Electric Shower Pressure Query

[Pretty Mouth]

Yes shower is generally being used on high setting mode instead of economy mode however even on high setting mode the temperature dial would only be set to about 50% as 100% is almost kettle temperature. Aware the hotter you put it the slower the water trickles through. However was wondering whether as on cold we are only getting 0.75 bar whether there are gains of 0.25 being lost somewhere/make much of an improvement? As on cold no heating elements are used therefore no bottleneck, should be a straight flow through.

I will have a go and experiment with the settings again, good point about a potential heating element being bust, would there be a way to test this? I believe the unit is dated 02/14, most likely manufactured date however it most likely is 3-4 years old now?

The only thing I can think of is run it on high setting, then change down to economy setting and see if there is any difference in the water temperature.

If no difference in temp, then I'd expect an element has gone completely. If it runs cold, without any heat at all in economy, then I'd also expect an element to have gone. If it is noticably cooler in economy setting, but there is some heat, then I'd expect the elements to be working as they should be.

 

[brianmoooore]

Electric showers follow a simple equation: Power input = flow rate x temperature.
Rearranging, temperature = power input/flow rate, so, if the temperature is correct and the flow rate is low, the power input must be low as well.

The only thing I can think of is run it on high setting, then change down to economy setting and see if there is any difference in the water temperature.

If no difference in temp, then I'd expect an element has gone completely. If it runs cold, without any heat at all in economy, then I'd also expect an element to have gone. If it is noticably cooler in economy setting, but there is some heat, then I'd expect the elements to be working as they should be.

 

[Avo Mk8]

As above, the flow and temperature you get from an electric shower is determined by the laws of physics.
Mira published the graph below to illustrate the performance of their showers.
(from this publication: https://www.mirashowers.co.uk/media/1453/miras-guide-to-electric-showers.pdf)

Assuming cold water is coming into the house at say 15 degrees, and you like a nice toasty shower to be at 40 degrees, you need the shower to heat the flow of water by 25 degrees.
The graph indicates that to achieve a flow of 6l/min, you need at least a 9.6kW shower element.

The original post #1 suggested the shower is rated at 8l/min at 1 bar. That may be the max flow you can get out, but the rise in water temp you would get from a 9.8kW shower would be about 18 degrees, so would feel cool! If you then compensate by turning the shower temperature up (which just reduces the flow) you would be down to about 6l/min to get a comfortable temperature.

From the OP's observations I am wondering if the shower is actually performing more or less consistently with the graph below?
If so, maybe the conclusion is that a more powerful shower would improve everyone's showering experience!

 

[brianmoooore]

Pretty Mouth's tests that I quoted above will determine if both elements are working, and if they are, it's likely that the problem is just unreasonable expectations.
I've also had the odd complaint of poor electric power flow which turned out to be tht the supplied shower head had been replaced by one intended for showers fed from a hot water system. Electric showers give the illusion of flow by using very fine jets in the head. If this is replaced by a head with larger jets, you get to see how poor the flow really is.

 

[Dave1UK]

Is scale a problem where you live (ie hard water). De-scaling the unit/hose and head can often make it seem like new!

Yes we do have a bit of a scale problem but nothing serious. Yesterday I took the unit apart, and checked the piping also the filter and they are spanking clean, 0 signs of any scale. When initially performing the flow test I tested it with the shower hose and head and also without i.e. just directly from the electric shower itself just to try and rule out any bottle necks with the hose/head.

The only thing I can think of is run it on high setting, then change down to economy setting and see if there is any difference in the water temperature.

If no difference in temp, then I'd expect an element has gone completely. If it runs cold, without any heat at all in economy, then I'd also expect an element to have gone. If it is noticably cooler in economy setting, but there is some heat, then I'd expect the elements to be working as they should be.

Tested this yesterday, put it on economy mode and about 80% temp turn and that's a reasonable heat although very poor flow rate in comparison to max/high mode and about 60% temp turn for a bit of a hotter heat.

As above, the flow and temperature you get from an electric shower is determined by the laws of physics.
Mira published the graph below to illustrate the performance of their showers.
(from this publication: https://www.mirashowers.co.uk/media/1453/miras-guide-to-electric-showers.pdf)

Assuming cold water is coming into the house at say 15 degrees, and you like a nice toasty shower to be at 40 degrees, you need the shower to heat the flow of water by 25 degrees.
The graph indicates that to achieve a flow of 6l/min, you need at least a 9.6kW shower element.

The original post #1 suggested the shower is rated at 8l/min at 1 bar. That may be the max flow you can get out, but the rise in water temp you would get from a 9.8kW shower would be about 18 degrees, so would feel cool! If you then compensate by turning the shower temperature up (which just reduces the flow) you would be down to about 6l/min to get a comfortable temperature.

From the OP's observations I am wondering if the shower is actually performing more or less consistently with the graph below?
If so, maybe the conclusion is that a more powerful shower would improve everyone's showering experience!

View attachment 109616

Will take a look at the link and graph appreciated.

Pretty Mouth's tests that I quoted above will determine if both elements are working, and if they are, it's likely that the problem is just unreasonable expectations.
I've also had the odd complaint of poor electric power flow which turned out to be tht the supplied shower head had been replaced by one intended for showers fed from a hot water system. Electric showers give the illusion of flow by using very fine jets in the head. If this is replaced by a head with larger jets, you get to see how poor the flow really is.

I personally rarely use the electric shower downstairs but have previously and to me it worked fine. However after the complaints from family members thought I'd investigate.

________________________________________________________________________________________________________________________________

To add I wanted to check the whole setup and cabling. So I did yesterday and to me it seems like a possible cowboy installation? As trying to figure if installing a higher kW unit would be possible but it wouldn't with the current cabling. I'm dubious if even the current setup is appropriate and not currently overloaded!

So we have the 9.5kW electric shower which is using a 6mm cable connected approximately 1.5m through the wall going to a isolating switch outside the bathroom (switch between the electric shower and mainboard power panel). This then feeds through the kitchen going to the utility room just outside under the stairs into the mainboard this is approximately a further 5.5m so total of 7-8m of cable. It's fused to a Crabtree B32 61 MCB breaker (rated 32A?).

The 9.5kW unit according to the manufacturers spec should have a 40A breaker? Heck even the 8.5kW needs a 40A unless I'm not understanding something along the lines. The 7.0kW/7.5kW would of been fine for the 32A and 6mm cable.

I have also read conflicting views elsewhere whether a 6mm cable under a certain total length is suitable as a replacement for a 10mm under certain conditions?

So now I'm wondering whether enough power is even being delivered to the unit to operate at it's full potential? Or would the unit not operate at all otherwise?

 

[brianmoooore]

An undersize cable would not affect the power delivered to the shower on such a short run, and a 'poor connection' would quickly show itself by burning out the joint and cooking any insulation present.
I'm fairly convinced that what we have here is an expectation that an electric shower will be a match for a well installed conventional one, which just isn't going to happen.

 

[Pretty Mouth]

I agree with Brian, I think the unit is operating as it should be, just it's not living up to expectations.

 

[brianmoooore]

@Dave1UK Are you certain that the shower head in use is the one that was supplied with the shower?

 

[nicebutdim]

I personally rarely use the electric shower downstairs but have previously and to me it worked fine. However after the complaints from family members thought I'd investigate.

Could the issue simply be one of urealistic expectations from family members comparing one shower with the other?

I feel the same after spending time in a hotel, then returning home to less than desirable water pressure.

 

[Not Mike]

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