Wiring query for Gravity system

[PhilGP]

I have been trying to work out the wiring on my existing system and came up with these options - I can't check the wiring completely as it is all hidden.

Option 1:

Option 2:

Are either of these correct for a Gravity DHW and pumped CH system?

There is no thermostat on the hot water cylinder.
The boiler is a Glow-worm SPACE SAVER 52.

 

[D_Hailsham]

1. If you have pump it is not a gravity system

2. What type of valve do you have (make and model)

3. What are you trying to achieve?

 

[Nige F]

1. If you have pump it is not a gravity system

you must be a young`un from Hailsham ....I was fitting C/H with pumped rads and Gravity primaries, in that town and others in Sussex in the `70s.

 

[D_Hailsham]

... you must be a young`un from Hailsham

Flattery etc ; thanks for accepting my location.

I was fitting C/H with pumped rads and Gravity primaries, in that town and others in Sussex in the `70s.

Accepted; I was only talking in general terms. Many posters, including this one, automatically assume that, if there is a F/E tank in the loft, the system is gravity.

 

[PhilGP]

1. If you have pump it is not a gravity system

2. What type of valve do you have (make and model)

3. What are you trying to achieve?

1. I 'assumed' I had a gravity system from responses in another thread. - Yes the hot water tank is in the loft.

2. I dont know the valve type but it is just a 2 port valve with a manual override lever. I will try to find out the model number (if any) of the valve and pump and post back.

3. I am trying to replace an aging Danfoss 3060 programmer with a modern digital one. I would like to be able to control the Water and Heating seperately but the current programmer cannot do this and the current wiring suggests it's not possible anyway.

 

[D_Hailsham]

What does the valve look like?

or

 

[PhilGP]

this one.

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

 

[D_Hailsham]

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.

 

[PhilGP]

It's proving difficult to map out all of the pipes but heres a first part.
The boiler only has two (28mm?) pipes going from the ground floor up to a bedroom where at least one of them ends up in a cupboard.
This photo shows the pump and valve but I cannot clarify which pipes are water and which are heating.

It looks like the main flow goes into the pump and then is split. Part goes up into the loft - presumably to the hot water tank. The second part goes down to the valve - presumably to control flow to the rads.
This would fit my first diagram where the room thermostat goes direct to the valve. Also confirmed by the colour of the cable (black) going into the programmer.

We had the house rewired recently and whilst the boards are up I noticed the CH pipes run under the floor (upstairs) in 28mm pipes and then into multiple microbore pipes. This is not via a manifold but just a 4-into-1 connector at the end of the 28mm pipe.

Valve: Honeywell V4043H1007 5
Pump: Grundfos UPS 15-50x18 Model A Mk.II (Class F)

 

[D_Hailsham]

The boiler only has two (28mm?) pipes going from the ground floor up to a bedroom where at least one of them ends up in a cupboard.

And what happens in the cupboard?

It looks like the main flow goes into the pump and then is split. Part goes up into the loft - presumably to the hot water tank. The second part goes down to the valve - presumably to control flow to the rads.

Do you mean the hot water cylinder (a closed container) or an open tank?

If you are correct then you have a pumped CH and HW system without any separate control over the HW temperature (How do you control the HW temperature?)

But it is unusual to find the HW cylinder in the loft as there would be virtually no difference between the water level in the cold water tank and the cylinder; and it is this which determines the hot water pressure.

Can you get up into the loft and find out how many tanks/cylinders there are and what pipes etc?

This would fit my first diagram where the room thermostat goes direct to the valve. Also confirmed by the colour of the cable (black) going into the programmer.

Have you checked that the valve opens and closes when you turn the room stat up/down?

Do you have any idea how old the heating/hot water system is or whether it has had any additions or changes since it was first installed?

 

[Softus]

But it is unusual to find the HW cylinder in the loft as there would be virtually no difference between the water level in the cold water tank and the cylinder;

That's an another assumption. Whilst it's true that it's unusual to put a DHW cylinder (aka tank) in the loft, 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.

