Hot water control pads

my husband and I are building our second house and we are yet to go to selections.
We are contemplating getting control pads for the hot water but I don't really understand how they work.
Well I understand that they make the temperature of the water hotter or colder but what I don't understand is how many control pads we would need.
Do I need one per bathroom. If I have one per bathroom does it control all of the things in the bathroom eg if I have a bath and shower in the bathroom does it control the temperature of both or just one?

Any advice, pros or cons would be great to hear

They are simple. Only one controller can be active at any one time. The water temperature will be what ever that controller is set for (and the others will change accordingly).

Personally think they are a great idea, as you only heat the water to what you want rather than overheating and cooling by mixing in cold. So means for example when you have a shower, you set your temp and turn only the hot water tap on.

There are also controllers which will only allow a certain amount of hot water to be utilised before turning off (great for rationing shower time)

How many all depends, but most systems only accept around 3 anyway. So ideally kitchen, bathroom and ensuite.

The kitchen controller may be able to set a higher temperature than other rooms. Depends upon many things such as brand and local laws etc. In my house my kitchen controller can go to 60c, but the bathroom and ensuite only 50c.

Some brands also have a pre-heat function, though this also needs a pipe from the furtherest hotwater outlet back to the heater and an additional box at the heater. Basically when you press preheat, the box draws water from the futherest outlet, thus pulling through hotwater, as sometimes it can take 5-10 seconds for hot water to start flowing out of far away outlets.

Thankyou for your reply

We had one at our old house. We had one control pad which was in the kitchen and we set the water temp for the whole house via this. It was great not having to turn the cold water on at shower time.


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Yeah reckon if you have an instantaneous hot water heater like this it is crazy not to have control pads, for the reason I said above, what is the point of heating water to only then cool it to what you desire, when you could just set it and use the hot water tap. Doing that you also get the same temperature everytime without having to make adjustments to your hot/cold mixture.

I don't know about elsewhere, but from what I have heard instantaneous gas must heat the water up to 70 or 75 degrees to get rid of the legionella bacteria, it then has to go through a tempering valve which drops the temperature back down to less than 50 degrees (although you can bypass a tempering valve if the water is going to the kitchen or laundry only).

Storage hotwater, be that solar or heat pump, needs to remain at 60 degrees or hotter.

Why the difference? storage stays at that temperature for longer which kills the bacteria slower. Instantaneous is hotter so it can kill the bacteria quicker.

Partially right. If you have a tank, then the water needs to be heated to a minimum of 60' to kill legionella bacteria. But if you have no tank then there is no risk of bacteria as water is not being stored as legionella needs warm temperatures to colonise.

Where you might be confused is if you have a solar system, ground pump etc with a storage tank, and instantaneous as a booster, then yes the booster needs to be able to heat to at least 60 to kill the bacteria and then tempered down for safety. Same is true for tanks only. But if using a pure instantaneous and no storage then there is no legionella concern and it can simply heat to the temperature required.

Thanks for the update AJW.

Can the control pads be added later without too much problems? We have a Kelvinator 26L included in our tender but we didn't get the control pads.. if we decided later to have them installed, would that be possible? And if it is, would it be expensive because it wasn't added at the time of the install of the HWU itself?

In theory yes it is possible to do after but a few caveats.

Firstly if you don't have controllers the output temperature can be max 50 degrees but with controllers max 60 set by the kitchen controller only. (Think this is still the case).

Now depending upon brand and model you may not be able to get 60 as retrofit.

I will give you an example. My house had controllers from the outset so I can set 60 in the kitchen. My neighbour has the same model an Rinnai infinity 24 but not originally fitted with controllers. I retrofitted them for him but could not get it to go to 60. The infinities have switches inside to change the max temp but turns out the model he had was fixed to max 50 and ignored the switches.

I knew about the legionella aspect re tanks but always wondered how solar setups worked. Thanks for clearing that up AJW.

Stewie

Is not having 60 such a big deal though? I mean if it's already switched permanently to be 50 and you connect controllers and find out that it is "stuck" on 50, is that so bad?

I assume there is some amount of wiring that would need to be fed back to the HWU? My father is a licenced electrician, so wiring wouldn't be an issue.. just would be fiddly I guess.. but no more fiddly than putting in a new circuit I guess.

It doesn't get stuck on 50 just that 50 is the maximum. If it was stuck controllers would be pointless. The pint of going higher in the kitchen is higene. Wiring is not much just two wires generally and the controllers of the brands I know Rinnai and Reheem come with cable. One difference is Reheem the bathroom, kitchen and 3rd controller are different parts but Rinnai you can use 4 identical units and they sort themselves out and you do some button pressing to set the kitchen controller.

OH Rinnai also has a wireless option too. You wire the wireless transmitter to the heater and away you go. You can also have 3 wired controllers too. But not much help if you have different brand.

Ok thanks. We'll think about it after we move in.

We have a 24L Rinnai - probably 12 years old, and I remember we had problems with the low output of the shower head resulting in a sudden temperature drop so I downloaded a later version manual for the26e which has a diagram for all the dip switch settings ( jumpers ).
I'm pretty sure by looking at the diagram - page 26, you can change one of the settings ( computer programming ) so that your neighbours issue is fixed.

Stewie

Have the same document, but that is what I was getting at in the post above. The model he had it didn't matter what you dd with the switches 50 was the max that could be selected. Apparently it was a compliance thing. No controllers out of box= fixed 50 degree max (even had a sticker on the front stating this), with controller you could change the maximum temperature using the switches, which then allowed you to choose higher than 50 on the nominal kitchen controller but max of 50 on the bathroom controllers.

One thing I never have understood with this method is the controllers don't know what tap is running. So if the kitchen is master and set to 60 and you turn on a bathroom tap you get 60!

I guess as you say if there is one model where you can't adjust the dip switches then that is that.

I would have thought that there would be a bit more electronic trickery built into them these days where the individual controllers "talked" to the main unit but obviously not, even allowing for the fact that it has a small computer chip inside.

Stewie

It is not an issue of smarts in the controller, the issue is the controllers, nor the heater know which tap has actually be turned on. All that happens is a hot tap is opened somewhere, water flows through heater, heater senses this and decides to heat it to the temperature set on the controller that currently has priority.

It wouldn't be hard to put a flow switch in a pipe to know what tap is opened, but that of course adds complexity and cost, and doesn't help much if two hot taps are turned on at once as which one has control?

Does anyone know if they help with priority?

Example I am in the shower and my MIL (we are including a granny flat in our build) puts the tap on full blast down the other end of the house. In our current house, this seemed to cause an issue, frequent bursts of cold water in the shower.

Priority just means the controller with priority is the one that is setting the temperature.

Controllers have no effect on water pressure though if you have controllers and only run the hot water tap when showering etc you won't get a temperature drop just a pressure drop.

If you run hot and mix with cold then the same issue applies. But that would for the most part be a silly thing to do anyway.