Quote:
Originally Posted by jim lee
Further to my post above. I have spent an enjoyable wet afternoon in the garage grubbing around with my old thermostat. First I again heated ii in a pan of water and measured its lift. The results are:
Temp Lift
Cold Zero
72Deg C Just begins to open
86Deg C 1.5mm
90Deg C 2mm
94Deg C 3.5mm
96Deg C 6.5mm
98Deg C 8.5mm
99Deg C 9.5mm
Thus all appears well apart from the movement before 86 Deg C. If that could be eliminated, it would appear it would then open at about the right temperature.
Withis in mind, and following my thoughts in the post above, I filed 1.5mm from the end of the central rod. The unit was then reassembled and the heating test repeated. The results are:
Temp Lift
Cold Closed
86Deg C 0.5mm (I could not detect opening before this temp, but clearly it did so)
90DegC 1.5mm
94Deg C 2.5mm
96Deg C 6.5mm
98Deg C 7mm
I could not manage to get 99Deg C this time as the gas cannister on my heater began to run out.
I think these results show that the opening temperature can be adjusted by altering the effecgtive length of the central pushrod. One obvious way this could hppen in service is due to the compression or degradation of the sealing ring on the main valve. As only small dimensional alterations are required to bring about a change of opening temperature, this may also be affectd by plastic creep of the housing, especialy around the valve seating area.
I offer these thoughts and results to any who may be interested.
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I have just finished reading this long thread and I am wondering if the hard solids found within the wax by T-CUT are causing the push rod to start from a position further out of the wax capsule.
This would reduce the gap between the push rod and the plastic housing and so cause the thermostat to open at a lower temperature as Jim Lee has shown.
I note the measurement of 28mm of rod coming out of the wax capsule and wondered if this was constant in all cases including new thermostats
Cheers, Pete