Talk me into (or out of) a whole house heat pump to replace dead oil boiler

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semipro

Minister of Fire
Jan 12, 2009
4,026
SW Virginia
Surely there are some on line HVAC load calculators which can be used? I mean you need to know the heating and cooling loads and then add a few percentages. Down here in Texas the rule of thumb is one ton (12000) BTUS of heating or cooling for each 500 square feet.
Poor assumptions about HVAC needs have caused a lot of problems with improper dehumidification and resulting mold issues. Usually with the idea that "bigger is better".
Relatively simple calculations of heating/cooling loads and required system sizes can be done using well know prescriptive references such as "Manual J".
A good reference here: https://www.energyvanguard.com/blog/hvac-design-done-right-manual-j-s-t-d/
 

begreen

Mooderator
Staff member
Nov 18, 2005
88,225
South Puget Sound, WA
Holy cow! I had the same unit installed last summer for $6500, including new ducts in the basement. It looks like the units went up a bit in price, but no where near the cost difference. That being said, I couldn't be happier with the Bosch system. The bump to my electric bill has only been about $20-40/mo for cooling. Used it for heat in the shoulder season, and didn't notice much increase in electric bill then either.
The Bova 2 is more efficient than the Bova 1. Looks like Bosch developed these units in China with Midea.
 

EbS-P

Minister of Fire
Jan 19, 2019
802
SE North Carolina
Poor assumptions about HVAC needs have caused a lot of problems with improper dehumidification and resulting mold issues. Usually with the idea that "bigger is better".
Relatively simple calculations of heating/cooling loads and required system sizes can be done using well know prescriptive references such as "Manual J".
A good reference here: https://www.energyvanguard.com/blog/hvac-design-done-right-manual-j-s-t-d/
I think that with variable speed compressors and air handlers the manual J will be less utilized and installers will go with their gut feelings then add a ton and call it good. My dad could not get any he was getting quotes from to do a manual J. He even offered 250$ They just asked if the old system did ok and kept the same size. I have tried the online free tools. I never got very good results. I rushed through and it always over calculated the load. The the shade, maybe I underestimated wall insulation, the 3/5 daylight basement basement and the crawl space.... just to many variables. Or maybe I just like the house temps different than design spec.

For installs we’re heating demand is more than twice cooling I really think variable speed compressor and air handler are the way to go. My two stage handles all but the coldest week well but i doubt even then the heating load is twice the max cooling load.

Evan
 

NoGoodAtScreenNames

Feeling the Heat
Sep 16, 2015
406
Massachusetts
The utility rebate is administered by an energy efficiency company. They require pre-approval of the design before the work can begin in order to qualify for the rebate. First step in that is a consultation with customer which for me happened yesterday.

A lot of the same advice I’m seeing here. They were mostly concerned about right sizing the equipment so it can cycle down appropriately for the zone. He also seemed a little skeptical of a drop in place without a good thinking about the existing ducts. At a minimum he said we should reseal all the existing ducts including the hidden runs in the first floor walls going upstairs. He recommended something like this for the hidden runs:

https://aeroseal.com/

Lastly, he wasn’t as concerned about heating strips. He seemed to favor doing getting something that had good cold weather performance which for my area he said to design for 8F. Like many of you said he thought to use the boiler as the backup and see how it performed in real life and upgrade the service only if needed down the road.
 
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woodgeek

Minister of Fire
Jan 27, 2008
4,373
SE PA
I'd be the first to admit you need a pro consultation. I'd think that to get to 8°F on HP alone you would need more than 5 tons total, which means an upper story and lower story air handler. A $5k rebate would help alleviate the pain.

And a 5 ton system on the existing ducts is NOT going to be a simple drop in, bc you would be upsizing the existing ducts, in hopes of saving money. But at some point on that, there will be diminishing returns.

As I said, the defrost cold blasts are only when the there is snow or freezing rain packing the outdoor unit, actual 'frost' melts pretty quickly and the hot ductwork absorbs a lot of the cold air before it reaches the registers. If the registers aren't pointed at where you live, you still might not care...or might only notice a few times a season.

