FridgeMate HOWTO

[Pale_Ale]

That was certainly my impression Geoff, that both the FridgeMate and the Adloheat devices were both nothing but a switching device.

In the case of the FridgeMate it's just logic controlled, which works on a series of conditions using the thermostat device as an input parameter.

i.e at a temp setting of 18C with a 15min cycle

IF temp > 19 AND cycle > 15 then SWITCH_ON
ELSE SWITCH_OFF

It doesn't actually regulate the fridge temp as such. It just switches on and off according to variable values.

[rwh]

Thanks heaps Geoff, I'd been wondering what the reason was.

[geoffclifton]

That's right PA, in the end they are just a switch but the fridgmate has a lot of programmable conditions, including use as heat controller.

Better point out here I'm not agreeing that the aldoheat (or any other) hydraulic bulb thermostat does not protect against frequent cycling. Be crazy if they didn't tho. Just as with the delay of the bulb warming back up the switch itself may be a sprung over centre toggle just like a light switch.

Cheers, Geoff.

[OldBugman]

pssstt geoff I'm a refrigeration mechanic.

My point being that you dont NEED a delay on timer. ofcourse it's just one more little nice piece on the control circuit.

[geoffclifton]

My point being that you dont NEED a delay on timer

Hi Bugman.

If the fridges thermostat is not functioning, ie always a closed switch as the fridge is above its designed temp range, then something tells me that you DO need a delay function in the external controller that prevents restart without allowing a decompression rest. I'd appreciate your explanation of why you say you DON'T need the delay on an external controller.

Cheers, Geoff.

[OldBugman]

Geoff,

Because a mechanical thermostat that is used externally will have an inbuilt differential.

eg

compressor runs till it achieves it's setpoint of 12deg, turns off. fridge slowly warms up till fridge temperature gets to 14 deg(2k differential) and the thermostat closes circuit and starts the compressor which then brings it back down to temperature.

The time it takes for the fridge to raise in temperature is the delay.

It is no different to how thermostat within a manufactured fridge works, not all fridges have them mounted on the evaporator plates some measure the space temperature.

If your thermostat is clicking on and off like a telegraph key you have issues.

[geoffclifton]

Thanks Bugman, we ARE on the same track. Your previous message could have been miscontrued as saying you don't need the delay but what you were saying is you don't need the timer as the 'warm back up' time produces the delay. I guess that with the fridgemate it's just a nice bit of extra insurance especially if the probe is measuring cabinet air temp and could change more quickly with an open door than a probe fixed to the evaporator.

Yeah I saw your quip 'radiators are for cars', same deal, different name Most wouldn't know which one is the condensor or evaporator.

From your mechanics point of view what would you suggest is a good minimum decompression time between cycles and are there substancial differences between pumps? ie. some tightly built systems may need a much longer decompression time and some pumps my have big enuff motors to happily cope with warm starts.

Cheers, Geoff.

OT
Just to mention my interest in refrigeration came about with motorhome fridges trying to get maximum cooling frim minimum battery drain. It's amazing how inefficient domestic 240v fridges are compared to well built DC units. Mains power is very cheap and easily availabe compared to battery charging.

[OldBugman]

Geoff,

The longer the compressor stays off the better, but ofcourse your trying to achieve conditions inside the fridge while doing it. Not just cycling is to be avoided but excessive runtime.

Timer- Didnt say it was a bad thing, just a little bit extra in the control.


Motorhomes- Nothing beats the old absorption fridges, which dont use a compressor but actually an electrical elements or gas pilot. But ofcourse they have some draw backs. All really depends whether or not your on the move alot in your campervan.

[afromaiko]

I can confirm that the Fridgemate also has a programmable differential setting. By default it comes set as 3 deg C range, but the instructions recommend 1C for fridge and heating operation.

I have my brew fridge differential set on 1C with a 5 min delay, but I recently set up another Fridgemate for a mate to use with his keg fridge. He had a problem with the fridge coming on too often at low temps (around 2C) so we bumped the differential out a bit (to about 3C range) to stop that happening since temperature control wasn't so critical for his application.

