|
Home > Archive > Home Repair forum > January 2006 > Disadvantages of two furnaces in series?
You are viewing an archived Text-only version of the thread.
To view this thread in it's original format and/or if you want to reply to
this thread please [click here]
| Author |
Disadvantages of two furnaces in series?
|
|
|
| Hello all,
I'm about to duct in a wood furnace in series to an electric one (both
forced air).
This is what several pros have told me is the best way.
But surely the one that's on at any moment will have to push or pull
all the air through the fan blower of the other one? Would that not
constrict the air way incredibly?
-Dean
| |
|
|
dean wrote:
> Hello all,
>
> I'm about to duct in a wood furnace in series to an electric one (both
> forced air).
>
> This is what several pros have told me is the best way.
>
> But surely the one that's on at any moment will have to push or pull
> all the air through the fan blower of the other one? Would that not
> constrict the air way incredibly?
>
> -Dean
Put the electric furnace ahead (upstream) of the wood furnace and remove
the fan assembly from the wood furnace.
You will have to rewire the system correctly in order to make it
workable. I would recommend that you have a pro make this conversion
for you, and preferably one who has done this before.
BTW, the wood furnace should offer little restriction to airflow. If
necessary you can bump up the blower speed.
Richard Perry
| |
|
| They should not be put in series. They should be put in parallel, with
automatic dampers in both the supply and return ducts, and a 2 stage heating
thermostat.
"dean" <deanbrown3d@yahoo.com> wrote in message
news:1138517475.840453.139570@g47g2000cwa.googlegroups.com...
> Hello all,
>
> I'm about to duct in a wood furnace in series to an electric one (both
> forced air).
>
> This is what several pros have told me is the best way.
>
> But surely the one that's on at any moment will have to push or pull
> all the air through the fan blower of the other one? Would that not
> constrict the air way incredibly?
>
> -Dean
>
| |
|
| Richard,
I think I see what you mean: remove the wood furnace blower completely,
and wire the electric furnace's blower to be used instead. Correct?
| |
|
| Bob,
I think I am beginning to favor the parallel method. I searched for the
last hour or so for "Automatic Damper" and the like, but I'm finding it
hard to see anything to get a pic of what it looks like. Could you give
me a brief description of how it works so that I am not in the dark?
This is a motorized damper?
| |
|
| How will you be using this system? Will you be using wood in the daytime and
electric at night, or will you be using wood both day and night, and only
using electric when you go away for more than a day?
"dean" <deanbrown3d@yahoo.com> wrote in message
news:1138545074.171254.52950@z14g2000cwz.googlegroups.com...
> Bob,
>
> I think I am beginning to favor the parallel method. I searched for the
> last hour or so for "Automatic Damper" and the like, but I'm finding it
> hard to see anything to get a pic of what it looks like. Could you give
> me a brief description of how it works so that I am not in the dark?
> This is a motorized damper?
>
| |
| Edwin Pawlowski 2006-01-29, 11:21 am |
|
"dean" <deanbrown3d@yahoo.com> wrote in message
>
> I think I am beginning to favor the parallel method. I searched for the
> last hour or so for "Automatic Damper" and the like, but I'm finding it
> hard to see anything to get a pic of what it looks like. Could you give
> me a brief description of how it works so that I am not in the dark?
> This is a motorized damper?
I've seen such a thing but don't know the brand name. Heater goes on, the
damper opens. heater goes off, it closes. Sounds like a better method than
in series.
>
| |
|
|
Edwin Pawlowski wrote:
> "dean" <deanbrown3d@yahoo.com> wrote in message
>
>
>
> I've seen such a thing but don't know the brand name. Heater goes on, the
> damper opens. heater goes off, it closes. Sounds like a better method than
> in series.
Nevertheless, it isn't. On systems with a backup unit, otherwise called
a redundant system, such as on several facilities that we maintain, the
damper is the way to go. But that is because we have two complete
systems, including evaporator coils in each, one of which is an
emergency backup system. The idea is that conditioned air can continue
to be supplied in the event of any sort of failure of either of these
units. If they had a common blower feeding them, then a failure of that
blower motor or its control circuit would leave the building with no air
conditioning at all. The second unit is called a redundant system.