But you will need backup, either the boiler or strips.
 

clancey

Minister of Fire
Feb 26, 2021
1,018
Colorado
I am curious and is that Windhager--pellet--a back up system for your boiler in the picture velvetfoot? A lot of stuff there and I was just wondering? If this is so and I am on the right track here (which I doubt--lol)--do you save a lot of money by having the pellets over the oil and why the two systems? c
 

velvetfoot

Minister of Fire
Dec 5, 2005
10,055
Sand Lake, NY
I am curious and is that Windhager--pellet--a back up system for your boiler in the picture velvetfoot? A lot of stuff there and I was just wondering? If this is so and I am on the right track here (which I doubt--lol)--do you save a lot of money by having the pellets over the oil and why the two systems? c
As I alluded to earlier, I haven't been using it since the price of oil went down and pellets did not. What you can't see is 6 tons of pellets on pallets off to the right. It was a project after I did right after I retired. I originally wanted a wood boiler, but I ran into a snag with getting a propane tank for storage. Oddly enough, I'm getting a 1000 gal tank for the gen delivered on Tuesday, but as I said, it's a rental, lol.
 

semipro

Minister of Fire
Jan 12, 2009
4,026
SW Virginia
As I said, the defrost cold blasts are only when the there is snow or freezing rain packing the outdoor unit, actual 'frost' melts pretty quickly and the hot ductwork absorbs a lot of the cold air before it reaches the registers. If the registers aren't pointed at where you live, you still might not care...or might only notice a few times a season.
I'd agree with all of this but I'd note that the outside coil on our Mr. Cool Universal will freeze up when the humidity is high regardless of precipitation (of course maybe that's what you're referring to re frost). Ours is located where it's not exposed to rain, snow, etc. and the coils still freeze up.
The cold blasts of air from the registers are a minor nuisance and the reverse cycling of the HP to defrost reduces system complexity and lifetime costs.
 
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sesmith

Feeling the Heat
Dec 11, 2009
261
Central NY
Have you checked with anyone who does ground source heat pumps? Likely more money up front but would be an ideal solution so long as you find an installer who knows what they're doing. We put one in our previous house up north here. I'd do it again. Best heating system we ever had. We now live in SC in the winter months. There it made sense to do a new more efficient air source heat pump. But up north here, I wouldn't do air source unless they're getting as good on the low end now as the minisplits are doing. You'll end up spending a lot of the winter with the heat strips running. With ground source you don't have that issue. Properly sized, you'll use the aux strips very little. Ours was extremely efficient. We actually quit burning wood in that house as I wasn't cutting it myself anymore, and it would have cost more to heat the house with wood than with the heat pump if I had to buy firewood.
 
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peakbagger

Minister of Fire
Jul 11, 2008
6,349
Northern NH
Ground source heat pumps can be very efficient but its a function of if the house was designed for low supply temperature heating. Air based systems have to have larger ducts installed in conditioned spaces while hydronic systems need properly designed and installed radiant heating or lots of radiant emitters. It comes down to if a house is set up for 85 deg F supply temp and the ground source is 40 to 50 degree F year round the COP is very high compared to air source unit which may need to deal with 0 deg F.

The down side is bit up front cost to drill the wells or install the ground loops. The very general number in my neck of the woods is 300 feet of well for one ton of heating. Unless someone is doing a lot of excavation, ground loops (slinky style) are also expensive and have some issues where the ground source can start to run out of capacity and start to cool down in heating season and heat up in cooling season. These also tend to be complex custom systems where technicians have to be well trained. In my rural/vacation area many of the techs end up driving up from the more urban areas and maintenance and repairs are expensive. I have talked to local firm that does a lot of geothermal (mostly heavilly subsidized) and they are not interested in 2 to 3 ton install, they start getting interested above 5 tons.

For a new house, there is lot to be said for spending the money for complex heating and cooling system on upgrading to a Passivhaus or Pretty Good House design and minimize both heating and cooling to the point where the systems are quite small. Add in some solar panels and net metering, and those homes can easily be net zero even in cold climate. The best heating and cooling costs are the ones you do not need to spend by designing in low heating and cooling demand. Unless someone is willing to gut a place, super-insulating and low supply temps are hard to retrofit.
 
