I have a heat pump and no outside HVAC. We are having below freezing temps
all day long. Should I turn on my emergency heat during this very cold
(for us) weather?

Thanks!

On Dec 17, 9:16*pm, wrote:
I have a heat pump and no outside HVAC. *We are having below freezing temps
all day long. *Should I turn on my emergency heat during this very cold
(for us) weather?

Thanks!

What is an “outside HVAC”?

wrote in message
...
I have a heat pump and no outside HVAC. We are having below freezing
temps
all day long. Should I turn on my emergency heat during this very cold
(for us) weather?

Thanks!

Is it cold in the house?

On Sat, 18 Dec 2010 00:16:27 -0500, wrote:

I have a heat pump and no outside HVAC. We are having below freezing temps
all day long. Should I turn on my emergency heat during this very cold
(for us) weather?

Thanks!

Are you cold? Are you too cold? Did you put on a sweater?

On Dec 17, 11:16*pm, wrote:
I have a heat pump and no outside HVAC. *We are having below freezing temps
all day long. *Should I turn on my emergency heat during this very cold
(for us) weather?

Thanks!

Only if you are cold???!!!

On Sat, 18 Dec 2010 11:43:15 -0500, wrote:
According to what I have been reading, heat pumps do not work well below 40
degrees

What you read is incorrect. Yes, there is a point at which the
efficiency of the heat pump is less than that of the resistance heat,
but that point is roughly 15F, not 40F. Newer, more efficient heat
pumps might lower this point a little, but the problem is basic
physics, so it won't get much lower.

And as already pointed out, the heat pump might switch to the
resistance heat automatically. This likely depends on age and
manufacturer. Also note that most heat pumps will add the resistance
heat when the inside temperature drops about 5F below the set
temperature, but this is separate from the efficiency cutover. This
auto-add at 5F below is the reason you are always advised not to set
the thermostat down (very much anyway) at night when you have a heat
pump. If you disable the resistance heat (which is a viable course of
action in the southern US), then you can ignore that advice and save
some money, albeit at the tradeoff that it may take quite a while to
bring the temperature back up.

Edward

Edward Reid wrote:
....

... If you disable the resistance heat (which is a viable course of
action in the southern US), then you can ignore that advice and save
some money, albeit at the tradeoff that it may take quite a while to
bring the temperature back up.

One alternate ploy rather than disabling them entirely is what the
installer of our system did routinely -- he used a thermister inline w/
the emergency heat that kept them out of the control circuit w/ outside
temperatures were above about 20-25F.

--

On Sun, 19 Dec 2010 02:43:09 -0500, Edward Reid
wrote:

On Sat, 18 Dec 2010 11:43:15 -0500, wrote:
According to what I have been reading, heat pumps do not work well below 40
degrees

What you read is incorrect. Yes, there is a point at which the
efficiency of the heat pump is less than that of the resistance heat,
but that point is roughly 15F, not 40F. Newer, more efficient heat
pumps might lower this point a little, but the problem is basic
physics, so it won't get much lower.

And as already pointed out, the heat pump might switch to the
resistance heat automatically. This likely depends on age and
manufacturer. Also note that most heat pumps will add the resistance
heat when the inside temperature drops about 5F below the set
temperature, but this is separate from the efficiency cutover. This
auto-add at 5F below is the reason you are always advised not to set
the thermostat down (very much anyway) at night when you have a heat
pump. If you disable the resistance heat (which is a viable course of
action in the southern US), then you can ignore that advice and save
some money, albeit at the tradeoff that it may take quite a while to
bring the temperature back up.

Ours throws in the resistance (aux) heat with only a 2F hill to climb; dumb.
With our house in VT (hydronic system), we'd set-back the thermostat about 6F
(65F down to 59F) at night and weekdays. Here we have to keep it set at
66-67F (no set-back capability and the forced-cold-air system) to be anywhere
close to comfortable.

On Sun, 19 Dec 2010 08:21:16 -0600, dpb wrote:

Edward Reid wrote:
...

