Oil based home heating and immersion - Can i heat the radiators without heating the main water tank?

EmJey

I have a typical oil burning system at least 30 years old with water-filled radiators in the rooms and a main copper water tank with a few rotary valves on the pipes connected to it, one main valve beside the tank and 2 higher up clearly not meant to be accessed as easily. There is also a typical electrical socket beside it with a single on/off switch. There is a thermostat on the boiler which is in it's own hut outside, set to 60c

I need the room heating in winter quite a lot but i don't need hot water from the taps nearly as much so is there a way for me to heat only the radiators without heating the immersion water tank at all? I should say i'm only assuming that it's an immersion tank but i'm pretty sure it is. Can you tell i don't know what i'm doing? What does the electrical switch and main valve do? Can i turn one or both off to stop the tank from heating up?

The main tank will go cold after about 60 hours without the heating being on so it seems a terrible waste to have it sitting at 60c all the time when i might not use it once during that time.

Thanks in advance.

Gerry1

Any boiler can be set up to give CH, DHW or CH+DHW, you just need a suitable programmer and valvegear and to set it up accordingly.

Any immersion heater should be left switched off because it will be more expensive than oil.  Use it only if the boiler breaks down or you run out of oil.

EmJey

Gerry1 said:

Any immersion heater should be left switched off because it will be more expensive than oil.  Use it only if the boiler breaks down or you run out of oil.

Ok, so there's no way for me to do what i want without additional gear? The switch was always in the on position but the water tank only ever heats up if i have the outside boiler turned and burning oil. Is that the right thing?

molerat

Pictures of your set up would help.   What are these rotary valves - motorised or manual ? How do you time the heating ?  Do you have separate programmable channels on the timer ?

I assume the switch by the tank has a cable running to an immersion heater, if it is turned on on but does not heat the water then it could be a dead element.

Gerry1

It sounds like you have a primitive control system that was typical of its time, one that offered only DHW and CH+DHW.  It should be relatively straightforward and inexpensive to allow the CH and DHW to operate independently of each other. It was the first thing I did when I moved in many moons ago.

However, without knowing the full details of the existing system it's not possible to be specific about any additional items such as motorised valves that may be needed.

The immersion heater(s) should be independent of the boiler: they're only intended as a fallback if the boiler isn't working.  The big mistake is to leave them on, especially if the thermostat(s) are set higher than the one calling for heat from the boiler.

EmJey

molerat said:

Pictures of your set up would help.   What are these rotary valves - motorised or manual ? How do you time the heating ?  Do you have separate programmable channels on the timer ?

I assume the switch by the tank has a cable running to an immersion heater, if it is turned on on but does not heat the water then it could be a dead element.

I apologise for the lack of images but i have it all carefully wrapped up in layered sheets of newspaper. It's a very simple tank with a red manual rotary valve beside the tank and 2 more similar ones above on other pipes and clearly not meant to be accessed very easily. Those valves and the on/off electrical switch are the only controllable elements at the tank. The oil boiler has nothing but a simple thermostat attached which is outside and the in-house control for it is just an old style on/off/timer switch with the timer being the 24 hour wheel method with depressed switches to turn it on at the required times.

I've turned the valve off and electric switch off as it seems to be all i can do but i suspect that's not going to do what i want. I know not to run the hot taps with the valve off.

matelodave

Old four-pipe systems frequently had a gravity heated hot water tank and a pump to circulate heating water through the radiators
Has the boiler got two large pipes going to the tank and two smaller pipes which feed the heating circuit.
.
They may also have a timeswitch/programmer which had a clock with a switch that gave you hot water or hot water & heating (but not just heating on its own). they may also have a simple room stat to switch the heating pump on and off when the timeswitch was set to heating. Really crude systems didn't have the room stat - the pump just ran all the time when the heating programme was selected, sometimes. with a thermostatic valve in the tank return pipe to control the tank temperature. There may also be a check valve in the hot wter circuit to prevent reverse gravity circulation.

If that's what you've got then it can be done but you will probably need to fit a tank stat & motorised valve to the tank and a different programmer to enable hot water and heating to be switched independently. I've had two systems like like this, both of which I modified by adding motorised valves to the tank return ( the valve must be in the return leg of the tank to avoid closing the system vent pipe)

Other later systems with a fully pumped primary would usually only have two pipes coming from the boiler and have had one or more motorised valves, usually with a tank stat & room stat together with a simple programmer like the one described above above.

We need more information on exactly what make & model of boiler, and the make and model of any controls and where they are situated as well as info on what pipes come out of the boiler and where they go.

Have a shufti at this - he goes on a bit but it should give you some idea of what might be possible depending on what you've already got.
https://www.youtube.com/watch?v=Q_nkFNLTYHo

MWT

It may be easier at this point to ask a local plumber for a quote to do whatever is necessary to get separate control of your heating and hot water then tell us what he proposes before proceeding...

EmJey

matelodave said:

Old four-pipe systems frequently had a gravity heated hot water tank and a pump to circulate heating water through the radiators
Has the boiler got two large pipes going to the tank and two smaller pipes which feed the heating circuit.

If that's what you've got then it can be done but you will probably need to fit a tank stat & motorised valve to the tank and a different programmer to enable hot water and heating to be switched independently. I've had two systems like like this, both of which I modified by adding motorised valves to the tank return ( the valve must be in the return leg of the tank to avoid closing the system vent pipe)

Thanks for the info there. It does have the 2 thick main pipes and 2 smaller ones that are fairly hot to touch and also another 2 small pipes that are cold tho one has a very mild heat to it. There's no control other than 4 manual rotary valves, 2 on the main feeding to the bottom of the tank and 1 on a small cold pipe and 1 on a small hot pipe.

I'll try to get someone to take a look at it but i don't really have the resources to invest in this at the moment. There's no way i can get a pic of the connections as the tank is tightly packed against the walls. I'll leave it at that other than to ask, given the meager info i've supplied, what you think might happen if i turn either of the small pipe--1 hot, 1 cold--valves off?

Gerry1

Unless there's a bypass, the pump may whinge and die if you strangle it !