Hi All, I've just moved into a house that has a "Glow worm - economy plus" boiler (in the kitchen), it also has a controller (in the kitchen - see below for more details) and a temperature control (in the lounge).
I'd like to replace the controller, currently a Honeywell ST699 controller, unit was not marked with a model but I have looked at several honeywell units and this seems the most likely.
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this I can program 2 on / off times or manually control the central heating and the hot water. I'd like to be able to set:
CH - on at 7am off at 8:30 am on at 5pm off at 10 pm Hot water - on at 7am off at 7:30am
If I switch the CH to TWICE and the hot water to ONCE, then the hot water is on from ON1 (7am) until OFF2 (10pm) not ON1 and OFF1 !
I don't like the way that the hot water and central heating can't be controlled independantly. Surely if I can control the system manually then I can replace the timer/controller and have the functionality I require ? Could you suggest a suitable alternative controller that will give more flexiblilty ? Can I use a Honeywell ST6400C controller instead ?
Yes, this is a very useful feature. It basically allows you to set morning and evening times, but fill in the middle on weekends or when you take a sickie. It is very standard for programmers to work this way.
Why do you want to control the hot water independently? I normally stick mine on 24/7. Modern insulation standards mean that you won't waste much energy doing so. Also, if you have a gravity hot water heating circuit, you'll be unable to turn off the hot water when there is a call for heat from the heating circuit anyway. (You'll also get pitiful reheat performance by modern standards).
P.S. the model you have looks identical to the one I've got on my old system (shortly to be RIP, hooray!) However, mine seems to have a mind of its own and doesn't seem to come on when instructed. Horrible thing. It is particularly annoying setting the clock. It will only advance the minutes at a grotestquely slow rate. I think it needs about five minutes to advance by
12 hours. Life is simply too short to bother.
If you are still convinced you want independent control, consider other manufacturers too. I quite like the Horstman stuff, for example.
P.S. the link you gave had prices on the high side. Unless you get some sort of discount, try (amongst many others)
I'm not sure whether your system is fully pumped or not. As others have said, if hot water is by gravity circulation, you're stuffed and cannot have heating without hot water.
Lets assume that it's fully pumped in which case you will have a 3-port valve (or 2 x 2-port valves) and a cylinder stat. I assume that the temperature control in the lounge is just a room stat?
One possible solution to your requirement is to replace the room stat with a programmable stat. You can than set your existing timer to switch the hot water on and off at the times you wish - and switch the heating to continuous (manual). The heating will then actually be controlled by the programmable stat - which enables you to have different temperatures at different times should you so wish, as well as being OFF when required.
Thanks for the replies. After a bit of an experiment it seems I may have got this wrong :(
I thought that I could control the hot water independantly, but it seems that I can switch it ON indepedantly, but if I switch the central heating on then the hot water is on anyway...
It just seemed a bit of a waste leaving the hot water "reheating" all day... and the water gets VERY hot... after climbing around in the airing cupboard and ripping up a floorboard it seems my system is setup a little differently than I thought... I thought I had one of these Y designs that had a valve somewhere between the boiler and the hot water tank, but the only thing I can find is the pump (above the boiler).. no valves anywhere (unless it is under the floorboards in the hall).
Anyway, the hot water is very hot and I found the temperature setting on the hot water tank, it's set to 70 deg C so I might lower that to
60 deg C.
Doesn't seem worthwhile ripping out the pipes and connecting a valve and a new programmable timer. Seems I have 3 options
live with it and see how much the gas bill is after winter.
get a combi boiler installed (can't really afford this at the moment)
get a programmable stat (thanks for the suggestion, didn't know about them)
Would this mean that the hot water would be on whenever the programmable stat called for heat ???
Any ideas which stat I could use, the current one is an old brown honeywell thing with no model number on (or in) it. I could take a photo of it and the small wiring diagram that is on the inside of it, and upload it on the web somewhere ??
You may have gravity circulation. Could you describe the number and sizes of the pipes coming from the boiler. You should have a gas supply pipe and two pipes for the central heating. If you have two more pipes (possibly larger than the others), you have gravity circulation. This is bad.
I'm still not quite sure whether your system is gravity or fully pumped. It was beginning to sound like gravity - in which case you *can't* have heating without hot water - except that you mentioned being able to set the hot water temperature.
What sort of control is it which enables you to do this? Is is a thermostat strapped to the side of the tank, with wires going to it? If so, it must be controlling something - such as a 3-port valve or zone valve. Where do the wires go?