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sesmith

Feeling the Heat
Dec 11, 2009
261
Central NY
Yes. Can't agree more. In his case, I'm sure his duct system would need to work to handle the extra flow needed for a heat pump system. Once done, he would have super efficient ac and heat. Can't stress enough that you need to find an installer who knows how to engineer and size the system. Good design is super critical for geo systems, or bad things happen. Ours was done in trenches, not slinky style though. We had plenty of space that they did straight lines in the loops. Never had any issues with capacity. We did have to replace all our ducting and increase capacity. I do miss that system. It was way quieter than the heat pump system we have in our SC house. Don't miss the cold weather, though.
 

begreen

Mooderator
Staff member
Nov 18, 2005
88,225
South Puget Sound, WA
It was way quieter than the heat pump system we have in our SC house. Don't miss the cold weather, though.
Time to change the avatar location?
 

sesmith

Feeling the Heat
Dec 11, 2009
261
Central NY
Well...yes and no. We retired a couple of years ago. Sold the house and moved to another one in SC. Kept a piece of forest land we had 4 miles up the road from our old place and put a cabin on it. So from spring to fall we alternate between the cabin in central NY, and a boat on the Great Lakes. It's a rough existence, never knowing where we belong, but someone's gotta do it. I still get my wood heating fix in the shoulder seasons at the cabin, but once the snowflakes fly, we're outta there.
 

maple1

Minister of Fire
Sep 15, 2011
10,783
Nova Scotia
Geo can be a very hard thing to justify if retrofitting. I looked into it 10 years ago just before my boiler swap. Would have been 20k for the in ground and heat pump side, and somewhere between 10-20k more for a distribution system overhaul. Also had a couple friends tell me their power bills ended up being quite a bit higher than they were anticipating. From pumps running 24/7, I think. But maybe their anticipations weren't realistic.
 
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peakbagger

Minister of Fire
Jul 11, 2008
6,349
Northern NH
Geo can be a very hard thing to justify if retrofitting. I looked into it 10 years ago just before my boiler swap. Would have been 20k for the in ground and heat pump side, and somewhere between 10-20k more for a distribution system overhaul. Also had a couple friends tell me their power bills ended up being quite a bit higher than they were anticipating. From pumps running 24/7, I think. But maybe their anticipations weren't realistic.
My limited experiences is that there are a lot of good geothermal salesmen ;). Our state was throwing a lot of money for incentives and unrealistic promises were made. Lots of summer places were built that looked good but lots of glass, open fireplaces, square footage with suspect attention to detail for energy efficiency all mean that these homes are relative energy hogs so even if there method of heating is more efficient its still a steep bill. The other aspect is that as seasonal homes the temptation is to keep the temps low during non occupied periods and then crank it up when the owner shows up to use the place. Low supply temps means slow heating response so there are usually far less efficient auxiliary resistance heaters in the system to augment the geothermal heat.
 
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sloeffle

Minister of Fire
Mar 1, 2012
834
Central Ohio
My limited experiences is that there is lot of good geothermal salesmen ;).
I couldn't agree with you more. When I bought my geo system I had a guy tell me that I needed 200' of pipe in the ground for every ton. I had friend that took that advice, and he said his heat strips come on quite often. The system I have now has 600' of pipe in the ground per ton. Slinky vs well vs horizontal pipe is another debate I had also.
 

sesmith

Feeling the Heat
Dec 11, 2009
261
Central NY
My limited experiences is that there is lot of good geothermal salesmen ;).
Unfortunately, that's been the case. Luckily, our installer was an engineer who knew how to design systems, and ours worked out even better than his predictions. He was able to calculate up front just what it would likely take in kwh to heat our place and cool it, and heat water. How do you find a guy like that? I have no idea. I worked with his dad (also an engineer), so based on that, he was our guy. Not sure what the incentives are now, but when we installed ours the payback was about 7 years over oil (federal incentives included). Unfortunately, the incentives and the hype made too many installers who shouldn't have got in the game "geo experts". Many of those went out of business leaving customers on the hook with marginal systems. Not sure if the playing field has weeded out the bad ones yet. Like anything else you contract out, you have to do some research on the product and background check the contractor.
 

