heating programmer

[JohnW2]

Sorry but I don't see where there is a safety issue if no cylinder stat is present.

I'm not sure why you're sorry - that is what I, and others, have been saying since the very start of this discussion (unless the perceived 'safety issue' is that, without a cylinder stat, the temperature of the DHW would probably be higher than if it were thermostatically controlled).

Kind Regards, John

 

[kbdiy]

Was being slight cryptic with that but I totally agree there is no safety issue. Just puzzled why it was raised to the OP in the first place.

 

[JohnW2]

Was being slight cryptic with that but I totally agree there is no safety issue. Just puzzled why it was raised to the OP in the first place.

Yes, I think we all are (a bit puzzled). As I said, I suppose it could be that it was thought that, without a stat, the DHW temperature would be ('dangerously') higher than what it probably would be set at if thermostatically controlled - but, as I said at the start, I don't really buy that as a valid argument!

Kind Regards, John

 

[Taylortwocities]

I was thinking that maybe the intention is for the tank stat to provide an OVER temperature control (much like a safety control in a Megaflo, etc).

This works by allowing the boiler to continue to heat, but will shut it down if things get too hot. But I'm only guessing...

 

[D_Hailsham]

Nobody seems to have considered the possibility that it is a "gravity HW, pumped CH" installation. These usually have no cylinder stat and rely on the owner turning the boiler temperature down in the summer, so the HW does not get too hot.

The cheapest solution (but not most efficient) is to convert to a C-plan. The better solution is to convert to S plan or Y plan.

 

[JohnW2]

I was thinking that maybe the intention is for the tank stat to provide an OVER temperature control (much like a safety control in a Megaflo, etc). This works by allowing the boiler to continue to heat, but will shut it down if things get too hot. But I'm only guessing...

The usual primary function of a cylinder stat is obviously to control the temperature of the DHW, by controlling a (2- or 3-port) MV (the auxillary contacts of which will usually, in turn, control the boiler) - and, as such, will come into play if "things get too hot" (DHW becomes hotter than intended/desired). However, as I've said, "things getting too hot" will not damage the system - the very worst that happens is that DHW temp will rise to close that of the water coming from the boiler - that might be 'too hot for comfort' for a user, but won't hurt the system.

Kind Regards, John

 

[JohnW2]

Nobody seems to have considered the possibility that it is a "gravity HW, pumped CH" installation. These usually have no cylinder stat and rely on the owner turning the boiler temperature down in the summer, so the HW does not get too hot.

That possibility may not have been mentioned explicitly, but ....

Let's face it, traditional solid-fuel indirect water heating systems didn't have (and really couldn't have had) any thermostatic control - and, as plugwash has implied, I think you'll probably find a good few current-day systems with no cylinder stat.

Kind Regards, John

 

[D_Hailsham]

as plugwash has implied, I think you'll probably find a good few current-day systems with no cylinder stat.

I agree that there are still systems with no cylinder stat, but they will have been installed many years ago, possibly over 20. I converted a system to C Plan in 1992, so cylinder stats, and the appropriate zone valves, were available then.

 

[JohnW2]

I agree that there are still systems with no cylinder stat, but they will have been installed many years ago, possibly over 20. I converted a system to C Plan in 1992, so cylinder stats, and the appropriate zone valves, were available then.

... and long before that. The system (by no means new) I inherited in about 1978 had a cylinder stat and zone valves.

Kind Regards, John

 

[Lectrician]

There are loads of systems out there still relying on the boilers built in stat to regulate temperature. Cylinder stats are a fairly recent thing. You do see old ones (in F), but more common to see none than old one.

 

[JohnW2]

There are loads of systems out there still relying on the boilers built in stat to regulate temperature. Cylinder stats are a fairly recent thing. You do see old ones (in F), but more common to see none than old one.

Yes, we seem to be generally agreed about that (although, per my pre-1978 one, they clearly have been available for a long time)....

as plugwash has implied, I think you'll probably find a good few current-day systems with no cylinder stat.

Kind Regards, John

 

[kbdiy]

Nobody seems to have considered the possibility that it is a "gravity HW, pumped CH" installation. These usually have no cylinder stat and rely on the owner turning the boiler temperature down in the summer, so the HW does not get too hot.

I think you will find that's exactly what I was referring to in my earlier post when I said:
"but gas back boilers go back donkey's years, when the more sophisticated control mechanisms were not commonplace and thermosyphon principles were used to heat DHW rather than the pumped methods in use today."