Calling all HVAC experts

[Riteway]

My house has a natural gas, forced air furnace and a central A/C unit that are pushing 25 years old, so I've started to think about what my options are when one (or both) of them bite the dust. Would sure appreciate some advice on what would be the "best value" replacement options, over a 20 year period. For instance, I'm not sure if it would be better to go with a new A/C unit and gas furnace, or a heat pump with a backup gas furnace, etc...

The house is a moderately well-insulated 2,000 sq ft rambler, constructed in 1975. Average low temps during the winter months here are in the mid-30s, and average summer high temps are in the mid-70s. We generally get one to two weeks of 90+ temps a year; 100 or over is extremely rare.

My wife and I are avid wood burners (new insert installed last year), and generally spark one up every evening between October and March-ish. We'll burn 24 hrs a day on the weekends and during cold snaps. Because of the supplemental wood heat, I don't have a desire to pay the extra money for a high efficiency gas furnace; probably wouldn't be cost-effective for us.

 

[peakbagger]

Unless your electric power rates are high, you are in the sweet spot for a modern cold climate central heat pumps. You can save more depending on your layout switching to cold climate minisplits which saves duct loss issues tied to using central heat pump. Its worth having an energy audit done first to see if there are any low hanging fruit to knock off to get you load down. My guess is one of moderate hanging fruit will be duct loss and duct insulation as most AC ducts were sized and built to be cheap, not necessarily efficient. If you have any solar capability its nice partner to minisplits.

 

[EbS-P]

So I think a heat pump with gas backup could be great. My trane unit had gas backup as an option. But based on your location your heating needs are far greater than you cooling. That makes sizing a single stage heatpump difficult. Those are the cheap models. I bet you could get by with a two stage model. It the ideal solution would be a variable speed compressor, but those are expensive and if you have gas backup heat the extra heating capacity doesn’t have to handled by the heat pump.

I like my trane 16 seer two stage with variable speed blower. Gas backup was an option my model. I don’t think my model was really intended to be a heater first. Looking up Seattle’s heating and cooling degree days your combined total is similar to mine. Your electric cost is cheaper then mine. Doing some rough math says that upgrading from a 16 Seer to 22 seer variable speed unit the potential savings are 3000$ over 15 years. I doubt that makes up for the extra cost of a variable speed unit.

My recommendation is a 3 ton(I know nothing about the heating cooling demand and base this off of my similar square footage) two stage unit with a variable speed blower and gas backup. If there was a deal on 14 SEER single stage I would consider it with the understanding it is probably oversized for cooling, won’t do a great job at dehumidification and could short cycle.

Your climate is not extreme don’t let someone sell you something you will not realize the savings on (your cooling season is short, you burn wood and have as backup heat).

I am no expert. Just some thoughts.
Last point. Your 1% winter design temps are warmer than we have here in the south and very rarely does gas get installed as a backup. It’s almost always resistive electric. (Well and my wood stoves

Evan

 

[Riteway]

Thanks for the comments fellas! Very helpful. I really like the idea of having an energy audit done--seems like a good investment right there.

 

[fbelec]

i've wired a dual fuel they save a lot of money if not burning wood. i would also consider your age. i don't know how old you are. if you are getting up there in age then consider something good because if your up there in age wood will get old quick so you want something you'll be able to pay the utility bill when money gets a little short. just a thought.

 

[peakbagger]

Check with your local utility for an energy audit. In New England the utilities have hefty energy conservation budgets and the availability of the funding is frequently tied to an audit. There will be big push to get home heating and cooling off of fossil fuel and onto renewable electric power so expect incentives for heat pump type technology.

 

[begreen]

A heatpump in this region is a natural fit. With gas backup and the wood stove to boot, you will be in good shape. We've had a good heatpump system since 2006, though once it gets below around 45º we mainly heat with wood unless we are away or sick. Our system is a 2 stage heatpump with a variable speed air handler. This means it uses less power and is much quieter when the heating needs are low, but has the reserves when the demand is higher, like when switching from nightime set temp to daytime set temp. We have also used it for AC kind of rarely, except for this last summer when it ran pretty much non-stop for a week in late June.

