I replaced 4 ton with a 5 ton?

With that said, I know the Bosch inverter units use 5 ton condensers for 4 ton conversions, by changing factory settings inside the condensing unit the condenser will operate as a 4 ton unit.

I say this so that people reading this realize that up sizing an older system is not the proper way to solve problems (not saying this is what you did). Some people for whatever the reason are under this impression that bigger is better when it comes to heating and or cooling.

Given that you replaced all duct work as well, gives hope that 'IF' 5 tons is needed the duct work system is sized to handle it. (hopefully)

The problem with trunk line duct work design (for residential market) in my opinion is it is much harder of a design to get air velocity or 'throw' from register to work properly in all scenarios in residential construction lay outs.

Trunk line design is typically used in commercial setting because of the need for long straight runs. The trunk is sized at first larger and gradually smaller so that the trunk will pressurize to distribute air evenly from each of the ducts that come off the trunk. So you have a long straight run with no turns twist or bends in the main trunk. Then ducted supplies come off this long straight run to supply air to rooms.

Commercial has the advantage typically of more than one trunk line ducted system so that once air in one system is going one way it continues that one way direction with minimal turns. Other systems will then be trunk lined going the opposite direction. Commercial application and Residential application are completely different animals.

This doesn't mean you can't pull this trunk line duct design off in residential setting but it's typically much more difficult due to typical sizes of residential construction, not to mention structural differences from residential to commercial.

The reason why I've taken the time to discuss duct design issues is that it can and does have an effect when the structure is under 'temperature extremes'. Under these parameters every flaw (if any) will come out and show limitations of your system... no matter how great, every system has it's limitations.

On to the heating part: A heat pump pulls heat from the air (outside) when in heating mode. Problem with that when the temp outside is -25 degrees!??

There is still heat in that air and the heat pump will attempt to extract it, but if there is moisture in the air it will cause the heat pump outdoor coil to freeze up and eventually require defrost. If the heat pump goes into defrost it is not making any heat for indoors... not a good thing with -25 degrees temp outside.

So the heat pump goes into defrost while activating auxiliary heat (typically electric strips, but not always) so the structure still gets heat while the heat pump is in defrost cycle.

Once heat pump exits defrost cycle --- because it's cold (-25 in your case) the heat pump say's OMG I need to exit defrost and start pulling some more heat from this frozen air and transfer it indoors.

So if your poor heat pump is always running... It has to, because of the temperature extremes it is under.

If you shut it off, it can't make the heat or cooling that the structure requires. One advantage with all electric system is that a solar grid can reduce your costs further. BUT: typically solar is not worth the cost unless your utility rate is around 20 cents per KWH. This may change as prices for solar panels go down, but there is always maintenance / repair costs to solar grid array as it ages, not to mention the real estate needed for the panels to sit and soak up that southern sun.

What is your location and the size of your house?

Why did you increase the size from 4 to 5 tons? Did the contractor do a load calculation to determine the size? Did he measure the duct work to determine if it can handle the increased air flow?

Heat pumps needed to be sized for cooling capacity. You will find out in the summer if the equipment is over sized.

Set the temperature to what is comfortable to you. Your thermostat will determine when the auxiliary heat strips should be turned on. You have to figure out what algorithm it uses to make the decision.

Appreciate all the answers. As far as 5-ton, yes we had a professional HVAC evaluation and it was undersized originally. When the house was built, it was a jack-leg who did it, not an actual HVAC company. To put in perspective, in the hot months, we had to keep it at 78/79 just so that it would cycle properly and not run 24/7. And thankfully, it was just cool enough, because I get hot easily and would not have been happy.

We upgraded some ducts to 8," added a couple more 6," and they re-worked the returns to proper sizing. Like I said, this was all done professionally. We can definitely notice a huge difference. In the farthest bedroom, there is actual air coming from the vent! Before it was a trickle and neither warm or cool.

Plus, we just added more insulation in the attic.

@Austin Air.....interesting you mention solar. I sell it, actually, and am putting in an array in the Spring. I'm getting it at cost, plus $1,000, so in our case, new HVAC with the insulation will make solar a no-brainer. Pays for itself.

The solar argument for or against changes a fair amount when you install it yourself and maintain it. However, it will probably be a grid tied solution if I was going to place a wager.

Grid tied solar varies in relation to how nice local utilities want to play. What I mean by this is there will be times when the solar array produces more energy than your house can use, so the solar array dumps this back on the grid. In Texas, the power companies (last time I looked into it) cap how much energy they will pay you for and in some cases what they pay for is actually production costs, not what they charge you for the same energy. So in essence, you could become a supplier to the middle man, that doesn't pay you full rate (what they charge you for the same power).

