Biomass heat exchanger - what pump size?

[Fat hen]

We had a 80KW heat exchanger (5ftx10ft) fitted up to our 120kw biomass boiler. Positioned in front of the tunnel fan. I trusted the Hetas plumber to select the right gear for the job.

Now Ive tried it and the heat it produces doesnt seem enough. Its not enough to make the boiler work hard and not enough probably to make a difference to the air blown into the tunnel. (previously used a gas space heater). He fitted a Grundfos 15/50 pump which is typical for central heating systems. My feeling is that the pump may not be right and should be more powerful to get the heat exch kicking out 80KW. Its a 120 boiler so at 80Kw it should be running at 75% capacity surely, ie working hard.

Any suggestions on this most welcome

 

[Bruce Almighty]

Apart from the pump, what size pipe are you using ?

 

[Fat hen]

Pretty wide 1"

 

[Bruce Almighty]

2" or 3" would be better
Sorry I have no answers but these are some of the issues I am trying to work out before we set up a similar set up

 

[Fat hen]

The pipes they attach to on the exchanger are 1" too.

 

[sjt01]

Can you measure water temperature in and out of the heat exchanger, and air temp in and out, to give you some idea of performance. If water temp out is only just less than water in, then you are not getting enough airflow. If water temp out is only just greater than air temperature out you are not getting enough water flow.
Have you got a spec sheet for the heat exchanger? Check the design flow rate for the unit, then check the pump spec.
Is the pump on its max setting? Is there an airlock in the pipework? There should be automatic air vents at the high points on the pipework, are they working OK? Is the pump running in the wrong direction?
Lots of possibilities!
Stephen

 

[Turra farmer]

Don't put fan to close to exchanger or you will pull a cold spot in it very quickly

 

[Fat hen]

Ok thanks stephen I'll look into this.

Pump is on top setting. There is a pipe vent. Water temp in and out is shown on buffer tank for the whole system. Had it running overnight do should have cleared the last airlock by now