dslreports logo
 
    All Forums Hot Topics Gallery
spc
Search similar:


uniqs
6089

Camelot One
MVM
join:2001-11-21
Bloomington, IN

Camelot One

MVM

Heat Pump versus "emergency heat"

Let me start by saying I am from Indiana. And in Indiana, a furnace is either gas or electric, both working on the same general concept. Heat source in the unit, blower blows air over it, out through the vents. I can remember more than a few mornings of waking up and hoovering over the vents, almost getting burned by the hot air coming out.

But this is my first all electric house in Texas. It uses a heat pump, with the backup emergency heat - which seems to be the same as normal heat up north.

I'm told a heat pump is much more energy efficient. But so far I'm not convinced.

Ran some very un-scientific tests the past couple days. Roughly the same temperature outside, I'd let the house get down to 64 degrees. At that point I'd kick on one of the two forms of heat. Normal heat (heat pump) took almost an hour to warm the house to 68 degrees. Emergency heat took 15 minutes at the most. The difference is almost certainly the temperature of the air coming out, the heat pump blows warm air, while emergency heat blows hot air.

While I can see the heat pump using less power on a per hour basis, if it has to run 4 times as long to put out the same amount of heat, is it really worth it?

whizkid3
MVM
join:2002-02-21
Queens, NY

whizkid3

MVM

Is this a system with electric heating coils inside of ductwork?

If so, I would say the emergency heat would use less electricty. Both will use about the same electricity to provide the same heat; however, the blower is running longer, and drawing more electricty, the longer it runs.

Give us some more details on the system.

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

1 edit

SandShark5 to Camelot One

Premium Member

to Camelot One
I'd say it's a draw, energy usage-wise.

DataDoc
My avatar looks like me, if I was 2D.
Premium Member
join:2000-05-14
Hedgesville, WV
·StarLink
·HughesNet

DataDoc to Camelot One

Premium Member

to Camelot One
I did a little research on this and the "emergency heat", or second-stage heat (first-stage being the heat pump itself) actuall comes on any time the heat pump can't meet the heating demand.

"Q. What is the "auxiliary" or "emergency" heat switch on my heat pump thermostat? How does it affect my heating bills?

A. Most heat pumps are supplemented by electric resistance heating elements, which provide additional heat in very cold weather and "emergency" heating if the heat pump's compressor malfunctions. The supplemental heat comes on automatically when the heat pump is unable to meet the heating demand, while the emergency heat is switched on manually. Excessive use of this supplemental or emergency heat can increase heating costs significantly. Most heat pump thermostats have a small light that indicates when the supplemental or emergency heat is operating." from »energyaudit-scg.sempra.c ··· ?ID=elec

Here's plenty more links, most point out it's costly to run EH when you don't need it.
»search.live.com/results. ··· m=CHROME

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

1 edit

SandShark5

Premium Member

While it is true that the second-stage heat (auxiliary or supplemental electric heat) comes on when the first-stage heat (heat pump) can't handle the load (room temperature more than two degrees colder than thermostat setting), it is rare that they will both run at the same time under normal conditions. An example is if the owner manually set the temperature down to 64*F at night before bed. In the morning, the owner moves the temperature up to 70*F (more than 2*F). At that time, both the heat pump and the auxiliary (supplemental) electric heat will run. When the temperature reaches within 2*F of the thermostat setting, the auxiliary (supplemental) electric heat shuts down and the heat pump takes over from then on. The thermostat, at these times, is in the "normal" heating mode.

Emergency electric heat mode has to be switched on at the thermostat manually. This should only be done when the outside unit has malfunctioned. Some thermostats that are capable and wired to sense an outside unit malfunction, will show a trouble light to indicate to the owner that the outside unit has malfunctioned. If the owner is not home or doesn't notice, when the temperature at the thermostat falls more than 2*F lower than the thermostat setting, the auxiliary (supplemental) electric heat will take over on its own.

Edited to add details and clairify.

SparkChaser
Premium Member
join:2000-06-06
Downingtown, PA

SparkChaser to Camelot One

Premium Member

to Camelot One
A heat pump is more efficient to a certain outside temperature. That where your back up or resistance electric heat kicks in. However, you can't operate it like a normal furnace. Playing with the thermostat will defeat the whole system.

I would think in Austin you should be doing well with a heat pump. Does your heat pump have a SEER rating?