I don't know how this goes in Missouri, so you should check for yourself. If you're still set on solar --- it's best to cut your electrical use first then size the solar array properly.

Most of the pros for solar reside in areas like California where the utility rate is 20 cents or more per KWH.

I have an all electric home, and I think the utility rate needed to be in the realm of 15 cents a KWH just for me to break even. So for those reasons I decided not to pursue it. If all you do is break even, once you throw in maintenance and replacement costs there's really no reason to do it except to say 'you can do it'.

I think once you fall under normal weather patterns your system should be quite energy efficient. The Bosch Inverter heat pump is new, so there's really no bad news as of yet for this brand. I have several hand tools made by Bosch that continually impress me.

Because Bosch Heat Pump inverter is new, there is no real distributor support for this brand yet. So that is really the only bad news as of yet for this brand... if you need parts I've talked to a few distributors in my area that suggest the wait time for parts could be two weeks to a month or longer. So for those reasons I currently do not install this brand.

Yes, my plan is to compare this Jan. and Feb. to last, factor in the percentage of how colder/warmer, and how much my energy costs drop, especially with all-LED bulbs and double the insulation in the attic. That's why I'm waiting until March or April to install the array. All-electric here, too, and our utility credits are about 50% of retail cost. So, I'll be able to pretty accurately assess how many panels I'll need at about 85% to 90% of anticipated new kWh usage. I'm thinking with the new HVAC and insulation, we should save around 30% to 35% over previous years.

Since we'll also be able to deduct the interest on the mortgage, I don't want the system to produce 100% or over and have a lot of credits built up. Again, they're at a wholesale rate and you cannot roll them over year-to-year. You want just enough in there to offset the days or stretches of days you have shading. Plus, I'm doing a ground mount on my acreage and it'll face a busy highway. So, I'll also put up a sign advertising solar so I can deduct as a business expense. But all-in-all, Missouri is currently a solar-friendly State. Panels and MicroInverters I'm installing have a 20 year and 25 year workmanship warranty, respectively. Hopefully won't have any issues, but by the time I need to replace both, I'll have saved well over the cost of a new system.

Yes, Bosch is a great brand. I have Bosch tools, too, and they were the supplier of spark plugs for VW and Porsche, so have been around a long time as a company. I too was a little concerned that this is a new brand, but the other 2 companies I got bids from said they would go Bosch first, over Trane and Carrier, esp. since it was a lower cost. Our service mgr. friend who works for the company who installed it, lives about 3 minutes away, so if there's an issue, he's right there. Hopefully it'll run for a long time without needing parts, so when I need one, readily available. 3 year parts/12 year labor warranty. Like anything, crapshoot though.

yeah everything is a crapshoot, so it's good you understand that going in. You have a few other advantages in that Missouri tends to have less really destructive storms. Not only hail type storms, but also winds and lightning strikes. So those were other concerns I had being in Katy, Texas.

If you have the real estate for ground mount, that is a huge advantage as well... that will make maintenance and repairs a snap. The advertising bonus is also a good idea.

As far as HVAC manufacturer's go, there is no perfect brand. If Bosch brand for HVAC becomes the national holy grail one day, they have a long road in front of them currently. I've installed eight different brands so far and they all have their strengths as well as weaknesses. Which is really the only reason I keep looking for the elusive 'new' brand.

If not for being so impressed with Bosch hand tools, I probably wouldn't have looked into this brand as much as I have.

We do get some severe weather, but in my 40 years, I haven't made a single hail claim. These panels are rated for golf-ball size hail, plus covered as well under HO Ins. Plenty of land for ground mount. Hay field perfectly facing South.

My guy was pretty adamant about Bosch. He replaced his system in '17 with Bosch, as well. Like I said, they do sell other brands. Hopefully we'll get a couple of decades out of it.

FYI. The Bosch heat pump is made by a Chinese company called Midea. The compressor and inverter board are made by Mitsubishi. I am not sure what involvement Bosch has other than perhaps licensing its name?

@gregolsen14

Midea's base design is a SEER14. Bosch's unit is 18 SEER. There is a youtube video from hvac talk where a Bosch rep talks specifics.

