Advice for a replace on a 10 seer York

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potatowolf

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Hi everyone,

I'm actually posted here for a well pump right now as well so our cup runneth over as they say.
So theres a 20+ year old 10 seer york unit that the compressor failed- At least we are fairly certain of that. Originally I was going to come on here and troubleshoot but at this point, i'd ask what replacement options would be good for them. The internal unit fins look shot,
and the load skyrocketed for about 2 months toggling into aux heat last year.

I was looking at some updated rheem and bosch units, but haven't completed my search. I suppose what got me interested is seeing a what i can only call a "DUCTED VERTICAL" mini split system by lg LV361HV4 where its an indoor unit and outdoor unit (so no spider wires on the side of the house or cassettes) so like a traditional unit,but don't know how people's experiences are with those. Looking at some other posts here seems like people are happy with minisplits in general but I have concerns as they are close to scranton pa and it can get pretty cold here up north.

Question is - Could they get a mitsu or fujitsu whole house split with airhandler and everything, and be ok with their existing ductwork. and yes I understand i know im in for it probably.

Also thanks for your patience in reading my hot mess of a post.
 

Fitter30

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The higher the efficiency of the equipment the more training service people have and maybe a laptop with the correct program. Contractor is as important as the equipment. Check with your utility companies for rebates. Have to ask yourself how the old equipment heated and cooled the house to address any problems. That lg variable refrigerant flow with matching air handler other brands that you listed have the same type of equipment.
https://www.seerenergysavings.com/
 

potatowolf

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The higher the efficiency of the equipment the more training service people have and maybe a laptop with the correct program. Contractor is as important as the equipment. Check with your utility companies for rebates. Have to ask yourself how the old equipment heated and cooled the house to address any problems. That lg variable refrigerant flow with matching air handler other brands that you listed have the same type of equipment.
https://www.seerenergysavings.com/

tried to contact mitsubishi to get a local guy for quoting, it also seems like any of these units regardless of what anyof us pick, will need a heat strip ( will have to confirm design temperature for this) as those cold feb winters / artic blasts will definately put us in aux heat.
 

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Dana

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SFAIK only Midea (under a number of nameplates, including Carrier) & Fujitsu (including Rheem-badged Fujitsu) compact-ducted type air handlers can be mounted vertically. "Full size "multi-position" air handlers from Mitsubishi, LG et all can be mounted in upflow positions as well, but those bigger air handlers usually don't have nearly the modulation range of the compact duct cassettes, and that's important for optimizing both comfort & efficiency.

Most of the compact units have somewhat limited air handler power, and won't be able to drive all duct systems. With any replacement unit the duct system has to be analyzed. As a rule of thumb (I hate those), if the duct velocity is <400 feet per minute at the highest modulating speed of the air handler even the compact duct cassettes can usually work without major changes to the duct system. Many existing systems have ducts undersized for the existing air handler but still get away with it due to gross oversizing of the AC or heat pump, despite the higher static pressures. With ECM "inverter drive" air handlers running the max rated static pressure is likely to burn out the air handler motor, whereas with cheap split capacitor motors on old school single or 2-speed units high static pressures will chew a bit more power, but the motors will take the abuse.

So the first order of business is to properly size the thing for the actual heating & cooling loads and pick the smallest unit that covers (or almost covers) both the 99% and 1% design loads. The handiest freebie load tool I've found on the internet most appropriate for heat pumps and minisplits is the BetterBuiltNW HVAC tool, which has appropriately default U-factors (unlike most Manual-J tools), and is less likely to sub-optimally oversize the system.

With load numbers utilizing the NEEP search page to search by vendor, cassette/head/air handler type and max heating capacity @+5F (the slider in the upper right) is an appropriate place to start.

The LV361HV4 puts out 35,000 BTU/hr @ +5F but can only modulate between 16000-43,000 BTU/hr @ +47F (the AHRI test temp), a 2.7:1 turn dep.oown. (See p.7 in the manual.) This is pretty typical for that type of air handler. In contrast, a mid-static compact ducted -36RLGX delivers nearly 33K @ +5F, but can throttle down to 9.2K (and up to 48K- a 5.2 : 1 turn down ) @ 47F. While the mid-static Fujitsu ARU36RGLXD is only rated for 0.8" w.c. @ 1200 cfm, that isn't much different from the 1.0 max @ 990cfm rating of the LV361, yet it has nearly twice the modulation range.
 

potatowolf

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Hi again- I haven't given up on the topic it was just finding some time in between to get back on things. I had to write this over a few times.

I had to re-read your response a few times, just because im starting out when it comes to all this, (im still on sensible gain vs latent gain, how to size existing ductwork etc) and i have a few questions as well hopefully i can be clear.

