Author Topic: HVAC replacement  (Read 1072 times)

fdubz

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HVAC replacement
« on: August 22, 2019, 10:56:57 AM »
Thanks in advance for input!

We are having to replace our 15 year old HVAC unit and would appreciate any and all advice.  It is a fancy pants Carrier infinity system (original to house) and we do not want/need that level of sophistication. I don't think?

Our house is 3 floors with an unfinished basement, about 1200sq ft on main floor (living room, kitchen, master) and 500sq ft on top floor (guest room and office).  The condenser unit for the upstairs is fine.  We do most of our living on the main floor and that is the condenser unit that has failed.  To fix all of its problems would be $4-5k, so based on the age of the system (15 years) we have been advised to replace the system.

We are in a rural area with no gas lines.
We live in the mountains and sub 40 degree temps are the norm from mid-Oct to early May, but not a ton of sub 20 degree days.
Normal thermostat temp for us is 64-67 in winter, 71-75 in summer.  Electricity is usually about $75/mo in summer and $120/mo in winter.

Should we consider something besides replacing with another electric heat pump?  Is 'top of the line' the best idea or are there solid, simpler models that are still efficient?  What else should we be looking at?
Thanks so much!


Syonyk

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Re: HVAC replacement
« Reply #1 on: August 22, 2019, 12:42:49 PM »
A modern air source heat pump is going to be a good bit more efficient in the winter than a 15 year old unit - they've really improved the low temperature performance of those over time.  Whatever you get, make sure it's set up properly so it doesn't randomly run the backup coils.  I'm happy with how our Nest thermostat runs the heat pump in the winter, but I'm not sure I'd buy a Nest over an ecobee or something else these days with how Google is messing with Nest.

Our heat pump can keep up even down to 0F, and it's not an amazingly high end unit.

Given that it only cost me about $4k to get the heat pump added to our house (it came with an electric furnace that is now the backup coils), I think a new unit probably makes sense for you, though I expect you'd pay a lot more than what I paid (just a 2k sq ft manufactured doublewide).

ZMonet

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Re: HVAC replacement
« Reply #2 on: August 22, 2019, 06:09:40 PM »
We were in a similar situation last year with a 15 year old heat pump.  We shopped around and eventually replaced with a Carrier unit.  The consensus from my research seemed to be that there are diminishing returns for going with the high-end systems.  I've been told a lot that the difference in units is largely the warranty, with different manufacturers basically having the same parts but with different badging.  The difference is the warranty.  Other than that, consensus also seemed to be that a good installer was very important as a bad install good seriously shorten the lifespan of the unit.  I will say that we've seen about a 20-25% reduction in our energy costs YoY, so the old unit was definitely not very efficient.

Takk

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Re: HVAC replacement
« Reply #3 on: August 23, 2019, 08:03:31 AM »
15 year old unit is about average for lifespan, so it's understandable they suggested to replace. (Source: ASHRAE Equipment life expectancy chart; google)

From my experience, with that low of electric bills, even if we selected a less efficient option, it would be worthwhile from a life cycle cost effectiveness standpoint. (Payback from low electric will not pay for the premium in cost) SEER/HSPF is how the units are measured, which is flawed but at least puts things on the table as similar. higher number is better. If you get the performance in EER or COP it is much better as it follows direct conversion rates.

In my opinion, get prices for one step up, etc. and see difference of SEER and HSPF compared to the price. General rule of thumb, (which depends on environment and usage) is that 1 SEER point is around 50 dollars a year of savings. more savings where it runs more often, less savings where it runs less often; thus likely you're looking at if it costs more than 750 for 1 step up in efficiency, it's not worth it with a simple payback, and if you are investing the difference in cost, it never really pays back unless it's very low cost (somewhere in the sub 400 dollar range for an increase in 1 step). (not related to electric strip resistance heating, which is what you want to avoid if at all possible, but you still want to have just in case-This is Emergency heating; this is what the poster previously was mentioning with the NEST thermostat)

Final question about looking into anything else:  Not really, any other options are more sophisticated and cost more. a simple heat pump system is the way to go for cost, and ease. with only 120 in electric cost in the winter I'd say you're likely doing just fine with what you have and don't need to look into insulation or windows, or even leakage. Your current thermostat probably works just fine as well, but always good to confirm how it operates.

