Rookie Alert. New to Heat Pumps for Heating. Basic Questions...

Smitty77

We've always had separate Natural Gas Furnace and AC units. Replaced two separate systems in our home (Downstairs and Upstairs) with Bosch BOVA 36 (Upstairs) 60 (Downstairs), combined with Trane Dual Source Gas Furnace for Auxiliary Heating. And finally Nest 3 Thermostat's for reach system.

We very seldom use our Upstairs System, so my questions are focused on the down stairs systems. And my focus is learning about Heat Pumps and their Heating aspects.

We're in a moderate temperature zone along the coast, with low temps during winter typically 42-50F (Occasional dips into the high 30's, but none so far this year.).

Downstairs area is ~2000 sq ft, with some rooms having 14' ceilings. Insulation of the home is say a 7 on a scale of 10. And windows though dual pane, were and remain junk (Replacing these later this year.).

Basic Questions:

-BOVA 60/5 Ton system. Is taking ~3 hours to raise the inside temperature from 63F to 68F in the AM. Outside temps 43F to about 49F at the end of these 3 hours. With the ~30 year old contractor grade Carrier Gas Furnace - this would have taken maybe 45-60 minutes.

Do Heat Pump heating, just take longer? And should it be that much longer?

-Nest 3rd Gen - I have temp set to come on at 6:00AM to 68F, and then down to 57F at 8:45AM. But I also have Early-On set, which as I understand it (And researching Nest Forums too, and admit still learning how the Nest Learning Thermostat works (Need a 13 year old to assist:)!)), will learn the heating characteristics of our system/home and factor local current weather - and 'back up' the starting of the heating to 'reach set temperature' at 'set time'.

It does seem to be starting a bit early, but still is no where near the Set temperature, until very close to 8:00AM.

Does anyone know how long it takes a Nest Smart Thermostat to Learn the system it is in? (Days I certainly expect, say 5-7, and then constant refinement over time. Does this seem correct? Or is my thinking way off?).

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I'm trying to determine if I have higher expectations for the Heat Pump Heating then I should? Or, if I need to get the Heating Contractor to come back out and validate everything is set properly.

Recall I'm a rookie to Heat Pumps, and it is a new to us system. And I may not be as smart as the Smart Thermostat too:)!

Appreciate any feedback or suggestions.

Best to all,
Smitty

TAG

It's math. My guess is the "old" gas furnace had more output .... it's all about available BTU's

Look at the heat curve output of the HP at various temp ...... that is what you will get. It's not uncommon for gas heater years ago to be 2x what was really needed ....

HP -- don't like setbacks that are more then a couple degrees. The point is for them to maintain.

The nest could be your problem as well -- it's overthinking and not just keeping the system on a set temp

Smitty77

Thank you both for your info sharing.. And yeah, I don't have my infrared gun with me (In our RV in another state, of course!). But by the feeling of the hand at register test, confirm the lower temperature output compared to the older gas furnace:)! And I expected that from my 'internet research' - but I was thinking maybe a 25-35% lower heat output - this 'feels' like it is a 50-60% lower output...

We have solar on this home. And are in an area where we have various Time of Use differences in Kilowatts charging by our utility. As with most TOU plans, our nighttime hours are the lowest costs. So my goal was to have the heavy lifting of the Heat Pump heating take place before the 6:00AM increase of Kilowatts changing. Thus using Nest to set the desired temp to 68F at 6:00AM, and using the Early-On feature to 'reach' that desired temp by 6:00AM. (Then go into sustaining/maintenance mode until we have it step down at 8:45AM. Typically in winter months here, if we get the downstairs up to 68F by 8:00-9:00AM, then with the old furnace turn it off - we'd hold maybe down to 67F for most of the day.).

The TOU 'Peak Charges Hours' start at 4:00PM here. So I again have the target temp set to 68F at 4:00PM, with Early-On feature established - to 'reach/obtain' that temperature by that time... And again have the set temperature set to 57F at 8:45PM.

Usually overnight, the downstairs would dip down to 62-64F or so, before I used to have the old Furnace scheduled to start up at 6:00AM - and it would reach 68F the majority of the time by 6:30AM or so...

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I'll dig into the BTU spec of the BOVA 5 ton unit, and see what I should expect with outside temps in those temps between say 40-45F.

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My goal is to learn this system and how to use it. But lucky we don't have the dramatic low temperatures to work with that much of the nation has had lately.

