HVAC specialists here ? wanna go electric

Deschodt · 08:59 AM

Here's my deal. I got solar and make lots of free power. I still get a partial bill from my utility because of a gas water heater and furnace. I plan on getting rid of gas altogether soon.

My central heating gas furnace is old but functioning... The ducting is between the downstairs and upstairs floors and horrible to access, poorly distributed/balanced overall, old and nasty. It also eats up 1/2 of my basement space. The furnace sits below an added AC unit so they are together like a borg cube so they share all vents and registers... selectively blocking registers or vents has not worked well.

To add to the fun, my downstairs is always 10-15F colder than upstairs due to sun /tree exposure, so in theory I only ever need AC upstairs 1 mo per year - never down (to get upstairs down to 78F in summer downstairs gets.... to 65!!!). And vice versa with heat, heat up for downstairs, upstairs is too hot, wasteful... but I'm OK with heat everywhere just in case. Only one thermostat, no zoning doable, I asked, without a complete redo and multi units per the HVAC folks.

I am tempted - pondering - investigating - the cost/benefit of going mini splits. Current system is wasteful and impossible to Zone without a complete $$$ redo. Vents are yucky and 1/3 date to 1960s. It's gas, $$$, electrical is free to me. With mini splits I could control temp per room - like having many thermostats, I'd have one per BR so 3 + 1 for each main room - nothing for office or Bath (tempered climate)... say 5 total ?

Do they make less ugly efficient ones now ? Does this make no sense ? I understand each mini needs its own AC lines and stuff outside, but I cannot see it messier than the current setup - my HVAC storage room looks like the bowels of the Enterprise and I would get back so much room. Is it stupid price wise? The quotes for new electric furnaces are high, add new vents and it gets astronomical... Zoning to them means 2 units... Even stupider, since currently AC and heat share All the vents..
Final bonus q: don't need AC at all downstairs, EVER - can I get a split mini there with no AC lines ?

Hoping some of you went thru that and know more.. thx !

masraum · 02-15-2024, 09:52 AM

The outdoor portion of a mini-split system can support multiple indoor units. I assume it's based on the manufacturer, but I think I've seen options where you could have 5 indoor units that all connected to the same outdoor unit.

I believe it's possible to have indoor units that essentially replace a ceiling vent (kind of look like a vent, but obviously, inside the wall/ceiling take up more space.

I've also been told that it's possible to have a single indoor unit work to cool 2 adjacent rooms.

My understanding is that the mini split route is supposed to be very efficient, but I think the initial cost is higher (per indoor unit cost), and there's also the matter of potentially having that indoor unit visible anywhere that you have AC.

I'm far from expert and haven't pulled the trigger but have done some research (not exhaustive) and talked to an AC guy.

Tobra · Tobra's Garage

Gas is the most efficient way to heat your house, cook, water heater, clothes dryer, everything

Deschodt · 02-15-2024, 10:11 AM

Quote:

Originally Posted by Tobra

Gas is the most efficient way to heat your house, cook, water heater, clothes dryer, everything

I hear you, but efficient is not necessarily cheapest... I pay $200/mo just in gas in winter, all my electrical is FREE and I make power to spare. My choices are electrical furnace or split mini... Gas is coming out. Sorry if I was unclear ;-)

908/930 · 908/930's Garage

Im not a pro. A couple things to check. To start with do you have enough amperage left over in your existing electrical panel? 200A panel? Check with building code you could be required to have some air circulation using your existing ducts or changed to HRV. As Masraum said there is ceiling cassette units available, a little pricy but clean looking. Really don't think gas is more efficient, modern heat pumps can be near 300%, running cost depends on utility price.

Some of the new mini splits are an easy DIY install. For your last question about the AC lines, the lines used with a mini split do both heating and cooling, basically the system just runs flow backwards to flip the hot and cold side.

masraum · 01:46 PM

Quote:

Originally Posted by Tobra

Gas is the most efficient way to heat your house, cook, water heater, clothes dryer, everything

Wouldn't that depend?

If you can get away with a heat pump, I would think a heat pump would be as efficient or more efficient than gas. I assume the difference is for someone like me, when your heat pump is only good down to around 45º, and after that you have electric elements to provide heat. On days when our low is 20 and the high is 40 or even days when we have 24-48 hours of temps at 40, our electric element heat runs all day, and that costs a fortune.

And I wonder about comparing gas cooking to induction cooking efficiency-wise. When cooking with gas, a huge portion of the heat flows up past the pan and heats your house (not great in a warm environment where you run the AC 8-9 months of the year). Induction only heats the pan. Of course, I don't know how much power that takes and how that would compare cost-wise to the cost of similar gas to heat a pan.

cockerpunk · 02-15-2024, 11:57 AM

Quote:

Originally Posted by Tobra

Gas is the most efficient way to heat your house, cook, water heater, clothes dryer, everything

depends on what you mean by efficiency. thermodynamically? maybe ... we are seeing power plants being able to hit some pretty seriously good efficiency numbers these days, esp with combined and stacked cycles. power plants are also much easier to keep clean than any local production would be. with thermodynamic efficiencies' close to 50%, thats better than almost anything you can do locally.

sounds like financially, and infrastructure-wise ... certainly not in this case. converting more and more to the freely available solar would save money, increase efficiency, increase robustness, and decrease infrastructure needs.

wdfifteen · wdfifteen's Garage

Quote:

Originally Posted by Tobra

Gas is the most efficient way to heat your house, cook, water heater, clothes dryer, everything

This reminds me of my days as an engineer. They never give a straight answer to a simple question. Apparently they aren't the only ones.

"I'm painting my house green. What's the best brand of house paint?"
"You should paint it red."

billybek · billybek's Garage

Heat pumps have come a long way in the last few years in being able to produce useable heat in lower outdoor ambient temperature conditions.
The efficiency suffers as temperatures drop but when you're producing the power yourself, no big deal.
We can see temperatures close to -40 deg (C or F, take your pick...). I will stick to gas.

masraum · 02-15-2024, 06:27 PM

Quote:

Originally Posted by billybek

Heat pumps have come a long way in the last few years in being able to produce useable heat in lower outdoor ambient temperature conditions.
The efficiency suffers as temperatures drop but when you're producing the power yourself, no big deal.
We can see temperatures close to -40 deg (C or F, take your pick...). I will stick to gas.

I'd be completely happy to get a heat pump that worked well down to about 15-20º installed. From what I understand, that shouldn't be an issue these days.