How long should I heat this boiler up for?

[camdenish]

In the spirit of trying to save gas I have been playing around with the time controls on the water tank.

The thing is I don’t really understand how it works. I think the small black tank is the emergency immersion tank, and the big green tank is the standard everyday one? Am I right?

In the morning I’ve been giving it 40 minutes to heat up from cold. Well coldish, as it won’t have been on since the night before. Then I have a shower. I’m wondering if I could cut this time down so the boiler is heating WHEN I am having a shower.

We might need another shower in the morning and the n some hot water during the day, not loads as we do dishes in the dishwasher. Then I put it on again in the evening for two hours. But I think I’m putting it on too early. I think it should be on while the showers baths are needed. Rather than in prior to theses, and off during them.

Of course I’m trying various different configurations but I thought someone may know how long a tank like this needs to heat up.

We don’t have the radiators on much as it’s quite a warm house. I don’t know if this makes a difference either way.

The black one is there to provide a head of cold water which ensures that the green one is always full. As you draw hot water from the green one, it is topped up with cold water from the black one. The black one is in turn automatically topped up by mains water via a ball valve.

Is it hot enough for a shower after 40 minutes? If so I'd try 30 minutes. If you put it on when you start your shower it will be cold unless there was some hot water left last night.
It's not the sort of system that heats water on demand.

It won’t make an awful lot of difference having the boiler on when you are showering. You will be drawing of water at a faster rate than the boiler can heat cold water up. You need to make sure you have enough hot water in the tank before you start showering or running a bath.

Does the dishwasher have a hot water feed. Most don’t.

Drawing off water

Oh, thank you!

I am glad to know what that black one is now. If I put the immersion heating switch on, is it trying to heat the green boiler water?

The dishwasher and washing machine are both cold fill.

I’m going to try having the boiler on later in the mornings, so that’s about 30 minutes before I shower.

It’s annoying not having instant hot water when people want showers at random times in the day but it is what it is!

Trial and error is probably the best way, you are going about this the right way so far.

Things that will make a difference - how long your showers are, and how long the tank keeps water hot.

So tey out shorter heating times, but to be very scientific also time your shower. Then you can make sure you have enough for getting properly rinsed erc, but if you are very keen to save energy, only heat enough for that and you will get a gentle reminder youve spent long enough in the shower as the water starts to run cold...
The insulation (green stuff) looks reasonable so the tank should hold the heat ok for several hours, possibly longer, but again you can test it out by trial and error.

The immersion heater heats the green one, yes.

Only experience will tell you if 30 minutes before is long enough. Remember that the green tank is heavily insulated so hot water in it will cool down slowly.

I notice that there is thermostat attached to the tank. You can play around with the setting on that so that the boiler automatically stops heating when the tank reaches a pre-set temperature.

Brilliant, thank you. Okay m glad trial and error is the best way.

I’m playing around with trying to save energy and money whilst still keeping some flexibility. Good idea to time my showers. The kids and DH are a bit random but I think I have a fairly standard shower.

The thermostat on the boiler was set by the gas man who comes to service it once a year. I will play around with that as a last resort.

The immersion heater heats the water in the green tank using electricity. But your central heating boiler probably also heats it.
Is the C/H gas or oil?

It always used to be cheaper to use gas to heat water, only using an immersion for an unpredictable top up. However I really don't know now that gas prices have gone up.
Having the option of both you could compare.

Also be aware that the thermostat on the hot water should be a minimum of 60- 65C to kill harmful bacteria.

I hadn’t thought about the immersion potentially being cheaper than the gas boiler. It is mains gas. I think I’m scarred by a childhood of the immersion being a decadent expense.

I think the gas man must be checking the thermostat is at the correct temperature. I’ve checked myself and it’s set at about 64.

To save money perhaps to could stop the luxury of family members having showers at any time they fancy, and set up scheduled times (say on getting up or going to bed) and limiting the time allowed for a shower. If family members are using gyms, sports centres or schools, get them to shower there.

I don’t think my family members would appreciate that Brown. But they should be prepared for cold showers!

In most cases using the gas boiler to heat the water will be cheaper than using the electric immersion heater.

It isn’t in our specific case because our boiler is in an outbuilding with a very long pipe run to the hot water tank, also the boiler is very old and a massive cast iron lump so takes 30 minutes to warm itself up before it starts producing usable hot water.

Also be aware that the thermostat on the hot water should be a minimum of 60- 65C to kill harmful bacteria.

I’m not convinced that this is true, even more so after consulting a water treatment expert. Mains water is treated to kill bacteria before it enters the tank.

@etulosba I thought tanks should be heated above 60 degrees to kill off Legionella, which will grow at temps between 20 and 60 degrees.

excuse me saying, but it's not a boiler and it's not a tank, it's a hot water cylinder.

I think from the colour that you are in Ireland and I can't tell how old it is and how thick the insulation (there is colour coding).