TLDR; Likely grab the cheapest heat pump system, which may still be better than what you have due to increases in efficency, and a programmable thermostat for it (like NEST; but it may come with this option!) to confirm it uses heat pump as much as possible before it ever thinks about turning on the strip heat.

fdubz

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Re: HVAC replacement
« Reply #4 on: August 23, 2019, 08:18:40 AM »
Thanks so much for the helpful, detailed info!  I am certainly feeling better about replacing vs. fixing.  One question about the thermostat.  Several of you mention Nest and other programmable thermostats as being good at handling the heat pump. 

With our current fancy (complicated) Infinity thermostat we can set all sorts of times/temps from weekend, workday, vacation, you name it.  It even can set humidity levels, which I admittedly have no clue how to use.  Bc it's so involved, every morning and evening, I manually set the thermostat a few degrees higher or lower (a few degrees colder on summer nights, warmer for summer days when we're out and the opposite in the winter). 

Is the main benefit of the Nest, etc that it does this for you? Or is there some other way it "handles"?  I don't mind punching up/down each morning/night as it really depends on the weather that day how far I go up or down.

Takk

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Re: HVAC replacement
« Reply #5 on: August 23, 2019, 08:32:02 AM »
NEST is just user friendly, it advertises it's ability to self-program, which is useful for people whom do not know or do not wish to mess with programming it themselves.

As a note: a cheaper HVAC system likely won't be able to control humidity as well (What it does is turn on the coils with low airflow, draining more moisture out of the air), but in your climate that is likely not a problem.  (I'm in Florida, and we don't control humidity directly like the infinity system does normally, but it is an advantage in this area to be able to do so)

The usual control scheme is that the electric resistance heat comes on at a certain number of degrees off of setpoint. ie: you set it to 70, and it's 60 in the room, it turns on the resistance heat. vs if you set it to 62, it turns on the heat pump. Some systems have programming to allow there to be a timer + number off of setpoint before electric heat turns on, etc. I don't offhand have knowledge on residential thermostat control of the heat strips for the NEST or others; but likely your control is fine with your fairly low bill. In my climate, we just remove the wiring for the heat strips, but it doesn't get very cold here.
« Last Edit: August 23, 2019, 08:51:26 AM by Takk »

simonsez

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Re: HVAC replacement
« Reply #6 on: August 23, 2019, 01:44:15 PM »
While shopping around, be cognizant of any rebates your energy company may provide.  Mine does $500 for SEER 15, $600 for SEER 15.01-17.99, and $700 for anything with a SEER at 18+ when you update your air source heat pump, up to $650 on updating central air, up to $1800 off geothermal, and $50 off programmable thermostats.

Good luck!

BTDretire

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Re: HVAC replacement
« Reply #7 on: August 24, 2019, 10:57:54 PM »
15 year old unit is about average for lifespan, so it's understandable they suggested to replace. (Source: ASHRAE Equipment life expectancy chart; google)
  I believe you are correct that a 15 year old unit maybe ready for replace, but a 30 year old unit is also just ready for replacement! In other words, "they just don't build then like they used to."
 I replaced my 33 year old unit about 10 years ago, this new 10 year old unit is now on it's 3rd fan motor.
I didn't put in the OEM replacement this time, I got a better motor.
 I have a friend that has 35 years on his, he is a technical guy and has checked everything on the cooling and heating units, he checked the heat exchanger for leaks and it is still good. He is ready to replace the unit, the condenser unit out side, had a lot of the aluminum fins blown off in the recent hurricane. His service guy keeps putting him off. Florida is busy in Summer for air conditioner guys.
 Now, if you're going to say the old units are not as efficient as new units, I agree. 
They were built to last though.

fdubz

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Re: HVAC replacement
« Reply #8 on: August 26, 2019, 07:58:00 AM »
Thanks everyone!  We are moving forward with replacing our heat pump and got a quote this weekend from an HVAC guy who comes highly recommended from multiple people we trust.  I think it seems very reasonable.  Anything else we should ask?
 
"Install 2 ton outdoor 14 SEER Deluxe Heil heat pump with new pad for unit to sit on and with 4 3 inch snow legs. Install 2 ton indoor air handler and 10 kw heat package.  Install water overflow safety switch. Add a Honeywell Pro 5000 large screen thermostat.  Total: $4900"

We have that same thermostat for our upstairs and like it.  We may upgrade to a more programmable thermostat later, but are happy for now.