Open Heating System (Vented) and Thermostat Cylinder???

[galegp]

I have a Seal Heating System Vented. I don’t have any control over the hot water in the cylinder therefore I am getting a plumber to fit a tank thermostat and a motorized valve with the intention to close the supply of hot water to the tank when the water inside reaches the 60 degrees.

My question is the following, and I seem to read difference things in internet. If I program the hot water for one hour and the boiler heats the water in the tank to 60 degrees in the tank then motorized valve shut down supply but would boiler shut down? I read someone saying that in my type of heating system the boiler will be on for one hour regardless the motorized valve shuts down supply of hot water to the tank. Is that correct?

Thanks.

 

[stem]

It all depends upon how the system is wired, but yes if done properly the system should shut down when there is no demand for heating the radiators or hot water. This is now part of the building regulations (in the UK) to conserve energy by not running a boiler unnecessarily when there is no requirement for heat.

In practice there is a microswitch installed inside the motorised valve for this purpose. When the valve is opened, the microwsitch is operated and turns on the boiler. When it closes, the microswitch is released and the boiler goes off.

Some boilers require the pump to 'run on' for a few minutes after the boiler has gone off to stop the boiler overheating because of any residual heat from the burner or heat exchanger, but you don't say what sort of boiler you have, so if it's a bit unorthodox it's difficult to say. If you tell us what you have, someone on here may be familiar with it and be able to advise.

By the way, I don't understand what you mean by "Seal Heating System Vented" systems are either sealed, or vented.

 

[galegp]

By the way, I don't understand what you mean by "Seal Heating System Vented" systems are either sealed, or vented.

Sorry it is actually an open system – vented – with an expansive tank in the attic.

How does the motorised valve speak to the boiler?

When I asked my local plumber, he explained it to me as once the motorised valve shuts down and there is no water going to the boiler this will shut down. I asked him if there was any wiring between the motorised valve and the boiler and/or programmer and he said no. Maybe he is right but it just did not sound right to me. If there is no water going to the boiler, would this not get damaged (even though it may shut down eventually)?

By the way, the boiler is an outdoors warmflow kabin pak 21-26k.
http://www.warmflow.co.uk/products/boilers/k-series_he/kabin_pak_he_pre-wired

 

[stem]

It's difficult to explain in a post, but there's a useful diagram if you click here. Look at S Plan, Hot Water Calling. The wire shown flashing blue, that passes through terminal 10 shows how it's done.

Sorry I've never heard of your boiler, so I can't comment on the minimum 1 hour running period you mention.

 

[galegp]

Sorry I've never heard of your boiler, so I can't comment on the minimum 1 hour running period you mention.

Thanks for the info. Much appreciated.

Sorry I think I did not explain it well. I mean when you set the hot water in the timer to run for one hour. But in practice it does not take one full hour to heat the water in the tank, I’d say more like 20 mins. Does it now make sense?

 

[Madrab]

In a single valve 3 port Y Plan -

Simply put, the programmer is on calling for HW, the HW cylinder stat sends the signal through to the 3 port motorised valve telling it to open to hot water coil (Pos B) and sends a signal to the Boiler's switched live to turn it on. Once the cylinder stat says it's hot enough, it turns off the signal to the Boiler, shutting it down and resets the valve.

For you plumber to say there are no connections between the components not strictly true, they may not be directly connected but that's how it works there are indirect switched connections.

The pump overrun, where the pump runs on for a minute when the boiler shuts down, is part of the design to remove the excess heat from the boiler until it cools enough avoiding any damage.

 

[stem]

Madrab is referring to a three port valve which would control the hot water and also the central heating. This is known as a Y-Plan. I had assumed from your original post that the plumber was only fitting a two port valve just to the hot water cylinder.

But in either case it would still be usual for a boiler to be switched off when there was no demand on it.