Water heater for kitchen sink

[Crossy]

With all these problems, there's an easy way and a hard way.

 

The easy way is a small tank heater with a 1.5kW element plumbed into the existing cold supply and powered from a regular outlet. All modern tank heaters have the relevant safety devices built in so it's not a complex task.

 

Once it's heated up you have enough hot water to do the washing up. Then it re-heats fairly slowly until you need more hot water.

 

QED

 

 

[longball53098]

I installed a Fujika branded multipoint heater under the kitchen sink back in 2010 when we built the house. 6000 watt model at the time and it still works well. Electric connection hardwired direct to a breaker in my CU. The heater gives us tons of instant hot water at the sink in kitchen. Of course it is plumbed with a mixer tap for adding cool water. The newer models now have electronic controls to adjust the hot water temp and keep it at or below the set temp. When this one should fail I would put that style in place. My Thai wife loves the hot water to do her dishes and other things.

[Beachcomber]

15 hours ago, plus7 said:

Beachcomber, thank you very much for your underestimated comment. Initially I didn't understand it completely and skipped it in my mind.

Only now I realized what you actually meant.

Thank you, thank you!

 

 

You are welcome, "Steam Pressure Relief Valve" is not a phrase that readily springs to mind.

 

In your situation things are not so bad. The Hot water unit actually is not sealed even though the tap at the sink is closed. 

 

The inlet pipe is still open and theoretically, any build up of steam from a faulty unit could have a relief route pushing the water in the inlet pipe all the way back to the village supply, relieving the pressure in your unit.

 

Don't know how your neighbors would feel about having hot steaming water coming out of their cold tap. ????

 

 

 

 

[plus7]

A technical guy came to me and said that new line will be problematic. Have to cut ceiling and so on.

He offered a switch between nearby aircon (rarely used) and heater.  So the current could flow either to aircon or to the heater.

He didn't provide any details what kind of switch and how it looks like.

What do you think, is it a good idea ?

Would be great of the switching could be remote controlled.

[Crossy]

45 minutes ago, plus7 said:

A technical guy came to me and said that new line will be problematic. Have to cut ceiling and so on.

He offered a switch between nearby aircon (rarely used) and heater.  So the current could flow either to aircon or to the heater.

He didn't provide any details what kind of switch and how it looks like.

What do you think, is it a good idea ?

Would be great of the switching could be remote controlled.

 

You could just hook both to the A/C line, the breaker, if appropriately sized of course, would protect the cable.

 

I'd actually lay odds that it would never actually open even with both on together. Not really good practice but ...

 

What size cable and breaker go to the A/C?

[plus7]

17 minutes ago, Crossy said:

What size cable and breaker go to the A/C?

Crossy, thank you very much for your attention to my topic. All comments really help to understand what I need and what should/can be done.

 

From the breaker, which has "C20" on it, goes 4 sq.mm. wire. Then at some point it is twisted with 2.5 sq.mm wire that goes to aircon 12k BTU.

At this "twisting" point I want to install something that splits current either to one or to another device.

Probably breaker need to be upgraded to C32 (I have it for existing heaters)

 

 

[Crossy]

OK 4mm² is good for a 32A (stretch to 40A) breaker so flat out 7kW or so.

 

Your 12000 BTU A/C will pull about 1,200W or 5.5A when at full chat.

 

Assuming there's a good splice (crimped, not just twist and tape) you could safely hang a 6kW water heater on there with no issues.

 

NOTE:- Although 32A is over-size for 2.5mm² cable there's no possibility of overload as it has a fixed load on the end. UK wiring regs would permit provided a short at the end of the 2.5 would open the breaker (it will be fine unless that's a loooong bit of 2.5) 

[xtrnuno41]

8 hours ago, plus7 said:

xtrnuno41

Thank you for your comment. As I found out I need a water heater device, not a shower heater device. Those devices are 6kw.

I have a spare 30ma RCBO and wires for never used hot water wire in "guest bathroom".

Do you think those wires could be connected somehow ?

It is 2-story house RCBO on 1st floor, kitchen on ground.

They could say pooling a whole wire from up to down is problematic or "not possible, sir".

 

 

 

Both are heating up water. I just would simply use the shower heating device , common in Thailand, and the 3.3 kW is more then sufficient to get hot water, as they are used in showers for hot water.

 

With a 6 kW you increase power, the 4 mm2 is still capable enough. You ll have I=P/U , 6000/230= 26-ish A.

