Programming DHW/CH independantly on an old Honeywell & CH bypass (pics)

[barki]

Hello


My Honeywell programme is one of these...

I find it very annoying that it doesn't allow me to progamme the DWH and CH independently, i.e they both come on and turn off at the same time.

I wouldn't be so bothered, expect that, when they are both one, the system seems to priortise/favour the central heating over the hot water. I.E - after an hour of running, the radiators are all blasting heat, but the hot water in the tank is only luke warm, whereas it'd usually be piping hot after 20 mins without the CH on.

I've got two questions;


- I have two diverter valves, one marked Hot Water and one marked Heating. At the end of the heating valve pipe, I've a shut off valve marked 'Heating Bypass', which is closed tight. I'm wondering if I need to open this to midpoint, to bypass the CH circuit partially, and allow the DHW to get hot, even when both diverters are open?

I may have totally mis-understood what the bypass does....very grateful if anyone can shed some light!


- My other question is, I'm thinking about swapping the programme for a more modern Honeywell, like this;

Obviously with the plan that I could separate DWH and CH timings, but would the backing plate & wiring configuration be the same between these two? I don't mind some fiddling with the wiring, I just want to avoid digging out the wall.





One more thing - I can't find a thermostat in my house, anywhere (not even on the unvented cylinder!)?......is this unusual!?



Cheers!!!!

Tom

 

[barki]

Whoops pics don't work....


Current programmer is a Honeywell ST699, I was thinking for upgrading to a ST9400...

 

[AGAS]

try again with pictures

 

[barki]

One of these....

https://www.google.co.uk/search?sit...4.501.aQs9-xKCCRg#tbm=isch&q=honeywell+st9400

Instead of one of these


https://www.google.co.uk/search?sit....4.501.aQs9-xKCCRg#tbm=isch&q=honeywell+st699

Sorry the pictures wont fkin work!!

 

[barki]

Can anyone help? I just want to know if I can programme the DHW&CH independently with the a more modern unit, and that it'll fit the backplate.


P.S - I can't find a thermostat anywhere in ym house....is this unusual?



Tom

 

[stem]

Much depends upon the current set up of your system. The plumbing layout may not accept separate control of the heating and hot water. To start with, you system will probably need to have motorised valves. Either '2 Port Motorised Valves'

Untitled

• stem
• 26 Mar 2010
• 6

Or a '3 Port Motorised Valve'

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• stem
• 1 Apr 2010
• 8

is this what you mean by:

I have two diverter valves, one marked Hot Water and one marked Heating.

Regarding:

I've a shut off valve marked 'Heating Bypass', which is closed tight

This is normally to maintain a flow of water through the boiler in the event of the radiators being switched off at their individual valves, either manually or because they are TRV's (Thermostatic) usually it is cracked open slightly, however, if this is what it is for, then opening it anymore will not help, in fact, it may make matters worse, because it then means that there is a third route for the water to take.

When this is clarified, we will need to know about the existing wiring. But, unfortunately we can only make assumptions, because without being able to see your photographs we are working blind.

 

[barki]

Hi again,

Stem - thanks very much for taking the time there - very much appreciated


Here are some photo's now. There are two, 2-port motorised valves which are both working (I can hear them operating when I operate the control).

Below is a photo of the layout, showing the bypass valve to the right also (I've now cracked this open).


Also here is a photo of the existing programmer, the boiler (perhaps not relevant!) and the unvented cylinder set up in the loft, which has not temperature control on it, unlike 'normal' cylinders I've had in the past.

Very grateful once again for your help


Tom

 

[D_Hailsham]

I wouldn't be so bothered, expect that, when they are both one, the system seems to prioritise/favour the central heating over the hot water.

The system has not been balanced correctly.

At the end of the heating valve pipe, I've a shut off valve marked 'Heating Bypass', which is closed tight. I'm wondering if I need to open this to midpoint, to bypass the CH circuit partially, and allow the DHW to get hot, even when both diverters are open?

Not a good idea - see above. Whether a bypass is needed depends on the boiler.

An Automatic bypass is now the correct thing to use as it only operates when required, not all the time which is inefficient

If you do not have a room stat, the most suitable replacement for the ST699 is the Honeywell Sundial RF² Pack 2 Wireless Enabled Programmer and Thermostat. This consists of the ST9420 Programmer, which will replace the SR699, and the DT92E wireless thermostat. Wiring changes will be required.

The cylinder thermostat is inside the box at the bottom of the cylinder.

 

[stem]

What you have posted looks promising, the programmer that you have looks like a Honeywell ST699 and that is capable of separate control for heating and hot water already, however, as you say, the first and last times are the same.

I was thinking from your first post, that you couldn't have one operating without the other, but you can, you could for example have the hot water on all day, and the heating on twice just in the morning and evening.

So, there will be no problem installing a programmer that has separate times, you system and wiring is compatible. However, many folks have programmers that work in the same way as yours, but don't have the problems you describe. So as has been said already the controls aren't really the problem it is probably a balancing issue.

 

[barki]

Once again I thank you for your time.

Regarding balancing - googling it, I just come up with a load of info on balancing radiators....rather than balancing DHW/CH, is this something I can DIY?

The Sundial pack looks good, and the wife likes it. I'm happy with wiring so long as I don't need to dig out the walls etc.

Cheers very much again

 

[D_Hailsham]

Regarding balancing - googling it, I just come up with a load of info on balancing radiators....rather than balancing DHW/CH, is this something I can DIY?

You just treat the cylinder as another rad. There is normally a gate valve on the flow or return of the cylinder coil which can be used to balance the flow through the coil.

Balance the rads first, setting the controls so only heating is running and HW motorized valve is closed.
Then, with heating still running, turn the HW on, setting the cylinder stat so the HW valve is open.
Adjust the gate valve so the temperature drop across the coil is the same as across the rads.

 

[barki]

Tha ks very much for that, i'll give it a go.


P.s I assume I leave the bypass valve alone?

 

[D_Hailsham]

It really depends on which boiler you have. You said it's a Wallstar, but the exact model would be helpful.

 

[stem]

The Sundial pack looks good, and the wife likes it. I'm happy with wiring so long as I don't need to dig out the walls etc.

You have a Sundial installation already, or to give it its full title a Sundial S Plan. Basically its a name coined by Honeywell that refers to separate control of the hot water and central heating using motorised valves, room and cylinder thermostats.

It you want to have separate times set for the hot water and central heating, you just need to change your existing programmer for one that has the facilities you require.

 

[D_Hailsham]

It you want to have separate times set for the hot water and central heating, you just need to change your existing programmer for one that has the facilities you require.

But the OP doesn't have a room stat, which is why I suggested the Sundial RF² Pack 2 Wireless Enabled Programmer and Thermostat, which consists of the ST9420 Programmer (replacing the ST699) and the DT92E wireless thermostat.