Generally the things will operate down to zero throughput.

Hi,

Yes; there really is no limit to the turn-diwn;the big question is what type of arrangements you have for the condense side as water hammer can become a problem as the steam flow rate reduces.

Basically you want the condensate to drain freely from the heat exchanger surfaces without water logging occurring as when this happens the incoming steam can react concussively with the water. If you are working into a vacuum then the chances are very good that the surfaces will remain free from stagnant water; whereas if you are using the steam pressure to force the condensate back through the return pipework then waterlogging is virtually guaranteed to happen.

Some installations avoid this occurring by the use of an air admittance valve above the steam inlet which avoids a vacuum developing whilst the condense is taken by gravity to an atmospheric pressure hot well via a simple float trap. This also permits the heat exchanger to remain free of accumulated condensate; with this arrangement you either dump the condensate, gravity drain it back to the boiler or pump it.

Clearly you must plan the position of the steam and condense pipe work carefully to avoid creating a situation which prevents natural clearance of the water.

Hope this helps.