OTOH, in the case of the wood stove the idea behind it usually isn't
redundancy, but rather it only provides the customer the option of using
different energy sources. You wouldn't for instance want to configure a
typical heat pump/gas dual-fuel system in parallel as you described for
the wood furnace/electric heat above, though you certainly could if you
wished to. It isn't however economical to do so. Same with the wood
heat/electric system. Typically the evaporator coil, if cooling is
supplied as well, is located directly on top of the wood stove with a
length of duct between them. In that length of duct (plenum) are located
a typical insertion fan/limit to operate the common blower when wood
heat is provided, and a line-voltage stat's element which is used to
lock out the electric heat when the plenum temp rises above preset value
to prevent overheating in the event that both units are producing heat.
Burning wood cannot be cycled off with a stat. The Longwood furnace
comes close, by using a t-stat controlled damper door, but still no cigar.
Economy may take a back seat to redundancy in your area in all cases,
but it doesn't in my region of the world. Redundant systems and
dual-fuel systems have completely different end goals in mind. There are
wood burning systems on the market however that are designed to be
coupled to an existing central air system, that are already configured
controlwise, i.e. that require no field engineering of safeties etc.,
simply follow their pre-engineered instructions.
Richard Perry
| |
|
| Wood full tme (except on vacation) but would like the electric to kick
in if its enabled and if the wood runs low, for example if I'm too
tired to fill up
| |
|
| If you were leaving one off for a long period of time, then you could
probably get away with manual dampers. If not, then you'll probably want
automatic dampers. There are several types on the market. Some can be wired
to the thermostat, and some can be wired to the equipment. You'll have to
see which one works best for you. Check out 'Metal-Fab' and 'Zoning'.
"dean" <deanbrown3d@yahoo.com> wrote in message
news:1138554628.300327.199410@f14g2000cwb.googlegroups.com...
> Wood full tme (except on vacation) but would like the electric to kick
> in if its enabled and if the wood runs low, for example if I'm too
> tired to fill up
>
| |
|
| Thanks for the info, that was very useful. Let me just describe exactly
what I have:
1. Existing heat pump/electric heater and air conditioner system, with
1HP blower fan.
2. Wood furnace with no air con, but with 3/4 HP blower. It has a
plenum temperature fan/limit control, which controls and air opening in
the front door for combustion. Separately the thermostat controls the
combustion.
If its in series, I would have to either remove one fan, or make sure
they both come on together, as I think there would be too much
bottleneck to push air through a turned-off fan.
Its one of these:
www.charmaster.com
(The wood only system charmaster wood controls).
Dean
| |
|
| What I am looking for is a mechanical damper, not a powered one. I
could put into the cold air return so that it can only suck, and not
blow out. Put one just before each furnace. Not sure if there is such a
thing, but I think I have seen similar ones on roofs that have louvred
slats that open when the fan is on, and close automatically when the
fan is off. If its made properly and balanced, it would not offer much
resistance.
Dean
| |
|
|
dean wrote:
> What I am looking for is a mechanical damper, not a powered one. I
> could put into the cold air return so that it can only suck, and not
> blow out. Put one just before each furnace. Not sure if there is such a
> thing, but I think I have seen similar ones on roofs that have louvred
> slats that open when the fan is on, and close automatically when the
> fan is off. If its made properly and balanced, it would not offer much
> resistance.
Dean, you should probably think twice about taking the advice of this
person, who is obviously not a professional in the field of HVAC. You're
going to burn down your fucking house if you continue with your present
plan.
http://www.canren.gc.ca/prod_serv/i...Id=103&PgId=606
"[...] The add-on is placed beside the existing furnace, and special
ducts are installed to connect the two units. The air passes through the
original furnace, then through the add-on and into the ducts to be
distributed throughout the house. Note that ONLY AN EXPERIENCED
PROFESSIONAL should install an add-on."
Scroll down the page to near the bottom for a drawing that depicts the
proper installation.
Richard Perry
| |
|
|
dean wrote:
> Thanks for the info, that was very useful. Let me just describe exactly
> what I have:
>
> 1. Existing heat pump/electric heater and air conditioner system, with
> 1HP blower fan.
> 2. Wood furnace with no air con, but with 3/4 HP blower. It has a
> plenum temperature fan/limit control, which controls and air opening in
> the front door for combustion. Separately the thermostat controls the
> combustion.
>
> If its in series, I would have to either remove one fan, or make sure
> they both come on together, as I think there would be too much
> bottleneck to push air through a turned-off fan.
