Advice on Install a new Electric Shower (currently unvented cylinder)

[Jan2238]

Advice on Install a new Electric Shower for shower cubicle and keep using the unvented cylinder water heater for bathtub

I have an Unvented Cylinder Water heater 125 litre (MegaFlo) in an apartment of ( 15 years old)
Currently it is not really capable of delivering enough hot water for more than 2 showers. Some days even the first shower is only. That’s why I would need to install a new electric shower. I do understand I need an electrician to rewire the cable for electric shower and plumber to do water pipe part. But I have an issue for water part. Can any plumber gives me an advice on this issue?

-Currently use mixer shower tap in shower cubicle, cold and hot water coming from the water cylinder.

install a new electric shower , If need to convert mixer shower valve tap back to individual cold and hot water tap. Because only Cold water inlet pipe for electric shower. Does it require the water boost Pump? Do I need the isolate the hot water inlet in area of Shower cubicle. As currently the hot and cold water coming from the cylinder tank . I would need some advice. Thank you.

 

[SimonG]

By the time you've paid for shower, making good in shower, plumber and electrician for an inferior showering experience you could go bigger cylinder.

 

[Jan2238]

By the time you've paid for shower, making good in shower, plumber and electrician for an inferior showering experience you could go bigger cylinder.

Thank for your comment. However, my apartment does not have enough space for bigger cylinder.

 

[gpbeck]

How long do you heat your cylinder for? Are you just using the top element? And what is the thermostat setting?

 

[Jan2238]

How long do you heat your cylinder for? Are you just using the top element? And what is the thermostat setting?

Hi, Gpbeck, thank for your reply. 2 hours is required to heat whole cylinder. Boost mode is using the top element . It can heat up very little hot water only. The full tank of hot water is just for 1 shower for 15 mins only. Hot water is really not enough for 2 showers for 2 persons. However ,I would need at lot of hot water during the day time and evening time. That's why I would need to install a new electric shower. I need advice from the plumber if need to convert my current a mixer hot and cold water tap to individual cold water inlet for electric shower. My current hot water system is unvented cylinder.

 

[EvilDrPorkChop]

Put a flow restrictor into your current shower of what would be the same as an electric shower. Your 125l will last you then.

Also check that the stats are set at 60oc. As others have said, you could increase the size of the cylinder rather than put in an electric shower. Seems a daft idea to me.

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[John.g]

Perhaps increase the cylinder temp to 75C, install a TMV to reduce to 60C before distribution, this will give a extra 38 litres at 60C, a 30% increase, assuming mains at 10C.

 

[gpbeck]

So are you heating the bottom thermostat?

 

[gpbeck]

Hi, Gpbeck, thank for your reply. 2 hours is required to heat whole cylinder. Boost mode is using the top element . It can heat up very little hot water only. The full tank of hot water is just for 1 shower for 15 mins only. Hot water is really not enough for 2 showers for 2 persons. However ,I would need at lot of hot water during the day time and evening time. That's why I would need to install a new electric shower. I need advice from the plumber if need to convert my current a mixer hot and cold water tap to individual cold water inlet for electric shower. My current hot water system is unvented cylinder.

So are you heating the bottom thermostat?

 

[Jan2238]

So are you heating the bottom thermostat?

I do not know if heating the bottom thermostat.

The unvented cylinder is wired with Horstman Economy 7 control ( takes 2-3 hours to heat up)
By Timed mode, the cylinder will heat up the water daily from midnight 12:00 to 3:00am only. The full hot water will be ready in the morning. I think it is heating the bottom. f require extra water, just push Boost button. However, it can supply very little hot water by boost mode. I think it is heating the top only.
However, one full tank of water just for 1-1.5 shower in the morning and need to wait another 2 hours to heat again.

I think I may need an electrician to remove this Economy 7 control so it allows to set manually on/off in different time slot. As the current E7 controller limits to heat up hot water one time a day. And it will take 2 hours to boil.
I would need unlimited hot water supply constantly. So I keep thinking to install a new electric shower.

 

[Chuck]

The unvented cylinder is wired with Horstman Economy 7 control ( takes 2-3 hours to heat up)
By Timed mode, the cylinder will heat up the water daily from midnight 12:00 to 3:00am only. The full hot water will be ready in the morning. I think it is heating the bottom. f require extra water, just push Boost button. However, it can supply very little hot water by boost mode. I think it is heating the top only.

I assume you have the 'Electronic' version of the controller. If so, the standard set up for that controller is as you say. The boost button energises the upper immersion heater only and there is one timed on period that defaults to the middle of the usual E7 cheap rate period. You can, however, add additional timed periods that heat the whole tank. The user instructions explain how to do this.

It takes 26 MJ to heat 125 litres of water from 10°C to 60°C. A 2.4 kW heater running for three hours also delivers 26 MJ. So your night time heating period should give you a full tank of hot water. Once you've mixed the 60°C down to 40°C (which is still a bit hot TBH) you're using more than 200 litres of water for a single shower. As a rule of thumb you can get one nice long shower out of at 125 litre tank (15 litre per minute for 15 minutes). If you fit a more economic shower head, e.g. Mira ECO (7 litre per minute) and spend closer to 8 minutes showering you should be able to get up to four showers from the same tank.

 

[John.g]

Won't go through the dreary calcs but a 2.5kw heating element will heat the cylinder easily in 2.5hours and a 3kw element in 2 hrs so it looks like you are heating from/with a bottom installed element. If this is the only element fitted then "boost" which generally only means a timed heating period of maybe a hour or so will/would require the same time of 2/2.5 hrs to increase the temp to 60C again.
What you may have is another element installed higher up in the cylinder and very easy to verify just by looking at the cylinder which heats say 30litres, the boost function could possibly bring this heating element on and would only take 30 to 40 minutes to heat to 60C but obviously only 30 litres or so available at this temp.

Re electric shower, A 9kw unit will give a continuous HW flow (only for showering) of 4.3LPM at 40C (10C mains) and will be as low as 3.8LPM in winter and as "high" as 5.2LPM in summer, as long as you are aware/happy with this then yes, why not?.