Mira Advance Flex 8.7KW v 9.8KW

[Harry Bloomfield]

It's fine for everyday use, the electric thermostatic models are a lot pricier for not much more spec.

They are a lot more complex electronically, but electronic complexity is cheap to reproduce. I would suggest the difference between a basic, control the temperature, by adjusting the flow, shower - and the electronic versions, is like night and day. I would not want a basic shower on the place, using one involves far to much messing about, tweaking the flow constantly as you try to get a shower. Set your desired temperature, press the button, and simply get on with it.

 

[ebee]

I disagree Harry.
Unless a lot of users with different prefferences then simples.
The Flow Rate (therefore heat rate) has only to be altered fractionally throughout the year.
Most of the time, once you find a setting you stick with it for weeks/months, no problem.

 

[SUNRAY]

As landlord I have a duty to maintain the property. There are certain things I keep in stock so I can attend to failures in a timely manner: taps and washers (including reseating tool), ball valves and floats, copper pipe fittings and olives, shower unit and a few spares. As a landlord I'm very aware that things don't last as long in rental properties as they do owned properties... why? I don't know. I for one will not provide electronic equipment if I can avoid it due the the rediculous failure rate that tenents manage. Even things like dimmer switches I imediately remove when they vacate.
Yes Electronic complexity is cheap to manufacture but at failure where instant repair is expected it takes longer and costs more to repair inteligent showers than replace with simpler unit.
Showers with multiple controls are not suitable for situations where carers frequent to assist showering, how do I know that? I listened to my father-in-law and changed his electronic all singing all dancing shower (which I sold on Ebay for £130) for a 10.5KW basic unit and marked whe temp/flow knob and cold/low/high knob with a marker pen arrow and all the issues of changing settings simply disappeared.

As said before we use the unit on low power which I assume is something like 7KW and at this time of year we move the flow rate about 5mm to cope with the variation of supply temp, hardly an arduous process.

They are a lot more complex electronically, but electronic complexity is cheap to reproduce. I would suggest the difference between a basic, control the temperature, by adjusting the flow, shower - and the electronic versions, is like night and day. I would not want a basic shower on the place, using one involves far to much messing about, tweaking the flow constantly as you try to get a shower. Set your desired temperature, press the button, and simply get on with it.

Sorry Harry I simply cannot understand that. All I do is turn the knob to 'LOW' and within seconds it's at the temp I expect, time after time after time, add a very slight adjustment twice a year. And in rental will automatically remove a complicated thermostatic unit as they are far too much hassle to train the tenents and far too expensive to keep repairing/replacing on a regular basis.

Oh and no silly shutting down when someone else in the complex flushes their toilet being reported as a fault on a regular basis.

 

[JohnW2]

The bog standard showers are fixed heaters and you control the water flow rate to alter the temperature. .... That is good enough for lots of folk but by no means all.

Agreed, on both counts.

They all have a "Thermal Cut Out" of some sort to disconnect 1 or more elements but are still capable of being extremely (scalding) hot until the water flow has flushed a bit.

I suppose that is inevitable to a degree. However, if there were some sort of 'cut-out' designed to operate at, say, about 45,one would not really expect 'scalding hot' water to ever occur, would one?

Other models have thermostatic controls and they are often run by electronics.

If the user has separate ('manual') control over flow rate, I would think that it would have to be pretty clever to 'work well', since it would presumably require power supplied to heating elements to be 'continuously variable' ('modulated') - since I would not think one would get satisfactory temperature control if the element was just on/off, or switchable between just two or three levels of power?

Kind Regards, John

 

[Harry Bloomfield]

If the user has separate ('manual') control over flow rate, I would think that it would have to be pretty clever to 'work well', since it would presumably require power supplied to heating elements to be 'continuously variable' ('modulated') - since I would not think one would get satisfactory temperature control if the element was just on/off, or switchable between just two or three levels of power?

As in triac controlled? It on and off rapidly, to match the average power to what it required to match the demanded temperature. I notice no variation in temperature, during a shower.