Is this unit in lieu of a standard vertical air handler we've come to be familiar with (Singlezone Ducted, Centrally Ducted?)vs (36RGLXD) ill assume i'd have to modify the ductwork somehow if i went that route, or found where they "met up" in the basement.

On another note, we had a family friend who does hvac talk to us for a moment and he effectively said the same thing about commercial units that are under 16 seer- that they are the same fundamentally only branded.

I have been looking at GREE, RHEEM, YORK, LENNOX, and GOODMAN in the meantime as I havent given much attention to the standard 16 seer units available.

I'll give the HVAC sizing tool a try - as ive tried to do a separate manual j on my own a few times and with coolcalc as block load ( 24,500 cooling 59,000 heating and 1175 CFM which sounds really off) but i like that hvac.betterbuiltnw has the design temperatures in place for major weather locales amongst other things ( i gather that i didnt read the ashrae handbook thoroughly and my Heating db cooling db values were different-)

before i continue ill try to provide some information that could be of value such as ductwork old unit sizing etc.

As ridiculous as this sounds- Could I swap out the fan for my own fan ( 1200 cfm 1/2 hp motor ) from another unit? or could they go for a booster fan to 'help' an air handler do its job for static pressure? they loved the idea of getting a more modern unit (mitsu/fujitsu), but it makes me think that any in comparison would be better to what they currently have.

Also you mention modulation i dont even know where to begin with that- assuming that its how the unit can stepdown in order to save electric or operation efficiency related,I never factored that in.

I'm willing to help them install the system and then get a guy to charge it post-install, i was hoping that we could use the existing ductwork in a 2 story 2050+ sqft without considerable modifications.

Thanks for reading
 

Fitter30

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Buy a matched system don't reinvent the wheel. 16 seer air handles have ecm blower motors in them with a design coil and expansion devices.
 

WorthFlorida

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As maybe been hinted by others, most new air handlers and condenser fan motors are ECM. They are expensive and are regulated totally different than the motors in your old SEER 10 model. As you stated many HVAC units are a label only. Most all of them use the Copeland Scroll Compressor and all are now made with aluminium coils. Government requires a Minimum SEER 14 but for a few dollars, SEER 16 is achieved. SEER 14 is pretty much standard as far as a controller board. Seer 16 there may be some difference. SEER 18 and above is where controllers and in some cases thermostats are a proprietary. This is all about conventional HVAC as you have now. The duct work for new HE units need larger ducts than when SEER-10 was the norm. New systems will work with undersized duct work but the efficiency may drop. A good tech will know if the ducts are too small.

Mini splits I know very little about, Dana is an expert in HVAC and he has thousands of posts on this forum. He knows Mini Splits better than anyone on this forum.
 

Dana

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What he said.

A 3 ton minisplit is a bit overkill for the previously estimated 24,500 BTU/hr cooling, since they usually have over 40K of peak cooling capacity at AHRI test conditions (but tested for their SEER efficiency at 36,000 BTU/hr.) But it wouldn't come close to handling a 59K heating load, so it's important to get better numbers if you can.

If your York is married to a fossil-burner furnace for heat, using last winter's fuel bills run the fuel use numbers against heating degree days to estimate the heat load as outlined in this bit o' bloggery. This is really a measurement of the heat load (crude and imperfect as it may be). Using wintertime only numbers reduces the inherent error from solar gains and/or domestic hot water heating using the same fuel.
 

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Hey @ Dana thanks for stopping by! I am taking the coolcalc initial block load i did back then with a grain of salt. - They seem to be more concerned with winter heating performance, which is difficult since their system is straight heat pump no furnace. It likely wont fullfill those colder jan feb drops where its 5 degrees or less. I should more accurately say it does "perform" but I can only assume comfort is a concern- as they generally had to include a space heater in the second floor to compensate. One was suggesting it was a filter restriction issue ( theres a reusable filter in the air handler). I am looking at systems with better winter loads if anything, also the HSPF seems to play a role in this which i didnt account for in the beginning. That post is stickied somewhere for others? I had it originally but I didnt know anything about design temperatures at the time. Would sizing up to a 3.5 ton compensate for the heating load conditions or is that risking a short cycle situation for their house?
 
