Continuous flow for bathroom and storage for kitchen

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27th January 2008, 09:45 AM
GrahamC

Continuous flow for bathroom and storage for kitchen

My wife and I are building a new home and we are trying to work out what hotwater system we would like.

We like the temperature setting capability of the continous flow type and the dribble capability of the storage type. (We dribble hot water tap as we wash dishes).

So we were thinking about getting a continuous flow system mounted next to the bathroom and laundry that also feeds into a small storage unit (30L) under the kitchen sink for the kitchen.

The advantages of such as system is that
a) We can set the bathroom temperature independant to the kitchen.
b) We don't have the minimun flow problem of the continuous flow system in the kicthen because it is fed by a tank.
c) We get instant hot water in the kitchen because the tank is next to the kitchen sink.

What do people think? Can anyone see any serious problems or disadvantages?:roll:
27th January 2008, 09:54 AM
Uncle Bob

What's with this dribble thing? Is it to keep the water hot? If so maybe looking at a the options of having a heater installed around the base of the sink.

I'm fairly surprised that your building a new place but not including a dishwasher.

Edit: Oh, and as for your original question, I can see any problem with that, might be a good idea that the water heater is on a drip tray with a drain to waste or somewhere.
Anyhow a plumber will be along to answer this in black in white (I was a plumbers mate for a couple of years).
27th January 2008, 10:22 AM
GrahamC

The dribble thing is more of a trickle. Wash the dish in the sink and rinse it in the trickle / dribble.

You start washing as soon as there is a few centermetres of water in the sink. At the end of the wash the sink is rather full.

Oh yeah - we will have a dishwasher. I have never used one, so we don't know how much we will use it.
27th January 2008, 05:44 PM
Smurf

Quote:

Originally Posted by GrahamC

Oh yeah - we will have a dishwasher. I have never used one, so we don't know how much we will use it.

I've been living in this house for 3 weeks now. It has a dishwasher. I have not yet checked if the plug fits the sink as I haven't used it...

As for the original question, seems reasonble but remember you'll be paying for peak rate electricity for the kitchen unit. Not a huge cost in practice but don't expect to be saving on running costs with two systems as any saving in reduced loss in pipes (since they will be shorter) etc will be offset by the higher rate for power used.
27th January 2008, 08:01 PM
Barry_White

Graham

If you are building a new house you will probably find that you will have to install a Solar hot water system to meet your point requirement of the new environment laws of BASIX.

I don't know if you realise it or not you have to reach a 100 points under BASIX.
27th January 2008, 10:30 PM
GrahamC

thanks for the feedback

Thanks for the feedback everyone.:2tsup:

I think I'll go for it (providing it fits in with basix) If it doesn't, I'll just get it put in afterwards - shouldn't be too expensive if I make sure the builder caters for it.

Cheers.
27th January 2008, 11:06 PM
ian

Quote:

Originally Posted by GrahamC

My wife and I are building a new home and we are trying to work out what hotwater system we would like.

We like the temperature setting capability of the continous flow type and the dribble capability of the storage type. (We dribble hot water tap as we wash dishes).

So we were thinking about getting a continuous flow system mounted next to the bathroom and laundry that also feeds into a small storage unit (30L) under the kitchen sink for the kitchen.

The advantages of such as system is that
a) We can set the bathroom temperature independant to the kitchen.b) We don't have the minimun flow problem of the continuous flow system in the kicthen because it is fed by a tank
c) We get instant hot water in the kitchen because the tank is next to the kitchen sink.

What do people think? Can anyone see any serious problems or disadvantages?:roll:

in response to (a) get two temp controllers for your (gas fired?) continuous flow HW system.
Mount the master in the bathroom and the slave in the kitchen.
get whatever temp HW you want where you need it

apart from the DW I recommend that you get a double sink
soapy water in one — rising water in the other
items waiting to be washed in one — rinse vegetables, drain the pasta or rice in the other
etc

as to BASIX requirements
I think that a gas fired continuous HW system will help you comply
but
a 30 or 50 litre under sink electric unit will give you negative points
check the BASIX calculator at http://www.basix.nsw.gov.au/information/index.jsp

ian
28th January 2008, 08:01 AM
Fuzzie

A dishwasher is one of those power tools that does get used more than the corresponding hand tool in our house :2tsup: Some designs get down around the 7litre level for water usage which is fairly efficient.

