[Els]

Looking to upgrade new home
Currently have FHW Baseboard oil fired boiler heating the upper level of a raised ranch style home
Would li,e to add a central AC system. How does this work with a boiler instead of a FHA furnace.
Thinking new compressor outside, new duct and registers in attic feeding down from ceiling. But what do I need to fan force the air
Are there prepackaged systems
Where would I look
Thanks
Els

 

[SeniorSitizen]

A/C units have been installed in attics since the 1950s and has been acceptable. Try searching for HVAC attic installs.

 

[Els]

Thank you

Nice pic
Will look up attic install

 

[DOUG1111]

A/C units have been installed in attics since the 1950s and has been acceptable. Try searching for HVAC attic installs.

Good work!! Looks pretty!!

 

[roughneck]

Ducts installed in an unconditioned attic space that aren't used with space heating can often sweat and drop out of the ceiling registers. This will not be an issue if the ducts are used for both heating and cooling.
If you wanted to keep the boiler, you could always do a hydronic coil for heat. Maybe even do a hydronic hybrid heat pump, with the boiler serving as back up heat.

 

[user_12345a]

Leave the radiant heat for heating, put separate system for a/c.

The radiant heat is far more comfortable and efficient than attic forced air with ceiling registers.

Not fond of ducts or equipment in the unconditioned space; would have far lower cooling bills with mini-split heat pump system. The mini-splits could almost eliminate the need for burning oil.

Modern mini-split heatpumps can heat decently at very low outdoor temperatures. Most "central air" style heatpumps are lousy for heating at low temps unless grossly oversized for cooling, fall back on electric backup which offsets the savings compared to burning fossil fuel.

Putting ductwork into the attic originated in the US from the "cheap energy", era - now there are better alternatives. Ducted residential central a/c pretty much is a post-war north american thing; most of the world that has a/c uses minisplits, they have only more recently come to north america.

 

[supers05]

The oil may be cheaper to heat with then a heat pump, even a newer ductless split. It depends on electricity and oil prices. The oil boiler however may not be so efficient, if it's older.

In most cases like yours though, ductless heat pumps are the way to go. You use the boiler when it's cold outside, and the heat pump when it's just a bit cool outside, and for a/c. You'd have to put an inside unit in most rooms however, and may not be practical for your house. (probably will work fine)

Fan/coil unit's would be impractical as a retrofit, so I wouldn't go down that route.

A central a/c with or without a water heating coil would be easiest and likely fairly cheap. (hydronic coil) This is where you use your boiler's hot water to heat the air passing through the unit. (in the attic) They can heat faster than baseboards and still be comfortable but you'll notice the difference. People use this method when they want to recover the floor space of the rads. If you keep the rads, then this is mute.

The main questions to start with are:

1) do you have any a/c at all? I'm guessing not from your post. Would you want this system to cool just the upstairs or the whole place?

2) is this going to be a DIY project, or are you hiring someone?

3) are you keeping/replacing that boiler in the near/medium term?

Cheers!

 

[user_12345a]

The oil may be cheaper to heat with then a heat pump, even a newer ductless split. It depends on electricity and oil prices. The oil boiler however may not be so efficient, if it's older.

The prices will fluctuate over the 15-25 year life of a mini-split system; it doesn't make sense to make a decision based on today's prices.

The heatpump gives an alternative affordable source of heat. At a decent electric rate heatpump running with a cop of 2 to 3 should be competitive with gas and cheaper than oil. But right now oil is artificially cheap.

 

[supers05]

The prices will fluctuate over the 15-25 year life of a mini-split system; it doesn't make sense to make a decision based on today's prices.

The heatpump gives an alternative affordable source of heat. At a decent electric rate heatpump running with a cop of 2 to 3 should be competitive with gas and cheaper than oil. But right now oil is artificially cheap.

It all depends on location. In Ontario, a COP of 3.9 - 4.1 during offpeak/midpeak is required just to beat the current price of NG. On top of that, our electricity rates are loosely tied to the price of wholesale NG for at least the next 20 years. Electricity prices are often even higher for rural locations. Every case just be considered separately, and individually.

Cheers!

 

[user_12345a]

OP is burning oil, presumably no gas available.

But I say it's best to diversify especially when the price of oil has been so volatile over the last 10 years. Also nice of the boiler breaks down.