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doggydoggen
02-06-2015, 09:17 PM
Hello
My first post here..=)
I have a question for you experts.

I have a vitrifrigo C41 cooler with a BD35f compressor (31w compressor)
i want to "Turbo charge it" to make it freeze better
Google around and i found out that the compressor have several rpm range 2000, 2500, 3000 and 3500 and that it is possible to change the rpm by change a resistor to make the rpm to go up?, is this possible to do?
i think the larger vitrifrigo C65 ho has 45w compressor has the same BD35F but have higher rpm settings?
here are some spec about the rpm i talk about.

http://www.novakool.com/support/bd35f_compressor_data.pdf

and im from Sweden so my english is a bit rusty im afraid, but i hope you understand what im writing..=))

/Doger

Brian_UK
02-06-2015, 10:25 PM
Which controller do you have for the compressor?

Yes, it is done with a resistor but it depends on the controller model

doggydoggen
02-06-2015, 11:27 PM
Im not sure what you mean?, but the controller is a 5 digit led controller/thermostat?
is this what you mean?, the fridge have a option with a digital controller, but i dont know if it is possible to buy that one and instal it?

and for Decisions, i think you should go for the fishing..=)

doggydoggen
03-06-2015, 01:49 AM
it seams like i could buy this board?

http://www.go2marine.com/product/384640F/frigoboat-speed-control-board-for-danfoss-bd35f-bd50f-compressors-with-12-24-volt-switch.html

mikeref
03-06-2015, 08:46 AM
BD35F is a variable speed compressor with the module attached to the side.
I don't advise buying that 38 Dollar module.:(

The picture you posted shows a module for $200. ( You get what you pay for.)
With no resister in the control circuit, the compressor will run at 2000 RPM. A 1.6K ohm Resister (From memory) will bring the RPM up to 3500 RPM.
Raising the speed can cause a series of problems.

doggydoggen
03-06-2015, 12:58 PM
Hello mikeref

I have no problem to understand, but writing can be difficult..:)
i think the compressor is set with lowest 2000 rpm and i want to try to set it to 2500 rpm
what kind of problem do you think can happend?
the 38 dollar module are a simple variable resistor, maby better and cheaper to fit a 300 ohm resistor?, but i dont want to ruin the compressor ofcourse

xxargs
03-06-2015, 02:02 PM
Also from Sweden and english is not so good ;-)

Many of this type of box have automatic adjustning RPM depend temperature inside boxes, ie. if setting on freezer temperature - compressor going to maximum RPM first after inside cabinet going under -5 - -10 degree C.

You seems have more advanced controller compare to mine on Waeco CDF18-box, but even if using simple analogue controller on my WAECO, is still adjusting compressor RPM up and down after inside temperature as well.

---

Cooling capacity (in Watt measured) is almost fixed by length of capillary line inside box and is waste of effort and energy if compressor running maximum RPM if inside cabinet is still over 0 degree C.

ie. - not more liquid refrigerant going trough capillary line even compressor running maximum, is only emptying out evaporator more of refrigerant vapour and low pressure make cold spot around outlet from capillary line, capacity not increase, more likely decrease depend smaller (but cooler) usable area on evaporator, higher pressure difference between high and low side and pumping capacity per rev on compressor going down and COP going low.

If above 0 degree C in cabinet and if compress forces to running in full RPM, sucking capacity is overzised compare to liquid refrigerant flow in capillary...

But if cabinet temperature are -18 degree C, is different - depend of low temperature, density of vapor is low in evaporator and compressor needs have high sucking capacity with high RPM to make enough liquid refrigerant in condenser to feed capillary enough with liquid refrigerant with not so much flash-gas.
In this situation, compressor working almost undersized even if running in maximum RPM

doggydoggen
03-06-2015, 02:22 PM
Hello XXargs
We have talked before on the swedis heatpump forum..=)
anyway, it seams like i should forget this task and live with the excisting cooling power of my freezer..=)
but one thing, the cooler is rated at 31w and this seams to be the lowest settings of 2000rpm on the bd35f, then if the cooler has had variable rpm, then the rating of 31w watt should be higher?
or am i thinking wrong?

mikeref
04-06-2015, 10:11 AM
The BD35 is a variable speed so that it can be used in various sized portable coolers/ Freezers and a combination of both...up to certain volume. Your Compressor is set at that speed for efficiency.