And admit, the Nest Gen 3 Learning Thermostat is another opportunity to learn too!! (And I think set with a normal 'schedule' Start/Stop of two main timeframes - is not too fancy:)! And hoping the Early-On feature will work the way it is stated in the manual. (Still trying to find out how many days or weeks that should take, for the Nest to learn our specific house/system/weather... No luck on that yet!).

Thanks again for info, and still welcome more input and 'Tip's & Trick's' on Best Practices with Heat Pumps in general:)!

Smitty

EBEBRATT-Ed

@Smitty77

As the others have said heat pumps put out lower temperature air probably 20-30 degrees over your return air so 65 + 30 is 95 which won't feel very hot. And you get less output the colder the outside temp.

Did the contractor do an accurate heat loss/gain calculation?

Smitty77

I feel the company did a top notch job thru the full process. Great communication all the way. And I have left a VM for the gent/specialist/tech that worked thru the equipment evaluation phase. I believe the equipment was proper for both systems. New ducting too. 

Suspect most of my questions in functionality - is a result of being new to heat pumps... 

But sometimes new products have problems. And mistakes can happen at install. 

Thanks for asking about proper sizing...

Smitty

Campyman

I install heat pumps all the time on the West Coast and they definitely have their use. Around here they cost about the same to operate compared to a NG system, but they are safer in that there's no CO poisonings risks. Generally most heat pumps will achieve a 25 degree delta t (meaning rising in supply temp compared intake temp) but a gas furnace is closer to 40-50 delta. Here's my suggestions.

Around here most people only reduce their nighttime setback temp by 3 degrees or so in order to ensure the zone will be up to temp in the morning, and this also helps prevent the costly backup heaters from coming on.

Second, please get rid of the NEST right away. Nest thermostats look fancy but I can't even count how many control boards I've had to replace over the last decade because of those awfully unreliable things. You're better off with a honeywell pro8000 with an outdoor sensor.

Smitty77

I've read the responses again, and will do a few things until I feel I have a better grasp of things:
- Turn off Early-On
- Set the Schedule to lower the temperature to 64F, when not wanting 68F
- Back up the times on the Schedule to start going towards 68F 90 mins earlier then when want to achieve 68F

I'll share that the Heating and Air Install Company is sending out their troubleshooting Tech, to ensure all of the parameters of the downstairs system are set properly. They felt that something must be not quire balanced/set correctly between all of the components. As they said the system is properly sized to be able to raise the downstairs are from the 62-63F to 68F in certainly under 90 mins, and closer to under 60 mins. This is based upon many other systems they have installed along the Southwest coasts of California.

Nest Gen 3? Well, not sure what to think now. I did read enough to know that earlier generations had some teething problems. And I have not yet looked to see if I have a Common wire in our setup. I am certainly not fixed on keeping it, especially if it is more problematic then the 'value' it adds. But, I will go slow and learn more before swapping it out. (I did get a chuckle out of one comment I read on Google Help for Nest Thermostats "The Nest is not as smart as it thinks it is. And the 'Smart Learning Thermostat's' written sales features - are not always seen in real world usage." (This was back a few years, and I think it was E generation.).

Thanks again for the input. And I will not be shy to follow-up with more questions ahead...
Best to you all,
Smitty

Smitty77

The install company sent out their 'Trouble Shooter Tech' along with another gent I think was adding to his knowledge base. I was unfortunately gone for most of the 3 1/2 hours they were working on things. Bottomline, was an obstruction in the refrigerant line, of course, restricting flow. They drained, flushed, and recharged the system. And then ran some, my wife said 'parameter tests' to ensure heating and cooling work working within the specs for the unit. (I did catch them literally as they were walking to their van. I asked if they new if the restriction was cased by contaminate in the line to start with, or was introduced at install. And a solid answer 'No way to know for sure.'.) And it really does not matter to me, glad we caught within the first four days of operations...

I'm going to reset the Nest, so it can start 'relearning' our system/house/weather.

I'm going to keep Early-On off for awhile, and see how things work. Will back up the schedule to start a 5:00AM to 68F tomorrow, and see how long the unit runs to reach that temp. (Do not expect it to be 3 - 3 1/2 hours now:)!).

And, I'm also going to keep investigating and learning about Nest, specially the 3rd Gen. And note, I did confirm that our set-up includes a Common Wire feed.

