This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1918 edition. Excerpt: ...in reduced fuel bills. The average increased cost for down draft boilers in a $100,000.00 school building will not exceed $300.00 and they pay for themselves in a couple of years' time. Third--Vacuum Apparatus. To be efficient the steam circulation must be accomplished quickly without requiring a high steam pressure on the boiler, in fact, the steam should be circulated at, or near, atmospheric pressure, and only during extremely low temperatures should it be necessary to run the steam pressure up over three or four pounds, where a low pressure vacuum system is installed with a pump. There are a number of efficient vacuum pumps on the market different only in their method of operation. The 'Sparks' automatic steam pump consists of a large tank with a steam connection and a cold water supply, each supply having an automatic valve to open and close the line. This is one of the most economical of pumps and extremely simple in operation. When the vacuum is set for a certain number of pounds and the vacuum drops below this, the reduced vacuum releases the valve, opening the steam line and steam enters the tank, the heat from the steam expands the valve on the cold water line releasing a fine spray of cold water which condenses the steam quickly, producing the required vacuum, and this vacuum immediately acts on the valve to the steam line closing it until the vacuum again drops. The pump operates in this way automatically and keeps the vacuum constant at little expense. The electric pumps are operated by a small electric motor which is started and stopped automatically by the simple method of opening and closing a circuit. The vacuum drops below the pressure set and the switch closes the circuit starting the pump motor, which runs until the vacuum is...
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