use the HP and electric back up in combination with 6 stages of elect BU to reach the indoor setpoint. If the outdoor temp goes below the lower setting of the lockout range (say zero degrees) the system will only use the electric back up as the source of heat to get to set point.

I do have a temp set back during the workday. I drop it to 73 then back to about an hour before we get home. I guess I could have caught it at that point but wouldn't a smart system take into account a certain amount of time to get to set point before calling for help from the BU heat?

The stat displays "Defrost" when the HP is in defrost mode, so it wasn't that.

fsq4cw The DX system had a leak in the underground field. We were a little ahead of the technology (or our vendor was behind) that the copper piping did not a slight charge set on it to prevent corrosion. We were quoted $5-7K to hand dig to the manifold and test the earth taps of which we had 7. They claimed that "if" they could find the leak and it was anywhere but the solder points they could clip and seal that tap. After that, there was no guarantee it wouldn't happen again. I spoke with another customer who had the same type of system but larger. They had 3 different leaks over time. So we opted to give up on that system. It was a great system when running and it created 100% of our domestic hot water. :-(

So am I using old thinking when using a modulating system that setbacks are not an efficient idea? I still like it cooler at night to sleep.

What an absolute shame! It sounds like the replaced DX system was a 5-ton EarthLinked GSPH. I can’t say you made a bad choice; you made the right choice for you.

It’s questionable whether anode protection of the copper ground loops would have made a difference, unless you live in an area with known acidic soil.

We have a different type of DX GSHP (Nordic DX-45). Faced with that dilemma, I too would consider replacement but as I work in the field (literally, consulting for drillers & installers) I would probably opt for re-drilling the defective groundloop, as that borehole can easily be determined at the HP. The other consideration would be a complete Waterfurnace replacement – ground loops and all – ou¢h!

Regarding setbacks & heat pumps, I’m not a big fan. I prefer to ‘set it and forget it’!

IMPO

SR

You're in Canada? I'll guess that your "set it and forget it" advice should maybe consider and depend on electricity prices. How much do you pay per kwh?

Cost per kW here in Quebec is ~9.2¢CND w/Tx. I generally consider units of energy (kW) when doing calculations or comparisons. Your comment is a fair and reasonable one that gave me pause to think and consider.

I believe I would still ‘set it and forget it’ if I lived elsewhere, including a warmer climate, if using a HP. If natural gas was the source of energy I would likely use setbacks wherever I was living.

BTW: At a rate of ~9.2¢ & a COP 3.5, the cost per kW of heat put into the house is ~2.63¢CND including all taxes. (~28¢ CND /hr. Total - for a 3-ton GSHP

{Or ~21.75¢USD/hr. at today’s exchange rate}).

IMPO

SR

Are you using kW (kilowatt) when you mean kWh (kilowatt hour)? A kW is a unit of power, a kWh is a unit of energy.

A rate of $0.092 CND equals $0.072 US. Some people in the US pay triple that rate, and most people double.

The OP stated he likes it to be cooler while he sleeps. His current setback is set to 73 during the day, which is still warm for most people. A setback may be for comfort and energy savings.

A programmable thermostat lets you "set and forget it". But if you have a heat pump with back up heat strips, then you need to understand what it does coming out of a setback condition. If your back up heat is a fossil fuel furnace (gas, propane, fuel oil) then it is not issue unless maybe you live in Canada and have access to low electric rates!

kWh when referring to cost of electrical energy.

SR

fsq4cw, It was a 3.5-ton system from a company that I believe the owner of and the owner of Earthlinked were partners at one time. I went with the local one as Earthlinked was in Florida at the time. I knew there is a high level of limestone in our area and my raw untreated groundwater is at a PH of 5.6. The local guy should have known that as he is only 30 miles away. I questioned him at the time about this topic and he said that the copper he used was thicker walled than standard. I got a quote from Earthlink for a new ground loop at 11-13K. If I had it repaired and had another leak in 5 years it would have been the same cost as getting the new Lennox system. The same with the cost of the new loop @ 13K.

I loved that system once I got the correct setting on my stat so the electric back up wouldn't come on. That DX system also had the hot water as a priority so if the heat was on and then the water tank called for the heat source it would stop heating the house until the water hit the setpoint, then switch back to heating the house. I really wanted to go with the Earthlinkedset up, but the other half wanted no part of DX again. During my search, I was onboard for the Nordic ATA series which was still an air source HP, but theirs could provide heat way below the temp specs of the US manufacturers HPs including what I ended up with. Its true with some of the newer split systems but they came in at $30K. The only reason I did not go with Nordic, it was getting into November and they were still testing the product. I was not ready for primetime. I wish it was, I would have gone with the Nordic and it also did a domestic hot water preheat.

I also know that a Geothermal system would not have struggled like the air source did this winter with almost a month in the mid-teens or single digits.

"A rate of $0.092 CND equals $0.072 US. Some people in the US pay triple that rate, and most people double."

Or more. On my last bill, usage at the so-called baseline (8.5 kWh per day in my micro area, at this time of year) is at 20 cents. Beyond that (and I'm usually double the baseline or more for the overage) is 28 cents. So, it's 28 cents as a marginal cost of usage, nearly 4X.

I happen to be in a utility-expensive part of California, other places can be a bit lower. All electric homes get a higher daily baseline but still heat pumps of any kind, absent a large home solar system, are prohibitively expensive to run and as a result very rarely seen. Natural gas heating is predominant. Houses in areas without natural gas service most frequently use propane gas.

Though I now question just how efficient the geo really was because after it went offline I added the Lennox system, I had to turn the electric elements on in my water heater and I added a Chevy Volt (partial EV) in 12/2016. In 2017 11K of my 12K miles on the Volt was powered by electric. We never had a surplus of generated power from 2013 through 2016 because the utility pays out on any by May.

The cost of electric here is about $0.14 per KWh. In 2013 we went solar with a 10.5 KWh (42 250 watt panels ground mounted) system since our house is 100% electric with no access to natural gas. We sized the system when we had the DX geo system. The first electric bill we received since 2013 happened when all of our banked generation ran out in January because of how cold it got this year.

On the setbacks. I like to drop it to about 69 at night, then bring it up to 72 in the morning, back down to 70 during the day and up to 73 by 6 PM.

Those are moderate set backs, so I would almost suspect something maybe off with the equipment. What is the outside ambient like and is there any recent snow fall?

No its clear all the way around the unit and we have not had much snow this season, but especially when I saw this happen.

I did get a number of critical error code 901 displayed on my i30 earlier this winter. I contacted the HVAC co. who installs and maintains the unit, but they claim not to find any issues. This was when I had the lockout was active.

I just want to run this system as efficiently as possible.

I noticed that you said out door ambient is 62 and looking at flow chart I posted it discusses a balance point as to how this is passed to auxiliary heat.

So maybe this setting isn't set right. Something to check. If that doesn't do it, then I suspect a problem with the equipment, possibly refrigerant charge related.

Hi Austin Air, Thank you again for continuing to offer information. Are these settings in the installer menus if the I30 stat? Where would I see this?

yes, I believe these would be accessed from the thermostat installation set up.

It's best if you call your installer and have them reset it to a proper value as well as do a complete inspection on the system to ensure there aren't any other outstanding issues such as refrigerant charge problems.

The manufacture warranty can be voided if you attempt to make repairs to this system.