If you have the opportunity to heat it with a gas boiler, it will probably take around half an hour (depending on boiler, cylinder and plumbing method). If you have a timer, set it to come on half an hour before you get up in the morning, and half an hour before you come home in the evening. This will give you a full cylinder. You can set the timer to go off at times when you do not expect to need much hot water, which will save a small amount due to waste heat loss from the pipes.

It is probably around 100 litres, and using the electric immersion heater takes about 100 minutes (but an immersion heater may not heat the entire tank).

A gas boiler typicaly has between four and ten times the power of an electric immersion heater, but cylinders may not be able to absorb heat so fast, especially if old.

Where I am, electricity cost me around 16p per kWh, and gas around 4p per kWh, so it costs about four times as much to heat the cylinder using electricity as using gas. Have a look at your bills or tariff to see what you pay.

For economy, use the gas boiler, and turn off the electric immersion heater except for those days when the boiler breaks down and is awaiting repair.

As you have the square cold-water tank above the cylinder, it will tend to be at around room temperature, and is open to the air, so yes, it is possible to get infected and support bacterial growth. If you use plenty of water it will tend to get flushed out, but you can't expect it to be sterile. if it has a close-fitting lid, that will reduce risk of dust, dirt, spiders and mice falling into it.

btw the boxy white thermostat strapped to the side of the cylinder will call for heat if the cylinder is below preset temp, and stop calling when temp is reached. This means that it will not start the boiler firing unless it needs heat, and also you timer is in an "on" period.

Ohhhh, a hot water cylinder. I say!

I’m in London and am assuming that it’s 10 years old, as that’s when we moved in, and I know there wasn’t any heating until just before we did so assume it was new then. Heated by a Vailant. I guess that is the boiler.

Brilliant. I’ll check my energy tariffs, I think mine are more than that and about to go up more.
I am in London

oh, London?

Cylinders in UK are usually copper, red jacket, yellow foam, light green foam, light blue foam (in order of oldest to newest) and the insulation, and heat transmission, get better with each version. I have only seen dark green on Irish cylinders. But if it is ten years old, it should be pretty efficient and quick to heat from the boiler.

Yes, Vaillant make good gas boilers.

I can see some lagging on the pipes, but if you have any exposed ones, insulate them to improve efficiency a little more. I expect they are mostly 22mm diameter (banana sized) and some 15mm (finger size). The thicker grade of lagging is better if you have room for it. It can be cut and mitred with a serrated breadknife. The felt version is only useful to stop pipes rubbing against joists and floors and making a noise.

I have a similar set up (posted a thread recently, like you, asking what all the parts did as I wasn't sure either!). I also had photos. My header tank is in the loft though, I don't have a little one above it (now I'm quite concerned it has mice and spiders in it!) I have been playing around with the timer programmes to try to reduce gas usage. Won't know until next meter reading in a few days, whether it has made any difference though.

Our control box allows a different setting every day of the week and 3 different times on and off each day, so very flexible. DH initially set it for several hours morning, lunchtime and evening. I tweaked it down to 30 mins morning before my shower (short shower!), an hour at lunchtime and 2 in the evening. DH complained at first, but that's because he was randomly washing up late morning and he uses way too much hot water and likes it really hot .
When he's back at work I'll probably skip the midday one and have it come on at dinner time.

Our tank doesn't appear to hold that much, considering how big it is though, so it does need to be on for a few hours if we're using water for washing up and baths.

so yes, it is possible to get infected and support bacterial growth.

That’s a good point. The water entering the tank isn’t straight from the treated main.

I have a tank- yellow foam lagged :)

When the kids were small I could get away with an hour a day in the evening. The tank stays warm for quite a long time.

Now they’re teens i have it on for an hour about 9pm so the water is hot for dh and dc1 shower’s. Then again for 30mins at 9 am to top up for the day and in case anyone wants an evening shower- i usually shower at work, dc2 at the gym, but there is enough water for one or two quick showers if necessary.

That does us- with a tank you need to think about when you want the hot water, and also try and work out how long your water stays warm for.

even a yellow one will stay hot enough for a bath the next day (if you don't use it). yellow must be at least 30 years old, I think.

but, unless your airing cupboard is really tight, you can add a red jacket over the top, and pipe lagging, and heat loss will be tiny.

Red jackets are not widely sold now, because almost everyone has a (fairly) modern cylinder, or one of the alternatives, but you may find one on ebay or in a hardware or plumbers merchant.

Be careful not to tear the thin red wrapper. you can occasionally wipe it with a damp sponge to remove dust or fluff.

As for drowned wildlife, loft tanks should have a close-fitting plastic lid, and a (black) insulating jacket, which is actually to prevent them getting warm in summer.

I wonder why ours is green? I wonder if the sub contractors were Irish?

I only have two hot water off and on times in a day, but I think that should do as the water dies seem to stay hot.

I remember those red jackets, we had one on the older growing up. Most of the pipes are lagged,but I’ll have a look again and do any that aren’t.