Gas boiler off for 4+ days - water still hot. Huh?

[RumbleStrutt]

I’ve been testing our boiler to see how to use less energy. Turns out for mine it’s a lot cheaper to have it on for a fixed time per day than on a ‘constant top-up’.

So I’ve been trying for 1 hr per day. 3-4 showers a day, 1-2 washing up bowls per day plus v occasional bath. Still loads of hot water so thought I’d reduce the time but as a test turned it off completely to see how long it would last.

It hasn’t been on since Weds and we still have really hot water. We don’t have an emersion heater. We’ve had loads of showers (due to the heat), although quick ones and not very hot, plus a couple of cool baths plus usual washing up.

what’s going on??!! We do have a massive tank but I need to check the meter as can’t believe we still have hot water with it off for so long.

Anyone else has this?

Are you sure you don’t have an emerison!

It has been incredibly hot so could it be that?

It's very hot, you have a large tank and probably some incredible insulation.

Lived here 7 years and not aware of an emersion or it’s been on forever! I really should have checked the meter before I started this experiment. Going to take a reading now and again in the morning. Really weird!

Does the shower definitely run off the water cylinder? Ours is electric so it heats its own water.

Yeah definitely off the tank. Off to get the meter reading! Not complaining just seems odd.

What sort or boiler is it, have you got an electric showe, are you sure theres no immersion in a cupboard

My water tank has a built in immersion, it is set to heat several times a day and I’ve switched it off at the wall and on the fuse box. There’s a switch on the wall nearby the tank that’s just a switch, no markings on it or anything.

It’s a Valliant boiler and a huge Megaflo water tank.

Definitely not an electric shower. I had new bathrooms installed 6 months ago and bought the showers for the builder. Also never seen an immersion heater switch.

only explanations are:

• it stays warm ages due to hot weather, using less hot water as cool showers and good insulation
• controller gone funky. It’s a Honeywell one and seems to be working fine as haven’t heard the boiler click on since all timers are turned off but it’s possible something on without my realising

Ok, will report back on the meter readings tmrw as don’t have a smart meter. Hmmm.

Good to know @Fluffycloudland77 . Will also check that.

Google tells me that megaflow tanks have an inbuilt immersion heater running off electric from the cold water sysrem

Yep, your mega flow keeps water stored in it hot using electricity not gas. Not sure what you've switched off but it's not the hot water!

Sort of correct. The Megaflo has an optional immersion switch so you can have hot water if your boiler fails, but you shouldn't be using it if your boiler is working fine.

But modern tanks keep water hot for a long time too so with that and the heat I'm not massively shocked. Just check your immersion switch isn't on as it'll be costing a fortune in electricity if so.