CH all the while - Honeywell Sundial Y Plan auto or manual?

[hsabbers]

Hi,

Had a few problems with our Potterton Suprima 50 boiler that has resulted in a few visits from the Heateam chaps. To cut a long story to the short current problem, the engineer replaced a thermistor yesterday and said all should now be well. However, since he left, it’s transpired that, in fact, the CH runs all the while – even if it’s just HW set on the timer.

We’ve booked a return visit but earliest appointment is Tuesday. In the meantime, I’ve had a look in the boiler cupboard – where the engineer had a brief poke yesterday – and found that the Honeywell Sundial Y Plan diverter is set to Manual. My guess is that this may be the problem – should the diverter valve be set to Auto?

I’ve had a look at Honeywell’s documentation for this product but, so far, I’ve drawn a blank. So any help/advice appreciated.

Harry.

 

[Gasguru]

Yes, set it to Auto

 

[hsabbers]

Yes, set it to Auto

In fact, on closer inspection it actually looks like its in a mid-position -- see the photo I just snapped. Is this how it should be?

Untitled

• hsabbers
• 10 Sep 2011
• 1

 

[flameport]

Looks fine - there are only 2 positions, and when not in Manual (locked behind that little tab to the right) the valve spring / motor should position the valve as required.
If you move the lever towards Manual and then release it, you should be able to feel/hear the spring pulling the other way.

There are several possible causes:
Incorrect wiring - however if the system worked before and no wiring has been changed, this can be elminated.
Motor in the valve head has failed - a common fault, although normally you would just get hot water and no heating in that scenario.
The valve has mechanically jammed or broken - possible but unlikely.
The programmer has busted up and is not operating correctly. Fairly likely if it's an old one and the power has been turned off recently - the backup batteries run down and then all kinds of bad things can happen. Did the time need to be reset on the programmer?

 

[Gasguru]

Lever looks about the right place and is not in the manual position. If the boiler is firing up then it's not likely to be a boiler problem (unless the timeclock is fitted to the front of the boiler) so its a controls issue.

First check turn all the power off to the heating system. You should feel resistance as you move the lever from auto to manual....the lever should then return slowly under spring pressure.

 

[hsabbers]

Looks fine - there are only 2 positions, and when not in Manual (locked behind that little tab to the right) the valve spring / motor should position the valve as required.
If you move the lever towards Manual and then release it, you should be able to feel/hear the spring pulling the other way.

There are several possible causes:
Incorrect wiring - however if the system worked before and no wiring has been changed, this can be elminated.
Motor in the valve head has failed - a common fault, although normally you would just get hot water and no heating in that scenario.
The valve has mechanically jammed or broken - possible but unlikely.
The programmer has busted up and is not operating correctly. Fairly likely if it's an old one and the power has been turned off recently - the backup batteries run down and then all kinds of bad things can happen. Did the time need to be reset on the programmer?

Sorry for delayed response - had to get kids to bed. Anyway, I had a play with the lever and there does seem to be spring pressure if pushed towards Manual - so that's expected behaviour, I guess. However, when at the midpoint there's no spring pressure all: the lever can be very easily moved between Auto and the (unlabelled) midpoint with no resistance.

That aside, I have now moved the lever to Auto and tried again -- and everything seems to work as it should. In other words, I now get only HW when HW is on. When I then switched on CH, I did hear a small click or two coming from the Honeywell valve but the lever doesn't move to the midpoint, which is perhaps what I'd expected from the logic so far. However, CH does not seem to work fine. So, perhaps it's not meant to move from Auto at all?

I appreciate all the help and will keep the engineer visit booked for Tuesday but in the meantime, it does now all seem to be working (at least, the boys had a nice warm bath).

 

[D_Hailsham]

That aside, I have now moved the lever to Auto and tried again -- and everything seems to work as it should. In other words, I now get only HW when HW is on. When I then switched on CH, I did hear a small click or two coming from the Honeywell valve but the lever doesn't move to the midpoint, which is perhaps what I'd expected from the logic so far. However, CH does not seem to work fine. So, perhaps it's not meant to move from Auto at all?

You shouldn't have to move to valve to Auto; it should go there automatically. If it doesn't the valve is probably sticking.

When the power to the system is completely off - setting programmer to CH and HW OFF is not the same - the valve lever should be in the Auto position. When the lever is moved you should feel resistance all the way - there should be no "slack". If there is some slack, it means the valve has stuck partly open to heating.

Lubricating the valve spindle with silicon lubricant may help.

The lever may not move visibly when you turn the heating on. You can tell if the valve has opened by checking if the lever is stiff (not opened) or slack (opened).

 

[hsabbers]

Thought I'd post the conclusion, in case it helps someone in the future...

The Heateam chap came today and yep, the diverter valve was sticking. So, he replaced that and all seems fine. So far, anyway!

Thanks to all.