Just joined this forum this week, and have done lots of searches and reading - and will continue to do so over the months ahead. Feel I've accelerated my knowledge base quite a bit in these last few days. So thank you to all of you who have responded here, and also posted elsewhere... (I RV quite a bit, and in the last 10+ years have made some great online, and many times followed up within person, forum friends. I value these kinds of forums, where experts, enthusiastic members, and rookie members - all share. (I, and others, share by asking questions that at time can case a chuckle to veterans of a forum:)!).

I'll be reading ahead, and will post follow-up questions ahead as needed,
Best to all,
Smitty

TAG

As pointed out above -- the delta of the heat pump is smaller vs a gas furnace. IE: The temp of the air in the return to the temp in the supply. If a gas furnace has twice the BTU input ... heat it can deliver ..... it is going to heat the space twice as fast.

The other factor is your hand. The air from a gas furnace is hot -- you can feel it being hot and it is something people are used to feeling. 95 degree air from a HP does not feel as hot .... but, it's plenty hot enough to heat a space if it is coming out 24/7. It's the same as radiant heat. My friend called me after his system was in to tell me it was not working -- he said the water was only 75 degrees. I said to him -- Is the shop warm? He said yes ... it's working I said and 75 degrees is more than enough. To him the water was cold to the touch -- but it hotter then the temp he wanted in the space ..65 degrees.

Your system if it's all new will have variable speeds -- so as the HP nears the set temp it should ramp down to maintain the temps ..... as the sun warms outside the unit will lower it's output as the sun goes down the unit will ramp up to meet the output of the houses as it gives up more heat w/o the sun and the falling outdoor temps.

With the Nest you are messing this all up -- the unit shuts off and then the nest tells it to start -- it has to run on high ..... then the nest does it again ...and again. Or you do it. The amount of setback is really about the house.

I have a variable speed carrier unit -- it has 5 set speeds. Most of the day it's running on one or two -- as the temps drop at night it moves up -- on colder nights it may hit 4 .. or even 5 if we get under 10 degrees. The key with the setback is to watch the house as it gives up the heat ... you can usually get away with a couple degrees. No point in fighting the coldest temps at 4 am when on a weekend no one is up until 8am. It's the same with AC -- at 2pm in the afternoon. Don't fight the sun -- let the temp go up two degrees w/o any comfort loss and it's easy to recover at 5pm when the sun is not as hot.

The problem with heat is you are often trying to heat up a colder house at the coldest part of the day -- so the house is warm at 6am.

You don't save much if the unit needs to run its brains out for 2 hours -- when it could have been running along at a lower speed.

Does Bosch make a smart Thermostat --

Smitty77

Thanks Tag - Very similar heating and cooling relationship for the RV/Coach I mentioned. Electric heated floor tile generates a heat mass that provides a constant variable of heat. We augment it with our AquaHot Diesel/Electric (Double Electric Elements, so about 2700W of electric heating in the Hydronic Unit.). In temps down to mid 30's, the floor heat along with the AquaHot on High Electric for both elements - we're quite comfortable. Down I usually turn on the Diesel Burner when temps get down into the low 30's and below. And the Diesel fires up as needed, to assist the Dual Electric Elements. We find that it is easier to maintain a heat, the to regain a heat... Same thing with cooling, as X's 3 15K BTU AC's work pretty hard to keep us cool in 105+ temps... And if we don't keep the temps down, we struggle to regain coolness until the sun goes down.

On setting I did not share in my last post, is that I've changed the Low Setting Temp on my simple two phase schedule to 64F (Which we seldom drop down to in our upstairs area, and usually for two or three months we drop to downstair area system. So now have the unit set to come on at 5:15AM to 68F, then drop to 64F (Which it typically would not drop to during the daytime. Only when we (And don't laugh, it's all relative:)!) cold spell. Wed the out side temp on reached 57. Noing this was the forecast, and that the downstairs system was not performing well (Restriction in refrigerant line.), I left the temp at 68F all day.). Our second time of heating, is now set for 3:15PM to 68F again (But again, most days the house is at, or above those temps, even in winter.) and then at 8:45PM I have it set to 64F again for overnight. And as mentioned in my last post, I now have 'Early-On' off, so this 'Smart Thermostat', is basically set up as a normal thermostat with two set time 'warm zones' of time.

