House Battery and Energy Management

@OffGridInTheCity will probably chime in but at that voltage there really isn't much usable power left. Maybe 200mAh per cell if lucky.
Also if your cutout is above the cell spec of generally 3.0V you extend the life of the cell considerably. Same goes with not charging the cell all the way to 4.2 but to ≈4.0V
Also in my study https://secondlifestorage.com/index.php?threads/behaviour-of-cells-in-parallel-take-2.8857/ I found out that below that voltage cells, especially in frankenstein packs/batteries will contribute differently to satisfy the load. Which can cause some cells to stress far more than others leading to premature failure.

Wolf
 
@OffGridInTheCity will probably chime in but at that voltage there really isn't much usable power left. Maybe 200mAh per cell if lucky.
Also if your cutout is above the cell spec of generally 3.0V you extend the life of the cell considerably. Same goes with not charging the cell all the way to 4.2 but to ≈4.0V
I have a 14s lithium-ion battery bank - e.g.48v nominal. I've found that my discharge curve knee is right at 49.5v - e.g. 3.54v/cell. @Wolf is correct that there just isn't much power below 3.5v/cell - its *dramatic* and why stress the cells for almost no power? Better to just build a bigger battery in terms of life span.
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In my particular case I could cut-off sooner and charge a bit higher... e.g. 3.57v - 4.04v for example - but I don't have *any* insight if moving the operating range up/down a bit will extend the cycle count beyond that Battery University graph.

Also in my study https://secondlifestorage.com/index.php?threads/behaviour-of-cells-in-parallel-take-2.8857/ I found out that below that voltage cells, especially in frankenstein packs/batteries will contribute differently to satisfy the load. Which can cause some cells to stress far more than others leading to premature failure.

Wolf
This is another reason, and it manifests in my battery as significantly diverging pack voltages below 3.5v/pack. I know it seems like you should be able to go to 3.4v/cell or 3.3v/cell or even 3.0v/cell but its like going over a cliff - no significant power below the knee.
 
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I haven't had any interesting progress to note here for quite a while. But things are still happening. Here's a short update:

The front door has been repaired rather than replaced. The door frame still needs some work, and the weather strip needs replacing. I also want to add a storm door to the front. This will help protect the old door from further weather damage, and add some insulation value.
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The basement door (and part of the wall) still needs to be replaced. Don't know if I mentioned it before, but the basement used to have a garage door leading out to the back patio. At some point, someone walled it in. Not a high quality job either. The old door is rotting off its hinges, and the threshold is already gone. I want to replace the whole flimsy wall with a 2x6 frame, and get double doors put in. Then I can do most of my small engine type work inside instead of out on the patio. (It rains here a lot.)

The basement is still in the process of getting additional insulation. (It's a "daylight" basement, so some walls are exposed to the outside air.) I've actually made some progress here, furring out some walls, and adding expansion foam and rigid insulation in various nooks and crannies that have been leaking air (and bugs, and vermiculite) pretty much since the house was built 80 years ago. I also refurbished my grandpa's old work bench. So it's now part of the basement improvements:
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The main floor walls (cinder block) need insulation. Cinder block has an R-value of 2 (or so I've read). They're furred out with 2x2s and insulated with vermiculite, which adds another 3, I think. There are companies, if I can find one locally, that inject basically a truckload of expansion foam, into the cavities of the cinder blocks to insulate without having to tear the place apart.

The attic still needs proper ventilation and insulation. My son and I have actually been working on this recently. There is some electrical work that needs doing before we can insulate. Some of which has been done. And we have fans, and vent covers, and power cable now to do the ventilation work. Hopefully this spring before it gets too hot.