I'm not sure about the flow dynamics, but wouldn't the idea of using the water out of the small storage tank at a trickle mean it would then try to refill from the continuous system at a trickle? I assume the flow dynamics of the continuous system then wouldn't turn the heater on so you would just be refilling with cold water drawn through the continuous system. You may as well just plumb the storage system into the cold water already at the sink?

I understand the reason you want different heat levels at different points. Beware of solar systems in this regard. We replaced our electric storage with solar and it is a problem sometimes getting hot enough water in winter and below scalding water in summer. I'll eventually get around at looking into tempering valves for summer and putting the auxiliary heater onto regulated/offpeak supply for winter.

Maybe run the solar system into a tempering valve upstream of the continuous flow system for the bathroom and directly to a small storage system under the sink? At the rate you would use at the sink you would most likely just be topping up with the cold water flushed through the pipes from the solar storage.
28th January 2008, 08:05 AM
quriouskey

Quote:

Originally Posted by ian

in response to (a) get two temp controllers for your (gas fired?) continuous flow HW system.
Mount the master in the bathroom and the slave in the kitchen.
get whatever temp HW you want where you need it

You know that doesn't actually make any difference. You still only get the one temperature at a time - if someone's in the shower at 42 deg, you either wash up at 42 or wait till the shower is finished - and you still need to turn the tap on pretty hard to get the heater to start up at all.

Quote:

Originally Posted by ian

as to BASIX requirements
I think that a gas fired continuous HW system will help you comply
but
a 30 or 50 litre under sink electric unit will give you negative points
check the BASIX calculator at http://www.basix.nsw.gov.au/information/index.jsp

ian

The basix calculator doesn't have an option for more than one water heater. I guess if you're using gas instantaneous for your major usage (bathroom, laundry) you just select that and ignore the little electric storage heater in the kitchen.
Liz
28th January 2008, 08:14 AM
GrahamC

Quote:

Originally Posted by Fuzzie

I'm not sure about the flow dynamics, but wouldn't the idea of using the water out of the small storage tank at a trickle mean it would then try to refill from the continuous system at a trickle? I assume the flow dynamics of the continuous system then wouldn't turn the heater on so you would just be refilling with cold water drawn through the continuous system. You may as well just plumb the storage system into the cold water already at the sink?.

True that it would not activate the continuous system, but it also would be used slow enough for the storage system to be effective.

In cases where the tap was full on, then it would not matter that the storage system would run out of water, the continuous system would take over.

However, I take your point, If all I draw off in the kitchen is simply enough for the water from the continuous system to fill up the hot water pipe, then I might as well save money and just connect it to the cold water system.
28th January 2008, 09:25 AM
GrahamC

basix and multiple hot water systems rules

Heya guys, some very useful info...

http://www.basix.nsw.gov.au/help_det..._dwellings.htm

If you are installing two different hot water systems, you can nominate either for your basix compliance!:oo: How do you like those apples!:2tsup:

This means in my situation, I can elect to use my 5 star continuous flow system for my basix compliance and still get to use my ?? star tank in the kitchen - :) :) :).

:B:B:B:B:B:B
28th January 2008, 12:20 PM
bricks
Quote:

Originally Posted by GrahamC

So we were thinking about getting a continuous flow system mounted next to the bathroom and laundry that also feeds into a small storage unit (30L) under the kitchen sink for the kitchen.