I don't think the Heat Pump industry has been pumping hot air for the last 30 years . I mean yes they have

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

SandShark5

Premium Member

said by SparkChaser:

A heat pump is more efficient to a certain outside temperature. That where your back up or resistance electric heat kicks in. However, you can't operate it like a normal furnace. Playing with the thermostat will defeat the whole system.

I would think in Austin you should be doing well with a heat pump. Does your heat pump have a SEER rating?

I don't think the Heat Pump industry has been pumping hot air for the last 30 years . I mean yes they have
Yes, it is true that heat pumps don't do very well in really cold temperatures, typically below 35*F. This is mainly due to the fact that in the heating mode, the heat pump is extracting heat from the ambient air.

Camelot One
MVM
join:2001-11-21
Bloomington, IN

Camelot One

MVM

Well I think I may have tracked down part of the problem.....the thermostat. I have a Trane TWE48 series air handler, and a Honeywell 7500 series programmable thermostat.
According to the Trane website, this unit has a variable speed blower. It seem that when the thermostat is set for normal heating mode, the blower runs on low. When I set it to EM Heat, the blower runs at full blast.

So it's not just the difference of temperature at the heat exchanger, but the amount of air going into the house. It's just a trickle of air from each vent on normal heat.

I made sure everything was wired correctly on the thermostat, and went through the manual on which system mode it should be set for, but there is nothing about a variable speed blower option. I'll call their tech support number tomorrow. (they are closed on Sunday)

robbin
Mod
join:2000-09-21
Leander, TX

robbin

Mod

There is no need of the blower to run fast with a heat pump -- it provides a little heat on a constant basis (when in the lower 40's it will run most of the time). The heat strips, on the other hand, are sucking the Kilowatts and need the faster air current.

The heat pump is going to be more efficient. It has nothing to do with the speed of heating the room. However I think the heat pump plays out around 40.

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

SandShark5 to Camelot One

Premium Member

to Camelot One
Trane TWE air handler blower speeds are set inside the air handler by a series of DIP switches and were set by the service technician who installed the system based on several technical factors. Based on what you've told us, I don't think you have a problem, at least as far as the blower speeds are concerned. The thermostat, regardless of the brand or model, will not control the variable speeds of the blower motor, so there's probably no need to call tech support.

Camelot One
MVM
join:2001-11-21
Bloomington, IN

Camelot One

MVM

Well right now our weather is running 55H and 40L. The "heat pump" is running the AC unit more to keep the house at 68 degrees than it did to keep it cooled to 75 when it was 100+ outside.

So unless I'm missing something, I'm looking at a higher electric bill to heat the place than to cool it. Which is the opposite of what I am used to.

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

1 edit

SandShark5

Premium Member

I think because you're not used to using a heat pump and the fact that you're under the assumption that heat pumps are "much more efficient" is the issue. More efficient than what? The electric company wants you to believe that heat pumps are "more efficient" than conventional gas furnaces so they can provide all of your energy needs. This is one of the primary reasons our company doesn't recommend heat pumps. As mentioned, the colder it is outside, the less efficient they are, not to mention they sometimes have to go into defrost mode which brings on the auxilary heating elements, not to mention that they are more expensive up front, and not to mention there are more things that can go wrong with them. Personally, I wouldn't own a heat pump.

If you want more information and feedback, try posting in »www.hvac-talk.com/vbb/fo ··· orumid=1 and get some feedback from other HVAC people.

Caddyroger
Premium Member
join:2001-06-11
To the west

Caddyroger to SandShark5

Premium Member

to SandShark5
said by SandShark5:

said by SparkChaser:

A heat pump is more efficient to a certain outside temperature. That where your back up or resistance electric heat kicks in. However, you can't operate it like a normal furnace. Playing with the thermostat will defeat the whole system.

I would think in Austin you should be doing well with a heat pump. Does your heat pump have a SEER rating?

I don't think the Heat Pump industry has been pumping hot air for the last 30 years . I mean yes they have
Yes, it is true that heat pumps don't do very well in really cold temperatures, typically below 35*F. This is mainly due to the fact that in the heating mode, the heat pump is extracting heat from the ambient air.
I have a 3 ton heat pump and it does a good job of heating my 1600 sq ft home. When the outside temp gets to 20 degrees then the thermostat will turn off the heat pump and use the furnace.
PhilAIV
join:2002-02-16
Carrollton, GA

PhilAIV to Camelot One

Member

to Camelot One
said by SandShark5:

The electric company wants you to believe that heat pumps are more efficient than conventional gas furnaces so they can provide all of your energy needs.
Sandshark is right. Heat pumps are more efficient than regular electric furnaces, but in most cases gas furnaces are much more efficient than heat pumps and conventional eclectic furnaces.

