ELECTRIC HEATERS

Waipa Post, Volume 44, Issue 3190, 14 June 1932, Page 6

ELECTRIC HEATERS

IN MILKING SHEDS. ADVICE TO DAIRY FARMERS. There are over 2000 electric water heaters in the Thames Valley Power Board's district installed in milking sheds. Recently electric water heaters have come in for criticism from those who compare them with fuel heaters. In a letter to the Mataraata branch of the Farmers' Union the board's chief engineer wrote as follows:—■ " The Power Board engineers do not think that a 600 watt element is suitable for all water heaters. A 600 watt element in a 15 gallon tank, properly lagged, will, 'under normal circumstances, boil one gallon of water per hours from cold. If the period during which the element is working is 20 hours per day, then 20 gallons of boiling water can be obtained per day and no more. If 21 gallons of cold water are added during the day, to replace 21 gallons drawn off, then they will not get boiling water. They may on certain days have drawn off 25 gallons of boiling water, because at previous times the full heat capacity of the tank has not been drawn upon, and because the tank has been of such water capacity that the excess heat could be stored in the water. In other words the larger size tank has given the farmer greater flexibility in the use of boiling water. But he must use his storage intelligently. He must still remember that he can get only one gallon of water boiled for each hour the 600 watt element is in service. " It is true that not more than about 13 gallons can be drawn from a 15gallon heater. The remainder of the water is to prevent the element becoming uncovered, and as a consequence burnt out. If more water was not added later, and the element was still'in operation, it woud not be long before sufficient water was evaporated to uncover the element, with the same disastrous result. • " Some farmers state that they do not use nor require more than eight gallons of water at a milking, and that they always have their water boiling when they start milking. This would naturally be expected, but it is quite possible even in this case that the eight gallons of water they used was well below boiling point, due to a wrong use of their cold water feed. If the cold water is allowed to mix with the hot before all the hot water required is taken out of the tank, the later quantities of water will be much colder than that initially taken off. "The question of sterilisation has been raised, and certain authorities in the dairying world have stressed the great importance of this. It is suggested that if boiling water were available in the hot water cylinder when milking is finished, the question of sterilisation would be solved. I would point out that in many sheds the hot water is taken from the hot water must necessarily be colder water much necessarily be colder when it is in the bucket than it was before it left the cylinder. The bucket of hot water is then carried along to the teat cups, and these are placed in the bucket, causing a still further drop in temperature. The piping system, causing still another drop in temperature. Quite often, I understand, the one bucket of water is used for more than one set of teat cups, making the position still worse as far as temperature is concerned. In many cases the temperature of the water, after it has passed through the piping system, is so low that the hands can be held in it without injury.

" If boiling water is a necessity for sterilisation at the beginning of the system it is also a necessity at the end. It would appear therefore that no sterilisation is possible where such methods as above mentioned are used. "In a well lagged cylinder the temperature drop, when the heating element is cut off, is only two to three degrees per hour. We will assume that the water in the cylinder has dropped from 212 degrees F to 200 degrees F during the period the element was cut off, i.e., 12 degrees, which is a large drop. The hands cannot be held in water hotter than about 120 degrees F; so that in passing through the milking system from the hot water' cylinder the temperature has dropped about 80 degrees F, or over 660 per cent, of the drop in the cylinder itself because of the power being cut off. It would appear to be a case of straining at a gnat. "I do not suggest that the water in the cylinder should not be as hot as it is possible to get it, but I do say that the present system, even if the water in the cylinder was boiling, that only a fractional part of the trouble has been dealt with. If a sufficient quantity of water was available the temperature at the end of the pipe system could be very considerably higher than 120 degrees F, but it can never reach the initial temperature. "An alternative, if a temperature of 212 degrees F, is absolutely neces-

sary, is to use steam of sufficient temperature that everything is subjected to at least 212 degrees F. It can be done, and is don.?, but it is all a a matter of expense."