Drayton Tapstat Valve

[Stoff]

Hi everyone
My heating system consists of a motorised valve for the heating and a Drayton Tapstat valve for the hot water. The system is in the region of 25-30 years old.
Recently a bit of a throbbing noise has developed when the hot water only is running. If the room stat is turned up, thus opening the motorised valve and allowing water to the radiatores the noise stops. I have a feeling that the cylinder valve is possibly not fully open. It is turned up to MAX and the sensor on the end of the caplilleray is laying on the floor and not in contact with the cylinder. I have fitted a cylinder stat wired to the programmer to start the pump & boiler when required.
a) does a sticky valve seem the likely cause?
b) how can I test it?
c) would I be better off replacing it with a motorised valve?
Your opinions and advice would be very much appreciated.
Happy New Year to all
Stoff.

 

[spraggo]

Need more info as the tapstat is meant to be used on gravity systems with no infuence from a pump.

 

[JohnD]

the sensor on the end of the caplilleray is laying on the floor and not in contact with the cylinder.

The sensor is supposed to be in close contact with the cylinder, under the insulation. It is essential that the thin capillary tube (which looks like wire) is not kinked, cut or broken. The mechanism is very similar to a Drayton Radiator Valve with remote sensor, so I suppose you could unscrew the head and see if the pin is seized.

It is OK to have a cyl stat as well as the tapstat, this is a bit more economical as it prevents the boiler from firing just to keep itself warm.

Off topic:
does anyone still use these? I have a spare one in its box that I never needed to use, and a Cyltrol too. They are very expensive new...

 

[Stoff]

Thanks for the advice John, I'll try this at the weekend. Is it fairly obvious how to take the thing apart yo check the pin?
Stoff

 

[JohnD]

IIRC you unscrew the collar at the base of the head, which holds the head onto the valve. Turn it to max heat before removing or refitting it so that the plunger is not pushing against the pin. The pin should move in and out freely if you press it. Do not apply any sideways force or it may break off. You can try applying a little lube with a very fine paintbrush to help the pin slide, or spray it in.

BTW as you seem to have a fully pumped system now, with a cyl stat closing a motorised valve when up to temp, the cylinder return will be hotter than when it was gravity, so you might do well to just take the head off and leave the valve fully open. It will be quite hard to remove it from an old cylinder.

 

[scoobydo123]

JohnD

I am after a tapstat, the system in a property I have just completed on has a Cytrol valve but would a Tapstat give me better control?

Cheers

 

[JohnD]

I believe it will, as the sensor is clamped to the cylinder, at a height of your choosing, where it detects when the cylinder contains enough water, at the temperature you set on the knob. The Cyltrol only reads the temperature of the water passing out of the coil.

In my experience, the Cyltrol tends to seize in time (they are mostly very old by now) although I do also happen to have a new one of them!

 

[scoobydo123]

How much do you want for the tapstat?

Cheers