Your spare RCBO ( i red ) is C20 A, you will have to replace it then (C30), when using a 6 kW device. And that is just when it is in stable condition working. The current is even bigger in a spike when you turn it on. But ok that would be short time, but if you operate hot water several times in a row, it all could add up. Every time a spike. That is with a shower heater.

With a boiler only when temperature water is below setpoint. With a boiler you also have coming cold water in instantly, also mixing with the hot water. It s constructed the cold water is pressing out the warm water, but also then starts mixing, simply it is in contact with the hot water.

 

Is this device a boiler (?) then only switches when temperature gets below setpoint. I guess it is. The tempcontoler is in the bottom, some away from the  heating element. 

You have several household of them from just 10 ltr up to 120 ltr, but you cant install them all in a cabinet, only the little ones. But see my former remarks about boilers, cq multipoint heaters. I even said there should be a relieve valve on it, but maybe that is a safety demand in my country. I have a 15 ltr with that.

Kitchen was way of from my gas multipoint (heater) and it took too long for me having warm water, so spilling cold water, also leaving warm water pipe filled with warm water for nothing. There for i built in cabinet, as they call it here, close in boiler. Now my gas multipoint is  singel point.

 

I see the situation changed and you had someone coming. Also as  somewhere is a 4 mm2 cable going from fuse box C20 to a joint for airco where 4 mm2 goes into 2.5 for airco. As you said , you could use it as well for the heater. Good.

 

Making a box with 2 switch(es)? Or airco or heater? The cable to the heater should still be 4 mm2 and the switch must be able to handle the current.

Probably as they do in Thailand use a fuse capable in current.

But then you and others have to be aware, just ONE of the switches is on and thats tricky.

Not really desirable.

 

If they put in a real "or switch", meaning or airco or heater is on, not both at the same time. That is THE way, safest.

Just one switch standing or left or right, choosing desired device.

Of course the switch must be able to handle the highest current. 

Of course you can make it remote control, but then you need to do way more things. Or "auto switch" with a built in priority handling. 

 

As if both on the same line are on and working at full capacity, you ll have 26 + 5 (Crossy reference airco) =31 A., in case of the 6 kW heater. Up till limit cable. Fuse can be C32, but is also on working "limit".

With some switching the fuse could be blown out. Not a shortcut then, but the fuse is heated up and breaks. Thermal trip.

[plus7]

xtrnuno41,

Thank you for your comment. Yes, there are "smart switches" that support high current and wifi and remote stuff. They can even report current, temperature...Technical progress is coming. Never thought that I would need something from "smart home" department.

 

I was told shower heater models are not supposed to have valve on the outlet (like kitchen sink).  Instead, they have valve on input stream. Of course they handle it, but not long.

 

 

[xtrnuno41]

1 hour ago, plus7 said:

xtrnuno41,

Thank you for your comment. Yes, there are "smart switches" that support high current and wifi and remote stuff. They can even report current, temperature...Technical progress is coming. Never thought that I would need something from "smart home" department.

 

I was told shower heater models are not supposed to have valve on the outlet (like kitchen sink).  Instead, they have valve on input stream. Of course they handle it, but not long.

 

 

Cant come up with a technical reason to control in- or out let.

In Thailand it is not like western way, where we have separate cold and hot connections. In the tap, we mix the streams and quantity.

Thailand has pipe coming out of wall, easy to solid connect a tap on it then and then lead to device. Easy way to connect then the shower right on it and ready for shower. Cheap way. Control quantity with one solid tap and temperature with electronic control. 

Im assuming you are going the western way with tap? 

To make 2 connections cold and hot, so you can choose and mix with the handles?

 

 

[lopburi3]

9 hours ago, plus7 said:

I was told shower heater models are not supposed to have valve on the outlet (like kitchen sink).  Instead, they have valve on input stream. Of course they handle it, but not long.

Believe both types are available - the kind you would need is called a multi point.

[Crossy]

8 hours ago, xtrnuno41 said:

Cant come up with a technical reason to control in- or out let.

 

The shower type are intended to operate with the outlet open (shower head only), so if it all goes wrong and the heater boils it vents though the open head, so no need for a safety blow off in the heater to stop it blowing up, less $$$.

 

Many will actually function just fine with a tap on the outlet, but they are missing that vital safety device.

[degrub]

And when it does go wrong with a closed kitchen tap, the bursting heater internal line or joint will spray whatever volume present in the unit of superheated water followed by hot water. Any flesh in the way of the water/steam  mixture will get instant 2nd and 3rd degree burns.  
 

How likely depends on the details of the unit’s control design and built in safeties. That is what the thermal pressure relief valve guards against.  Works the same for an ordinary tank type water heater  with the only difference being the volume.