Conversion from steam to heat pump mini-splits in NYC Co-op

Tferg811

I am working on an evaluation of converting our 7 story 18 unit NYC residential Co-op from gas fired steam to Heat pump mini-splits. Our boiler is reaching end of life and will need to be replaced for next winter. The tenants are attracted by mini-split's individual control, no-banging noise and no window units for AC. I am looking for any successful or unsuccessful examples of conversions and lessons learned.

Steamhead

They won't like how much it costs to run those things in the winter. Plus, some of our customers' mini-splits won't keep their homes above 55 degrees when it gets that cold.

And have you considered the cost of heavying-up the electrical services to the units, to have enough power to run a mini-split?

Have one of our Steam Men replace the boiler and optimize the system. There are plenty in NYC.

mattmia2

Steam won't bang if it is installed and maintained properly...

pecmsg

With minis you will still need a back up source of heat, What will it be?
What are you doing for common areas, hallways, fire escapes, laundry, basement?

KC_Jones

Look up the cleaning procedure for the mini split head, can't ignore maintenance when considering these changes.

For many people the cleaning procedure, either done by residence or paying someone, is a deal breaker.

CantabHeat

Mini split heat pump in the northeast will be like having an anemic forced hot air system. The quality of heat isn’t there in the heart of winter. Not to mention electricity in NYC ain’t cheap!

Get a steam pro to get you a good working steam system.

TAG

I did my first mini to heat a small writers cabin that the previous owner of the property built. I used one of the original hyper heat units -- they were wall/floor units marketed to replace a radiator.

It's worked great for years -- Mid Atlantic. It's perfectly sized for the small space and the condenser sits on the other side (outside) of the wall from the inside unit.

I don't even want to think of the disruption and complexity of trying to retrofit a system into a large building ... start adding up the radiators and put $5k next to them. The potential problems .

tim smith

Pretty complex job to pull off but quite a few of them done here in Northwest. I think the latest Hyperheat units do a great job. NYC of course is a fair amount colder but still not out of the realm of their capabilities. Electrical is always one of the big issues in old buildings. Really hope the main service is already capable of handling it. Makes for a much less costly install. I am a boiler fan but sometimes you have to weigh the pros and cons especially when a/c is in the mix. Cost is really dependent on type of building. Access for piping from roof to units in each apartment. Condensate drainage is always another challenge.
good luck

Jamie Hall

pecmsg said:

With minis you will still need a back up source of heat, What will it be?

What are you doing for common areas, hallways, fire escapes, laundry, basement?

This, combined with the electrical service question, would -- to me -- be a major stumbling block. The problem is that many of the mini-splits and similar units use electrical resistance heat when it gets below a certain temperature (depends on the unit). That's a lot more watts than the running as a heat pump -- and all the units in your building will try to do that at more or less the same time.

Do you have the electrical service to handle that?

If your project were to bring the steam up to speed and use it in the colder months, with the mini-splits in the shoulder seasons, that would at least be reasonable from the engineering and comfort point of view.

That would also have the advantage that you still had the steam for comfort. It may come to pass that regulations will change in such a way that if you get rid of the steam, you may not be able to change your mind a few years down the road...

ethicalpaul

If it makes sense go ahead and install the mini splits for cooling and for heating during spring and fall but keep the steam for the winter

SuperJ

For what it's worth, my office is heated and cooled by a VRF system in Toronto, Canada. It's a cold climate LG system.
It's adequate, and management raves about the savings versus the previous office setup with gas fired rooftop units.

I would say the perimeter comfort is not quite as good mostly due to lack of ductwork with the ceiling cassettes.

My point is that it can work. I have a Mits cold climate wall mount (FH series), that covers the living room, dining, kitchen. It works great, but I have a wood stove that I run when it's truly cold. Not because the HP can't keep up, but because I love the strong radiant heat of the wood stove.

kenjohnson

Mini-split user here in a much colder climate in NY than NYC.

They work and they work fine. The occupants will love them. Make sure to get the HyperHeat (Mitsubishi) or equivalent units that will output rated BTUs to something like 5 deg F or less and near rated output to -17 deg F. They produce a nice warm heat (well above 100 degrees) even at low temperatures, and are quiet, and they air condition also. These units cannot be compared to the crappy carrier, lennox, etc. ducted heat pumps I grew up with 25 years ago that could barely create 75 degree heat when it was 40 degrees outside.

There is no backup resistance heat on these mini-slits - a major selling point, in my opinion, as they can't be accidentally operated in a mode that seems really nice to the user (strong, hot heat) that is costing a lot of money.