Ye Olde furnace could be replaced with a modern heat pump. I've been trying to figure how many BTUs of heat pump I need, but I don't think I'll be able to do it properly without hiring it out. I've read that the standard X number of BTUs per sq. ft. is wildly inaccurate, as it doesn't take into account the local climate, or the efficiency of the house. (I'd rate ours as "poor"). The bad efficiency of the house might cancel out our mild climate, but I'd rather not guess. I did get to measure the current draw of the furnace recently. Its on two 2-pole breakers labeled "blower" and "furnace". Blower got 42.5A and furnace got 20A. I think the labels may be swapped. But no matter, that's 15kW total, which seems to be normal for an electric furnace of my sized house. It has a label, but I don't really understand it:
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Air ducts could be improved for better air circulation. My ductwork is an amalgamation of different heating eras. I think the original furnace was oil powered, based on the antient thermostat I found buried in the wall during some renovation. I'm pretty sure some of the older ductwork is oversized, and some of the newer stuff is right in the way of a window. So I need that moved. Also, there are no air returns in the basement or on the second floor. I think we could add them pretty easy. But I'll have to consult with an HVAC company to be sure.

I was considering a tankless water heater for a while. Based on what we need, I don't think it's a good match for us though. Even though they use fewer kWh that a traditional tank, their immediate current draw would be something like 112A instead of the more reasonable 18.8A. I don't have the option for propane or natural gas appliances. Electricity is cheaper in my area than those anyway.

Now I'm looking into heat pump water heaters. Seems they draw only about 21A, and are still use less energy than traditional tanks. Also, the cold exhaust could be vented outside in the winter, and into the kitchen in the summer. At no extra electrical cost. Some of them even have "smart" thinamagigs in them that let them use even less power during times of day when we're not likely to use any hot water. So I'm pretty intrigued by these things at the moment.

I haven't made any progress on the battery/solar side of things except some recent research. Folks here have been helping me with that on this thread. Though I am pretty happy with how the research is going. I'm getting closer to nailing down actual parts and products I can use vs. just theory.

I've also been getting a lot of wiring replaced. Old stuff looks like this:
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I have too many projects to post a log. I'd get depressed with what isn't done if I logged everything :p

Nice work on the door, btw. Doesn't even look remotely like the same door. Other than the door #.

That old wire. YEEKS!!!! 😬 The stuff they used to use in the old days, scary. No wonder so many places burned down. I worked on a house where they had just insulators, and "bare" wire! The bare wire would go from insulator to insulator and then a pigtail to the receptacle. You gotta turn the power off just to put your arm in the wall to do......what ever.
 
Thanks!
The door had many layers of paint that had to be removed, as well as significant water damage. It took quite a lot of time, but the repairs turned out to be way cheaper than buying a new door. Most of the door was still quite solid though. And if it's the original door, that makes it 80 years old. Hopefully my repairs will allow it to last a few more decades.

I enjoy writing up my larger projects. Especially the ones that span multiple years, I can go back and refresh myself on what I've done, and the tips that other people have left for me. It can get discouraging when projects get put on hold, or just don't seem to progress as fast as they should.

Good old "knob and tube" wiring. I have the slightly newer version where the wires are insulated, but still go through ceramic knobs and tubes. I have a whole bucket of those that I've pulled out. Believe it or not, the insulated version is actually very good. Lacks a ground, but otherwise, wouldn't really be need to be replaced. I can still read the printing on the insulation of the stuff I've pulled out.

The worse stuff is that black precursor to modern "Romex" style wire. That stuff hasn't aged well at all, and was installed very poorly. It at least has an undersized ground wire. But I bet that stuff has caused the most fires just because people in that era seem to have wired things up as dangerously as possible. I've rewired two old houses now, and both were fires waiting to happen. I've found junctions with no boxes hidden in the walls or in the attic under the insulation. Splices with no wire nuts. Just a bit of electrical tape. 12 AWG 120V wires piggybacked on 60A 2-pole breakers. An ungrounded water heater. I could go on.

On the subject of electrical, I was looking into whole house surge suppressors. Last time I looked they were huge and super expensive. Now they're pretty compact and much more affordable. Not to mention easier to install. I've heard rumors that they're now required by code for new main panel installations. I'm thinking of getting one just for fun.
 
On the subject of electrical, I was looking into whole house surge suppressors. Last time I looked they were huge and super expensive. Now they're pretty compact and much more affordable. Not to mention easier to install. I've heard rumors that they're now required by code for new main panel installations.
Yeah, the GFCI and AFCI breakers makes things a lot easier to install them to make circuits safe. They are a little pricey, but a lot safer, too. And smarter. And easier to install. And easier to replace. And more pros if I think long enough :p
The American SEC regulations are requiring them to be installed for certain new/retrofit installations. If you have, or are installing, the receptacle version, then you don't need the breaker style. I'm not sure what the other requirements are for required installation of them
 
I agree about the GFCI/AFCI, but I think you misunderstand. I mean a whole house devise that helps protect against brief over Voltage events. Like a surge protector in a power strip but at the main panel. It somehow takes the excess Voltage and "shunts" it to the ground wire before it can damage stuff. Like this guy at Home Depot.
 
