Inherited a seemingly ancient CH system...

[Agile]

It only needs just one extra two port valve which can be fitted in the vertical return pipe from the cylinder .

And perhaps a new wiring box as we cannot see what is being used now.

Less that £100 of parts to save perhaps that in the first year. With the benefit of more constant hot water temperature.

 

[greenstarthree01]

Hmm. At the moment then, with just the one 2-port valve, is the system simply pumping water around both the CH and HW 'zones' whenever the timer clock reaches an on period? And the water it's pumping around is only heated by the boiler if the room thermostat is turned up, or the cylinder thermostat reads the water temp as low? That would explain why the pump runs but the boiler doesn't fire, right?

From what I've read this morning, the suggestion of adding a second 2-port valve would make it an 'S Plan' system? And with that system, we could have CH & HW, just one of the two, or none, in which case the timer clock could hit an on period without the pump running?
That would be more what we're used to (with a combi we only programmed for the heating as HW was on demand), and I can see how it would save a lot of energy.

Are we talking something like this?
https://www.buyaparcel.com/p/heatin...-with-2-x-22mm-2-port-motorised-valves-cp222/

 

[Smithy the plumber]

Hmm. At the moment then, with just the one 2-port valve, is the system simply pumping water around both the CH and HW 'zones' whenever the timer clock reaches an on period? And the water it's pumping around is only heated by the boiler if the room thermostat is turned up, or the cylinder thermostat reads the water temp as low? That would explain why the pump runs but the boiler doesn't fire, right?

From what I've read this morning, the suggestion of adding a second 2-port valve would make it an 'S Plan' system? And with that system, we could have CH & HW, just one of the two, or none, in which case the timer clock could hit an on period without the pump running?
That would be more what we're used to (with a combi we only programmed for the heating as HW was on demand), and I can see how it would save a lot of energy.

Are we talking something like this?
https://www.buyaparcel.com/p/heatin...-with-2-x-22mm-2-port-motorised-valves-cp222/

Yes, its best to buy the complete control Pk, you can have two motorized valves or just one 3 way valve, shop around for prices, Danfoss/Drayton or Honeywell as well

 

[Agile]

I would not advise buying a whole pack.

You would tend to go for the cheaper ones which are not very good.

You only need one two port valve and could buy a genuine Honeywell from Ebay or a ( good ) copy from Toolstation.

Its such a simple improvement which will pay for itself in a year!

 

[Smithy the plumber]

I would not advise buying a whole pack.

You would tend to go for the cheaper ones which are not very good.

You only need one two port valve and could buy a genuine Honeywell from Ebay or a ( good ) copy from Toolstation.

Its such a simple improvement which will pay for itself in a year!

he can do, but it sounds like he only has a basic timer, needs to upgrade to a proper programmer & add that to the cost of a valve + the existing one looks in poor condition ,cylinder stat is off the Ark just better to renew all controls

 

[greenstarthree01]

Thanks both. Although I presume our current controls would operate twin valves properly in a basic manner, as they're a bit old and limited I was going to say I would be keen to upgrade those as well while I'm at it. As i say the room stat is Fahrenheit and the "programmable" timer is a clockwork and pins affair. Suppose we were a bit spoiled at our last place having a combined wireless stat and programmer, which had 5/2 day modes etc.
Good to know to keep an eye on the quality. Would it be safe to say the valves are the most important bit to ensure are decent?

 

[Smithy the plumber]

Thanks both. Although I presume our current controls would operate twin valves properly in a basic manner, as they're a bit old and limited I was going to say I would be keen to upgrade those as well while I'm at it. As i say the room stat is Fahrenheit and the "programmable" timer is a clockwork and pins affair. Suppose we were a bit spoiled at our last place having a combined wireless stat and programmer, which had 5/2 day modes etc.
Good to know to keep an eye on the quality. Would it be safe to say the valves are the most important bit to ensure are decent?

As long as you get a well known control Pk, you wont have any trouble in the future replacing anything that does break down,

 

[stem]

So it would appear that you do have the same set up I described earlier. When the timer is 'on' the pump and boiler are powered continually, then once the cylinder is hot, the boiler stops cycling due to its internal thermostat. When heating is required the motorised valve is opened to allow water to also flow through the radiators.

This begs the question, if there isn't a motorised valve on the hot water system, what is the cylinder thermostat doing?

 

[greenstarthree01]

So it would appear that you do have the same set up I described earlier. When the timer is 'on' the pump and boiler are powered continually, then once the cylinder is hot, the boiler stops cycling due to its internal thermostat. When heating is required the motorised valve is opened to allow water to also flow through the radiators.

This begs the question, if there isn't a motorised valve on the hot water system, what is the cylinder thermostat doing?

