No. of temperature sensors required in cold storage?

[dipankarmohanty]

Hi:

I'm really interested in the area of sensors in cold storage applications. Currently I'm aiming for food storage, pharmaceuticals storage and the food manufacturing sector.

Just wanted to know::confused:

1. whether there is any calculation for installing the number temperature sensors in a warehouse? e.g. according to volume like say 7 sensors in a 70 cubic feet room or something like that?

2. Does the amount of sensors change according to the application e.g.: do the number of sensors vary in food storage than pharmaceuticals storage or tissue storage etc?

3. can you give me some idea about the life span of these sensors and their price ranges.. Does anyone know about websites that'll give me an idea?

[smpsmp45]

The issue is why you are keen for so many sensors. AS you are aware that when the door is opened up or there is a fresh loading the temp fluctuations could be there giving the wrong indications. All could be interested in knowing the product temp which is critical for any product & not the room temp so as to say.

If you add more sensors you are adding more confusion to the system as on which indications you are going to control the system.

Life span of the sensors as per our experience is almost 5 / 6 years unless the wire breaks or something.

There are lots of manufacturers in India & our experiene is good with almost all of them.

But find out the reason for these many sensors or you could land up in big trouble.

[dipankarmohanty]

smpsmp45, I just gave an example of 7 sensors. So what according to you should be number of temperature sensors in 70 cubic feet. and I'm looking at wireless sensors. So do they have a similar lifespan of 5-6 years? I thought they were like for 10 years.

Are these type of sensors required - humidity sensors, gas sensors and motion sensors in cold storage?

[Samarjit Sen]

Hello Dipankarmohanty,

The best place to locate the sensors in a Cold Room is behing the Evaporator so as to assess the return air temperature. Generally only one sensor is used. But please ensure that they do not touch any part of the Evaporator. They are usually PT 100 type.

At the most you can have another sensor away from the door and away from the air flow of the Evaporator.

There is no calculation as to how many sensors are requied. The sensors are meant to show the temperature of the room.

[dipankarmohanty]

So you are saying a maximum of 2 sensors per 70 cubic feet? I assume those are temperature sensors. But is it required to implement gas, humidity and motion sensors in cold storages?

I'm asking this because some perishable items require certain humidity and gases. In that case is it important to have such sensors installed. Motion sensors because of safety - if someone gets caught inside the room by accident. If so, how many?

[Samarjit Sen]

It is not 2 sensors per 70 ct. What I can understand that you are referring to CA Cold Storage. Here you have sensors for the gas which are provided by the CA System, In case you need to measure the RH, then you need to have a sensor for the Humidity. There is no fixed rule for the number of sensors. If it is an ordinary Cold Room then one sensor for the temperature is good enough. If the room has a humidity to be maintained then either you opt for a seperate sensor for the humidity or you get these electronic controllers from Carel or Dixell which has the sensors to indicate and control the plant as per the Temperature and RH.

To be honest, I do not know as to why you want to install a number of sensors.

[nh3wizard]

In most of our cold storage facility's we use 1 sensor per evaporator to control that unit. There is no set number of sensors per cubic foot or square feet.

[smpsmp45]

Actually 70 CFT room is very very small. We do provide emergency exit indicators , but the concept is different. That is used in large cold stores where in there is a movement of fork trucks etc. I had seen one of the best system & that consists of a fluorescenet thread running all over the cold store so if the person istrapped at any place, the thread is pulled & it gives the signal. That is again helpful in a very large cold store & you cn imagine that person meets with an accident somewhere inside ( like palet falling on him etc. ) & he may not be able to reach a point wherein the normal indicators for trapped persons are provided.But for this walk in cooler of 70 cft size he can just bang on the walls ( & it works - my practical experience). I do not think that providing so many sensors can help in anyway except for the confusion. One more point is that anyway system can not be controlled with so many indicators / sensors.

[SteveDixey]

Air on to coolers at least. Plus say two general air temperature probes for a store of say 60 metres x 30 metres square and 6 stows high.

However, it depends what you are looking to prove or check. Over several days I did some actual measurements of temperature gradients in large cold stores over different heights and distances from evaporators.

Like most things, human factors were nearly always causing problems. You may get product stored that is "warm" affecting an adjacent sensor, air flows blocked by product stows, people leaving doors open constantly and air movement caused by reach trucks. If any sensors "saw" these problems, it triggered alarms and generally made life difficult as QA were always complaining about "high" store temperatures.

The only real check is core temperatures of products, but 10 000 fish blocks are bit difficult to wire up ;)

If you have two or three probes, the best idea might be to average the readings by getting the software to do some sums, (say a four hour and 24 hour average).

Steve

[lana]

Hi there,

I think there is no rule on this one. I mean how many sensors to put in a cold room. If temperature and RH fluctuation is very important around the room then you have to put more than one sensor.

In one of my cold room projects, I put 8 temp. sensors and 6 RH sensors all around the room to see the fluctuations.

If you put more than one sensor then you have to decide which one is your controlling sensor (thermostat). Or you can use the average temp. for this.

Actually, this depends on the designer and the client whether he likes to pay for the cost.

Cheers

[smpsmp45]

Hi lana,

You are on the forum after along time!!!

Did you connect all the sensors in series / parallel or they were independent?