Wiring query for Gravity system

[tomba]

Hi,

I haven't read through all the details of the previous posts, but when it comes to discussions about the basics of how heating systems work, I recently found a couple of good introductory training presentations on the Pegler website.

One of them covers the basics of heating systems, and it covers both the 'wet' side and the electrical/control side of things:

http://www.pegler.co.uk/training/index.htm

Cheers,

Tom

 

[PhilGP]

The old programmer isnt broken but it's clunky and difficult to turn.
Every time I turn the dial it feels like it's going to break and sometimes the dial goes round without actually turning the shaft behind.
I would like to have a '1hr boost' of heating or water without having to clunk the dial around and then remember to turn it back.
I would also like a 5/2 day program - I'm not too bothered about 3 cycles per day though.

The wiring to the current programmer just doesn't feel right - ok it's working but I'm worried that the plumbing and wiring have been done to match the 3060. (i.e. HW+CH On, Both Off, HW only - but never CH only). Therefore trying to fit another controller (even if it supports gravity) is going to be a watse of time.

 

[Softus]

OK, now I understand.

You're right to be cautious and to plan ahead, but a new programmer is unlikely to be incompatible with the wiring, because it's simpler than you think.

You should be able to suss out from the new one which terminals to connect the wiring to. If you can't, then the manufacturer will help, and if that goes nowhere, then you can ask here.

 

[D_Hailsham]

DHW cylinder (aka tank)

cold storage cistern (which is not a tank)

Some definitions off the Net:

Cistern - A fixed container for holding water at atmospheric pressure, normally applied to the local water storage to flush a WC. It is normally fitted with a float operated valve and overflow pipe.

Cold water storage tank - A fixed container for holding water at atmospheric pressure usually used for providing a feed to domestic cold water and/or to a vented domestic hotwater system.

Hot water cylinder - A closed vessel (normally cylindrical) used to store heated water under pressure greater than atmospheric.

Indirect hot water cylinder - A hot water cylinder where the water heated by the boiler is fed through a coil of piping inside the cylinder to heat the domestic water. The tank (sic)often incorporates an electric immersion heater so that the tank (sic) can be heated when the boiler is switched off for the Summer.

You say "tomarto" I say "tomayto" .Take your pick

when it is done then the cold storage cistern (which is not a tank) must be raised such that level of water at peak demand doesn't drop below the height of the top of the pipe that draws water from the top of the cylinder.

Technically correct. I was just trying to point out, in laymans terms, that the tank/cistern which does the feeding has (in general terms) to be higher than the cylinder/tank being fed.

The hot water pressure in an open-vented system is determined by the difference in height between the water level in the CSS and whichever outlet is being used.

I must remember to read through what I have written before I post it
I must remember to read through what I have written before I post it
I must remember to read through what I have written before I post it
I must remember to read through what I have written before I post it

 

[PhilGP]

OK, now I understand.

You're right to be cautious and to plan ahead, but a new programmer is unlikely to be incompatible with the wiring, because it's simpler than you think.

You should be able to suss out from the new one which terminals to connect the wiring to. If you can't, then the manufacturer will help, and if that goes nowhere, then you can ask here.

I agree; from a wiring point of view, I could put in the new programmer without any problems - it couldn't be easier.

I'm just concerned that the new programmer might put out a signal for CH only (i.e. no HW) and my plumbing wont handle it.

What what I've learnt so far, my system isnt a gravty system but it doesn't look like it can handle CH without HW - i.e. I need the HW signal ON to run the pump.
The T7 does have a link for Gravity systems and I wondered if this link handled my situation - i.e.

Nothing required ---> HW output OFF, CH output OFF
HW+CH required ---> HW output ON, CH output ON
HW only required ----> HW output ON, CH output OFF
CH only required ----> HW output ON, CH output ON

 

[Softus]

Some definitions off the Net:...

Cold water storage tank - A fixed container for holding water at atmospheric pressure usually used for providing a feed to domestic cold water and/or to a vented domestic hotwater system.

I know most people call it a tank, but it isn't one. It's a cistern.

If you use the word "tank" to interchangeably mean 'a closed vessel' and 'an open topped vessel that has the ability to overflow', then how do you distinguish between the two? I ask because, in plumbing terms, it's really rather important.

 

[ChrisR]

The T7 does have a link for Gravity systems and I wondered if this link handled my situation - i.e.

Nothing required ---> HW output OFF, CH output OFF
HW+CH required ---> HW output ON, CH output ON
HW only required ----> HW output ON, CH output OFF
CH only required ----> HW output ON, CH output ON

I would bet money you'd find that it does just that. Ie when you turn the CH on, the HW will light up on the display and come on with it. That's what all the others would do! I have one on front of me - the instructions don't elucidate.