... If you disable the resistance heat (which is a viable course of
action in the southern US), then you can ignore that advice and save
some money, albeit at the tradeoff that it may take quite a while to
bring the temperature back up.

One alternate ploy rather than disabling them entirely is what the
installer of our system did routinely -- he used a thermister inline w/
the emergency heat that kept them out of the control circuit w/ outside
temperatures were above about 20-25F.

Neat idea. The problem I see with this is that there is something else to go
wrong and there is no way to know it's gone wrong until the worst possible
time.

zzzzzzzzzz wrote:
On Sun, 19 Dec 2010 08:21:16 -0600, dpb wrote:

Edward Reid wrote:
...

... If you disable the resistance heat (which is a viable course of
action in the southern US), then you can ignore that advice and save
some money, albeit at the tradeoff that it may take quite a while to
bring the temperature back up.
One alternate ploy rather than disabling them entirely is what the
installer of our system did routinely -- he used a thermister inline w/
the emergency heat that kept them out of the control circuit w/ outside
temperatures were above about 20-25F.

Neat idea. The problem I see with this is that there is something else to go
wrong and there is no way to know it's gone wrong until the worst possible
time.

Trivial to bypass if want/need to but it's a passive solution and a
device that has extremely long MTBF ratings...

(Which leads to a story of when sold the house, however; the buyer's
inspection wrote up a defect that the emergency heat was non-functional;
the buyer ended up paying to have the good idea removed 'cuz couldn't
fathom the benefit even when explained to him and I refused to pay to
"fix" something that wasn't broke but was a beneficial feature.)

--

zzzzzzzzzz wrote:
....

Ours throws in the resistance (aux) heat with only a 2F hill to climb; ...

That was (mayhaps still is?) pretty standard ordinary thermostat
setting/logic.

--

On Sun, 19 Dec 2010 13:05:52 -0600, dpb wrote:

wrote:
On Sun, 19 Dec 2010 08:21:16 -0600, dpb wrote:

Edward Reid wrote:
...

... If you disable the resistance heat (which is a viable course of
action in the southern US), then you can ignore that advice and save
some money, albeit at the tradeoff that it may take quite a while to
bring the temperature back up.
One alternate ploy rather than disabling them entirely is what the
installer of our system did routinely -- he used a thermister inline w/
the emergency heat that kept them out of the control circuit w/ outside
temperatures were above about 20-25F.

Neat idea. The problem I see with this is that there is something else to go
wrong and there is no way to know it's gone wrong until the worst possible
time.

Trivial to bypass if want/need to but it's a passive solution and a
device that has extremely long MTBF ratings...

There is *nothing* in a house that has extremely long MTBF, ratings
notwithstanding. In some areas auxiliary heat may only come on once or twice
a year. The owner may not even be home; frozen pipes.

(Which leads to a story of when sold the house, however; the buyer's
inspection wrote up a defect that the emergency heat was non-functional;
the buyer ended up paying to have the good idea removed 'cuz couldn't
fathom the benefit even when explained to him and I refused to pay to
"fix" something that wasn't broke but was a beneficial feature.)

Buyers are fickle. Buying a house is a very emotional time and anything out
of the ordinary can cause strange reactions and some not so strange (e.g. not
to believing the seller or agents).

zzzzzzzzzz wrote:
....

There is *nothing* in a house that has extremely long MTBF, ...

Nonsense. Thermistors are extremely reliable devices as are virtually
all passive devices.

The likelihood of the thermistor being the failure point is multiple
orders of magnitude lower than that of any of the other components it's
associated with, including the power grid itself.

--

On Sun, 19 Dec 2010 16:14:23 -0600, dpb wrote:

wrote:
...

There is *nothing* in a house that has extremely long MTBF, ...

Nonsense. Thermistors are extremely reliable devices as are virtually
all passive devices.

Nonsense yourself. IT's not about the device. More such stuff is damaged
than fails on its own. MTBF is meaningless.

The likelihood of the thermistor being the failure point is multiple
orders of magnitude lower than that of any of the other components it's
associated with, including the power grid itself.

Other items are discovered at times other than the worst possible. This is a
bad design.