split AC Systems

[verizonbear]

In my never ending journey to find a house I did see one midcentury house I liked today at at very attractive price however it did not have central air and had an oil fired boiler, in talking to the realtor she said many people opt for a multi zone split HVAC system. Wonder how well that would work in a northern climate with hot summer and frigid winters.

 

[volvoguy87]

AC

You have several options. You can do a mini-split AC system. This system utilizes a small compressor outside and refrigerant lines to an evaporator inside. Some compressors can serve multiple evaporators. Each evaporator requires 110 volts to run the fan, a condensation drain line, and the refrigerant line connections.

Another option is window units.

You can install a forced air system, but the ductwork is large and there are significant inefficiencies inherent in forced air HVAC. Personally, I hate forced air with a passion. I find it to be troublesome, poorly performing, incredibly inefficient, messy, and a poor utilization of space.

My favorite system (please bear in mind that I'm a professional historic preservationist and I deal with this a lot) is a fan coil system. To use fan coils for air conditioning, you'll need a chiller. A chiller makes cold water. This cold water is then pumped through the building via insulated pipes, just like in a hot water heating system. In each space you want air conditioning, you have a fan coil. A fan coil is like a car radiator with a fan on it. The cold water goes in one port, the fan blows the room air through the coil, and the warmed water leaves the coil from the other port to be returned to the chiller. Fan coils come in a variety of shapes, sizes, and orientations and are easily hidden.

Each fan coil needs a cold water supply connection, a warmed water return connection, a condensation drain line, and power to run the fan. Fan coils can be individually controlled, zoned, or controlled by a central thermostat. Since you can zone fan coils to your heart's content with only 1 chiller, you can save significantly on operating costs since you can cool as much or as little as you want whenever you want. Since fan coils require no ductwork, you don't have to tear out plaster, build chases, or deal with temperature loss or gain through ductwork. In fact, you can snake flexible supply pipes through the walls in a minimally-destructive pattern. A fan coil system isn't exactly cheap, but they are easily integrated into existing construction and tend to perform very well. Sadly, most residential HVAC is done via forced air because it's relatively cheap to install, particularly in new construction. Although it's cheap to install, it tends to be the least efficient and worst performing type of system.

I like radiators for heat because a radiator system has very few moving parts and is dead silent when properly functioning. Although you can heat with fan coils, I always recommend retaining radiators.

Is the oil-fired boiler for hot water heat, or steam? I love them both, but especially steam. Since the boiler is oil fired, you can burn bio-fuel or a bio-fuel blend to save money. Be careful, however, because many home heating oil burners and associated components may need new gaskets and seals if running high concentrations of biodiesel because biodiesel is a solvent. Some, but not all, seal materials are susceptible to being dissolved or weakened by high concentrations of biodiesel.

For more information, check out the link below. The website's owner has written some very good books on the subject of heating, particularly with vintage systems. And yes, it is not only possible to get top notch performance and efficiency out of vintage systems, it's relatively easy and highly recommended!

Clear as mud?
Dave

http://www.heatinghelp.com

 

[hydralique]

There is absolutely nothing to be afraid of in a properly sized and installed split HVAC system. All the word “split” means is that the condenser (with the compressor) and the evaporator are not contained in one box – the condenser is outside, usually on a concrete pad next to the house, and the evaporator is somewhere in the house in a sheetmetal box that also contains the blower. Often this is part of a gas fired forced air system, but it can also be all electric. The alternative to a split system is a package unit, which is one sheetmetal box designed to be mounted outdoors and which houses the condenser coil, evaporator coil, compressor, fan motors, and possibly a gas heater too. Package units are primarily used for commercial lease space jobs where they can be economically mounted on flat roofs and connected to a duct system located right below the unit. When a commercial tenant changes and the lease space is reconfigured it’s easy to change out the package unit for a smaller or larger one to suit the new tenant’s needs. They can also be mounted on a regular pitched house roof and connected to ductwork in the attic but it’s really not a good idea for several reasons: the package unit must be craned into place and then mounted on a special stand to accommodate the pitched roof, roof leaks are common due to trying to flash and seal the large openings required for the ducting, and any servicing must be done from the roof. Flat commercial roofing is designed to be walked on for building maintenance but residential shingles really are not and can be easily damaged by servicemen dragging Freon, fan motors, compressors, etc across the roof. Hence the superiority of the split system for residential use. 