I agree about the GFCI/AFCI, but I think you misunderstand. I mean a whole house devise that helps protect against brief over Voltage events. Like a surge protector in a power strip but at the main panel. It somehow takes the excess Voltage and "shunts" it to the ground wire before it can damage stuff. Like this guy at Home Depot.
Ahhh, well, in that case the best thing imho is to just have a UPS. Even if it doesn't need to run very long, say for a few seconds at most, would be fine. Most server grade UPS units are surge protectors as well.
However, having a second, or third, surge device wouldn't hurt either.

From my understanding, the way those devices work is they provide a short gap to ground. In electronics we don't see these devices as they really are, but with electric fences we can see them in all their glory. Basically they have two probes that are just barely close enough to not make a static jump at said voltage. When the voltage rises above a predetermined amount, the energy would rather take the shortcut to ground by jumping the air gap and follow the ground wire out.
In electronics these gap can be a lot closer than an electric fence as even at 480VAC is not enough to jump a gap that may only be a mm or so apart.
There are other devices called snuffers (if I recall correctly). They resist a change in current/voltage. And they force the build up to take another path. Possible these two devices work together in the HD link you provided.

The biggest issue with these kinds of devices is that they are usually a one and done device. They blow themselves apart during the surge. We had the snuffer type on our water well and the tank got hit and it looked like a bomb went off.

However, for $135, that's a lot cheaper than replacing equipment in the home, or the home itself depending on how bad the blast was.
 
I've been researching neutrals and multibranch circuits lately. Blew my mind when I found out that a common neutral between split phase circuits has less current than the hot wires. As my brain recovers from that revelation, I've been concerned about a multibranch circuit on my main panel. It's wired up pretty wrong:
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If I'm looking at it right, the two hots appear to be on separate phases. So at least there's that. But they really should be on a single 2-pole breaker.

The cable is 10/3 AWG with ground. It's one of those gray UF type cables. It splits at a junction box outside and the 15A one feeds an LED yard light. The other is 20A and feeds a couple outlets under the carport. I use them mostly for battery maintainers for motorcycles and lawn mowers, but I occasionally will use them for power tools. Well, not now, until I fix this mess. Since they're both outdoor circuits, I'd like to protect them with GFCI.

My first thought was to find a 20A 2-pole GFCI breaker. I've asked around the internet, and it's a little iffy as to whether such a breaker could actually protect a multibranch circuit properly. Some say yes and have reasons. Some say no and have reasons. They all say they're right and the others are wrong. I've also got an old Cutler Hammer main panel, and fancy breakers are kind of hard to find. And expensive when you can.

Another alternative is that I could get an outdoor rated sub panel made for 2 breakers and feed it with a regular old 30A 2-pole breaker since the cable is 10 AWG. Then I could use 2 single-pole GFCI breakers, a 15A and a 20A for each circuit. All much easier to find, and probably not much more expensive. In fact, both routes would cost about $180 after adding things up. Though if I do it this way, I'll want to upgrade some of the conduit and things while I have it all apart.
 
If I'm looking at it right, the two hots appear to be on separate phases. So at least there's that. But they really should be on a single 2-pole breaker.
Which one is the one you're saying is correct?? The Tandem or the Single breaker??

I've always used 2 standard breakers for hots. The larger breaker housing allows for better reliability, imho. Bigger springs, contacts, etc.
A Tandem breaker both ports are the same hot leg from the panel. So you definitely can't use both breakers for a 240V system.

Normally I've seen Tandem breakers only used for lights and small circuits, or a single outlet. I wouldn't use them for full room circuits, but that's just me.
 
