Heating Programmer quirk? Or working as expected.

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Is it normal for a digital programmer on a fully pumped open vent system (with a heat only boiler, three way valve, tank stat, central heating stat) to require central heating and hot water to be called for at the same time for the central heating to work?

Or should they work independently when requested on the programmer?

I had a full page explanation typed out, but I decided to go with the distilled straight to the point question.

I have more details if needed and if my question is not clear.
 
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If it has been wired so it can have individual programs, the clock also has jumpers to set it for the system design
 
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If it's fully pumped it should be possible to have independent control, but it might require a few wiring changes. Some programmers have a jumper or switch which allows you to select between gravity hot water and fully pumped, some have a mechanical linkage
 
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If it's fully pumped it should be possible to have independent control, but it might require a few wiring changes. Some programmers have a jumper or switch which allows you to select between gravity hot water and fully pumped, some have a mechanical linkage


Ahh, I thought that might be the case.

So, it looks like this programmer has been set up to allow individual calls for heating or hot water. But, the heating only works when both are selected. Because the programmer does not override the hot water to "on" automatically, you have to ensure both are manually "on" for the central heating to work.

@ianmcd This is a picture of the programmer.

56657.jpg
 
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OK it is set to fully pumped , if it was set to Gravity then when you press the CH button the HW button will come on at the same time whether asked to or not
 
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So does that suggests that boiler and pump are not wired to accept the individual calls?

The 3 way valve seems to be operating correctly. Other than this programmer quirk the system seems to run fine.
 
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Incorrect wiring, or the microswitch in the 3 port valve has failed.

I did a test using the thermostats.

Both thermostats set to "off/low".

1 ) Hot water only on the programmer. Turned up the tank stat until it clicked, and the boiler fired for hot water only.

2) Repeated the same for central heating: Both stats set to off/low. Central heating requested only. Turned up the room stat. No boiler fire/pump.

3) Repeated - Both set to off/low - requested both on the programmer.

a) First I turned up the room stat and the boiler fired and pump activated and it seems the 3 way valve opened for central heating.

b) Then, I turned up the tank stat, and I am pretty sure I could hear the 3 way valve motor activate at that point to heat the tank too.


Does this suggest the 3 way valve & microswitch is fine and it is incorrect wiring?
 
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I think it has always done this. I've been using it for a year or so (new house). I just went with it last year, but I knew there was a quirk with it.

It's the first time I sat down to work out what was going on.
 
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If you turn off the power supply and remove clock the backplate should have
N L hot water off in 1 hot water on in3 heating on in 4
 
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turn the HW off and confirm that the 3 port valve definately motors over to Heating only and not mid position
 
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turn the HW off and confirm that the 3 port valve definately motors over to Heating only and not mid position


I'll give that a try when I get a moment.

On the subject of the boiler. It is a heat only Glowworm Flexicom 15hx.

The manual says it is "fully modulating" but I see no guidance as to it's range.

There is no weather compensation. So I was wondering what is the best (as possible) way to run the boiler. Is it just a set at something like 75 degrees (a ceiling temp so to speak) and let the boiler manage itself along with appropriate thermostat use?
 
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turn the HW off and confirm that the 3 port valve definately motors over to Heating only and not mid position

So turn the HW off via the programmer, and while the boiler will shutdown (due to the potential wiring mix-up), the 3 way valve should still go to heating only?

How will I tell if it goes to CH only rather than mid position?
 
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