Zoning may be done in two primary ways; the classic way is to provide two or more independent systems, each with its own ductwork, heater and condensing unit. They are connected to separate thermostats in their respective parts of the house. Sometimes there isn’t space in the attic or HVAC closets for enough systems to adequately zone a house with several different exposures, in which case a computer driven automatic damper system can be used. This is a special plenum with motorized dampers that is connected to one evaporator coil but feeds into separate supply ducting. Each set of ducts has its own thermostat but it’s all modulated by the computer system. For instance, on a sunny mid-morning during the spring or fall a second-story bedroom wing with an unprotected southern exposure might need some cooling by 9:00, while a downstairs den with a protected northern exposure might still be chilly. Once the downstairs thermostat has shut the heater off because the den is satisfied the system will keep the blower on for a couple of minutes to exhaust the hot air in the blower and plenum. It will then change the damper position to direct the blower output into the bedroom wing and turn on the condensing unit to provide cool air. Once the bedroom wing is satisfied it will again exhaust the cool air and then shut down or if heat is needed in the den crank up the heater. In the summer you might have situation where both the den and bedrooms will call for cooling, but the bedrooms need much more. In that case the system might switch both the house blower and condensing unit into high speed and supply cool air to all ducts, but once the den is satisfied it will drop everything back to low speed and continue to supply just the bedroom with cool air. These dampers aren’t cheap but they work really well. I’ve designed a few houses with combinations of spaces and exposures that just can’t be addressed with only two zones, but by using one simple zone (no damper system) and one system with the damper you can have four zones as the dampers usually can accommodate up to three zones per system. 

I would not recommend a chiller system for a normal house. They are expensive and complex due to the need for pumps, piping, and heat exchangers in addition to normal ducting, fans and compressors, the availability of fan coil units in small sizes can be a problem given that they’re mostly made for commercial applications, and most residential HVAC installers and maintenance people don’t deal with them. Some years ago I worked on a large (12,000 sq. ft.) house with a very nice chiller system. It was all high-end commercial grade equipment but the homeowner had endured years of trying to find someone to maintain it who could get the system balanced correctly and was willing to deal with a very picky owner - commercial HVAC guys often do not like to deal with homes full of delicate finishes and furniture.

 

[combo52]

HEATING & COOLING HOMES

Steam and hot water systems are the most expensive to operate and least flexible at adapting to the frequent temperature swings that we often see here in Maryland. I would not ever want to use oil [ or propane ] for my only source of heat, it is just too expensive and oil is dirty and needs more maintenance and is just not in the national interest.

 

By far the best system for a house like you are describing is a standard forced air heating and cooling system. If natural gas is not available Install an 18 seer heat-pump and maybe leave the oil HW heating system as backup if it is in good condition. A good friend of mine here in Maryland just had two 18 SEER York split system HPs in stalled in his 1965 home. He opted to leave the oil HW heating system as backup, he is also a Verizon man.

 

Mini Split systems are sometimes  good for hard to cool areas of a home or additions etc. But I would not invest in one to cool the whole house if a forced air system can be installed. The main problem with these systems is that they are not that much cheaper and the life of them may be 15 or 20 years at best at which point your whole investment will have to be replaced. Generally they are difficult to get repaired [ and very expensive ] parts are a major problem as there is little standardization to 90% of the parts used.