Some things learned:
1) Get the best you can afford. This is a longterm investment. We are so glad we went for the 2 stage system and DC airhandler.
2) Design for the future. In 16 yrs we only used the AC maybe 5 times, until last summer. Our local installer is raising the AC design temp from 82º to 90º because these temps are happening more frequently. Our system is 3 tons. A replacement will be 4 tons.
3) Look at Japanese whole house systems from Mitsubishi & Daikin or American companies that use inverter-driven, variable-speed, compressor technology. It's quieter and more efficient.
4) Stick to companies that will have parts and service well into the future.

 

[EbS-P]

Our local installer is raising the design temp from 82º to 90º

Thats quite the jump. Probably warranted given system life is 20 years. Sobering. But think about that for a minute. Your system is now 33% larger and consuming more power at full load. I does it make sense to design your main system to that design temp? I would think only if it is variable speed compressor. It will come with extra cost.

 

[begreen]

Thats quite the jump. Probably warranted given system life is 20 years. Sobering. But think about that for a minute. Your system is now 33% larger and consuming more power at full load. I does it make sense to design your main system to that design temp? I would think only if it is variable speed compressor. It will come with extra cost.

Yes, our current compressor is 2 stage and I was assuming variable speed for the replacement.

 

[peakbagger]

I was in large downtow a few years back at a major institution on a very hot day talking about energy. At some point the manager of the overall heating and cooling plant came into the meeting and commented that he was running out of cooling for the facility. It was not that he had equipment that was not running, it was that the temperature and humidity conditions were several degrees above the recommended design temps for the city. Its a combination of warmer climate and the urban heat island effect. Covid has not helped as most commercial and institutional systems have been adjusted to crank up the amount of outdoor air versus recycle.

BTW, the Biden administration is planning on cranking up the phase out dates for HFCs which include R410A a popular refrigerant for mini splits due to lower temp range. The replacement non HFC refrigerants that will replace them require higher pressure and the cost of the units will increase.

 

[Bad LP]

I was in large downtow a few years back at a major institution on a very hot day talking about energy. At some point the manager of the overall heating and cooling plant came into the meeting and commented that he was running out of cooling for the facility. It was not that he had equipment that was not running, it was that the temperature and humidity conditions were several degrees above the recommended design temps for the city. Its a combination of warmer climate and the urban heat island effect. Covid has not helped as most commercial and institutional systems have been adjusted to crank up the amount of outdoor air versus recycle.

BTW, the Biden administration is planning on cranking up the phase out dates for HFCs which include R410A a popular refrigerant for mini splits due to lower temp range. The replacement non HFC refrigerants that will replace them require higher pressure and the cost of the units will increase.

Re: Higher pressures.
They didn’t figure higher pressures moving from R22 to 410A. I wonder if the new gasses will now require better line sets and exchangers.

 

[peakbagger]

CO2 based refrigerants are starting to be deployed in the grocery store industry. From what I read is all the components need to be upsized for the higher CO2 pressures.

 

[semipro]

Because of the supplemental wood heat, I don't have a desire to pay the extra money for a high efficiency gas furnace; probably wouldn't be cost-effective for us.

Agreed. Your temps are relatively moderate and the newer HP tech can provide efficient heat within your heat range. Why install gas backup at all unless you're concerned you won't be able to use wood for backup?
You can have your HVAC tech configure the system so that a furnace can be added more easily later if needed.

 

[Bad LP]

CO2 based refrigerants are starting to be deployed in the grocery store industry. From what I read is all the components need to be upsized for the higher CO2 pressures.

Well we know that they did not use stronger components on the first changeover. I'll use Mitsubishi line sets as an example. Mine were garbage and I'm aware of others leaked as well.

 

[Riteway]

Lots to think about here, I appreciate the responses. Leaning toward a heat pump/gas furnace combination. Considering the current supply chain issues and corresponding cost increases, I'm hoping to get at least a year or two out of my current system before having to write out a big check. Definitely want to avoid a R-410A unit, as I'd imagine that refrigerant will likely be unavailable within the next 10 years or so. My current A/C unit uses R-22, which was completely banned last year (except for existing stock and reclaimed stuff).