Question about 2 stage AC/Heat Pump

Posted by Art Todesco on October 26, 2009, 8:43 am

I just moved into a new house with an
Amana 2 stage AC/Heat Pump. It is
controlled by a Honeywell HZ432
multi-zone controller. For AC it 1st
kicks in on stage 1 and if the
temperature is not satisfied in 10
minutes (selectable on the HZ432), the
2nd stage will kick in. This is
especially good as I am in an area where
the temperature doesn't usually get real
high in the summer (western NC
mountains) which will allow unit will
run a bit longer to remove more
humidity. Now that it's heat pump
season, the same 10 minutes applies to
the heat pump. In my way of thinking, I
would like to see the heat pump go
directly to stage 2 so you can get as
much heat as possible. I have heard
here, many people complain about heat
pumps and the drafty feel, etc.,
however, in this house, the HVAC guy got
is right as I don't notice these
problems. BTW, previously I've had a
gas furnace for many, many years so I do
know how that feels. Am I thinking
wrong here? What are your opinions?
Thanks.

Posted by dpb on October 26, 2009, 8:58 am

Art Todesco wrote:

> I just moved into a new house with an Amana 2 stage AC/Heat Pump. It is
> controlled by a Honeywell HZ432 multi-zone controller. For AC it 1st
> kicks in on stage 1 and if the temperature is not satisfied in 10
> minutes (selectable on the HZ432), the 2nd stage will kick in. This is
> especially good as I am in an area where the temperature doesn't usually
> get real high in the summer (western NC mountains) which will allow unit
> will run a bit longer to remove more humidity. Now that it's heat pump
> season, the same 10 minutes applies to the heat pump. In my way of
> thinking, I would like to see the heat pump go directly to stage 2 so
> you can get as much heat as possible. I have heard here, many people
> complain about heat pumps and the drafty feel, etc., however, in this
> house, the HVAC guy got is right as I don't notice these problems. BTW,
> previously I've had a gas furnace for many, many years so I do know how
> that feels. Am I thinking wrong here? What are your opinions? Thanks.

'Pends on how you feel about economy vs faster response. There _may_ be
a way to change the operation to control on dT instead of/in addition to
simply time difference; the two-stage control on the geothermal system
we had did that; it was Water Furnace-supplied w/ the pump; I don't know
who actually built it.

You'll want to be sure to know whether that also is kicking in your
backup resistance heat as well, of course.

--

Posted by Art Todesco on October 26, 2009, 4:22 pm

dpb wrote:

> Art Todesco wrote:

>> I just moved into a new house with an Amana 2 stage AC/Heat Pump. It
>> is controlled by a Honeywell HZ432 multi-zone controller. For AC it
>> 1st kicks in on stage 1 and if the temperature is not satisfied in 10
>> minutes (selectable on the HZ432), the 2nd stage will kick in. This
>> is especially good as I am in an area where the temperature doesn't
>> usually get real high in the summer (western NC mountains) which will
>> allow unit will run a bit longer to remove more humidity. Now that
>> it's heat pump season, the same 10 minutes applies to the heat pump.
>> In my way of thinking, I would like to see the heat pump go directly
>> to stage 2 so you can get as much heat as possible. I have heard
>> here, many people complain about heat pumps and the drafty feel, etc.,
>> however, in this house, the HVAC guy got is right as I don't notice
>> these problems. BTW, previously I've had a gas furnace for many, many
>> years so I do know how that feels. Am I thinking wrong here? What
>> are your opinions? Thanks.

>
> 'Pends on how you feel about economy vs faster response. There _may_ be
> a way to change the operation to control on dT instead of/in addition to
> simply time difference; the two-stage control on the geothermal system
> we had did that; it was Water Furnace-supplied w/ the pump; I don't know
> who actually built it.
>
> You'll want to be sure to know whether that also is kicking in your
> backup resistance heat as well, of course.
>
> --

Thanks for the info. Actually, I wonder
about economy? Running on stage 2 will,
of course use more power, however, it
will get the heat delivered faster and
with less blower run time. The backup
heat is actually a 2 stage propane
furnace (Goodman). So far this season,
it has only come on during one cold
morning and I think it came on because
the outside coil was deicing.

