Remington HH-70T-KFA Service Manual Page 123

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Gas Fired Heaters
Component Description and Operation
High Limit Switch
High limit switches are switches that are normally
electronically closed, but will open electrical contacts at
a certain temperature. It accomplishes this with a bi-
metal sensing element. A bi-metal is a temperature
sensitive metal that expands with heat. Therefore, as
the heater runs, and as the bi-metal gets warm, it begins
to warp. When it reaches a certain temperature it will
open up the electrical contacts. The temperature varies from switch to
switch, and is listed on each switch. For example, if the markings on a limit
switch read L240, than the limit switch opens up electronically at 240 degrees and will lead to an open circuit shutdown.
Regulator
A regulator, by definition, is a means to adjust to a standard rate and /or to adjust to make your work accurate.
A regulator takes tank pressure and breaks that down to give you a known and consistent lower pressure out of
the regulators outlet. Every propane heater, regardless of how big or small, has to have at least one pressure
regulator. Each propane heater should indicate the inlet pressure ratings on the specification plate to assist in
selecting the appropriate regulator(s) for your application. For the purposes of this manual, there are three
basic types of regulators: the first stage regulator, the second stage regulator, and the appliance regulator. Your
heater may need to use any or all three of these regulators, depending on your heater and your application. Again, if you have any
questions about regulators, please call your local propane dealer or you can contact PHP anytime.
Tank Connectors
Tank connectors are the devices used to connect the first stage regulator to the vapor withdraw propane cylinder.
While all tank connectors serve the same function, the current industry standard is to use certain connectors with
certain applications only (certain applications meaning capable BTU output, whether or not there is an excess flow
valve, and whether it has left hand or right hand pipe threads). While there are many types of tank connectors on
the market, we are going to discuss just a few of the more popular ones only. The most popular tank connector is
the soft nose P.O.L., followed by the Acme tank connector.
Soft nose P.O.L. - The soft nose P.O.L. fitting is the fitting that most service people are familiar with and is still in
use today on all vapor withdraw cylinders over 40 pounds. The soft nose P.O.L. consists of the following component parts: The right
hand thread P.O.L. nipple which actually goes into the L.P. vapor withdraw valve on the top of the cylinder, the 7/8 hex nut (G1643)
which tightens the nipple into the withdraw valve, the o-ring (G1653-3) to help maintain a tight seal inside the valve, and lastly, the
excess flow valve which will shut off the flow of fuel to the unit if there is a cut or rupture of the gas supply hose. The excess flow valve
is the only non- replaceable part in the P.O.L. assembly. Soft nose P.O.L. fittings vary by BTU output as well as thread type, so it is
important to use the correct part number listed on the heaters breakdown.
Acme Tank Connector - The Acme tank connector has become more popular because of the new code requiring
the O.P.D. (overflow protection device) withdraw valve on cylinders of 40 pounds and under. The Acme tank
connector has a spring assembly mounted on the inside of the fitting itself to measure backpressure. The Acme
tank connector will allow only a limited amount of propane to pass through it until the gas hose is pressurized.
Once the hose is pressurized, the backpressure on the spring assembly will compress and allow the proper
amount of propane needed for the burn to pass through. In order to get this tank connector to compress the
spring assembly and allow the proper amount of fuel through, you need to close all the gas connections past the
supply hose. Then turn the propane cylinder on, and let the unit set until the fuel supply hose pressurizes. This
pressurization can take anywhere from 15 seconds to an hour. The Acme tank connector is actually available as a whole unit only, with
no user serviceable components. If any part of the Acme tank connector ever breaks or fails, then the fitting needs to be replaced. This
fitting also has an excess flow valve that will shut down the flow of fuel to the unit if there is a cut or rupture of the gas supply line.
Acme tank connectors come in two different varieties. The black handled Acme is rated for outputs of 71,000 BTUs or less, while the
green handled Acme is rated from 71,000 BTUs to 200,000 BTUs.
Various High Limit
Switch Examples
Phone: 800-362-6951 • Fax: 800-255-7985
www.phpdistribution.com
Gas Heater Service Info.
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