Alternatively, you could have a Cyltrol valve or similar in the return water flow. This is purely mechanical, and works like the thermostat inside a car engine - with an expanding bellows which cuts off the gravity flow when a certain temperature is reached.
[Just a long shot - I presume you're not referring to a thermostat incorporated into an immersion heater which, of course, would only have any effect when heating the water electrically rather than with the boiler?]
If you can clarify this, we can determine what is or is not possible.
The temperature sensor is strapped around the hot water cylinder, it's a Honeywell L641A1005 it has a white wire that disappears under the floorboards in the airing cupboard (might have to rip some up and have a look)
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I' had a look inside the controller and the model was marked as ST699B
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I slide the lower switch (Hot water) to "CONT" then I have hot water (after about 20 minutes) If I slide the middle switch (Heating) to "CONT" then I get CH & HW
Tech Info:
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does not have a wire for CH OFF (connector 4) So does that mean I have a "sundial Y" plan ???
User manual
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Join the club ;)
I've checked and I don't have an electrical immersion heater. Guess you could have both... ? Don't know why you would, but I haven't.
The boiler has 3 pipes:
thin (approx 10mm) pipe - marked "gas"
thick (approx 22mm) pipe - goes to the water pump then up into the airing cupboard
thick (approx 22mm) pipe - goes up into the airing cupboard
pipe 3 appears to have a drain tap on the end of it - is that for draining the central heating ?
The fact that there are only 2 water pipes going to the boiler - one of which is in-line with the pump means that you have a fully pumped system.
The fact that the tank stat is electrical, and has a cable which disappears under the floor almost certainly means that there is a zone valve (or possibly a 3-port valve) hidden somewhere under the floorboards.
At some point between the boiler/pump and airing cupboard both your flow and return pipes MUST split into two circuits - one for hot water and the other for heating. On the return side, this is probably just a T-piece. On the flow side, it is either a T-piece with a separate zone valve on each output or a 3-port valve which incorporates the T and the zone control in one unit.
You have almost certainly got either an S-plan system (2 zone valves) or a Y-plan (3-port valve). See
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details.
Either way, you appear to have the capability of controlling hot wat and heating separately *including* having heating without hot water - provided that it is wired correctly.
BUT, if you want them both to be timed but at different times from each other, you need two independent timers - and the ST699 only has ONE timer.
This was why, in an earlier post, I suggested that you should consider a programmable thermostat. This is a replacement room stat which switches on and off with rise and fall of temperature but ONLY within the times programmed into it. [Have a look at the CM31 or CM37 in the Honeywell catalogue which you referenced in your message].
You can thus set the clock on the ST699 to switch on and off at the times when you want hot water. You can set its heating control to continuous - which means that the heating will be on whenever (but only WHEN) the room stat says it should be. If this is a programmable stat, you can thus use it to control both the temperature AND the timing of the heating. As I said before, you will then be able to have heating *without* hot water - if that is what you want.
Yet more info... Operation "rip-up-the-floor-boards-n-have-a-butchers" complete ;)
Found a valve under my hall (upstairs) floor boards.
I have a Honeywell V4073A1039 The V4073A is a motorised Mid-Position valve... is it 3 port ? ie 1 input and 2 outputs ?
pipe goes from boiler to pump to valve (port AB): port B seems to go to the airing cupboard (HW tank) and then back (with feed to bathroom & back bedroom radiators ???) port A seems to go to the other rads.
Anyway, the (5 core) cable from the valve goes into a small junction box and then down do the main junction box in the kitchen (next to the controller).
But the cabling and plumbing (radiators connected to the HW return flow - HW tank to boiler ???) seems very different from the pdf I have from the Honeywell site, didn't have much time - I'll check it again tonight.
The short answer is YES, as long as it's installed properly.
It is now clear that you have got a Y-plan (more or less).
The V4073 is indeed a mid position 3-port valve capable of providing hot water only, heating only, or both together.
For this to work properly, there *must* be a Hot Water OFF feed from your programmer, and your cylinder stat must be the change-over type - with one input and two outputs. One of these outputs is live when hot water is required, and the other becomes live instead when the demand is satisfied. [You'll see what I mean if you look at the Y-plan wiring diagram at
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reason I said it was "more or less" Y-plan is that a couple of radiators seem to be doing something different!
It is not uncommon for the feed for the bathroom radiator to be taken off
*before* the mid-position valve - so that the rad will get hot whenever either or both of the hot water and the heating are on. In this way, your towells get aired in the summer when the water is being heated even when the heating is off. Is this what you've got?
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