You're right, it shouldn't be on a tandem breaker. But what I mean is that while one leg of the multibranch circuit is fed by one 120V bus, the other leg is fed by the other 120V bus. At least I think it is. The second circuit on the tandem breaker goes to the dishwasher, but doesn't share a common neutral. It's the outdoor light and outdoor receptacles that have the common neutral.

My point was that the breakers could both have been sitting on the same bus, which would have made the current on the shared neutral additive instead of subtractive. Which is why they're supposed to be on either a 2-pole breaker, or two singles tied together. That way they're sure to be on separate phases. Fortunately, the wire is oversized in this case, and the loads are small. So It may never have caused an issue.

But still, I plan to put the dishwasher on its own full sized 20A breaker, and put the multibranch circuit on two adjacent full sized breakers until I can get the sub panel installed. I'll save the tandem 20A breaker for some other use. Probably, it will just end up in the parts drawer next to the tandem 15A breaker.
 
Gee whiz, these smart meters are neat! I can see the exact point when I used the most electricity this year. Thursday, Dec. 22, 7:45pm. 4.66kW. Not coincidentally, the coldest day of the year. Unfortunately, our power usage seems to be going up instead of down. Maybe I can account for that. My son moved back in, and brought with him a space heater, A/C, mini fridge and computer. Also, we've been working on the attic and have had 4 access points open most of the winter. We just recently closed up 2 of them. But we're now where near done with the attic spaces yet.

2022 was weird. The rainy season persisted through the end of July. August through November were nice, and the new rainy season started in December. I had to turn the furnace back on at the end of November though. October turned out really nice. No rain, and we didn't need the A/Cs or the furnace. Lowest electrical bill of the year.

Anyway, I've been thinking about transfer switches. I'll need one when I set up my generator and sub panel. I was going to go with a manual one since the generator won't have auto-start. Most inverters seem to have ATSs built in, so when I go to install one, the manual transfer switch would become obsolete. I wonder though, if a stand-alone ATS could function as a fail safe during a power outage?

I guess there's different kinds of ATSs, but the one I have in mind looks like this:
ATS.png


If I understand it right, these two big contactors are sort of like relays. So if power from the grid is lost, the grid contactor immediately shuts off? I've tried to look into exactly how they work, but haven't found much. The interlock that keeps them from turning on at the same time seems to be like a 3-way light switch. I've never been able to figure those out either. Even though I've wired up at least three.

These things often have delay timers, but I think that's just for switching back on. I'm hoping the shut off is instant. I don't entirely trust an inverter to do the auto switching from the grid. They seem to have rather clumsy software. Also I could potentially get the settings confused or something. I'd sure feel a lot better with an independent auto-off switch to the grid if there were a power outage.
 
I wonder though, if a stand-alone ATS could function as a fail safe during a power outage?
Yup, very possible. I think Daniel uses his ATS for grid-backup. He runs off solar/battery primarily and if/when there's not enough juice there, it'll flip over to grid. He doesn't even notice the transfer. He's using the big ones kinda what you have pictured there. He even has a few videos on it

If I understand it right, these two big contactors are sort of like relays. So if power from the grid is lost, the grid contactor immediately shuts off?
Exactly correct. The big difference between a contactor and a relay is that the contactor has much larger contacts, beefier springs, etc. Kind of think the difference between a breaker and a light switch. Basically the same thing, but one is a lot bulkier/beefier

These things often have delay timers, but I think that's just for switching back on. I'm hoping the shut off is instant.
Most ATS's like this have transfer times <10ms. Again, Daniel covers this in a video with a scope hooked up to it during transfer.
I don't entirely trust an inverter to do the auto switching from the grid. They seem to have rather clumsy software.
Software doesn't 'really' control the transfer. The only thing the software does in this instance is tell it if it "can" switch. Once set, the hardware does all the lifting, no software intervention needed.
The switching is done via the loss of power through a transistor (of some sort, not sure of the exact type). When power is loss, the comparator detects the shift and pulls on the FETs to do the switching. (this is an over simplificiation of the process, of course)
There's no microcontroller involved in this decision making.