 

[Harry Bloomfield]

Sorry Harry I simply cannot understand that. All I do is turn the knob to 'LOW' and within seconds it's at the temp I expect, time after time after time, add a very slight adjustment twice a year. And in rental will automatically remove a complicated thermostatic unit as they are far too much hassle to train the tenents and far too expensive to keep
repairing/replacing on a regular basis.

Our last clever shower lasted 20 years, until it suffered water ingress damage, I was sorry to see it go, it had been so reliable. I replaced it with a similar, expensive model - I didn't pay extra for no reason - I wanted the 'set the temperature and forget' with tight control.

Oh and no silly shutting down when someone else in the complex flushes their toilet being reported as a fault on a regular basis.

Nowt wrong with that, it's to protect the unit from overheating, and the user from being scalded - I don't live in an HMO, I just mention I'm having a shower, and then no one uses any water until I;m done.

 

[JohnW2]

As in triac controlled? It on and off rapidly, to match the average power to what it required to match the demanded temperature. I notice no variation in temperature, during a shower.

It doesn't really matter how the switching is achieved - whether with a TRICI, a relay/contactor or whatever, but if it is only doing on/off switching, the heating of the water will also be 'on/off'. To achieve something approach a constant output water temp,that 'on/off switching' would have to happen at a fairly high frequency, presumably ideally some sort of 'PWM'.

Kind Regards, John

 

[Harry Bloomfield]

To achieve something approach a constant output water temp,that 'on/off switching' would have to happen at a fairly high frequency, presumably ideally some sort of 'PWM'.

Which is what it uses, via triacs - you cannot do that, with relays.

 

[JohnW2]

Which is what it uses, via triacs - you cannot do that, with relays.

Certainly 'nicer' (and 'quieter'!) with TRIACs. How practical it would be with a relay depends upon the switching required - we managed a lo achieve a lot with electromagnetic devices before semiconductors came along (think back to telephone exchanges a number of decades ago!)

Kind Regards, John

 

[Harry Bloomfield]

Certainly 'nicer' (and 'quieter'!) with TRIACs. How practical it would be with a relay depends upon the switching required - we managed a lo achieve a lot with electromagnetic devices before semiconductors came along (think back to telephone exchanges a number of decades ago!)

But would it, and all those high wattage resistors needed, all fit into a neat little box on the bathroom wall

 

[JohnW2]

But would it, and all those high wattage resistors needed, all fit into a neat little box on the bathroom wall

What are these "high wattage resistors needed"?

Kind Regards, John

 

[Harry Bloomfield]

What are these "high wattage resistors needed"?

Kind Regards, John

If you are using relays switching in and out resistors, in series with an 8Kw element, then they need to be high wattage. Other than that, is would have to be multiple elements switched in and out.

 

[ebee]

By the way. In my case the thermostat (used as a thermal cut off not as a thermal cut out) is a sort of antiscald idea I believe not used as a regulator I think, that is the point.
It is a bog stasndard dependant upon water flow for variation of heat but it does give a little protection from overheat/scalds. Of course a controlled run over of flow is far better than this "backstop" reduction . Of course a thermostat is (can be) better but if electronic it has more/greater point of failure.
I picked the terms "horses/ Courses" and "Blanket statements" quite deliberately

 

[JohnW2]

If you are using relays switching in and out resistors, in series with an 8Kw element, then they need to be high wattage. Other than that, is would have to be multiple elements switched in and out.

I thought you were talking about switching the element on/off, not switching resistors in series with it. The latter would surely be a ridiculous way to try to do it, wouldn't it (since you would need "kW-rated" resistors !!) ?

As you say, to have multiple (usually jsut two) elements is a common (and much more sensible) approach - but on/off of two elements strill will not give very smooth temp control.

Kind Regards, John

 

[Harry Bloomfield]

As you say, to have multiple (usually jsut two) elements is a common (and much more sensible) approach - but on/off of two elements strill will not give very smooth temp control.

Exactly, which is why mine uses PWM zero switched triacs.

Of course a thermostat is (can be) better but if electronic it has more/greater point of failure.
I picked the terms "horses/ Courses" and "Blanket statements" quite deliberately,

They still have to include a bimetal switch cutout for safety, electronics can fail, relay contacts weld up, triacs go short circuit.