heating radiators/heating hot water tank timings

User_Name_1

I have my radiators warm up between 5:30 PM and 8:30PM, would I save any money by setting my hot water tank to heat up at 8:30pm as opposed to say 2:30PM .My reasoning would be that the water going around the system would be warmer at 8:30 PM (from heating radiators), but the water would be heating up from cold at 2:30PM.

Or maybe have them both heating at the same time 5:30PM to 6:30PM, although I realize that the boiler will probably be not heating water for the full hour.

Would it make any difference in gas used ?

QrizB

When do you want your water to be hot?

If you want hot water in the evening for dishes / baths, heat the tank then. You'll use it sooner after heating and will lose less heat from your tank (as the tank will be less full) for the rest of the time.

If you want hot water mid-afternoon, heating at 2:30 would make more sense.

Lorian

Also needed to know if it's a condensing boiler or not, and if it's Y plan, S plans or a more modern hot water priority system. Also if it's an older copper tank or new pressurised one, and how well lagged.

markin

Im sure all boilers in the last 30 years are hot water priority, so you would want water heating just before heating time or just after so all the pipes are hot.

User_Name_1

Not sure if it's a Y or S plan or if the copper tank is pressurised sorry. The boiler is an valiant eco max pro the hot water tank came with a foam covering . The system was installed in 2006 so it's getting on a bit.

Qyburn

markin said:

Im sure all boilers in the last 30 years are hot water priority, so you would want water heating just before heating time or just after so all the pipes are hot.

In most installations the boiler won't know if it's running for CH, DHW, or both. Any priority will be set by the valves, pipework and controls.
In our S system there's no interaction between valves or controls, if both are on then both valves open. The only preference is if the DHW circuit has less resistance and there takes more of the flow.
I expect you could rig something up to inhibit heating if DHW is calling, if you could be bothered. And it would be counterproductive if your boiler output exceeds the amount of heat that can be transferred to the HW tank.
Does the Y system do this? I've never used it so not bothered to understand it.

Qyburn

User_Name_1 said:

Not sure if it's a Y or S plan or if the copper tank is pressurised sorry. The boiler is an valiant eco max pro the hot water tank came with a foam covering . The system was installed in 2006 so it's getting on a bit.

Look at the valve(s), Y Plan has one three port valve, S Plan has two two port (on/off). Should be reasonably easy to follow pipe or wires to see which.

grn99

S Plan here (two 2-way valves) and vented h/w cylinder.... I always wonder about optimum time to heat for the showers/bath (just before use?) and then the re-heat of that hotwater as the tank obviously fills with cold as the hot water is used, cooling down the remaining water in the cylinder. I used to re-heat it straight away but recenly have left it until the next timed event the following day. Not sure if that's helping or not.

Qyburn

We have the same, in our case with an oil boiler.

It depends on how well insulated your tank is. If you heat it in the evening, is the water still hot in the morning?  If not then you're better off stopping earlier in the evening, and running in the morning just before it's needed.

I heat HW in the morning just before we're up, then in the early evening.

One of my colleagues has some sort of fancy cylinder that he claims only loses 1 Deg C in a day. If that's correct then timing matters much less for him.

QrizB

My system is Y-plan, but I think we're in danger of losing the OP with this technical discussion of heating systems!

User_Name_1 said:

Not sure if it's a Y or S plan or if the copper tank is pressurised sorry. The boiler is an valiant eco max pro the hot water tank came with a foam covering . The system was installed in 2006 so it's getting on a bit.

One of these?
https://library.plumbase.co.uk/flipbooks/RE/vaiecomp18e_22986_t/mobile/index.html

That's a conventional condensing boiler. Nominally 90% efficient when new and working in condensing mode.

FreeBear

User_Name_1 said: The boiler is an valiant eco max pro the hot water tank came with a foam covering . The system was installed in 2006 so it's getting on a bit.

The foam on the tank is probably around 50mm thick. You won't lose a huge amount of heat, so the water inside will not be stone cold when you fire the boiler up. If you are wanting hot water at 20:30, I'd set the timer to heat the tank around 18:00. Set the tank thermostat to ~55°C - It will save on gas consumption, and any bacteria will be killed off within an hour or so.