Basically the inverter board is Bosch proprietary design. They also tweaked other parts a bit and you end up with a Bosch engineered product. Midea makes them to spec for Bosch. 10 year part and 10 year labor warranty. I just got one installed a few weeks ago. Phenomenal system

I have just read through this string- bold_as_love, with a few months of cooling now under your belt, have any further comments on the BOSCH system? I am in NJ and have just completed the second phase of 22kW (64 total panels) of PV. Here in NJ we have net metering, and an decent SREC price to drive the ROI to about 6 years. Late 2016 we had 10.4Kw installed on a detached building, and we were extremely pleased with the installer. So I re-roofed the house and had them back to bring us to 100% of our usage. We only had problems with the power provider, who seemed to turn a deaf ear to the fact that we had already installed 10.4Kw of solar, and they declined the approval until we showed "Usage at the meter" We installed a heat pump on the pool, and electric boiler for a three seasons porch that I had roughed in radiant tubing when I built the house in 2001. Once those two were running, the usage seen was justified, and the utility approved our application to expand.

We have plenty of power, I am still not desiring to "waste" that power, and I really like what I am seeing with the BOSCH unit, but I have a concern that everything is getting so complicated, I am destined for future, unfixable by me (incurable DYI guy)

My local Unico installer is dead against using the Unico / Bosch combo and wants to use a traditional HP . The existing Lennox / Spacepack system is getting dead-sticked into a final resting place, this year, the start of the cooling season has come early, and hard, Many trips to the local supply house and some sweaty evenings W/O upstairs air. We are running now, but need to pull the trigger on the direction to go, so any input is welcome.

Hello Mark and our PV system went live on June 18th. Our utility company is notorious for dragging their feet, for obvious reasons. Been sunny and very hot here, so we're averaging about 40 kWh per day, 24 panels. My utility company's website doesn't show daily usage, so I'll have to wait until my next full bill to see. But at 1,200 kWh per month, we should offset 100% easily. As far as the heat pump side, we averaged about 32% less electricity this winter than last, BUT it was 28% colder. So, very very pleased. Can't say quite yet on the cooling side, but at 19 SEER (yeah I know, not really 19), versus the old system that my HVAC guy was probably realistically 11 SEER, we should see quite a difference. I do know that we haven't had to supplement cooling with the (2) portable A/C units we used to wheel around to keep us cool while we slept. Going on 6 full months with the Bosch and I'd have to say, it's been a great system.

Mark,

I am in New Jersey and we installed our first solar array back in 2004 @7kw in 2006 we installed another 3kw and in 2010 another 12kw in a ground array for a total of 22kw. We have been running a 3.5 goodman 13 seer heat pump for the last 13 years and it has worked very well. our house is a little over 2500 sq ft and we always have a electricity surplus when we true up with the utility every April. I just ordered a 5 ton Bosch heat pump to replace the old goodman. I was going to wait until spring but decided to buy it now because of it being on sale. I suspect it is on sale because they will be coming out with a communicating model in the near future. As far as im concerned i really dont need a communicating heat pump since i can basically set the output using the blower since it ramps up and down based on suction temp. We have a variable speed 96% 2 stage furnace with a two stage heat pump T stat. It should be delivered today and i will wait until spring to do the install. I will update this thread in the future.

Carl

So, since I wrote in July, we dove in and installed the new system. I waited until after our "Cooling" season was over, so, if my DIY self was in over my head, at least it wasn't 80 and Humid at night!!! We are VERY happy with the system we have Unico /Bosch Bova Heat Pump Combo on both floors of the house, We didn't have many days to actually "need" the Cooling, but we had a few very humid days where it was amazing to have the new system up and running. Thanks to my Nephew, who was a great help, and with his experience and knowledge, not to mention some of his specialty tools, we now have the exact system we desire, and its working really great. Next year I will have him back to verify the charges under true cooling load, but per the charts and specs, its running, and heating well. one added bonus, we went for a Aprilaire 800 Steam Humidifier on the main floor. The primary "ALT HEAT" for the house is in floor radiant and we were always too dry. Now the entire house is at a well controlled 40-45% RH.

@mark0524 -- may I ask why you prefer heat-pump heat instead of your radiant floor heating?

@gregolsen14

We actually don't prefer the Heat Pump, The radiant is super nice, we are using the HP system primarily for Humidifier, and, with the Solar PV now on the roof, the supplementary heat is low cost as long as we have excess kWh being produced. We are learning the juggle of one vs the other. I also installed a Seisco Electric Boiler on a previously unused loop in a screened in porch. With louver windows, the room is now truly 3.5 season. Radiant is awesome, I cant understand why its not a popular here in US as it is in Scandinavia