The COP for these units is insanely good, even at low outdoor temperatures. Yes, even with NYC electricity prices (where natural gas also probably comes at a premium) I would guess that your overall fuel bills are less with the mini-splits.

Maintenance is nearly zero. Reliability is high. I had a 15,000 BTU Fujitsu in a renovation environment for three years keeping a poorly insulated 1700 square foot house in Central NY heated to 55-60 degrees all the time with a little help from a backup oil furnace (100 gallons or so of usage a year) and I never pulled the filter to clean it - still looked good. OK, if you have house cats, maybe you need to clean the filter. Point is, they are not maintenance burdens.

Jamie Hall

If I were the specifying engineer on those, @kenjohnson , I'd want an ironclad indemnity and rectification clause from the manufacturer, dealer, and installer on both performance and maintenance before my stamp went anywhere near the contract... them's mighty tall claims being made there.

pecmsg

Minis are anything but No / Low maintenance!

pecmsg

Reliability is 99.9 % up to the installing contractor!

Steamhead

A couple winters ago, we had to replace a steam boiler over the holidays. Daytime high was 20° F if we were lucky. The house had those mini-splits, and they could not keep the place warmer than 55° F during that period.

This was enough to keep the pipes from freezing, but I would not want to have them as my only heat source.

SuperJ

I love steam and hydronics, and I agree if the steam system is salvageable it probably is the best option.

But, BTU's are BTU's and if you supply enough the space will be warm. It's possible to do a heat loss and size the equipment appropriately, ensuring it will work.

People have gotten complacent with load calcs and equipment specs, which works against mini splits. The output of mini splits are dependent on outdoor air temperatures which is a complicating factor that many people don't deal with properly.

I do agree that the process to clean high wall mini splits in particular is a pain in the butt. But the frequency of cleaning is overrated, and dependent on climate conditions and the environment. It seams that units in a cooling dominated climate that run continuously for months on end are more prone to getting dirty/mildew.

Personally I would try and select models that have proper filtration, or have the fan in front of the coil where it is not subject to getting wet. This means ducted cassettes, or floor mounted.

I have reservations about large VRF systems, and the implication of any refrigerant leaks. A nick in a line or a small coil could result in a 10's or hundreds of pounds of refrigerant leaking. At least until we move onto refrigerant with less green house gas warming potential. Until that time I would recommend a smaller system per unit, which would make the billing easier too.

SeanBeans

why reinvent the wheel? Fix the steam and live comfortably. Get a NYC steam pro out there like @JohnNY to get your system up and running the way it was designed to

kenjohnson

Jamie Hall said:

If I were the specifying engineer on those, @kenjohnson , I'd want an ironclad indemnity and rectification clause from the manufacturer, dealer, and installer on both performance and maintenance before my stamp went anywhere near the contract... them's mighty tall claims being made there.

Thankfully, when I install something in my home, I can assess performance and make a decision on what to do. I don't need someone to stamp my decisions.

I realize that I am just a simple homeowner with technical capability to assess manufacturer's claims and practical knowledge and experience in this topic - experience that has served me just fine as I have sized and installed a fully-functioning radiant floor heating system (with some excellent help and steerage from members here) and specified two mini-split systems, both that work just fine in colder climates than NY City. One of these systems replaced a natural gas-powered Monitor heater that served me well for 25 years. Those heaters were Japanese-made (as are many mini-splits) and were ubiquitous in Japan many years ago but are now mostly replaced by mini-splits. You don't see many gas heaters in Japan anymore, but you see a lot of mini-splits hanging off buildings. And yes, it is as cold in cities in Japan as it is in NY City.

I am sure that I will be told that I should leave the advice to the pros - fine, I can take those comments. I won't shy from offering counter-opinions when people ask "do these technologies work?" They do work, lots of people use them with no issues whatsoever, and their market share is growing, at the expense of many of the technologies favored by some of those who post unfavorably about them. I am not someone who markets or sells these technologies - I just use them, and they are cheaper to run, cleaner, and easier to maintain than the alternatives.

Am I arguing that we should replace all existing fossil-fuel technologies? No, I am clearly not. Each situation should be examined on a case-by-case basis, but in many cases, the payback of converting from an older fossil-fuel based system to something else is good, and in this posted case, it sounds like the residents would like more personal control over the heat in their units and some better air-conditioning in the summer as well. Whether the economics pencil out is something I can't determine, but the technology is certainly feasible in this case. It sounds like the building super should get a steam-heat pro to state what they can do and evaluate that against other alternatives that will also work.