Evaporative cooling question

Hi, got a question regarding the discharge of water from an evaporative system.
Are they supposed to constantly release water during operation? This evening while the unit, a brivis, had been running for around 4 hours I noticed a slight burning smell coming through the ducts. With the unit still on, I grabbed my ladder and torch and investigated. The house gutter which the evap water discharge pipe goes to, was bone dry. No sign that any water had been in that gutter at all over the last 4 hours. Is it normal to have no water discharging from a unit that's been running for 4 hours?
Here's some history on the unit.
Unit installed around 4 years ago, on the day of installation when they wrapped up they told us there was something wrong with the pump and that another guy would come later that day to replace it. Which he did, however I thought why would a new unit need a pump replaced? Over the following 4 years, the unit was constantly discharging water during operation, we could hear it dripping down the down pipe all the time. Around a month ago, the unit crapped itself and brivis repaired it under warranty, and now, here we are.
Any advice, tips greatly appreciated. Thanks

Edit: after posting here last night, and the evap being off for approx an hour, I heard the unit doing something and went outside to the downpipe and could hear water coming down it.

Older units would constantly discharge water but newer ones have a valve that will retain the water in the sump. Most will be programmed to dump the water at intervals.A four year old system should not discharge water constantly, only water escaping may be a bit of spray off the pads or a slight leak at the dump valve, if its constantly dripping lots of water it needs a service.