 

[jamiel]

I'm not sure that the comments here are completely helpful. A boiler with a split-system AC is a very nice combination which has lots of benefits and minimal drawbacks. Boiler/hydronic is a nice even heat system (gas or oil---depends on custom in your area...neither is definitively bad) which can be very quiet (virtually silent) which is a big plus. Split system AC rather than window units are a much better solution...small unit outside, linked to an inside unit(s)(often high-mounted, to provide better convective cooling) which allows great zoning and individualized comfort, with minimal aesthetic impact. I had a MCM house in Chicago built with forced air gas in which the owner ripped out the furnace and installed a hydronic system with baseboard convectors. The utility closet (house on a crawl) was in the bathroom (actually a great design---louvered door into the utility closet meant that there were never bathroom odors). The boiler was nearly silent---you couldn't hear the circulating pump, so you just heard the "whoosh" of ignition, then never heard anything else. That house had a big window unit in the living room, but I considered installing a split AC system (but ended up moving)

In other words, nothing in what you've said should necessarily disqualify the house...I'd love to have a boiler again!

 

[verizonbear]

Thanks for the feedback

Thanks to all for the feedback. The house is approx 1000 square feet 2bed/1bath , the oil boiler is original to the house built in 1953 and is the primary hot water supply too. If I plan to move forward with the purchase I would look at a 4 zone split system. There is no air handler present and the interior does not lend itself for a ducting retro fit. I think split HVAC is the way to go. I plan to keep the oil boiler primarily for hot water and eventually pull it out and replace it with an electic heat pump water heater, unable to determine if there is a gas line to the house.

The exterior of the house is stone, I plan to max out the ceiling isulation, the windows are original to the house single pane wood frame in good condition and will change those out within the first year. The kitchen is all electric and will require a complete renovation, sadly no vintage appliances present.

 

[toggleswitch]

Why go to electric if you have gas and/or furl-oil already?

In most parts of the country electricity, even when steeply discounted, costs more.

Electricity usually still comes from fossil fuels and only about 30% of the total energy in those fuels reaches the home as power when converted to electricity. Therefore, electricity for heating (resistance heating) is about 3x more costly than fossil fuels used directly.

If nothing else, a split system mounted near the ceiling (great for cooling) will not bring the level of comfort during heating season radiators or convector or even vents will that are close to the floor.

 

[yogitunes]

CountryGuy/Gary has these split systems in his house.......he really likes them.....lets see if he will chime in

 

[dj-gabriele]

Split systems are the most common air conditioning system in Italy in both residential and small commercial applications.

I can speak for myself having them installed since the early 90s. Right this year we changed the machines in the bedrooms. Instead of having three monosplit machines we put a single one on the roof connected to three indoor units.
The machine is inverter based so it can vary the heating and cooling output from 600 W to 7000 W, according to how many indoor units are on and how cold/hot we want.

The efficiency is fairly high with a EER of 4 and a COP of 4,2. Plus it has the advantage of having zero visual impact as the compressor is mounted on the roof.

The indoor units are virtually silent, even at night when there aren't other noises, I think the noise level is 25 db or something. You only hear the air flow when in "turbo" mode where the fan is at highest speed and so is the compressor.
Thermal comfort is great, in both heating and cooling but in heating you have to pay attention at having the unit well calibrated otherwise if it is too powerful for the room it is in, you'll have more temperature swing. For cooling there is the risk of leaving air that is too humid. The problem is way lessened with inverter units as they modulate the power.

Our new machine is guaranteed working in the -10°C to 43°C temperature range so heating in winter is not a problem as where we live temperature seldom gets under zero °C, just 4-5 times a year. Here in Bologna on the other hand, on the coldest days of December it went down to -15° for a couple of week so the air conditioner alone wouldn't have been enough. Well, unless we were to install a machine able to work up to -18°C!

 

[countryguy]

I have the split A/C system but it is strictly for cooling.  Two years ago when I wanted to get rid of my wood stove and electric baseboards I investigated installing forced air so that I could have central air but unfortunately it was not possible to do based on where my utility room is located, direction of the joists, etc.  I also live where natural gas is not available so my choice for fuel is either propane, oil or electric.  I opted to go with propane and installed a hot water boiler with radiant baseboards which just replaced the electric baseboards.  The system works great, the temperature is even and the humidity level in my house has gone way down so that no longer do I need to operate a de-humidifier (yes dehumidifer!) in the winter.  The split A/C works great in the summer.  I have the air handler unit installed in the bedroom because I wanted it to be cool to sleep - I can tolerate humidity/heat when I am awake but the unit is large enough that it keeps the rest of the house cool also.  I just have a fan in the hallway which blows the cool air towards the living room.  

