Help identifying valve and TRVs connected to HW cylinder

[theomegamale]

Hi

Prior to replacing my (asbestos) CWST and hot water cylinder in order to be in a position to fit a pump for a shower, I've taken an inventory of the pipes in the airing cupboard. I think I've identified everything with the exception of a couple of items.

Firstly, what is the brass fitting shown here to the right of the stop cock?

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• theomegamale
• 25 Aug 2009
• 1

It's connected to the return from the cylinder (see photo below).

And secondly, has anyone come across a TRV fitted to a hot water cylinder before?

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• theomegamale
• 25 Aug 2009
• 1

Can someone briefly explain what the purpose of this is, as I'm considering replacing the cylinder along with the CWST and would like to understand what the TRV is for and whether I need to re-fit this. Currently there's a copper wire connecting the TRV to a plate that is itself connected directly to the copper cylinder. If I get a lagged cylinder then this might not be so easy to reconnect.

thanks

 

[bellairaphon]

i can honestly say ive never seen that before but it looks like its been used as a cylinder stat. do you have a stat connected to your cylinder? if not i would suggest you have one fitted and remove the trv + the brass fitting is an auto air vent and is designed to vent any air build up in your system cylinder

 

[clf-gas]

The TRV, is being used as a cylinder stat. The brass fitting is an ARV. air release valve.

 

[kevnurse]

The TRV is a non-electrical method of protecting the home user from excessively hot water. This suggests to me that the TRV would have originally been fitted to an old system using a simple back boiler in a coal fire (ie a totally non-electric boiler) to provide the hot water. If you now have an electrically controlled boiler, a modern thermostat should be used to control the boiler and primary coil.

 

[Boilerman2]

Drayton Marketed these in the 60's & 70's it isn't a TRV, cos it aint fitted to a radiator, I think they called them Drayton tapstat or something similar, it would close when the sensor (strapped to the side of the cylinder like a thermostat) reached whatever temperature was selected on the control knob, they were very common on district heating schemes, their downfall was the lack of a boiler interlock

 

[doitall]

Drayton still make then as part of the C plan, the Cytrol is more commonly used.

 

[theomegamale]

Indeed, here's a pic of the sensor. It's strapped on with what looks like bell wire.

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• theomegamale
• 25 Aug 2009
• 1

So if I replace the cylinder, I should ditch the TRV/tapstat and fit a cylinder stat? What do I connect the cylinder stat to, is there a special kind of valve or does it need to connect to the boiler (which is 2 floors down, and if possible I'd like to avoid having to run a cable to it).

 

[doitall]

Be aware you are not looking at a standard set-up and could mean a lot of alterations, especially the electric side

 

[anotherbgeng]

the valve you have is a drayton ravi stat which is going to be at least 15 yrs old . as mentioned b4 these are old fashioned and potentially trouble some due to there being no interlock to the boiler to stop it firing ,,the other component is an AAV (auto air vent ) to stop air trapping.. Due to the age /design of your existing setup you are probably openind a big can of worms planning to change cylinder and tank,,,i would either leave well alone or if determined to change the cylinder etc factor in the cost of converting to fully pumped S plan ...If any reputable engineer looks at your current set up they would say the same and price the job according ly.....

 

[theomegamale]

Has anyone invented a remote version to save the re-wiring across floors, i.e. a box at one end connected to the cylinder to pick up temp and another connected to the boiler downstairs that passes the signal to the boiler?

Power on the top floor to the cylinder stat is not an issue if I am connecting a pump and hence routing the mains to the airing cupboard anyway.

 

[twgas]

I believe drayton do a wireless cyl stat, dont know if others do but I wouldn't be surprised.

 

[numpty1]

its a drayton tapstat,readily available as a two port or three port,the third is used as a bypass when connected to a gravity hot water setup.myson also make the tapstat as a 22mm.the rav that another poster commented about is known as a kov valve it too can be two or three port.on a fully pumped sys it can be controlled by electrickery as well as being mechanical.the cyltrol mentioned is a similar device always fitted on the return outlet of a cly on solid fuel/oil/gas gravity installs.thermo mechanical in operation and adjustable to the end user.the brass thing on the right is a auto airvent honeywell i believe.
yes danfoss do a rf cly stat which can operate up to 30m from the sender unit saves a lot of messing around with cables.

 

[holty]

i would say the mechanical cylinder stat in the pic is still classed as an interlock. same as using a honeywell c plan configuration.not a great idea and very crude.the danfoss rf cylinder stat has been very good every time iv needed one. yet your still going to have to hardwire a 2 port valve into the system.

 

[Shardie]

Tapstat, hadnt seen one for probably the last 10 years and then ended up having to chage one last month so they are still available.
Like TRVs are prone to seizing up and sticking the one i changed was 28mm and couldnt be freed even with the help of some WD and a lump hammer!!
Oh i do like a good blast from the past every now and then, think ill go dust off the moleskin!

 

[holty]

think ill go dust off the moleskin!

and paraffin burner while your at it