Experimenting

Solarventi controls include fan on/off, variable fan speed, and maximum temp.


Max. Temp? That has bothered me slightly since I first read about it. (http://www.solarventi.co.uk/ has some details, UK prices etc., and http://www.solarventi.com/ has .pdf documents and further info.)

In fact, I asked the installer, from solarventi UK, to clarify was the temperature setting the minimum temperature, or the maximum that air should be vented into the property.


Answer: it is the maximum. The setting is intended for summer time, when you don’t want hot air pumped into the house. It cools itself, by blowing the air out (I think?).


It struck me that I would prefer to also have a minimum temperature setting, say 20 degrees.
That would prevent the fan starting until the air captured in the unit has been warmed to at least match the temperature in the house?
I have slightly re-evaluated my point of view. The week and a half since installation I have not been in, or there has been very little hazy sunshine at weekends. The fan makes a little effort in hazy sunshine, and cool air appeared to be pumped into the house. Virtually nothing happened it seemed to me.


Saturday, 31st January 09, with a bright clear morning, and a little time on my hands, I could see what was going on. It seemed at first that cooler air than room temperature was entering through the vent. What should I do? Think.


The outside temperature started that morning about 4 degrees C.
I thought about the controls. How can I get the air temperature I want, and the fresh air I have boasted to the wife about, at the same time, on a cold day like this? The fan was on full speed, as I had left it.
At regular intervals, I experimented with the fan speed, and checked the temperature and humidity in the bathroom, at the vent, and 50cm away from it for an idea of general room temperature.


This was the concept I developed. Number 1. You can't really estimate to what temperature the air will rise. The air actually needs to be drawn through, otherwise you won’t know if the air at the fan has risen enough, nor if it is dry air (low humidity will have the beneficial effect of drying the room).

Number 2. If that's the case, what fan speed? So I slowed the fan speed, and found the air temperature produced at the vent into the bathroom increased. I figured the air has more time to warm in the unit. I was pleased to see the hygrometer (humidity gauge and thermometer) climb to 23.1 degrees C next to the vent, (2 degrees more than room temp) humidity was 58 in the room and gradually over the morning, the vent produced air as low as 41% relative humidity.

So with the fan on full speed I was letting cooler air in, but was it dry? Not as dry as it was by lunch time, when the unit seemed to be delivering on my expectations. By this time I had moved the fan up to half speed, and sacrificed a degree in temp. for what I considered to be loads more volume of dry air pumped in.
The upstairs in the house seemed fresher, but it also had a slight draft, as you would expect.

I am sorry to say lunchtime saw high cloud obscure the sun for the rest of the day.
But lesson learned, I think; when the system is struggling in early morning sun, in January, you will have to put-up with lower temperature air or turn the fan down low.
I have compromised for now and set the fan to just under half speed, for the next few days may be bright, but are forecast to be very cold.