Remember that the kegs/fermenters themselves will hold their temp well for ages, and it's mostly the air inside the fridge that will warm up and trigger it coming on.

[Pale_Ale]

Ok, makes sense, but wouldn't that mean that the differntial acting as a delay would depend on ambient temperature? A room temp of 30 degrees is not at all uncommon in summer and I'm thinking 8 degrees becomes 10 degrees pretty quickly on a day like that.

[OldBugman]

8 will become 10 slower than 3 deg will become 5 deg

[afromaiko]

Ok, makes sense, but wouldn't that mean that the differntial acting as a delay would depend on ambient temperature? A room temp of 30 degrees is not at all uncommon in summer and I'm thinking 8 degrees becomes 10 degrees pretty quickly on a day like that.

Yep, but your kegs/fermenter won't change much in that time. I actually have my Fridgemate probe stuck to the side of the fermenter under some good insulation, and have another digital thermometer probe in the fridge to monitor the air temp inside.

If I'm brewing a lager at say, 10C, the Fridgemate controller with 1C differential (lowest setting) will need to get to 12C before it clicks on. It then cools until the display reads 9C before switching off. I'm pretty sure that if it's been longer that 5 mins (my set comp. delay) since the last time the fridge was on then it will just ignore the delay anyway.

In the meantime, the inside air temp of the fridge may have risen to around 20C, then in the cooling cycle drops down to around 4C. Since I'm measuring the fermenter temp this is of no consequence anyway.

With my mate's keg fridge he's simply measuring the air temp inside, so that's why we set the differential higher. It was susceptible to much more/quicker variations in ambient temperature. Now it's working great, doesn't switch on as much and the kegs are still kept nice & chilled.

[afromaiko]

8 will become 10 slower than 3 deg will become 5 deg

Yep, even on really hot days it takes quite a while for the temp on the lager fermenter to raise from 10 > 12, so no need to be concerned about any compressor delay there.

[Pale_Ale]

That's fair enough, makes sense...I will be going a FridgeMate regardless of features as it is about half the price, quarter the price once you take into account it's heating contorller as well

[geoffclifton]

The fridgemate is a little tighter than that Afro.

With a set point of 10* and a differential of 1* it will cut in at 11.1* and out at 8.9* giving a 2.2* operating range. Bloody good little jigger

Cheers, Geoff.

[afromaiko]

The fridgemate is a little tighter than that Afro.

With a set point of 10* and a differential of 1* it will cut in at 11.1* and out at 8.9* giving a 2.2* operating range. Bloody good little jigger

Cheers, Geoff.

Without having a decimal point on the display to tell precisely on the unit - When set at 10C in cooling mode, as the temp rises it will wait until the display just clicks over 12C before switching on. It then drops until 9C is displayed before switching off. I've just sat out there in the garage and watched it do this cycle, very stimulating.. *yawn*

I wonder if the differential is only on one side of the range depending on whether in heating or cooling mode. (ie: when cooling the differential is only on the higher side of the set temp). My differential is currently set on 1 degree.

[Flippo]

As someone who is tossing up whether to purchase a fridge mate or not, and not being conversant at all with "fridge speak", asking the fridgys amongst us, is the Fridge Mate a good product or not?

[Flippo]

As someone who is tossing up whether to purchase a fridge mate or not, and not being conversant at all with "fridge speak", asking the fridgys amongst us, is the Fridge Mate a good product or not?

[OldBugman]

if you can or have a mate who can wire it up, definatly

[Ross]

As someone who is tossing up whether to purchase a fridge mate or not, and not being conversant at all with "fridge speak", asking the fridgys amongst us, is the Fridge Mate a good product or not?

I'm not a fridgy, but as the guy who sells them, they are great. If you are dissatisfied in anyway, you can return for a full refund.

cheers

Ross
CraftBrewer