The only way a heat pump will save you money is if: 1. your natural gas or propane is very expensive or 2. your electricity is very cheap.

(in my case I pay around 6 cents a KW, so electric is the way to go in my area.

robbin
Mod
join:2000-09-21
Leander, TX

robbin to SandShark5

Mod

to SandShark5
said by SandShark5:

I think because you're not used to using a heat pump and the fact that you're under the assumption that heat pumps are "much more efficient" is the issue. More efficient than what? The electric company wants you to believe that heat pumps are more efficient than conventional gas furnaces so they can provide all of your energy needs...
Maybe you missed part of the question. The OP has an ALL ELECTRIC home -- NO gas. The question is "Is the heat pump more efficient than the backup heat strips?" The answer is yes. Here is a quote from the US Department of Energy

"When properly installed, an air-source heat pump can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes."

SandShark5
Long may you run
Premium Member
join:2000-05-23
Santa Fe, TX

3 edits

SandShark5

Premium Member

said by robbin:
said by SandShark5:

I think because you're not used to using a heat pump and the fact that you're under the assumption that heat pumps are "much more efficient" is the issue. More efficient than what? The electric company wants you to believe that heat pumps are more efficient than conventional gas furnaces so they can provide all of your energy needs...
Maybe you missed part of the question. The OP has an ALL ELECTRIC home -- NO gas. The question is "Is the heat pump more efficient than the backup heat strips?" The answer is yes. Here is a quote from the US Department of Energy

"When properly installed, an air-source heat pump can deliver one-and-a-half to three times more heat energy to a home than the electrical energy it consumes."
robbin See Profile is right. Heat pumps are more efficient when it comes to the amount of heat they produce versus the amount of energy (electricity) they consume as opposed to straight electric resistance heat, to a point. At 50*F, the coeffieient of performance (COP) of air source heat pumps is about 3.3, which means that 3.3 kilowatt hours (kWh) of heat are transferred for every kWh of electricity supplied to the heat pump. Electric heating has a COP of 1. The COP of heat pumps drops as the outside temperature drops. Now, whether or not they are going to save you money in the long run, that depends on the costs of electricity, natural gas, heating oil, or other fuels, and how often the auxilary heating elements are used, which depending on how often that sucker defrosts, could be quite often. However, in a prefect world, heat pumps are the answer to our energy usage prayers.

Cho Baka
MVM
join:2000-11-23
there

Cho Baka to Camelot One

MVM

to Camelot One
One point to re-iterate is that heat pumps are not great (as alluded to already) at raising the temp of a stone cold house. A heat pump is not an effective way of raising the temp of a house from 50 degrees to 70 degrees if it is cold outside.

They turn off the heat at my workplace on the weekend, it takes until mid-day on Monday before things are tolerably warm. They are trying to save electricity in the name of global warming...

The use pattern of a setback-type thermostat has to consider this factor.

rfhar
The World Sport, Played In Every Country
Premium Member
join:2001-03-26
Buicktown,Mi

1 edit

rfhar to Camelot One

Premium Member

to Camelot One
I have never had a heat pump and likely never will but up here in Michigan they drill a well for a heat pump. Are the well type any better?

SparkChaser
Premium Member
join:2000-06-06
Downingtown, PA

SparkChaser

Premium Member

said by rfhar:

I have never had a heat pump and likely never will but up here in Michigan they drill a well for a heat pump. Are the well type any better?
They sure are in Michigan. The geothermal heatpump takes advantage of the fact that after a certain depth the temperature is a fairly consistant 55ish degrees.

BillRoland
Premium Member
join:2001-01-21
Ocala, FL

1 edit

1 recommendation

BillRoland to Camelot One

Premium Member

to Camelot One
We've had a heat pump here in North Central Florida since forever (ok, not literally forever, but since the mid 80s). It does a nice job of keeping the house at a fairly constant temperature providing the temperature doesn't get too cold. If its under 35 for any length of time, it obviously has to run longer and defrost more, and after a certain temperature point our thermostat seems to just give up on it all together and switches to axillary. As others have said a heat pump isn't going to take you from 60 to 70 in any quick fashion, but then again, its not really designed to. If I increase the temperature in my house past +2F where it currently is, the heat pump comes on and the auxiliary heat coils come on too until it gets back within that 2F range of where I have it set, then the coils kick back off and the heat pump finishes the job. It sounds like maybe your setup isn't doing that.