Shower PROBLEM Megaflo?

betty2hats

WE are currently renovating a house, turning it into a one bed flat downstairs and two en suite b&b rooms upstairs, this is so my mother can retire.
The house only has access to electric and we have pretty much decided on electric heaters throughout
We are having such a struggle trying to work out how to heat these 3 showers and to make sure there will be sufficient hot water for at least 4 showers in the morning.
we had decided on a megaflow 300l with 3+ immersion heaters, however we are being told that may be enough as when the cylinder empties all the water will turn warm when the cold water starts to fill. i was told previously that the tank would heat all the water in the night on a cheap rate and then the top element would heat the cold water as it flowed in thus getting hot water faster.

Very confused, please help if you can
thanks

GazLecky

Hi

The megaflo you are considering has 3 elements. You can connect each to either your standard or your off peak meter. Most people connect 2 elements (bottom and middle) to the off peak supply and the top one to the standard supply. The top element is then used to top up the hot water during the day if needed using more expensive electricity.

The outlet from the cylinder is at the top. As heat rises, this is where the water is at its hottest.

The cold water enters the cylinder at the bottom. Inside the cylinder there is a device to minimise mixing of the warmer water within the cylinder and the cold water entering.

In simple terms the cold water entering the cylinder pushes the hotter water up.

You will need a circulating pump on your hot water if the furthest hot water outlet is over 9m from the cylinder (measured as pipe length, not as the crow flies). The returning water will be cooler and will cool the cylinder as it enters at the bottom and is constantly circulating.

Don’t forget you need to think about legionella management. The water temperature in the cylinder needs to be kept above 60 degrees centigrade and the water temperature at the furthest outlet needs to be above 50 degrees centigrade.

Suggest you seek advice on the hot water system design as it needs to comply with various regulations; and to have a legionella risk assessment carried out once the system is installed. As you are planning to let the rooms, you will need to have a management system in place.

Might sound like overkill but if it all goes wrong and you end up in front of the man in the curly wig, the penalties are severe. Ignorance is no excuse. Google something like “Legionella Outbreak Fines” if you want to see how much it could cost.

The_Fat_Controller

Why not just put in instant electric showers ?
They will never run out of hot water.

Cardew

The_Fat_Controller wrote: »

Why not just put in instant electric showers ?
They will never run out of hot water.

I wouldn't because:


1. I would want to heat the water overnight at cheap rate..
2. The flow rate on electric showers are not good IMO - particularly in winter.

The_Fat_Controller

Two of the three showers are going to be in B&B rooms, so they aren't likely to be occupied 365 days a year.
What's the point of heating all that water every day if the rooms are empty ?
As for flow rates, that's a fair point, but also means if the property is on a metey your bills will be smaller.

Cardew

The_Fat_Controller wrote: »

What's the point of heating all that water every day if the rooms are empty ?

The OP stated:

We are having such a struggle trying to work out how to heat these 3 showers and to make sure there will be sufficient hot water for at least 4 showers in the morning.

Having just googled it would appear that the average shower lasts 8 mins and uses 62 litres!(not in my house!)


In any case I think people over-estimate the heat loss from a modern well insulated tank. My 300litre unvented tank loses 1.3kWh in 24 hours with the water at 65C. - (British Standard test) So in practice the OP would not lose anything like that amount. In any case the heat is not lost as it warms the fabric of the house.