Correct. You would remove the wood furnace's blower completely from the
wood furnace, wire the heat pump blower's selected speed tap through the
fan side of the existing fan/limit switch on the wood furnace, in
parallel to the heat pump's fan relay contacts, or optionally run a 24v
circuit from the heat pump through the fan side of the fan/limit that
will call for the indoor blower. The main difference in these two
methods is that wiring the motor directly through the fan/limit will
allow heating with wood even in the event that the heat pump control
circuit shorts, or becomes inoperative for any reason, thus allowing a
bit of redundancy in the system that won't be available if you run the
24v circuit through the fan/limit.
Unless the heat pump is configured to run on the same speed during all
modes, then a relay will be required in order to lock out any other
speeds that might be energized by the heat pump's controls. IOW, you
don't want two speeds of the blower to be energized simultaneously since
that would let its magic smoke out of it. The door damper on your wood
furnace will continue to operate on its own t-stat and the heat pump on
its own t-stat. As long as you have the additional high-temp limit or
temperature control installed that I spoke of earlier, then it won't
matter if both units call for heat simultaneously, though it is possible
to install yet another relay that will close the door damper upon a call
for electric heat. The limit side of the fan/limit switch will however
automatically close the door damper, so this relay would only serve as
an optional safety.
Being a heat pump, you'll need a second high-temp limit besides the one
above, that will need to be set somewhere around 90º to prevent the
compressor from running when there is wood still burning or smoldering
in the wood furnace. This is to prevent compressor damage. Since the
heat pump won't be able to run with even the slightest heat being
emitted from the wood, even after the door damper has closed, the house
temp will drop and the heat pump stat will eventually call for
resistance heat. As a result the heat pump won't run in heat pump mode
at any time when you are also burning wood. Just something to keep in
mind. As you might have gathered I have installed systems like this one.
Yours will be a triple-fuel system, which is quite simple compared to
the quintuple-fuel system that I put together summer before last
Richard Perry
> Its one of these:
>
> www.charmaster.com
>
> (The wood only system charmaster wood controls).
>
> Dean
>
| |
|
|
RP wrote:
>
>
> dean wrote:
>
>
>
> Correct. You would remove the wood furnace's blower completely from the
> wood furnace, wire the heat pump blower's selected speed tap through the
> fan side of the existing fan/limit switch on the wood furnace, in
> parallel to the heat pump's fan relay contacts, or optionally run a 24v
> circuit from the heat pump through the fan side of the fan/limit that
> will call for the indoor blower. The main difference in these two
> methods is that wiring the motor directly through the fan/limit will
> allow heating with wood even in the event that the heat pump control
> circuit shorts, or becomes inoperative for any reason, thus allowing a
> bit of redundancy in the system that won't be available if you run the
> 24v circuit through the fan/limit.
>
> Unless the heat pump is configured to run on the same speed during all
> modes, then a relay will be required in order to lock out any other
> speeds that might be energized by the heat pump's controls. IOW, you
> don't want two speeds of the blower to be energized simultaneously since
> that would let its magic smoke out of it. The door damper on your wood
> furnace will continue to operate on its own t-stat and the heat pump on
> its own t-stat. As long as you have the additional high-temp limit or
> temperature control installed that I spoke of earlier (set at somewhere around ~150º), then it won't
> matter if both units call for heat simultaneously, though it is possible
> to install yet another relay that will close the door damper upon a call
> for electric heat. The limit side of the fan/limit switch will however
> automatically close the door damper, so this relay would only serve as
> an optional safety.
>
> Being a heat pump, you'll need a second high-temp limit besides the one
> above, that will need to be set somewhere around 90º to prevent the
> compressor from running when there is wood still burning or smoldering
> in the wood furnace. This is to prevent compressor damage. Since the
> heat pump won't be able to run with even the slightest heat being
> emitted from the wood, even after the door damper has closed, the house
> temp will drop and the heat pump stat will eventually call for
> resistance heat. As a result the heat pump won't run in heat pump mode
> at any time when you are also burning wood. Just something to keep in
> mind. As you might have gathered I have installed systems like this one.
> Yours will be a triple-fuel system, which is quite simple compared to
> the quintuple-fuel system that I put together summer before last
Let me back up a minute to say that if your evaporator coil is upstream
from the wood furnace, which it likely will be, then you won't need the
additional 90º limit that I spoke of, and your heat pump will run
normally unless locked out by the ~150º limit (that *is* required).