EbS-P

Minister of Fire
Jan 19, 2019
802
SE North Carolina
Unfortunately, the incentives and the hype made too many installers who shouldn't have got in the game "geo experts". Many of those went out of business leaving customers on the hook with marginal systems
I am getting the sense that this is happening with solar installations now. Had a guy come over and say “oh your north facing roof is pretty flat let’s put 12-15 panels there” this was after I have to break out my compass to convince him what direction north was
 

sesmith

Feeling the Heat
Dec 11, 2009
261
Central NY
It is down in my area of SC. Solar took off the last few years. They used to have reps at Home Depot to try and sell you (before covid). I can't believe some of the crappy shingle roofs they put panels on that should have been reroofed prior to installation. Also can't believe the shading issues on some of the installations I've seen.
 
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NoGoodAtScreenNames

Feeling the Heat
Sep 16, 2015
406
Massachusetts
So I got another quote. This was for two 3 ton carrier units. One in the basement with with the existing duct work (cutting off the lines to the second floor) and another unit in the attic with insulated duct work for ceiling registers… $40K and that does not include upgrading to 200 amp service. As much as I’d like to get off fossil fuels, if I took the boiler replacement quote for $10k that’s $30k in heating costs to save with a heat pump before I break even. Burning wood, I don’t burn a lot of oil - let’s round up to $1,000 to make numbers easy. A true all season heat pump will take 30 years to pay off? As a retrofit I’m not sure anyone would ever take that deal.

Granted at some point I’ll need a new AC but I’d be better with the drop in Bosch for $15k, though I’m suspicious the existing ductwork won’t work well that option…

So I guess at this point I’m leaning towards fixing the boiler if it can be done and let it ride on the AC as long as I can. It’s sad, I’m the type of person who might otherwise pay a little extra for the green option, but I just can’t justify that with the amount of oil I actually burn through.
 
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EbS-P

Minister of Fire
Jan 19, 2019
802
SE North Carolina
$40K and that does not include upgrading to 200 amp service.
That’s steep. What are the odds those units last 30 years? So what if the duct work isn’t great, a 5 ton ac/heatpump replacement would carry you a long way for a long time with the wood stove. I agree spending money in the boiler as a backup to the future cheaper heatpump is the way to go. Plant a few more trees, buy some carbon credit or hang all your laundry on the clothesline what ever makes you feel better about still running the boiler. I think that’s the best decision. Personally I chose the clothesline. 7 big loads a week adds up.
Evan
 

Prof

Minister of Fire
Oct 18, 2011
556
Western PA
Holy cow! Yeah, I couldn't justify that type of price difference for the green option.
 

begreen

Mooderator
Staff member
Nov 18, 2005
88,225
South Puget Sound, WA
I think repairing the boiler is a good option, regardless. Then you have baseload heating covered. The woodstove is gravy on top.
 

NoGoodAtScreenNames

Feeling the Heat
Sep 16, 2015
406
Massachusetts
That’s steep. What are the odds those units last 30 years? So what if the duct work isn’t great, a 5 ton ac/heatpump replacement would carry you a long way for a long time with the wood stove. I agree spending money in the boiler as a backup to the future cheaper heatpump is the way to go. Plant a few more trees, buy some carbon credit or hang all your laundry on the clothesline what ever makes you feel better about still running the boiler. I think that’s the best decision. Personally I chose the clothesline. 7 big loads a week adds up.
Evan
At that price if I was just trying to throw money at reducing my carbon foot print I’d be better replacing my car with a BEV.

Thinking again about the drop in with the existing ducts. How much does the air handler location matter? Right now it’s in the basement on a far gable end. I would think tying it in at a more central - maybe 15-20’ more towards the center of the house may help ?