Replacing a heat pump

[Jeff Bartley]

Well I now know that 20 years is the limit on a Rheem heat pump. It had been freezing up over the summer and adding Freon didn’t help. So now I’m shopping heat pumps.

Can anyone recommend a brand? I’m getting quotes from a few local companies. So far I’m seeing mostly Carrier, Lennox, and Mitsubishi. From a purely visual perspective I like the vertical fan type (the Mitsubishi) for the outdoor unit but that’s not a real reason to buy a particular system.

One of my requests to the estimators was to also give me a price on a system to cool the shop. One was adamant that a mini split would be a terrible idea due to dust. The other two didn’t even mention dust being an issue.

It’ll be interesting to see all three quotes. Whatever the case I’m spending some dough really soon!

[Lee Schierer]

We recently had our heat pump replaced due to a compressor failure in our Bryant heat pump. We purchased a Carrier Infinity, which so far is working well and has made the house much more comfortable in the summer months with the humidity control feature. It is much quieter than the previous unit as well. The new thermostat has a few features that were not available on our old thermostat, such as a vacation setting, which I can program to automatically switch to vacation mode after we leave and back to normal mode shortly before we are scheduled to return home. There were some pretty nice rebates from the utility company and a federal government tax credit that helped with the purchase price.

With regard to heating cooling your shop. My shop is attached to the house and is both heated and cooled by the central system. I installed air filters in the return air ducts for the shop and they collect a lot of saw dust. I recently did some remodeling where I opened up the walls of a room where the return ducts pass. I was able to inspect the ducts and noted no dust build up in the ducts and do not see any change in the amount of dust in the central air filter even when I do a lot of wood working. I don't know if mini-split wall mounted air handlers have filtering capabilities. The mini-split units that go in an attic or crawl space do have air filters.

[Jim Becker]

The Mitsubishi unit you refer to is a lot closer to a high-efficiency mini-split if it's the one I think it is...really good system and there are a variety of interior air handler setups that make zoning a lot easier. I'd be looking really close at that one if I decided to upgrade our system here at some point. But for traditional heat pumps, there are only a few actual manufacturers...which means that buying the unit labeled with the "non-traditional brand" sometimes is the better value for the same specifications, although warranty terms "may" be different.

For the shop...no problem using the minisplit. Yes, you need to do dust maintenance more often (or fabricate a larger air intake filter system like Jay Bates did...YouTube if you want to check that out) but they are uber-efficient and provide year-round comfort. Obviously, having decent insulation and infiltration control is very helpful in a shop setting. There have been a number of conversations about this in the Workshops discussion area if you want to check them out.

[Michael Weber]

Other than the common reasons for freezing a mechanical issue could be a stuck or faulty reversing valve. Might have that checked. No idea of cost for replacement but after 20 years replacement may be the best option anyway.

[George Yetka]

I generally buy commercial equipment so For the house system I can recommend carrier though there are a few other out there that I wouldnt run into so I couldnt say

For DX splits, in general, Mitsubishi creates the tech and everyone else(daikin/LG) buy them and reverse engineer them and put them back out 1 year later. For my use I buy what the engineer specifies, 60% of the time it is Mitsubishi the next 35% are split between LG/Daikin the last 5 goes to sanyo.

For garage use I like the Mr Cool stuff because you dont need a contractor, I would get this work done on the house and throw one of these in by yourself for the garage.

[David M Peters]

I built my shop last summer and put in a mini split and also got the same "dust is terrible for mini splits" commentary from many HVAC contractors. But like Jim said, if you generally have a tidy space it won't be an issue.

One contractor had the smart idea to use a ceiling-mounted cassette air handler with standard air filters in front of it. I went with wall-mounted air handlers for cost reasons, though.

For what it's worth I have a Fujitsu Halcyon (their -15F unit) and it's worked great.

[Malcolm Schweizer]

I just got a quote today for central heat and A/C and he recommended Mitsubishi mini splits upstairs (due to difficulty ducting.). I like that because I can zone each room when not using them. I didn’t know that they now make mini splits that just look like a vent in the ceiling. I like that because I have a historic home and did not want a big wall unit.

He gave me two quotes: one for a heat pump, and one for A/C with a gas furnace. I like the gas furnace for this big old house. I’m new to this whole heating thing.

