Hi Evan
I have spent probably over a year analysing my cellar data and looking at cooling options.
Cellar: Underground, 20 square meters, 45 cubic meters. Insulated, vapur barrier and door seals.
I have finally decided on installing a split system (cooling only) in the stairwell of my cellar.
I currently use a Winland DPM-4 to monitor the cellar conditions, which has zone relay outputs. I will use the temperature zone to turn on the air conditioner (I will implement a 1 hour delay for hysterysis). The air conditioner has auto restart capability.
In Winter the cellar naturally goes down to 16 degC, in the height of summer it gets up to 22 degC. Daily temperature variation is within 1 degC, but it does get too warm in the summer months.
The installation of the split system will act to clip off the summer highs, and I should easily be able to control the cellar between 16-18 degC through the year. This is just a reasonable guess at this stage, but I may be able to do even better.
I will set the high trip at 17 degC. Once the temperature in the cellar is above this setpoint for 1 hour, the air conditioner will turn on and drag the temperature back down to desired levels. In the hour I don't expect the temperature to rise to 18 degC so this should maintain a tight control.
Cost was definately a factor in this decision, in terms of up front costs and also fixed costs throughout its life. The cost of the initial purchase will be less than half of that of a dedicated cellar cooler. Fixed costs (electricity) will be a lot better than if I were trying to keep the cellar below 15 degC year round.
The humidity currently sits higher than 70%. I only expect the cooler to bring it down say 20%, but this does depend on the duty cycle. A can increase humidty the old fashion way, or, can cheaply purchase a good humidifier if necessary.
The residential split system will also look nicer and will not be as noisy as well.
As I said, the above description of control is an initial reasonable guess, and I'm hoping to do a little better.