To me, in San Diego coastline, it's game to save as much electricity as possible, and try to shift the use of electricity of off **** Time Of Use Tiers. With our excess yearly solar and Net Metering, I'm trying to shift more of our energy needs over to electric from natural gas. And we have a budgeted plan, for back-up battery install in October/November timeframe. Which will allow me to augment our main power usage between about 4:45-7:30PM (Non Hot time of the year, no AC running) with batter power. Our solar should recharge the battery back up full each day. And we'll size it to always reserve a 50% Capacity, about three days of power outages support, while conserving electricity, for our normal home usage. (May add four more panels, as I do have the room, to ensure full battery recharge in case of power outages.) And again, this too is a game to me, as frankly I can always fire up the coaches 10K diesel generator, and provide power to house too..). (And sorry I went of Heating and Air discussion here, but gives you an idea of what and why I'm trying to set up:)!)

Back to heating:)! I'm hoping the 4F potential (Last night the lowest temperature I noted downstairs when checking the temperatures for nightly nature calls - was 66F. So last night, only a 2F drop.) variance from Warm setting to 'Save Heating Cost' setting - is not too much of a variant(?).

I appreciated, and luckily from my advance research on Heat Pump vs Natural Gas Furnace for our new system, found myself nodding - your explanation on the variable fans... Our system has the Bosh Heat Pump and also the Trane Dual Furnace variable fans. (Though I understand it, one of the units 'variable' is really something like 25 or so different speed settings (Not sure if it's the 25, could have been 50. Vs infinite variability.) (I looked at too many systems, and had three different contractors send their Tech's to assess our home and recommend various systems - I admit, I'm pretty sure I'm blurring the lines between Bosh vs Trane vs Lenox vs Carrier:)!

Today, with outside temps dropping to 46F, as mentioned we remained 66F as the lowest noted time at about 4:00AM, could have dropped below that before 5:15AM on to 68F setting, but doubt more then one more degree. The non restricted refrigerant lined downstairs system reached the 68F by 6:15AM... (Where as the previous few days, with it being hindered on refrigerant flow, it would take 2 1/2 - 3 1/2 hours, depending on how cold it was outside.

Going to let things run for a bit, may back up the AM time to 68F to 5:00AM - and see how things go... Summer time here will be a new learning curve, for cooling - but that's out aways:)!

Sorry to all for rambling as much as I do:)!
Best, and thanks,
Smitty

TAG

The Carrier 5 speed is just a more affordable option in the Carrier line vs going full variable speed. It uses a rotary compressor vs the more common Scroll in the split systems. I also liked that the Carrier unit could get down to 25% output. Some of the VS units are 40% at the lowest ... You really have to look at the heat and cooling loads at different temps and see how this fits into the usage. When looking at my houses/climate and HP outputs ... the match up was about what I needed. Had the low 25% -- and the next three were closer together .... the top (5) was a bigger jump. In AZ or AK .... having stage 4 closer to 5 may be wise. For my area -- when it's hot ...it's hot. Otherwise the stage 4 takes care of most of what we have when very warm. FYI -- You need a proper thermostat to run this ... one that is watching the inside and outside temps --- that's way I ask about if Bosch has a thermostat. The Bosch is different in how it modulates.

Smitty77

The Heating Tech from the company we went with, did a good job of describing (Which I had read about as I was researching, and was glad I had already learned most of what he was explaining:)!) how the Bosch regulates/modulates load speeds. As I understand it, the thermostat controls two basic steps: 1) Heat or Cool; 2) Set Temperature. The Heat Pump works in combination with the Exchanger, to determine how the Heat Pump should adjust speeds based upon demands. (Layman choice of words. But I think I have the gist of it.)

My former company, United Technologies, of course had the Carrier Unit under it... (Split off now.). But I still can get a discount for Carrier products. And the Furnace we were replacing, about a 35 year Carrier Crusader unit, of at for that time medium efficiency, served us well. (We did not have AC for the Down Stairs system, cold not afford it. But the up stairs System had another Crusader furnace, and a 2 1/2 ton Carrier Compressor. Other then needing a few recharges, it also served us well. So I took a close look at the Carrier line, and it was again in my top 3 to get different quotes on. 1) Trane; 2) Bosch; 3) Carrier. We ended up with a combo of Trane Furnace and Bosch in both systems. The Trane compressor was more efficient, but required staying with the Trane Thermostat's (Which become pricey compared to being able to use Honeywell or Nest or whatever Thermostat's when replacements are needed. And we replaced our older systems Thermostats three times in those 38 years. And, the Bosch compressor was substantially less expensive then the Trane I would have gone with. In our milder regions for winter and summer demands - the Bosch's compressor slightly higher energy consumption, would have I suspect taken 20+ years to pay for itself - IF we did not have the solar we do. With the Solar, it would never recoup the higher expenses.

