Can you convert a single zone/circuit CH system to dual zone

[wydths]

Hi,

My parents have an oil fired central heating system in their Bungalow which is around 34 years old. Although various parts of the system (Boiler, hot water tank pump etc) have been renewed over the years, the one thing that is now a constant source of frustration for them is that they have to heat the house to be able to heat the hot water because the system has a single circuit.

They are both in their 60s and I know that they (like many) worry about the cost of heating their home, especially when costs are rising.

I have just reviewed their electricity bill for the last 6 months and was horrofied to se how much they have used - the reason why? Because they were using the immersion heater in the height of the summer heat to heat the water because they couldn't stand having the heating on (the bathroom rads have no TRVs as they are the "safety" rads which prevent explosion as I assume there is no bypass valve fitted to this system)

So my simple question is, is it possbile to convert the system from single circuit to dual circuit using zone valves which would allow the hot water to be heated seperately?

I know the following about the system

Boiler - Boulter Oil Fired
Hot water - Gravity Fed
Pump - Seperate, but is next to the boiler (Grudfoss)
Time Clock - reasonably modern digital type, allows on/off twice a day with manual over ride.

They think they are looking at major work and costs and the installation of a entire new system.

Many Thanks
Duncan

 

[JayPage]

Reading through your post I'd say that only a small amount of work would need to be done. A motorised valve would need be cut into the cylinder flow and some control wiring. I'm assuming the cylinder has a stat in place already so it's just some control wiring needed for the 2port and maybe some mods in the control junction box.

 

[ALEC1]

yes zoning hot water and heating is necessary

 

[Galoka]

Dunno how much oil costs, and I don't know how much using oil compares to using elec to heat the water . Though friends of ours who have an oil boiler use their immersion for heating the hot water in the summer IIRC. I've had the immersion on this some of this summer as the gas CH/HW has been being fiddled with, and the hit on the bill is not what I expected (and very little gas consumption.)

How much do they have the immersion on? Running an immersion for 3 hours costs about a quid I set hours for 3 hours in total over the day - of course it's not on all the time. Mostly for us that was enough, though sometimes needed to boost it if we all had showers and baths close together (main disadvantage is that it only heats half the tank). and immersion only on in the summer months of course.

 

[picasso]

Gravity hot water is very inefficient , it would be better to convert to fully pumped on an s or y plan depending on the size of their house.

Just a thought you should be able to have hot water on its own, the pump should not run when you select hot water only, perhaps a miswired pump when it was renewed?

 

[simond]

An older system would typically have a'gravity' hot water circuit running though the cylinder, and pumped central heating. In other words, when HW is selected the boiler starts without the pump, when CH is selected the boiler and the pump start.

If both come on together they must have a very warm house in the summer. This format is meant to allow HW to come on without CH, but not the other way round.

It is possible that the prgrammer has been replaced and wired incorrectly.

Gravity HW is not very efficient, as the water flow through the boiler is slow and causes the boiler to endlessly cycle on/off. It also takes an age to heat a cold cylinder and usually results eventually in scalding water temperatures. If your cylinder has discoloured peeling insulation, it"ll be a gravity fed one!

The best solution is to change the system to fully pumped with zone valves as described earlier in this thread.

Regarding the merits of electric water heating, electricity currently costs around 14p per kw. Oil costs around 7.5p per kw, but you have to allow for the efficiency of the boiler, which is probably around 80-85%. Oil is most definitely cheaper then, unless you have a dual tariff E7 type electricity meter, in which case the electrical heating will be cheaper if the immersion is only energised between 12 midnight and 6am.