These things often have delay timers, but I think that's just for switching back on. I'm hoping the shut off is instant.
Yeah, the timer is just so if the power is flickering the ATS doesn't swing back and forth between sources. Otherwise there'd be a lot of spikes on the lines and potentially burn out the contacts in the ATS

Also I could potentially get the settings confused or something.
Nah, they are pretty straight forward on what the settings do ;)

Here's the playlist of Daniel's videos on the ATS's
View: https://www.youtube.com/watch?v=3enEGXv_TTk&list=PLOW-knRjfDQfMLzgwZXXhY_oohmcSGIoE
 
One other thing you need to think about is how ground and neutral are tied together but that must be done in only one place, usually closest to the source of power. If the neutral and ground are connected in multiple places then current will use the ground wire to conduct energy which is unsafe. This is the automatic operation often integrated into inverters to smartly connect or disconnect the ground and neutral depending on if power is being drawn from the grid or a generator or itself. Some inverters have multiple AC inputs so that for example one could come from the grid and the other from the generator and the inverter will manage it all smartly.
 
That answers a lot of questions! Daniel's videos were exactly what I was looking for but couldn't find. Thanks. One neat thing I didn't know is that those contacts use both an electrical interlock as well as a physical one. That's really cool.

My understanding is that for a portable backup generator like mine, it should be grounded through the main panel, rather than having its own ground. So there should be no bond to neutral inside the generator, and the neutral wires between grid and generator don't have to be switched.

I've noticed that every manual transfer switch leaves the neutrals connected. That is, the hot wires are switched but the neutrals are not. But every ATS I've looked at the neutrals are switched. Why is that? In my case, with an unbonded generator, the neutral doesn't need to be switched (I think), but is it ok if it is?

Well, I've made more diagrams because it's what I do. First one is what I plan to do this year:
Generator.png

I've chosen a 40A breaker for now because that is what the inverter I'm thinking of buying recommends. The panel is rated for 125A, and the ATS is rated for 50A. At most, the generator could deliver about 30A for a short time.

Next year, maybe I'll add the inverter and battery. I was looking at the pre-made server rack batteries they have out now. Pretty neat, but 3x more expensive than if I built my own. That includes the BMS and other hardware. I've been using a Daly smart BMS on a smaller battery for a while, and it sure is fun. Being able to change settings and get feed back as to how the battery is working is really nice. Unfortunately, the inverter/battery setup is going to be a kick in the wallet. We'll see if I can come up with enough money in a single year. But here is what I think the setup would look like:
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The inverter I'm looking at is a sort of central power manager. It can take inputs from grid, generator, battery, and solar, and route them to the sub panel. Wiring it up this way isn't the only option, but it would allow for using the battery during an outage, adding the generator if the battery gets low, and having the generator run stuff and charge the battery. When the grid is restored, it can be used to charge the battery through the inverter. With the grid powered, and the battery topped off, the inverter could be switched off until the next grid outage.

There are rumors that the inverter can still keep the battery charged through grid or solar even when the inverter itself is turned off. That is, the AC charger and solar charger components remain active when the actual inverter component is off. I don't know if that's true or not.
 
I've noticed that every manual transfer switch leaves the neutrals connected. That is, the hot wires are switched but the neutrals are not. But every ATS I've looked at the neutrals are switched. Why is that? In my case, with an unbonded generator, the neutral doesn't need to be switched (I think), but is it ok if it is?
MTS's are generally cheap, so less moving parts to make it cheaper. ATS's are usually a bit pricier. You could probably find some ATS's that only trigger the hots.
Is there really a difference, I doubt it. No different than if the Grounds stay connected across all connections. Afterall, N and G are bonded at the primary. So they "eventually" meet up at the same point. There isn't anything inherently wrong/bad if the N aren't disconnected.
 
I use several ATSs...

3 x 120v @ 30a Go-Power - looks like they're not very available. Go-Power is a know 'name' in RV world.

4 x 240v/120v @ 50a Progressive - https://www.amazon.com/Progressive-Dynamics-PD52V-Automatic-Transfer/dp/B003VAWNVK/ref=sr_1_1 I have 4 of these and after 4 years (~3,000 switchovers - e.g. twice per day) have replaced 2 of them. They have mechanically linked relays with electromagnet pullers and 2 of them got 'a bit off' after 3,000 cycles and the contacts wouldn't close. Nothing dangerous, just wouldn't switch the power and had to replace.