Richard Perry
| |
|
| Richard,
Thanks very much for all the very detailed descriptions! I never
thought about some of the issues you mentioned. You brought up a
particularly important point, about the heat pump not coming on and me
paying for resistive heat. If I used that as a back-up on my wood
furnace, it would probably end up being more expensive than just
leaving the heat pump to work. Makes running on wood alone now more
attractive.
Your point that I could run the electric upstream of the wood furnace
is a good one, but when I look at the blower hole in the wood furnace
it is very small, maybe 4x10", so if I take out the blower, that
constriction is still going to be there unless I butcher the thing,
which I don't plan on doing (the wood furnace has all kinds of
directional fins to direct the heat around the firebox and heat
exchanger so I don't want to mess with that.
Supposing then that I do stillI want them in parallel, and rely only on
wood on a regular basis. I want the wood to be utmost efficiency,
considering the effort it takes to collect the wood! So, I have a main
switch near the furnaces, to select one or the other, but not both.
Safe? Then I put in a one-way valve at the cold air return, on both of
the furnaces. No need to play with the plenums, the air can't get
through for this reason. I use two separate t-stats, but since we have
a safety interlock, only one will ever be doing any controlling.
How does that sound? As you can see, I am working this out now so I get
it right, and I want to know all the good options.
Dean
| |
|
|
dean wrote:
> Richard,
>
> Thanks very much for all the very detailed descriptions! I never
> thought about some of the issues you mentioned. You brought up a
> particularly important point, about the heat pump not coming on and me
> paying for resistive heat. If I used that as a back-up on my wood
> furnace, it would probably end up being more expensive than just
> leaving the heat pump to work. Makes running on wood alone now more
> attractive.
>
> Your point that I could run the electric upstream of the wood furnace
> is a good one, but when I look at the blower hole in the wood furnace
> it is very small, maybe 4x10", so if I take out the blower, that
> constriction is still going to be there unless I butcher the thing,
> which I don't plan on doing (the wood furnace has all kinds of
> directional fins to direct the heat around the firebox and heat
> exchanger so I don't want to mess with that.
>
> Supposing then that I do stillI want them in parallel, and rely only on
> wood on a regular basis. I want the wood to be utmost efficiency,
> considering the effort it takes to collect the wood! So, I have a main
> switch near the furnaces, to select one or the other, but not both.
> Safe? Then I put in a one-way valve at the cold air return, on both of
> the furnaces. No need to play with the plenums, the air can't get
> through for this reason. I use two separate t-stats, but since we have
> a safety interlock, only one will ever be doing any controlling.
>
> How does that sound? As you can see, I am working this out now so I get
> it right, and I want to know all the good options.
You can do whatever you want. Parallel will work, it just isn't the
best way. If you're serious about this installation then get a pro out
to look over the situation and to design it for you. I can't see it from
here. Good luck with it.
Richard Perry
| |
|
| My fundamental concern is the constriction going through either
furnace, when the blower is removed. I keep reading that even just a 90
degree bend cuts the air flow down by 20%, so what is pushing through a
constriction and whole second furnace going to do? Please keep
advising! I am only researching now, and I will get a pro in to install
it but I want to make sure I know what he's doing and that he's doing
it right.
| |
|
|
dean wrote:
> My fundamental concern is the constriction going through either
> furnace, when the blower is removed. I keep reading that even just a 90
> degree bend cuts the air flow down by 20%, so what is pushing through a
> constriction and whole second furnace going to do? Please keep
> advising! I am only researching now, and I will get a pro in to install
> it but I want to make sure I know what he's doing and that he's doing
> it right.
If the restriction cannot be overcome without interrupting even airflow
over the firebox, then another option is to run a bypass around the wood
furnace. This will require some pressure balancing, thus a bypass
damper will be required as well. The advantage would be an ability to
control static pressure and a simplification of control/safety issues.
Unless you want to wait for the wood fire to be completely snuffed out
before switching on the heat pump, then you won't want to go with the
parallel install. What will happen with a parallel install is that if
you switch immediately to heat pump after burning wood, then the wood
furnace will heat up and its fan/limit will call for it's blower, and
with the changeover damper closed off to the wood furnace that air will
have nowhere to go. If OTOH, you disable the wood furnace's blower on a
call for heat pump then the fire box will collect heat and become very
hot, possible hot enough to present a hazard. You'd either have to
allow the damper to switch back and forth, short cycling both units
until the wood cools down, or simply wait until it cools down before
bringing in the heat pump. Neither of these options would be acceptable
to me, in my own home.