What do people think? Can anyone see any serious problems or disadvantages?:roll:
- if your storage unit is coming from the instant heater it won't be hot when you want it, you'll need to drain 30lt of water off everytime you want hot water in the kitchen.
- you cannot install an new electric heater in a new domestic dwelling where there are other options ( solar/ gas), so you cant legaly do this unless the 30lt is exempt ( it might be due to size?)
- The underbench space will be non-existant, you'll need a safetrap plumbed to outside, you'll need somewhere for the relief lines to go to- ie a tundish of some sort. You need to fit the heater and all the pipework under the sink- so all the stuff you keep under the sink now will have to go somewhere else.
You'd be better off installing a low flow instantaneous heater to service the kitchen, or get used to rinsing in ...

wait for it

COLD WATER
28th January 2008, 12:56 PM
juan

Hws

Quote:

So we were thinking about getting a continuous flow system mounted next to the bathroom and laundry that also feeds into a small storage unit (30L) under the kitchen sink for the kitchen.

The advantages of such as system is that
a) We can set the bathroom temperature independant to the kitchen.
b) We don't have the minimun flow problem of the continuous flow system in the kicthen because it is fed by a tank.
c) We get instant hot water in the kitchen because the tank is next to the kitchen sink.

I strongly recommend a Rinnai 26 Plus with 2 controllers - no need for complications of another storage HWS. Get the unit dip switches set to allow 60 degrees output and then temper the bathroom. I installed this system and have a long run to the Kitchen and it works like a dream. I can trickle flow the water at the kitchen sink and it is steaming hot. It will take about 10 -15 secs to get hot water from stone cold but if you have a double bowl sink then that first colder run off can be used for rinsing.
28th January 2008, 04:20 PM
GrahamC

wikipedia to the rescue

I got this from wikipedia - this is exactly what I want to do....plumb the continuous into a small tank.....:B

Quote:

In western countries, where ambient temperature is colder, tiny point-of-use electric storage water heaters with capacities ranging from 8 to 32 litres (2 to 6 gallons) are made for installation in kitchen and bath cabinets or on the wall above a sink. They typically use low power heating elements, about 1 kW to 1.5 kW, and can provide hot water long enough for hand washing, or, if plumbed into an existing hot water line, until hot water arrives from a remote high capacity water heater. They are sometimes used when retrofitting a pump and recirculating plumbing in a building is too costly or impractical. Since they maintain water temperature thermostatically, they will supply hot water at extremely low flow rates, unlike tankless heaters.

http://en.wikipedia.org/wiki/Water_heater

This is what I need...

SN Compact "Point of Use" Water Heaters
http://www.stiebel.com.au/water.htm
http://www.stiebel.com.au/pdf/SNU-long.pdf

Except they are crap because you have to use THEIR tap wear!
28th January 2008, 04:51 PM
bricks

Quote:

Originally Posted by GrahamC

This is what I need...

SN Compact "Point of Use" Water Heaters
http://www.stiebel.com.au/water.htm
http://www.stiebel.com.au/pdf/SNU-long.pdf

Why re-invent the wheel!

This may not be permissable for installation in a domestic situation because it is an electric water heater and you have other options.

Plus you won't get a whole lot of water out of the unit before it just runs cold ( maybe 15 ltrs ).

What is the cost?

Remember that you also have to purchase the suppliers tapware aswell because of compatibility issues.
28th January 2008, 05:34 PM
GrahamC

Quote:

Originally Posted by bricks

This may not be permissable for installation in a domestic situation because it is an electric water heater and you have other options.

I don't know whether that applies in NSW. I certainly have not heard of it - not that I am an expert. I'd probably go for solar if the council didn't plant a forrest next to my place 40 years ago (which is north of me). The heat pump is too noisy - I may go for it in 10 years time though - probably no choice in 10 years time.

Anyway, I think the fact one has to go with their (the point of use guys) totally unstylish tapwear and the complexity, I would never go for it.

Back to the 25 litre tank, with a tray, taking up a whole cupboard I think.

I went to a mates new place yesterday and it took 3 minutes full bore to get hot water from the kitchen taps. I don't want that!
28th January 2008, 06:30 PM
juan

3 mins full bore

Your mate has a problem of design I would say. My run is currently 20 metres and it takes about 15 secs. with the Rinnai at 60 degrees