Not sure how my heating systems works

[fabgav]

Hi all,

new house, new joys!

I've got a primatic central heating system.

From what I can see there are 4 pipes coming out of the back boiler, 2 on the left, 2 on the right.
2 on the left go upto the primatic cylinder. the two on the right - 1 goes through a pump and up the other just goes up assuringly around all the radiators.

We have a old timer that can do heating+hot water, or hot water only.
Having said that with HW only the bathroom rad does get warm.

I was looking to change the timer to a digital 7day one.
The wires are live, neutral & earth in - 3 wires out to a junction box near the pump - blue to bother pump and boiler neutral, yellow to pump and red to boiler.

Is this a C plan? And if it is, is there a shut off valve in the boiler to stop the CH warming up, or do it just warm up to natural rise and because the pump is off, it doesn't circulate?

I want to change the programmer but the one I have Serviceplus S27R does not seem to allow HW only.

What sort of timer do I need? I thought a 2 channel timer would be what I needed.

 

[45yearsagasman]

By your description you have standard gravity hot water circulation and pumped heating. Just about as basic as it gets. To achieve independent control over hw and htg requires the addition of a motorised valve/s and the system converted to what is commonly known as fully pumped. This can be a few hundred depending on the amount of work required. Fitting just a new 2 channel clock will do nothing. How have you identified your cylinder as being primatic? How many storage tanks are there in your loft space?

 

[Hugh Jaleak]

A 'C' plan system has a motorised valve in the return pipework from the cylinder to boiler, which will close will cylinder stat indicates required temperature has been reached, to close off the gravity circulation to the cylinder. Your system may not have the valve and stat on the cylinder, which gives no control over HW temp, other than the boiler stat.

Sometimes find an anti gravity valve in the heating circuit to prevent gravity circulation, but not always. Possibly gravity circulation is causing the bathroom rad to heat up, but sometimes bathroom rads were connected into the HW primaries to allow towels to be warmed/dried during the warmer months when the CH wasn't required.

Wiring on these old systems is pretty basic too. HW on simply switches the boiler on, with boiler stat giving the control. With CH also selected, power is supplied to the pump to circulate water around the rads, possibly with a room stat in series to switch the pump on and off as required.

 

[fabgav]

[QUOTE="45yearsagasman,[/QUOTE]

Hi, I was not after CH to come on without water as I know this would require fully pumped, which is not a possibility with the primatic cylinder.
I know I have a primatic due to only one tank in the loft, and the pipe arrangement to the cylinder.

Hugh Jaleak, thanks for your info, interesting points about the HW stat. I imagine one of those would reduce gas bills a fair bit?
And yes the wiring is pretty basic on this system.

With regards to the programmer I have, why can it not do hot water only and then hotwater and central heating.
I thought this was one of the most common wiring requirements so what term do I need to look for in a new programmer?

 

[Hugh Jaleak]

Any twin channel programmer will suffice, although you may need to set some types for a gravity HW system using the dip switches behind the unit. Ultimately, I'd be looking to change the system to fully pumped in the long term if you want to reduce your bills, although as you're already aware, it does mean changing the cylinder.

However, with modern cylinders having a fast recovery rate, and more demands on hot water usage with modern living standards, its never a bad idea in my view.

 

[fabgav]

Cheers Hugh, the plan was just to get more control on the heating and hot water (ie, 3 days a week all family are out the house by 07:30 so we don't need the heating on all morning)

We are planning an extension within the next couple of year so I may research a newer system.........I really dislike the idea of combi's