Based upon your descriptions I'd probably go with a series installation
and a motorized bypass damper.
In the series configuration the heat generated by the wood stove after
it's door damper has closed won't present a problem, and there would be
no short cycling unless perhaps your backup resistance heat were also
engaged. I simple temperature control could be installed to lock out
resistance heat based upon discharge air temp. If your evaporator coil
is located downstream of the wood furnace, which again it probably won't
be, then the controls will be a bit trickier. It isn't a good idea to
have the evap coil upstream, since this will cause condensation within
the wood furnace in cooling season. This is the reason that the coil is
always placed downstream on a gas furnace, i.e. to prevent rusting out
of the heat exchangers. Most heat pump air handlers, OTOH, have the evap
coil within them rather than sitting on top of the air handler, so it's
difficult to relocate to a point after the wood furnace. So it seems
your practical options are to either:
1) Go ahead with the parallel install and put up with the changeover
issues.
2) Go with the bypass damper on a series install, remove the coil from
your air handler and place a boxed coil downstream from the wood
furnace. This will require some form of compressor lockout to prevent
the compressor from running when the discharge air from the wood stove
is above 90-100deg.
3) Place the evaporator coil in the bypass ducting.
HTH.
Richard Perry
| |
|
| Do you live anywhere near NJ?
Ok thanks for that further discussion, I need to chew over this some
more, off work time. I very much appreciate your time and effort.
Dean
| |
|
| >> I'd probably go with a series installation
and a motorized bypass damper.
In the series configuration the heat generated by the wood stove after
it's door damper has closed won't present a problem, and there would be
no short cycling unless perhaps your backup resistance heat were also
engaged.
Do you still mean to use the blower in the electric furnace, which is
upstream from the wood? The motorized bypass damper that you mentioned
- what is that bypassing? Sorry I'm confused about this point. Do you
have a telephone number and 10 free minutes?
-Dean
| |
|
|
dean wrote:
>
> and a motorized bypass damper.
> In the series configuration the heat generated by the wood stove after
> it's door damper has closed won't present a problem, and there would be
>
> no short cycling unless perhaps your backup resistance heat were also
> engaged.
>
> Do you still mean to use the blower in the electric furnace, which is
> upstream from the wood? The motorized bypass damper that you mentioned
> - what is that bypassing? Sorry I'm confused about this point. Do you
> have a telephone number and 10 free minutes?
The bypass is just a duct that runs parallel to the wood furnace. The
main air stream is split as it leaves the fan coil, some of that air is
fed through the wood furnace and the rest is fed through a duct that
skirts around (bypasses) the wood furnace. These air streams are tied
back together on the other side of the wood furnace. It's actually a
series-parallel configuration. Yes, we're still talking about removing
the blower from the wood furnace.
Just think about a stream that splits in two and then rejoins
downstream. Now put your wood heater in one branch of that stream and
your evaporator coil in the other, with your air handler located
upstream of this split.
Richard Perry
| |
|
| Ok, but that doesn't help push air through the wood furnace. In fact it
would reduce the air going through the wood furnace, some of it would
bypass the wood furnace (we are relying on the electric furnace's
blower). I think its quite important to have maximum air flow around
the firebox.
| |
|
|
dean wrote:
> Ok, but that doesn't help push air through the wood furnace. In fact it
> would reduce the air going through the wood furnace, some of it would
> bypass the wood furnace (we are relying on the electric furnace's
> blower). I think its quite important to have maximum air flow around
> the firebox.
According to your description the air handler has a bigger blower motor
than the wood furnace has. I would think that the air handler blower
should be capable of pushing sufficient air through the wood furnace.
In fact, some of it would have to be bypassed around the wood furnace in
order to prevent too much airflow through the wood furnace. At the
same time this bypassing of air will reduce the static pressure in the
plenum, allowing the blower to run more efficiently, and it will reduce
noise at the return as well. The purpose of the bypass damper is to
control the volume of air through the wood furnace or alternately
through the evap coil, as necessary. The damper will allow air to bypass
the wood furnace when the heat pump is energized, and will allow air to
bypass the heat pump evaporator coil when the wood furnace is heating.
You won't have a call for both units simultaneously. An interlock
circuit will prevent both from calling at the same time.