 

[PhilGP]

I would bet money you'd find that it does just that. Ie when you turn the CH on, the HW will light up on the display and come on with it. That's what all the others would do! I have one on front of me - the instructions don't elucidate.

I have an idea.
If you could post that unit to me I'll happily test the timers and put a meter on the outputs. If it does what I want, I'll re-imburse the postage costs.

 

[D_Hailsham]

What what I've learnt so far, my system isnt a gravty system but it doesn't look like it can handle CH without HW - i.e. I need the HW signal ON to run the pump.

From the photos and your description, you certainly don't have a gravity system as the pump feeds both the CH and the HW branch (assuming that is what happens at the Tee after the pump.

The problem is that you have no control over the hot water temperature, apart from turning the boiler temperature down, which is OK in the summer but not a good idea when you have the CH on, as the output of the rads will be lower than expected.

When the CH is off, or has reached the required room temperature, the motorized valve will shut the flow to the rads; but the flow to the HW cylinder will continue until the boiler reaches its set temperature, which could be as high as 80degC. The hot water coming out of the taps would then be a similar temperature, which is much too high - 60degC is the recommended norm.

The T7 does have a link for Gravity systems and I wondered if this link handled my situation - i.e.

Nothing required ---> HW output OFF, CH output OFF
HW+CH required ---> HW output ON, CH output ON
HW only required ----> HW output ON, CH output OFF
CH only required ----> HW output ON, CH output ON

The Gravity link only allows the first three options. The last, CH only, is impossible with your pipework for the reasons given above.

 

[PhilGP]

B&Q only have a small range of programmers but they do have a 'replacement' chart which lists all of their product range and a list of older/other units that they replace.
It seems that (as far as B&Q are concerned) the Tempus 7 is not listed as a replacement for the Danfoss 3060.

The two units they stock that ARE a replacement are the 'Drayton SM2' (£55) and the 'Sunvic Select 207XL' (£35). The data sheet on the Sunvic website shows all the required wiring changes required for the 3060.
I have decided, unless someone advises against it, to replace the 3060 with the 207XL. It has a link for pumped/gravity which, regardless of my current plumbing, will give me the functionality I currently have.

(NB: I have Cross posted this on another thread)

 

[Balenza]

Softus wrote

then how do you distinguish between the two?

By fitting "tank" connectors to tanks and not cistern connectors.
I bet you ask for "cistern" connectors though at your local merchants.
Why don't you burn those law books you have been reading and get some experience in the real world instead of bleating on like an argumentative court room jester ?.

Since most CSSs

What does CSS stand for ?.
Cold Storage Sistern.

 

[PhilGP]

I just found this Invensys compatibility chart - I found it useful - I hope others do too ...

http://www.heatweb.com/pdf/Invensys/Programmer Compatibility Chary.pdf

 

[PhilGP]

Tonight I'll try to map out the pipework and see where it all goes. I dont know if this will help at all.

That's a very good idea. We need to see how the boiler, pump, valve, rads(not all of them!) and HW cylinder are plumbed in.

From what you say, you probably have a Pumped CH, Gravity HW system (pace Nige F). This can be confirmed when we see the pipework diagram.

For what it's worth, here's what I think my plumbing looks like ...

A pumped system with a zone-valve for CH. No control of hot water temperature - apart from internal to the boiler.

We tried to move the dial on the programmer yesterday and it's now jammed in the CH+HW always ON which has confirmed my need to replace it.
I'm still not convinced I have the wiring correct but I'll simply replace the programmer and ensure I keep the current wiring - although I'll try not to make it look like a rats nest when I'm done.

 

[D_Hailsham]

Your diagram is typical of many older installations. As you say, the only control you have over the Hot Water temperature is via the Boiler thermostat.

Now that your time switch seems to have fallen of the perch, might this not be a good time to update the system with proper temperature control over the HW. This can be easily achieved by putting a zone valve in the feed to the HW cylinder and controlling it with a cylinder thermostat.

It is known as an S-plan

The valve will cost about £45 and the thermostat about £15

Info can be found on Honeywell's website.

http://content.honeywell.com/uk/homes/Catalogue/Sundial Plans/3.2 S Plan.pdf

 

[PhilGP]

Thanks for that.

The re-wiring is not a problem - I can fit the new programmer.
At the moment, I dont feel confident to do any major plumbing so I may leave that part until next summer and give it a go.

My plumbing skills are slowly growing. I have replaced/extended some existing pipework in order to fit two new radiators. This weekend I'll be replacing another and then fitting a new toilet, sink and pipework. Maybe after a few more jobs like this I'll take on a valve change.