BEST Temperature for DUAL FUEL Lockout HVAC!

[@maddrummerhef]

If you do your load calculation and Balance point worksheet you can find out at exactly what temperature the heat pump is unable to heat the home. Set the lockout for the compressor a couple of degrees above that point and bam you have the BEST temperature for a dual-fuel lockout.

[@jonwiersig5800]

My contractor installed a Sensi Smart (1F87U-42WF) thermostat. After talking to Sensi customer service it turns out that my new thermostat has no way to lock out the heat pump based on outside temperature. What do you think about me installing a Sensi Touch 2 or Ecobee smart thermostat that uses the outside temperature from the WIFI connection to set the heat pump lockout? Or do you have a thermostat you prefer more? Thanks!

[@dustinalexander5864]

The best option on the market to customize your lock out temperature is a Honeywell 8321 wifi thermostat and a hardwired outdoor temperature sensor. This will eliminate the "logic" that other smart thermostats use to guess what the current outdoor temperature is and when it's a good idea to make the change from heat pump to auxiliary heat.

[@jonwiersig5800]

Thanks for your suggestion. I am sure that the Honeywell 8321 would have been a better choice, but since Honeywell does not play nice with non-HVAC contractors, I installed the Sensi Touch 2 that has a configurable lockout temperature, that as you know, uses the outside temperature it obtains from WiFi. The Sensi Touch 2 worked fine this week when we got down to 12 degrees, quite unusual for Texas.@@dustinalexander5864

[@itiswhatitis5132]

In Minnesota, I like to set them to change over at no lower than 35 degrees F. This way, there's no chance of the outdoor unit having to go into defrost mode which in turn, would make the gas furnace fire to heat up the indoor coil which then sends the heat via refrigerant lines to the outdoor unit in order to defrost itself. That's for a standard split system. As for mini split A/C heat pumps, that's a different story. Some claim to operate as low as -22 but in my experience, they all start defrosting themselves at or around +15F to 0 degrees and lose efficiency. I watch my mini split heat pump indicator light and when it starts to defrost too often, I turn it off and then turn on my gas furnace. If it stays too cold for days, below 0, -10,-20, -30 or sometimes -40F below, I then start a fire in my wood stove. Yes, it gets that cold in areas of Minnesota! Great video and explanation! Just thought I'd share my experiences.

[@b-riair9114]

Won’t a heat pump defrost below 40 ish because in order to extract heat out of 40 degrees the refrigerant needs to be a margin colder.. much like an indoor coil in heat mode will need to get hotter than the temp inside to add heat? If the temp outside is 35 the refrigerant should not be that temp for heat transfer

[@itiswhatitis5132]

@@b-riair9114 Frost doesn't occur above 32F because it is water in the air that has frozen (wet bulb) and in order for it to freeze, it must beat or below 32F.

[@ButchWhitehouse]

I appreciate what your saying about there being too many variables for one answer. Has anyone written a calculator where you can input cost of electricity vs cost of oil to find out their own "sweet spot"?

[@sdoubledub1157]

hands down, this is the best I've ever seen. The other link is from him as well kzbin.info/www/bejne/Y3umq2iulr11oMU

[@pablopicaro7649]

Economics of it: most place in N.America Electricty costs 3x as much as Nat Gas per unit energy, than means use gas if COP is below 3 on the heat pump . for an Air-Air heat pump that is at abut 40F outdoor.

[@EcoEnvious]

I’m sure it’ll depend on humidity, as well. Thanks for the video!

[@jolyambong9300]

How to apply in your company sir?im living in philippines.3 years experienced in HVAC..

[@ryansteele3043]

I got a duel fuel system and I went to set a lockout when it got cold. I noticed there is a hp lockout and a aux lockout on the thermostat. What is the aux lockout for . I get the hp lockout is to stop the heat pump and use the furnace . But what is the aux lockout for ?

[@dustinalexander5864]

The aux lockout is the opposite of the heat pump lockout. You can tell the thermostat to not allow the auxiliary heat to come on above 40° for example. This will allow the heat pump to go into defrost mode momentarily when being used without turning the auxiliary heat on.

[@ridlfoot]

Nice explanation

[@km376]

Does the homeowner have a way of setting the lock out temp or is it already set by the person putting it in. Cam we change it .where is it set at is it sat up on the thermostat in the home? I've hit buttons odk what I'm doing I was wondering if I have moved the lock out temp or not or if it is set where the homeowner can or cannot change it.any info will help

[@dustinalexander5864]

It all depends on the type of thermostat or other equipment that may be controlling the change over point. Not all thermostats will allow you to set a lock out temperature. Many thermostats use a pre-calculated "logic" to determine when the best time to lock out the heat pump is.

[@KPHVAC]

The Mitsubishi Hyper Heat units are amazing! The SUZ SVZ Hyper Heat ducted air handler system is good to go at 5 degrees. We have done a lot of these with no heat kit in the air handler. For smaller well insulated homes I don't see much point in staying with a furnace in Western Washington climate. Now if you have weeks of below zero Fahrenheit I'd stay with gas.

[@NewHVACGuide]

Awesome!

[@crumdoggy]

Does the homeowner control the lockout point on a hyper heat? Electricity is more expensive than natural gas here and I don’t want to pay more even if hyperheat will work below freezing.

[@KPHVAC]

@@crumdoggy I'm not sure. I believe this could be done at the time of install or through the thermostat. I'm not a tech. A hyper heat unit might be overkill if you want to stick with a gas furnace.

[@PHamster]

How much current do the inverter system consume when heating? I’m curious about the efficiency of these system.

[@joebass5163]

I have a Daikin Fit 3 ton HP and it uses about 3kw in max heat mode. When the house is up to temp it uses about 0.6-2kw to maintain temp.

[@NewHVACGuide]

Most are minimal. Some draw an amp or two on average

[@jko0526]

What controls the lockout temperature on a heat pump system?

[@dustinalexander5864]

There are several ways, 1) Smart thermostat that uses built in logic in conjunction with weather data obtained from the internet for your area. 2) Analog fossil fuel control - Bill porter board for example - that has a dial where the temperature can be set and relays make the switch 3) A thermostat or zone board that has a hardwired outdoor temperature sensor can be set to change over at the desired temperature.

[@km376]

So the lock out temp is on the thermostat in the home?

[@NewHVACGuide]

Depends. Some systems have an external fossil fuel kit that may be mounted near the indoor unit. Some systems use the thermostat as their fossil fuel kit which would require the thermostat to control the lockout temperature

[@mrrodneyalong]

Its 40.

[@pablopicaro7649]

Economics of it: most place in N.America Electricty costs 3x as much as Nat Gas per unit energy, than means use gas if COP is below 3 on the heat pump . for an Air-Air heat pump that is at abut 40F outdoor.

[@dustinalexander5864]

It's much lower than 40° in my situation, electric is about 15cents per kwh which is very affordable however natural gas is not available so I use propane which costs 2.99 per gallon on average. It's more cost effective for people in a situation similar to me to allow the heat pump to run as low as 20° sometimes lower.