Space Heater ducting

[printcom]

This one might be off the beaten track a bit, but as we have a few cleaver chaps on here I thought I would ask. I have a large indirect space heater (Arcotherm EC85) which I use to heat a 15m x 20m barn that me and the missus use to train dogs. Problem is that it is too noisy and the dogs don’t like the blast of warm air coming out of the two 300mm vents. Does anyone know what is the best way to increase the ducting length without causing a back pressure issue. At the moment I am using a I meter 400mm piece of insulated ducting going in to a y piece and two 300mm insulated lengths totaling 7 meters going in to two diffusers. I need to move the heater further away from the barn which means increasing the ducting length and adding an additional 2 diffusers. The best idea I have come up with is to add a fan to suck the airflow through at the diffusers but that may be self-defeating as I am trying to cut the air flow down to the individual diffusers without causing back pressure. Plus there’s the cost of 4 x 300 mm fans and the associated noise.

Any ideas?

 

[captain-destructo]

do the diffusers restrict the airflow?
if they do why not do aaway with them and just use 400mm ducting and add ceiling fans to circulate the heat around the barn in the winter and cool things in the summer

 

[Gareth J]

To know for sure will be rediculously complex. Things you'd need to know to make a start;
-Fan curve
-motor power and performance
-resitance vs flow curve for the diffusers
-likewise for the pipe

Not to mention a hefty CFD program to plug it all in to.

Very vague advice? If the motor's chunky, the flow rate not huge and you keep the ducting as big or bigger than the current setup, you'll probably be fine. I'd try extending the current setup and test it. If performance is seriously reduced, add more diffusers. The other reason not to worry too much is that by restricting the airflow, you'll make the air hotter - the machine will still add more or less the same energy to the room over a given time.

Good luck!

 

[Rig Pig]

It will not be very efficient if you don't return the warm air from the building to the heater - more insulated ductwork!

 

[brightspark]

u will find warmair unit air intakes are at the base of heater and blow hot air out of the top so only pull in the cold air from below

 

[Rig Pig]

The op sounds like he is putting it outside the barn - hence the suggestion of feeding it air from the barn.

 

[Gareth J]

It will not be very efficient if you don't return the warm air from the building to the heater - more insulated ductwork!

Good point.

 

[CompoSimmonite]

What about infrared heaters instead - they heat solid objects rather than the air. Use existing space heater to bring building up to temp and then infrared when working with dogs in there. You can get diesel, lpg or electric versions.

 

[printcom]

Thanks for all the input chaps.
The barn I use for the dog training is a part of a larger barn which is separated by a stud wall, I am trying to find a way of moving the heater further away (to reduce noise) and decreasing the air velocity without the heaters internal thermal cutout tripping. Every time I increase the length of ducting (even with 400mm stuff) the heaters temperature cutout trips. I am guessing this is caused by too much air friction causing back pressure which in turn causes the temperature inside the heater to climb. As for using infrared heaters, I have got 6 1.5kw infrared heaters hanging on the wall and they are a waste of space. You have got to bear in mind that a field is almost as thermally efficient as this barn and besides there is a big difference in output between 9KW infrared and 85KW space heater. The shear cost of insulating this barn would heat it for about 10 years +
Methinks Er Indoors might just have to put up with what shes got, it don't look like the answer is going to be easy or cheap.
Mind you my Mali's don't care about the noise or air blast just her namby pamby collies