Oh, so do you think the cylinder water temp is actually controlled by the thermostat on the boiler (basically a dial numbered 1 to 6) rather than the one strapped to the cylinder?
I was thinking that the boiler stat simply controlled how 'fiercely', so to speak, the boiler heated the water, so the temp of the water sent to the cylinder / rads. Then the cylinder stat reads the overall temp of the cylinder as a whole, and if lower than its own setting, 'requests' the boiler to fire up and send it more hot water?

 

[greenstarthree01]

Also, is there any hard and fast rule as to what temperature the numbers 1-6 actually equate to? If I want to make sure the cylinder water is being heated to above 60 (hygiene reasons?) do I also need to make sure the boiler stat is up high enough, on top of the cylinder stat?

 

[stem]

Oh, so do you think the cylinder water temp is actually controlled by the thermostat on the boiler (basically a dial numbered 1 to 6) rather than the one strapped to the cylinder?

Yes, the cylinder thermostat is just a switch, 'on' or 'off'. It's 'on' if the water in the cylinder is below the selected temperature, and 'off' if the water in the cylinder is above the selected temperature.

The temperature of the water leaving the boiler is controlled by the boilers integral thermostat. The higher the boiler thermostat, the hotter the water leaving the boiler.

In the same way that the room thermostat operates the valve shown in your photo, to turn the radiators on and off, normally a cylinder thermostat is linked to a second motorised valve fitted in the pipe between the pump to the hot water cylinder. When the water in the cylinder reaches the temperature set on the thermostat it closes the valve and stops the hot water getting any hotter. Except you don't have a second valve fitted...... So what is the cylinder thermostat connected to?

There is a way of using the a cylinder thermostat as a boiler interlock without a motorised valve, but it only works when the central heating is not on. For it to function the boiler thermostat temperature must be set considerably higher than the cylinder thermostat otherwise the temperature set on the cylinder thermostat will never be achieved if the water from the boiler isn't hot enough to reach it.

Also, is there any hard and fast rule as to what temperature the numbers 1-6 actually equate to? If I want to make sure the cylinder water is being heated to above 60 (hygiene reasons?) do I also need to make sure the boiler stat is up high enough, on top of the cylinder stat?

Because the thermostat is fixed to the cylinder on site, there can be a few degrees temperature difference depending on the height that the installer fixes it, and an effect from the ambient temperature, because of this inaccuracy, some manufacturers use numbers instead of temperature values. The range of a cylinder thermostat is usually from around 40 to 80 degrees C, so the 1 to 6 should correspond roughly to that range. Generally I believe a temperature in excess of 60 is recommended for stored hot water to prevent the growth of Legionella bacteria.

 

[greenstarthree01]

The cylinder thermostat's cable goes back to the same wiring box as the pump and 2-port valve, but I've not taken off the cover yet to take a look (not that I'd necessarily understand it if I did...!). Would an image of the inside of this help?
There is also an immersion heater fitted, though this has its own physical switch of course and doesn't look to be connected to any other parts, so presumably the cylinder stat is not related to the immersion heater.

At the moment the cylinder stat is set between 60 and 65 as shown in the image, and the boiler thermostat is at 5. The hot water from the taps is very hot! Obviously room stat is set at minimum so no radiators are on, and we only have the timer set to on for an hour or so in the morning and again in the evening. I did notice this morning during the timers' On period that the boiler fired up for only a couple of minutes at a time, every, say, 4 or 5 minutes, though I was only around for that to happen 3 times or so. Not to throw something else into the mix but I've heard this might be dry cycling and thought that was avoided by making sure the boiler stat was set higher than the cylinder stat, similar to what you suggest Stem?

Whatever's going on with the current setup, it sounds like the most productive, easiest and bang-for-buck change to make first is to get a second motorised valve fitted, and upgrade the controls, so we can independently control the heating and hot water. Plus, we'll know once that's done that we at least have a relatively standard setup, which I can only imagine is going to make problem solving a bit easier!?

 

[Agile]

The disadvantage of buying a pack is they come with the supplier's choice of ( usually basic ) programmer/timeclock.

Buying the components separately enables a better programmer to be chosen.

But you must decide what you want.

I expect the existing cylinder stat will turn off the boiler as soon as they cylinder reaches the set point. That is as long as the boiler flow temperature is set high enough.

But adding the HW motor valve will be a massive improvement to the efficiency and thus save gas!

Tony

 

[greenstarthree01]

Yeah, so essentially building a 'pack' from individual parts means potentially more reliable end result. We previously had a Salus wireless control which allowed 5 on/off points per day and different settings on weekends. That level of control would be more than enough and the programmer seemed pretty good, however obviously as we were combi that was CH only.

 

[Agile]

You have demonstrated the problem of you buying a pack.

Most engineers would not want a Salus controls pack, deservedly or not!