When the fire dies down in the wood stove and it is no longer supplying
sufficient heat to the space, and when you aren't there to add more wood
or perhaps don't want to add more wood, then the heat pump stat will
energize the compressor, modulate the bypass damper open to the evap
coil, and at the same time the door damper will be closed on the wood
furnace. A small portion of the airflow will still be allowed to flow
through the wood furnace, just enough to prevent it from overheating and
from rising enough to lock out the heat pump again. I forgot to mention
that you'd have a temperature controller on the wood furnace that would
lock out the heat pump at a given temp. It is the drop in temp of the
wood furnace that would cause this same control to allow the heat pump
to take over. Now where was I?
Once the fire is completely out the damper modulates full open to the
evap coil, allowing full required airflow through it. There are several
other ways to control airflow beside this one. One is to have a second
damper, another is to place the coil downstream and have a normal series
installation. The bypass system is definitely more complicated than the
normal series installation, but it would provide an ability to supply
the correct airflow to both the coil and to the wood furnace as
necessary. Normally the wood furnace doesn't offer enough restriction
to pose a problem. The only reason that I suggested the bypass in your
case is that you had some reservations about getting all the air through
the wood furnace without it producing an excessive restriction to
airflow. Normally this isn't a problem, and the series installation is
rather straightforward.
If you want a less complicated system, then I suggest you either forget
about it, or make that hole bigger.
Richard Perry
| |
|
| Right I am convinced. Once again - thank you!
So, in the normal series installation (assuming 1HP is enough), would I
still need a lock-out to stop the heat pump running when the wood
furnace is hot? I've read sometimes that you have 2 thermostats, and
set the electric 5 degrees below the wood. However, I assume that
someone can fiddle with these, so I either get the interlock, or a
dedicated single thermostat designed for this type of system.
What would happen if the heat pump came on and fed warm air into the
wood furnace jacket? Would it not just turn down the door damper
because it doesn't need so much fuel? Would this be a hazardous
situation?
-Dean
| |
|
|
dean wrote:
> Right I am convinced. Once again - thank you!
>
> So, in the normal series installation (assuming 1HP is enough), would I
> still need a lock-out to stop the heat pump running when the wood
> furnace is hot? I've read sometimes that you have 2 thermostats, and
> set the electric 5 degrees below the wood. However, I assume that
> someone can fiddle with these, so I either get the interlock, or a
> dedicated single thermostat designed for this type of system.
>
> What would happen if the heat pump came on and fed warm air into the
> wood furnace jacket? Would it not just turn down the door damper
> because it doesn't need so much fuel? Would this be a hazardous
> situation?
The heat pump air won't harm a thing, it's in the summer when you're
running the AC that you don't want the evaporator upstream. The wood
furnace would quickly rust out. HTH.
Richard Perry
| |
|
| RP wrote:
>
>
> dean wrote:
>
>
>
> The heat pump air won't harm a thing, it's in the summer when you're
> running the AC that you don't want the evaporator upstream. The wood
> furnace would quickly rust out. HTH.
>
> Richard Perry
>
I was telling someone about this idea, That I would love to do something
like this in my next house I have custom built. I was ask why not have a
wood fuel boiler that used water circulated to a coil as a second unit
on the heat pump, then would just need to have the circulator pump shut
off when temp was not high enough and the heat pump take over.
Is this doable?
I think back to coal fueled boilers supplying steam to radiators, Just
the radiator would be in line with the heat pump.
| |
|
| Probably not unless you had some other type of hydronic heat system
connected to the wood boiler. When wood boilers get too hot, a circulator
has to come on to dissipate the heat, and a hydronic coil wouldn't have
enough capacity.
You can only do it with a boiler that can shut the fuel supply off on high
limit.
"MC" <mwclarke1@yahoo.com> wrote in message
news:0QTDf.13358$vp6.4554@bignews6.bellsouth.net...
> RP wrote:
> I was telling someone about this idea, That I would love to do something
> like this in my next house I have custom built. I was ask why not have a
> wood fuel boiler that used water circulated to a coil as a second unit
> on the heat pump, then would just need to have the circulator pump shut
> off when temp was not high enough and the heat pump take over.
>
> Is this doable?
>
> I think back to coal fueled boilers supplying steam to radiators, Just
> the radiator would be in line with the heat pump.
>
>
>
|
|
|
|
|