Electric Hot Water Cylinder

[Pete Deker]

Hi just had a new 150 ltr electric hot water cylinder installed, we don’t have any gas here.
It’s invented/ direct. It was heated for two and half hours went gent was here installing to test and then
another hour on boost, the water wasn’t used that day. Next morning I put the boost on
for an hour in the morning just because I thought fab a nice hot shower. I was in the shower
6-7 minutes and the hot water was finished. Is this normal am really disappointed and thought
It would last long enough to shower and wash my hair? Am I doing anything wrong ?
Any help would be appreciated thanks.

 

[Agile]

150 li is not very large but it all depends on how many live there.

You need to use the lowest immersion element.

Often a switch labelled "boost" is only connected to an element near the top to give a small amount of water for washing up.

You also need to measure your shower flow rate. Then you can see how long you can expect it to run for when all the cylinder capacity is available.

 

[Pete Deker]

Thanks, we thought the 2.5 hours on timed would have heated the lower part.
One person here sometimes two so hopefully 150 ltr is enough. What would a good flow rate be please?
Cheers

 

[Johntheo5]

A power shower can use a lot of HW but assuming say the whole 150L heated to 60C and a mains temp of 8C then you should get ~ 240L at 40C so the shower would need to be flowing 34LPM to use up the water in 7 minutes, very very unlikely?.
As above, a (bottom) 3kw element will take nearly 3 hours to heat to 60C from say 10C and at least 2H 20M to reheat from 20C to 60C.

Maybe you have a top mounted dual immersion.

 

[Pete Deker]

Golly it’s a minefield. it’s a Gledhill PLTDR150 so I didn’t need the extra external bit.

 

[Johntheo5]

Thanks, we thought the 2.5 hours on timed would have heated the lower part.
One person here sometimes two so hopefully 150 ltr is enough. What would a good flow rate be please?
Cheers

What power is the bottom element??, if 3kw then 2.5 hrs should heat 150L to 60C from 17C, should be almost OK?.

 

[Pete Deker]

Also if I don’t use the hit water today will it stay hot for use next morning? Thanks

 

[Pete Deker]

This my cylinders info if it helps you understand my questions, cheers

• 90 degree elbow for quicker installation
• High specification duplex stainless steel
• Floating baffle
• Lift up temperature and pressure relief valve for easier drain down
• 3kW incoloy immersion heaters for use as primary or back-up heat source
• Corrugated StainlessLite Supercoil for faster recovery times
• Internal Expansion Vessel Space saving and quicker installations
• Aligned tapping positions Improves ease of installation
• Colour matched components Improved aesthetics
• Wide base Improved stability
• Rubber connection labels and
• improved caps with foam retention
• Increased component durability
• Quality components Reliable, durable product
• Corrugated coil Increased heat transfer, compared to plain coil, and
• prevention of scale build up

 

[MNW67]

This seems to be your cylinder. There are two immersions, one at the bottom and one half way up. I've never had an electric cylinder. How do you choose which immersion to use?

What power is the bottom element??,

Both are 3kW according to spec. Can you put both on at the same time?

 

[Johntheo5]

Unfortunately Pete, because you have a internal expansion air bubble then the effective HW available is ~ 115/125 litres except they have allowed for this in the specification which I greatly doubt.
If you say, use 120L as your available HW at 60C then you will have ~ 195L availble at 40C.
The heat loss is 1.3kwh/24hr so a temperature loss of around 7C so temp after being off for 24hrs will be ~ 53C gives 170L available at 40C.

 

[Agile]

The lower one would be used if on a cheap rate night time supply.

Then the upper one would be used for a daytime boost . Or left on all the time to ensure hot water at any time.

 

[MNW67]

Unfortunately Pete, because you have a internal expansion air bubble then the effective HW available is ~ 115/125 litres except they have allowed for this in the specification which I greatly doubt.

Spec says 139L

What would a good flow rate be please?

What sort of shower head do you have? Anything over 10 litres per minute is a very good shower, IMO. If you use the main immersion and get the full tank to 60C you should have 200 litres of showering water at 40C. Unless you have a massive shower head, that should give you a good long shower. It sounds like you may only have had half a cylinder. What temperature is the cylinder set to?

 

[Johntheo5]

Spec says 139L

Where did you see this info?. (probably the stated capacity)

The PLTDR 150 is the second one down according to the sheet I'm looking at with a capacity of 139 Litres and a heated volume of only 100 litres probably due to where the lower immersion is located at 240 MM from the bottom in a 1118 MM high cylinder so 78.5% (theoretically) being heated, 139*78.5%= 109 Litres max, if I am looking at the correct info then I reckon it will be even less that 100 litres due to the air bubble, then again they give a stated heat up time of 154 minutes, a 3kw heating element will emit 7.7kwh in 154 mins or 2.57 hrs which will raise the temperature of 100 litres of water by over 66C, a final temp of say 76C???, doesn't make sense, it will raise 132 litres from 10C to 60C though??.

 

[Murdochcat]

Think we a bit more clarity about the set up

Are both immersions connected?

If so are you using 1 - top or bottom? Or both?

 

[Johntheo5]

I hope the heated vol isn't even less than 100 litres as my calcs show the dip tube has to extend down ~ "22" litres to create a air bubble great enough to prevent the final pressure not exceeding 5 bar or so with a full reheat.