Immersion heater advice needed - not enough hot water

[ZaraM]

Hello, I'd be grateful for any advice anyone can give me (I know very little about plumbing). Sorry this is a bit long, but I'm trying to give as much info as possible.

I only have electricity in my flat. I have an economy 7 immersion heater for hot water. I only have room for a very small cylinder - 1600 x 300.

Last week something went wrong, and the immersion heater stopped working. The plumber said the elements had blown, but he couldn't get them out. A week later, I have a new cylinder (same size) and new controller (Horstmann Economy 7 Quartz - manual boost). Cylinder's not currently insulated as the plumber had to cut off the jacket to get it through the cupboard door.

Everything is working fine - bottom element heats up water overnight on E7, top element heats up water when I press the boost button. The tank gets hot to the touch. But there's quite a difference between the hot water I get now vs. the old tank....

I always take a bath at night. So usually I: heat the water on E7 overnight, then boost it for an hour at 6pm (because by then the stored water is usually lukewarm, especially in the winter), in order to take a bath at 7pm. With the old tank, after a one hour boost, the water was very very very hot (almost scalding), and I could have a very hot bath. I only needed a tiny bit of hot water and a lot of cold. Result = hot bath and the hot water went a lot further.

But with the new tank, after I have boosted for an hour at 6pm, the water is hot - but I have to run the hot tap on full with only a bit of cold, and by about halfway through filling the bath the hot tap is only running warm. I haven't tried the power shower yet, but I imagine it will start to run warm then cold fairly quickly, as even the old tank wasn't brilliant.

My first thought was the thermostat - as the plumber suspected my old tank was very old / thermostat was set too high / might have contributed to it blowing. (NB I have lived here for 17 years, so it took quite some time for it to blow.) I've looked at the thermostats - they just have + and - (no temperature) and are turned all the way round to the +. So I guess I can't do anything about that?

My second thought was insulation - but the old tank wasn't insulated that well (it was so old a lot of it had fallen off).

Does anyone have any idea? Or do I have to resign myself to horrible warm baths forever?

Thanks!

 

[Dotty]

Could you post a picture of the cylinder please Zara?

 

[ZaraM]

Here are some photos Croppie, thanks. (The cupboard is very small, so the best I can do.)

 

[Ch4 plumbing]

Your main problem is your plumber has removed all the insulation on the cylinder, as soon as you economy 7 turns off the cylinder will start to lose heat rapidly (it's acting like a large radiator)

 

[Ch4 plumbing]

By the not evening[MENTION][/MENTION] it will be stone cold and your boost is not enough to heat the cylinder up to full temp!

 

[Best]

I am wondering if the cables to the heaters have simply been mixed up and the E7 wire is actually going to the top heater - thus only heating the top small amount of water in cylinder and the boost immersion is actually now the lower heater? That way you will only have a small amount of water heated on overnight E7 and then your boost heater will take forever to try to heat the whole cylinder. Worth checking first.
Only other thing is faulty heater.
The jacket missing of cylinder will not help. Why is the entire insulation been removed???
What width is opening? Also what is the width of the copper tank? Normally I would remove the door and any timber I can to increase the width and ONLY if I really still have to, then I will take a bare minimum slice of each side of insulation to get tank in. Can't see why you would need insulation removed!

 

[Unregistered]

Thanks for your replies. The plumber did initially wire them the wrong way round I.e. the E7 was going into the top element and the boost into the bottom. I worked that out by the next morning and he came back to rewire them yesterday and the E7 is now definitely heating it all overnight / the boost is only heating the top third. (Exactly as the old one did.) The cupboard opening is very narrow, as soon as I saw the jacketed cylinder I knew the insulation would have to come off. There's no way it could have got through the gap, even with the door off.

I have read that thermostats have to be set lower these days to prevent scalding water. Could it be that my old thermostat allowed the water to get to a much higher temperature than this one? (The water used to be almost scalding. It was probably installed in the 80s. In the summer I didn't usually need to use the boost for an evening bath, it was still hot from the E7.)

I think I need to get a blanket tomorrow and see if insulation helps. (Although even the first water after the boost isn't as hot as it was with the old tank. Maybe because the E7 water has cooled down a lot more?). I could also try the water in the morning to see how hot it is after the E7 has switched off (ie is it near scalding or the same temperature as the boost made it tonight).

 

[Best]

Do not put a blanket over the immersion heaters! They will overheat & thermostat will cut out on its safety cut off.
A proper cylinder jacket would be better. One same height as cylinder, but a jacket for a wider cylinder will be fine as you can overlap it well.
Use tin foil (bright silver side against cylinder) & tape it all together. Bit of a pain, but helps stop heat loss. Then fit jacket well, leaving the immersions uncovered and perhaps tape the jacket vertical joints up. Insulate the pipe leaving top of cylinder with tube insulation.
I really see no reason that all that good insulation was removed. If for example the maximum opening was only a little larger in width than bare copper cyinder, then the foam just needed shaved down each side of cylinder to allow it in. Maybe the cut off could have been glued on again when cylinder in place.

 

[AWheating]

Probably a combination of the cylinder being a smaller volume, the immersion being a little higher and the stat being set at a lower temp. Along with the insulation being missing.

If the foam lagging was on and the bottom heater warms to a good temp it should stay fully hot for many hours.

 

[Unregistered]

Thanks, that's really helpful. I meant am immersion tank insulation blanket, not just a blanket. Would that not be OK?

 

[ZaraM]

Sorry, that reply above was from me, didn't realise I had been logged out! The water this morning (after E7) is really hot, so I'm guessing the lack of insulation is causing the problem later in the evening, and the boost water isn't enough to fill the bath, so I'm also getting the lukewarm E7 water? I'll try some insulation today - thanks for the advice on that, Best.

 

[AWheating]

fitting a cylinder jacket or two and some pipe lagging on the first meter of pipe off the cylinder will def help you save heat and money.