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Dana

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Hey @ Dana thanks for stopping by! I am taking the coolcalc initial block load i did back then with a grain of salt. - They seem to be more concerned with winter heating performance, which is difficult since their system is straight heat pump no furnace. It likely wont fullfill those colder jan feb drops where its 5 degrees or less. I should more accurately say it does "perform" but I can only assume comfort is a concern- as they generally had to include a space heater in the second floor to compensate. One was suggesting it was a filter restriction issue ( theres a reusable filter in the air handler). I am looking at systems with better winter loads if anything, also the HSPF seems to play a role in this which i didnt account for in the beginning. That post is stickied somewhere for others? I had it originally but I didnt know anything about design temperatures at the time. Would sizing up to a 3.5 ton compensate for the heating load conditions or is that risking a short cycle situation for their house?

The risk is less about short cycling than it is about reduced system performance & lifespan. Upsizing a modulating heat pump for retrofit onto existing ducts runs a greater risk of running into high static pressure issues, burning out expensive ECM blower motors and delivering less than satisfactory heating (even when satisfying the thermostat.).

Measure the size of the supply & return plenum cross sections, and the cfm of the heat pump (or AC) at it's highest blower speed, then do some arithmetic. If the duct velocity of both the supplies & returns are <<400 feet per minute at the highest speed it's likely that your static pressures will stay <0.5" water column, and the blower will survive. If the duct velocities are >>600 fpm there will almost certainly be issues to address. Even a 400 cfm it's a good idea to do a more careful duct analysis.

Undersizing the heat pump to 0.9x the design heat load is not a big problem- that's what strip heat "toasters" are for. Even when running the toaster most of the heat will be sourced by the heat pump, so the impact on power use isn't as great as it might seem.

Re-run some Manual-Js to get a better handle on it. Consider doing some air sealing & spot insulation to lower those load numbers too. There is more comfort & efficiency to be gained by fixing the building than by upsizing the heat pump, though going for a cold-climate version (= higher COP @ higher capacity @ +5F) version is also worth the upcharge if you right-size it.
 
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potatowolf

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just to be brief for now i was looking at these two units both are 3 ton 16-17.5 seer-


Bosch BOVA-36HDN1-M18M
BOVB-36HDN1-M18M
---- air handler BVA036WN1M18 or BOVB-36HDN1-M18M, BVA-36WN1-M20
cop off ashp.neep.org comes out to 1.87

rheem
Condenser Model # RP1636AJ2NA
Air Handler Model # RH2V3621MTANJA

couldnt find the heatpump stats for the second but the ones of that same brand
particularly the cop come out to 2.0-2.2
 
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potatowolf

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ok so i did the manual j for the house finally, though i havent gotten to the duct section yet-
heres what the numbers look like so far-

heating 26.6k cooling 12.3k latent 2.2k

had to stop on account of ran out of time
 

Dana

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ok so i did the manual j for the house finally, though i havent gotten to the duct section yet-
heres what the numbers look like so far-

heating 26.6k cooling 12.3k latent 2.2k

had to stop on account of ran out of time

A modulating 2-ton or 2.5 ton heat pump with a cold-climate type compressor would be the best likely fit, depending on your local 99% outside design temp. The Midea/Carrier (and other labels of the same thing) 38MARBQ24AA3 / 40MBAAQ24XA3 pairing is good, but may need a heat strip "toaster" to cover cold snaps. If the static pressures of the system if low enough (<<0.8" w.c. @ 1000cfm) and the available space configuration would allow for a "compact duct" cassette (in either horizonal or upflow orientation) , the 2.5 ton Fujitsu AOU30RGLX might even do it without strip heat (again depending on your actual design temp.) At somewhat lower static pressures the 2-t0n Midea/Carrier 38MARBQ24AA3 / 40MBDQ24--3 compact duct cassette may fill the bill. (The naming/numbering conventions of the Midea /Carrier units are a bit hard to keep track of- with many similar numbers for both indoor & outdoor units of diverging description.)

Last thing you want here is an old-school single speed 3 tonner with oversized strip heat to cover a ~2 ton heat load + 1 ton cooling load. The old school unit will be cheaper up front, but far less comfortable. You may never make up the difference in cost on the higher efficiency, but when sized correctly modulation delivers a meaningful difference in overall comfort levels, usually with a bump in as-used efficiency too.
 

potatowolf

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They are thinking of settling on a rheem
Condenser Model # RP1636AJ2NA (two stage 16 seer )vs the bosch. They based it on bosch availability for parts and their overall place in the industry right now compared to other established brands. Id love the idea of a mini split but the ductwork system is based on the old 10 seer unit for a 1.5 story ish place the room configuration is also an issue - after looking in the basement whoever did the ductwork did a not so great job ill have to get a couple steel elbows and a flex duct or two, theres like 90 degree short bends on at least 3 of the runs- its turning into a hot mess. i was going to see what toaster they had originally but my list had a 10kw in mind. Time constraints/financing and the weather are likely affecting this decision
 
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