Was able to swap out relays inside the original box This was particularly important with the one I have mounted flush with the wall :)
 
Sounds like the ATS is definitely the way to go. My basement is cinder block, so everything is surface mounted. There's pros and cons, but I think I'm pretty happy with it being that way.

I've been trying to figure out my peak Watt usage. My smart meter is great, and measures my usage in 15 minute intervals. It all gets sent wirelessly to the PUD, and I can see it from their website or phone app. It's all expressed in kWh though, and I want Watts. Here's a view of the day back in December where I used the most energy (kWh):
PowerUsage.png

The highest peak here was expressed as 4.66kWh across a time of 15 minutes. I'm not sure this is the right way to do it, but I'm interpreting this as 4.66kWh/0.25h. If I actually do the division, the hours cancel out and I get 18.64kW. Or 18,640W. This seems like a plausible number to me. The furnace uses 15,000W, which leaves 3,640W for other appliances. It was in the evening, so we could very well have been cooking or doing laundry or something.

Its definitely a priority to get the furnace replaced with a heat pump, and get my attic insulated better. Also interesting to note that we don't use a lot of power all at once, but instead it's spread over a lot of time. Better to insulate the house soon and shorten the time I think.
 
The highest peak here was expressed as 4.66kWh across a time of 15 minutes. I'm not sure this is the right way to do it, but I'm interpreting this as 4.66kWh/0.25h.
Watts are the amount of power and "h" is the time element. When a graph shows 4.6kWh - it means a consumption of 4,600w over that hour. You can't tell the hi or low form this - just the overall consumption.

If I actually do the division, the hours cancel out and I get 18.64kW. Or 18,640W.
Because of the comment above, I'm not seeing a figure of 18,640w from "4.66kwh across a time of 15minutes" and I don't see a peak of 18,640w from the chart posted above.

This seems like a plausible number to me. The furnace uses 15,000W, which leaves
I can see a home furnace using 15,000w is if it was electric. This would be 62.5a @ 240v.
Do you have an electric (element) furnace?

FYI - I have a 4-ton (2600 sq ft) high efficiency whole house (forced air) heat-pump and absolute max is ~5,000w. That's roughly 1,250w per 12,000BTU / 1 Ton. Overall consumption jumps below 40F/4C and below 30F/-1C it's pretty much running max continuously. I've seen mine work a low as 18F/-8C but it can only maintain and not able to raise the temp.
 
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I've thought of another way to express the chart results that might make more sense. If I used 15kW of furnace power over the course of an hour, that would be 15kW*1h = 15kWh of energy, yes? So every 15 minutes, I'd be using the same power, but only 1/4 of the energy. That could be expressed as 15kW*0.25h = 3.75kWh. If I ran the furnace for two hours, that would be 15kW*2h = 30kWh of energy. Same amount of power, but twice the energy. If I use my weird math to go the other way: 3.75kWh/0.25h = 15kW.

Now, during that 15 minutes, the power could certainly have gone lower or higher. But the average would still work out to 15kW and 3.75kWh. Not an instantaneous measurement of peak Watts or Amps, but closer than any other tool I have at my disposal can get. I thought it was interesting to note that during very cold weather, I use more energy, but not much more power. The furnace uses 15kW of power regardless of how cold the house might be. But it does use more energy because it runs for longer time intervals. Makes sense; I just never thought about it before.

Applying this to the smart meter chart, that 4.66kWh being used across 15 minutes, I'd have had to use 4x the power. That is where I get the 18.64kW from. Though at any point during that 15 minutes, I could have been using only 15kw, or 25kw. Who knows? I suppose what I aught to do is get one of those clamp meters with data logging. Something that would give me actual Amps and could measure a maximum peak.

The furnace is indeed electric. The element and the blower are on separate circuits, but together they add up to almost exactly 62.5A at 240V. The breaker labeled "blower" uses 42.5A. I think that's actually the element circuit. The other breaker labeled "furnace" uses 20A. I think that one is actually the blower circuit. I'm not sure if that's enough to calculate the BTU of the furnace. I also don't know if I'd need the same BTU for a heat pump. I do know that the furnace is able to keep the house warm even in the coldest weather we get. Though our thermostat is conservatively set to 60-64F.
 
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