 

Gary

 

[verizonbear]

Toggle I am looking at it from a tax incentive and resale standpoint. The house has been untouched technologically wise since it was built in 1953. There is natural gas avaialable in the nieghborhood, this particular house likely does not have gas lines.

I will likely keep the oil fired boiled as a heating back up and for hot water, it will only be me and a 250lb Mastiff living there so I easily control hot water usage and the dishwasher and FL washer have on demand heaters so I can keep the temp lowered. The only draw back is the distinctive oil smell and the heat/cool loss from the flue damper

 

[yogitunes]

Also check with local contractors and the GAS company.......many rebates and incentives may be available........

When I bought my first house, the Gas company financed everything, super low interest, I only had gas piped to the house, not inside, but I got all new piping inside, a new hotwater heater, and my oil-fired boiler was replaced with a new gas one, plus got my stove and dryer hooked up, and opted for window units for cooling....

with all the rebates....I got the A/C's and the hotwater heater for free, basically!.....This was 1983, but my cost was around $1800.00 for everything...

worth a shot!

 

[kimball455]

Mini Split

The remodel replaced all of the window AC units and the antique large grate warm air heater witn mini splits giving me 4 AC zones. That is great when you only want a small part of the house cooled. During the summer season there are many days that you only need AC in the sleeping rooms not just to cool but because of noise. I live in Cape May, a tourist mecca and during season it can be rather noisy. Heating is a mod con boiler and baseboard. Three heating zones. Hot water is indirect from the mod con. All of this works quite well.
Harry

 

[petek]

We also have gas baseboard hot water heating which I greatly prefer to gas forced air. It's extremely quiet and every room is evenly heated with none of the temperature swings you get with forced air (which I grew up with and had in previous houses) . Our boiler is original to this house circa 1958 and works great. Our house is a 4 level split with approx 18 ft cathedral ceiling over the livingroom/dining/kitchen, only a 9ft half wall separates the kitchen from the living and diningroom. I had the original Mitsubishi mini-split replaced last year (it was 20 years old) and had a new Mitsubishi mounted in the same spot which is directly overtop of the stairwell up to the bedrooms, near the cathedral ceilings peak. It broadcasts cool air over the entire floor and also down the other two stairwells that lead to the groundfloor family/laundryroom. It doesn't cool the upstairs though which is probably why I should have gone with a 2 zone unit. That being said this unit is amazing. It is extremely quiet inside and outside. In fact I can guarantee that you could place the oustide condensor on your patio, place your lawnchair right beside it, sit drinks on it and you absolutely could not hear it running. Honestly it is that quiet and I have good hearing, less than a desk fan running on low speed.

That being said if you have traditional height ceilings/walls/rooms you aren't going to get cool air circulating between the rooms as well and may need to use a fan here or there

The one I have is a two ton unit with a variable compressor. It operates as low as 4800 BTU up to approx 24,000 as required.

I had 3 estimates of the different brands, Mitsu, LG and Lennox. The Mitsubishi was the most expensive but came with the best warranty 10 years on the compressor. The Lennox only had one year which is odd,, the LG I think had 5. Also iirc the LG's fans for the indoor evaporator units used 24 volt..so that might make a difference install wise.

Didn't want the heating/cooling/heat pump model either..the more complicated the more prone to breakage in my book.

Plan is I'm going to get a second unit for the upstairs bedrooms floor eventually and more than likely the condsor for it will be sitting on the patio below which is fine, it's that quiet. For now I have two portable a/c's up there that only get turned on about 1/2 hr before bed, otherwise we're not up there much anyways during the day so cooling that floor isn't really a priority.

Our neighbors across the road have the same old boiler we have and a 4 level split without the cathedral ceilings,,they had an all in one/condensor/evaporator unit installed in a large upstairs hall closet, there's no outside unit, and had it ducted to the various rooms. They've had a couple of ceiling leaks though but overall it works fine. Somehow the condensate trickled along the ducts or something.