Posted by dpb on October 26, 2009, 5:01 pm

Art Todesco wrote:

> dpb wrote:

>> Art Todesco wrote:

>>> I just moved into a new house with an Amana 2 stage AC/Heat Pump. It
>>> is controlled by a Honeywell HZ432 multi-zone controller. For AC it
>>> 1st kicks in on stage 1 and if the temperature is not satisfied in 10
>>> minutes (selectable on the HZ432), the 2nd stage will kick in. This
>>> is especially good as I am in an area where the temperature doesn't
>>> usually get real high in the summer (western NC mountains) which will
>>> allow unit will run a bit longer to remove more humidity. Now that
>>> it's heat pump season, the same 10 minutes applies to the heat pump.
>>> In my way of thinking, I would like to see the heat pump go directly
>>> to stage 2 so you can get as much heat as possible. I have heard
>>> here, many people complain about heat pumps and the drafty feel,
>>> etc., however, in this house, the HVAC guy got is right as I don't
>>> notice these problems. BTW, previously I've had a gas furnace for
>>> many, many years so I do know how that feels. Am I thinking wrong
>>> here? What are your opinions? Thanks.

>> 'Pends on how you feel about economy vs faster response. There _may_
>> be a way to change the operation to control on dT instead of/in
>> addition to simply time difference; the two-stage control on the
>> geothermal system we had did that; it was Water Furnace-supplied w/
>> the pump; I don't know who actually built it.
>> You'll want to be sure to know whether that also is kicking in your
>> backup resistance heat as well, of course.
>> --

> Thanks for the info. Actually, I wonder about economy? Running on
> stage 2 will, of course use more power, however, it will get the heat
> delivered faster and with less blower run time. The backup heat is
> actually a 2 stage propane furnace (Goodman). So far this season, it
> has only come on during one cold morning and I think it came on because
> the outside coil was deicing.

I doubt the time will be sufficiently reduced to be observable on energy
savings. I'd expect the added load to more than compensate while
running at the second stage. Remember, it's a fixed dH to raise the
temperature a specific amount irrespective of time. You'd have to have
actual performance figures to know how linear the power cost is vs heat
output at the two performance levels to get a computed estimate. Other
than that, it would take monitoring usage each way over a significant
time such that day-to-day variability would average out.

BTW, in marginal area, might want to consider an interlock on the backup
heat so it only comes on below (say) 20F or somesuch. Did that w/ the
geothermal system in E TN by adding an external thermocouple into the
control loop calling for the backup. W/ the geothermal (rather than
air-exchange) it made it essentially a non-starter that was almost never
needed. Air-exchange are much improved since the one that system
replaced, but am sure it would still have come on more often w/ a newer
one than w/ the ground source but wouldn't have been just a cool-morning
thing.

--

Posted by Larry Caldwell on October 26, 2009, 9:29 pm

says...

> I just moved into a new house with an
> Amana 2 stage AC/Heat Pump. It is
> controlled by a Honeywell HZ432
> multi-zone controller. For AC it 1st
> kicks in on stage 1 and if the
> temperature is not satisfied in 10
> minutes (selectable on the HZ432), the
> 2nd stage will kick in. This is
> especially good as I am in an area where
> the temperature doesn't usually get real
> high in the summer (western NC
> mountains) which will allow unit will
> run a bit longer to remove more
> humidity. Now that it's heat pump
> season, the same 10 minutes applies to
> the heat pump. In my way of thinking, I
> would like to see the heat pump go
> directly to stage 2 so you can get as
> much heat as possible. I have heard
> here, many people complain about heat
> pumps and the drafty feel, etc.,
> however, in this house, the HVAC guy got
> is right as I don't notice these
> problems. BTW, previously I've had a
> gas furnace for many, many years so I do
> know how that feels. Am I thinking
> wrong here? What are your opinions?
> Thanks.

Whatever rings your chimes. If you find a big blast of heat satisfying,
it's your house and your electric bill. The most efficient heating
system is one that never shuts down or cools off. A lower powered heat
pump will also create less hot and cold spots in the house. The second
stage is there for colder days when the smaller heat pump just won't do
the job. If you want to set the heat pump to go directly to stage 2,
you will pay a few extra bucks for heat, but other than that I don't see
it will do any harm.

--
For email, replace firstnamelastinitial
with my first name and last initial.

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