Since most CSSs are shorter than most DHW cylinders, a system with the CSS and cylinder at the same level wouldn't work at all, so your assumption seems particularly misguided.

...and it is this which determines the hot water pressure.

This is fundamentally wrong. 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. This is why there can be a marked difference between the pressure at a kitchen cold tap and the shower head in an upstairs bathroom.

 

[PhilGP]

Thanks for sticking with this one D. I'll try to answer these questions ...

Without ripping up boards it's difficult to see where any of the pipes actually go. I'm assuming to pipe 'out' of the boiler goes into the pump. The other pipe from the boiler is not so easy to trace - it may be one of these in the cupboard (see previous photo).

The hot water tank is indeed a sealed cylinder with foam on it and an immersion heater - which does work.

I have been unable to look all over the water cylinder but I am fairly sure there is no thermostat on it. There is, however, a temperature dial on the boiler which I am assuming controls the water temperature.

The house was built in 1961 and there is no real space upstairs to locate the hot water cylinder so the loft must have been the only choice.
The cold water tank and the C/H header tank are way up in the top of the loft. The bottom of the cold tank is more than 1m above the top of the hot cylinder.

The number and route of pipes up in the loft is complex but heres another photo.

I'm not at home right now so I cant do any more checks until tonight.

I will check what happens to the valve when the room thermostat is turned up/down.

I have no idea on the age of the heating system. The programmer has a 'Warranty 4/98' sticker inside but I found old newspapers near some pipes dated Jan 1978. It is very likely that it has been modified at some point in it's life.

 

[Softus]

The history of modifications is irrelevant, since the property has clearly had both a new roof and a new cylinder, and I would say within the last five years.

Your system is already fully pumped, but not fully controlled, so you need to add one 2-port motorised valve, one cylinder thermostat, a programmer, a wiring centre, and some wiring. The only moderately expensive part of this is the MZV, and your time.

BTW, if you're adding this many components then you might consider a Honeywell Smartplan system, but that would mean discarding your existing MZV actuator head (or possibly the entire valve).

I would ignore the existing wiring and run whatever new cables you need to. I would expect that you'll need more conductors from the programmer that you already have.

The Honeywell web site contains all the schematics you need, but if you can't find or interpret them then I can give you URLs.

 

[PhilGP]

The history of modifications is irrelevant, since the property has clearly had both a new roof and a new cylinder, and I would say within the last five years.

The previous owners were in for 19 years and did not touch the roof at all.
I dont know the age of the cylinder.

Your system is already fully pumped, but not fully controlled, so you need to add one 2-port motorised valve, one cylinder thermostat, a programmer, a wiring centre, and some wiring. The only moderately expensive part of this is the MZV, and your time.

BTW, if you're adding this many components then you might consider a Honeywell Smartplan system, but that would mean discarding your existing MZV actuator head (or possibly the entire valve).

I would ignore the existing wiring and run whatever new cables you need to. I would expect that you'll need more conductors from the programmer that you already have.

The Honeywell web site contains all the schematics you need, but if you can't find or interpret them then I can give you URLs.

Thanks for this information.

I dont actually want to do any work on the system. I simply want to know if I can replace the programmer with a modern programmer (i.e. Drayton Tempus 7).
Before I proceeded with this I need to be sure myself that the wiring is going to be ok.

Since Winter is nearly on the way and our whole budget has been blown on a re-wire, some plastering and a new kitchen, I'll leave the plumbing alone.


Thanks once again for the responses. I gues no two systems are the same.

 

[Softus]

The previous owners were in for 19 years and did not touch the roof at all.

I stand corrected.

Thanks for this information.

I dont actually want to do any work on the system.

You're welcome, but I'm confused about your goal(s).

I simply want to know if I can replace the programmer with a modern programmer (i.e. Drayton Tempus 7).

What do you want your existing programmer to do that it doesn't do?

Before I proceeded with this I need to be sure myself that the wiring is going to be ok.

You said this at the beginning, and I didn't understand it then. What you mean by "ok"?

Frankly, if you're not going to upgrade the system, there's no point in replacing a programmer that isn't broken.