Not trying to justify what I went with. It was a combo of I feel good components, and just important, is the companies decades of solid performance standing behind their installs, as well as I felt reasonable price for their expertise. (Nope, not the lowest bids, but that longterm consistency in 'doing the right thing', made the 7 -12% higher prices I feel warranted. --- ! And besides, it's a done deal now:)!

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With a grand total of now two days running at the new parameters, the Nest History (Which is good info to have.) showed 1 3/4HRS one day, and 2 1/4 the second day (But, a skylight had been left opened.. So before we closed it we warming the city!). All of this time, was in the AM, as it has not cooled enough in the PM to trigger the HeatPump to fire back up again. So non peak energy times, as part of my game, was glad to see this.

It has only got down to 44F overnight these last two days.

Still plan to maintain this schedule over the next few weeks. (We'll be gone, but my MIL live's in the home as we travel. Will come back and look at a bit longer span of history before Easter. Pretty sure I'll back my AM set to 68F time to 4:00 or 4:30AM - to try to get the downstairs up to temp while still on super saver hours... We'll see what history shows.

Having fun learning. And I can remotely monitor, and adjust as needed, so that's a nice features of these Smart Thermostats...

Best to all,
Smitty

TAG

The Bosch unit is an odd ball .... it's a great replacement unit when you keep your current furnace -- or if you just need the condenser on a relatively modern system.

What you gave up not going with the Trane HP and the matching thermostat --- was control over the whole system. If the Trane has a modulating furnace it would have been able to match output to need w/ VS fan ...same if the heat-pump is VS. Without the intelligent thermostat there is no staged control -- no learning.

The modern system analyze the ductwork -- learn how much time it takes to bring the temps up. YOU punch in the fuel and energy costs .... it does the rest.

Smitty77

Thanks Tag - I agree with your comments. And in a heavier demand for heat or AC I understand the potential in savings over the years ahead. I'm not at the home now, and the folder on the various systems and quotes I received are not at hand... Believe the Trane XV20i and other integrated components and thermostats - would have been ~$3.8K more then the combo Bosch BOVA/Trane/Nest Thermostat we went with. (Downstair systems only. And it is that system that is the focus, because the upstairs system is used so seldom.).

History for the last four days, shows 1 1/4 hour total run time for 3 days, and 1 1/2 hour on one of those days (And I believe that was the day I was showing my MIL how to manually override the system.). And the temperature for those days, has been typical of our February/March average temperatures. Dec/January we get a bit more coldness, and of course shorter daylight too. But I suspect that I'll see less then 5-7 hours total daily runtimes for those months (Just a SWAG!).

So with that short of daily runtime cycles, and with Electric being the primary power used for heating - it would take many, many decades to break even on that higher expenditure for the Trane total system.

AC? Yeah, that's a TBD delta, as I would expect to see those hours of runtime triple over the heating. And we have at risk of AC need from August into late October at times.

But as I thought things thru, and with our current Solar being more then sufficient to keep us close to breaking 'zero' on our Net Metering. (And AC was not in our Downstairs System before. But Heating the downstairs, primarily for MIL's comfort, will much less Electricity, and now Zero Natural Gas. And, I'm planning to augment our existing Solar with more panels too.

So I just did not see a payback/ROI for the full XV20i Trane components system. I also went with the Honeywell filtration, so I can use more generic, but good quality, filters in the years ahead.

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IF we were located in more extreme cold or heat locations, and even with solar, the numbers would probably tilt a different way on playback/ROI.

And finally, recalling I'm an admitted Rookie, armed only by Internet Research (Good and Bad, I'm sure!) - I feel the System we went with was KISS, in comparison to the complexities of and proprietary ($$) components of the all Trane system. And a major leap in efficiency over our 38 year old or so systems.

And with that admitted Rookie on Heating and AR disclaimer front and center - perhaps I made a bad, or not as good, choice. I feel both the Bosch BOVA and Trane and Honeywell units in these two systems are well built. Actually a bit better warranty on the Bosch, but minor in the scheme of things...

Suspect after a few years of usage, I'll know how things are going:)!

Best to you, and all. Have really enjoyed browsing many of the other posts/threads, good stuff and info sharing!!
Smitty