[Malcolm Schweizer]

Here is what they are offering as options- option 1 is central heat and ac up and down. Option 2 is mini splits up, central down.

465997

[Jim Becker]

Malcolm, what's nice about the Mitsubishi offering is that they indeed can accommodate situations like yours because of the variety of interior unit options they have including an interior air handler that can tuck into an attic and use traditional flexible ductwork to ceiling vents like you describe, including multiple zones when desired/needed. It's relatively easy to get the small lines "up there" in any home, either hidden or exterior surface mount, too. Mitsubishi really is the "bee's knees" with high efficiency HVAC these days! I'd like to do a similar system here to replace the existing heat pump/oil combo setup we have in our new-to-us home...the balance isn't great and it's a single speed system.

[Jeff Bartley]

Thanks for all the info folks. I was hoping to see the third estimate today, it’s the one with the Mitsubishi stuff.

Malcolm, I’ve worked in a bunch of historic homes with mini splits in different zones. It’s an awesome set up for a house like that.

Hopefully I’ll have another estimate tomorrow!

[Jack Frederick]

Jeff, given that you are looking at a replacement system the first place to look, imo, is the tightness of your ductwork. Most systems are grossly oversized. The contractor may match the size of what is there and be comfortable with it. No risk. If you have made improvements to the home you increase the oversizing. Years ago the DOE put out a report that said the the average US home looses between 18-42% of its energy in duct losses. If you go with a central system using the same ducting ask the guy what you can do on your own, if so inclined, to improve the performance of the distribution system. Ooops, have to run. Be back with more;)

[George Yetka]

Speeking of oversized, I did a side job and replaced a boiler for a guy. It was an old farmhouse with radiators. The original boiler was Steam but 40 years ago PSEG or someone like it came to the owner and said they would provide and install hot water boilers for free in exchange for monitoring them for fuel consumption/etc. There were 3- 500,000 btu boilers installed(only 1 was left working.) and the house was freezing so I calculated the house and came up with only needing 1-165,000 btu unit. I couldnt figure out why the house was cold until I realized that there was a basement loop that would have worked fine with steam but it was path of least resistance for the HW. They were running 1,500,000 btu of HW heating for 30 years and barely getting anything out of it. I re-piped it. The house was toasty warm in no time.

Bigger is not better, Right is better. Too big or too small and you will be wasting money or be Hot/cold.

Most older homes used HW or steam to heat. What was originally there? My grandparents have a huge farmhouse built in the 1850's It is HW radiators and baseboard with no AC(with the exception of the addition)
What is the insulation situation with your house? 1 story/2 story? attic/basement?

I would look up the sound information on the proposed Mitsu's just to make sure they are something you can sleep through. Most are quiet nowadays.

[Jeff Bartley]

Speeking of oversized, I did a side job and replaced a boiler for a guy. It was an old farmhouse with radiators. The original boiler was Steam but 40 years ago PSEG or someone like it came to the owner and said they would provide and install hot water boilers for free in exchange for monitoring them for fuel consumption/etc. There were 3- 500,000 btu boilers installed(only 1 was left working.) and the house was freezing so I calculated the house and came up with only needing 1-165,000 btu unit. I couldnt figure out why the house was cold until I realized that there was a basement loop that would have worked fine with steam but it was path of least resistance for the HW. They were running 1,500,000 btu of HW heating for 30 years and barely getting anything out of it. I re-piped it. The house was toasty warm in no time.

Bigger is not better, Right is better. Too big or too small and you will be wasting money or be Hot/cold.

Most older homes used HW or steam to heat. What was originally there? My grandparents have a huge farmhouse built in the 1850's It is HW radiators and baseboard with no AC(with the exception of the addition)
What is the insulation situation with your house? 1 story/2 story? attic/basement?

I would look up the sound information on the proposed Mitsu's just to make sure they are something you can sleep through. Most are quiet nowadays.

The first two contractors only looked at the existing unit and sized their recommendation on that alone. The third counted all the registers and noted their size and told me they liked to get the airflow correct.

That’s a crazy story about that HW system!

[George Yetka]

The first two contractors only looked at the existing unit and sized their recommendation on that alone. The third counted all the registers and noted their size and told me they liked to get the airflow correct.

