TRV on Primary coil inlet?

[ambert]

Went to a property this week, customer was saying that the hot water was too hot. In the airing cupboard the flow to the heating coil had a TRV on it with a remote sensor stuck on to the cylinder. The TRV was set to 2. I turned it down to 1. Asked if he'd call me back to see if there was any reduction in the temperature of the water.
There was no motorised vlave, So i guess the rads ran off another circuit. I've never seen this set up with a TRV before, just wondering if this is good practice?
Also the pipework below the TRV had a white deposit all over it. What would cause this?

 

[SimonG]

Old school. In between gravity and fully pumped. Cylinder reaches temp and head shuts down.

 

[mountainman]

The TRV in question was known as a Tapstat, fairly common years ago.
The white deposit is probably scale from a water leak.

 

[jtsplumbing]

Still lots of systems like this out there, worked well in the day, wait until you come across an old Servowarm set up with there hot water control ! must still be some left working, know of one in Plymouth.

 

[Best]

The pin on the TRV body could be stuck up and perhaps due to slight weep at gland. Therefore the cylinder would overheat.
Body is identical to rad TRVs really.

 

[jtsplumbing]

Honeywell was most common, and Drayton tapstats

 

[AWheating]

can still by them, danfoss make some i think.