Best Way to Add Independent Heat for 2nd Floor Unit in Duplex with Steam Heat?

[Joseph Kirk]

Hey everyone, I own a duplex in South Jersey (2-bed downstairs, 1-bed upstairs) with a steam heat system and could use some feedback from others who’ve dealt with similar setups.

The whole house is heated by a single steam boiler with one thermostat on the 1st floor. Upstairs has radiators but no thermostat or heat control, and the boiler can’t be zoned (steam, not hot water). I also have two gas meters, but the boiler is only tied to one.

My Plan:

• Leave 1st floor on the existing steam heat

• Install a ductless mini-split system for the 2nd floor (for independent heat + A/C)

• Shut off upstairs radiators

• Run mini-split off the upstairs electric meter

• Drain condensate outside via gravity (no pump or basement tie-in)

If I can keep the install under $4K, I’m moving forward.

Looking for advice on:

1. Anyone do this setup — how’s it worked?

2. Recommended mini-split brands for ~700 sq ft?

3. Any install issues to watch out for?

4. Any downside to just shutting off the old radiators?

Appreciate any input, lessons learned, or things to avoid!