That’s a crazy story about that HW system!

Even though he was down to the last boiler he was paying 600 a month in gas for basically no heat. Forgot to mention He received 8,000 for each existing boiler and 1000 for the water heater from insurance because Irene flooded basement.

[Jim Becker]

The third counted all the registers and noted their size and told me they liked to get the airflow correct.



This is the correct approach and the reason I use the HVAC firm I do. They consider what's required for "even comfort" throughout the home and engineer the solution accordingly. That approach sometimes takes a little more time, but invariably, it results in much higher satisfaction with the resultant system. HVAC resources that merely look at what exists and assume it's correct are falling short and just selling on price, IMHO.

[Jack Frederick]

The reason, one of the reasons, I bring up the ductwork is taht if it is done poorly, as it was in my home, with the technology in the mini-splits you can remove the duct work and replace with mini splits. I did that and netted out two good sized closets and storage under the stairway. As well the building is zoned. I have a dual for the upstairs bedrooms and two very high seer singles downstairs. With the solar system I installed last year we are H&C for zero dollars. I burn some propane for my Rinnai wall furnace on one side of the house. As to the central units, I’ve been out of that end of the business long enough now to be shy of suggesting one or the other. A fellow I know and respect likes the multistage Carriers. From a comfort standpoint, you want at least two stage. I would not hesitate to use a mini in your shop or the house, IF you have the contractor train you in how to remove the cover and possibly the blower wheel. From there, have him show you how to clean the coil and the blower wheel. It isn’t hard. It is a pitn. This assumes you have duct collection. Minis have the front facing filters that are easy to clean, but you can about throw the cat through them. When you look at the wall evap for minis you see the face of the coil, but at least 40% of the coil surface runs over the top and down the back. Out of sight is not out of mind;) Don’t tuck the unit so high that you cannot get at it. They allow you to be within 2” of the ceiling but cleaning one of those is tough. I represented Fujitsu in the six New England States for 14 years and find them to be everything that Mitsubishi is.

[Malcolm Schweizer]

Thanks for all the info folks. I was hoping to see the third estimate today, it’s the one with the Mitsubishi stuff.

Malcolm, I’ve worked in a bunch of historic homes with mini splits in different zones. It’s an awesome set up for a house like that.

Hopefully I’ll have another estimate tomorrow!

wow. I called the ac guy today to discuss the quote and it turns out it’s not two options- it’s one downstairs, one up. So- it’s not the $15k to 18k I thought it was- it’s $15k up, $18k down. 4500 square feet with 12’ ceilings. I’m getting a second quote now. I was budgeting $20-25k. Might have to up my budget.

[Adam Herman]

we had a 3 head Mitsubishi hyper heat unit in the last house, and it was great. the variable speed fan on the outside unit was nearly silent, and very smooth. the indoor units noise was just the "rush" of air blowing. nothing more. i plan on putting in another one in the new place.

[Alan Rutherford]

It's important to get the right size system and bigger is not better than big enough. It's worse. Look into "Manual J".

"Manual J is the protocol used for determining the amount of heating and cooling that a home requires to keep its occupants warm in the heating months and cool and dry in the cooling months. ... Your HVAC tech should use the latest software to aid in a Manual J calculation..."

A manual J calculation considers the volume of the house, area of walls and windows and the direction they are facing, quality of the insulation, where the house is geographically and more. It takes time to gather the information, which is why many companies won't do it or will fake it. There are a few free online systems for DIY Manual J. I used https://www.loadcalc.net/.

My original system was 2 1/2 tons and I had estimates for systems from 2 1/2 to 3 1/2 tons. I ran the numbers and thought 2 tons was enough. I had to sign a waiver to get the guy to install it instead of the 2 1/2 he recommended. It's been 5 years since it was installed and I was clearly right.

As for which brand: I went with American Standard because they are made by Trane and Consumer Reports liked them but the installation is probably more important than the manufacturer.

[Mel Fulks]

Got to be careful choosing a dealer. Worst experience was when we bought from a good company that an uncle of mine had helped start.
They brought in the big compressor and set it . Then they brought in the air handler and it wouldn’t fit….so they swapped it out . Those
two pieces have to match,but they never mentioned that. Less than 2 years out whole system had to be replaced.