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[Tony H]

Hi all.  At the moment in my commercial kitchen the hot water for washing up is supplied by a gas mersey main balanced flue water heater that has just failed. So I am looking for a replacement, either gas or electric. I have seen some under sink 2kw heaters which are a lot cheaper than a gas boiler similar to the one I have at the moment, but I am not sure they would be up to the job. The hot water requirements are about 10 litres every 10 minutes. Any body got any suggestions.

TIA
Tony

[powerslinky]

Have a look at a Redring Powerstream Eco  . . .  not sure if it is up to "commercial" use though

But runs a shower & a basin in a bathroom ok   HTH

Edit : around £140  I think  . . . heats the water as you need it  . . . no tank

[Bigron]

A quick mental calculation suggests that it might just about make it, assuming that you want the water not much more than hand-hot, i.e. about 50-ish degrees Celcius. Could you fit two, both to have spare capability and in case commercial use is too much for one?

Ron.

[Kevin Wood]

Let's say you want to water heated to 60 degrees C and incoming water is worst case at 5 C.

Water has a heat capacity of 4200j/kg^oC and you need 10 litres, which is 10kg.

Heat input needs to be 10 X 4200 X (60-5) = 2.31Mj

A 2kW element gives you 2kj per second. In 10 minutes, that's 2000x60x10 = 1.2 Mj

So no, 2kW is not enough. What's more, you'll need something that stores at least 10 litres of water so you can draw it off in one go, and most under counter ones only have a capacity of a couple of litres.

[Bigron]

Oops, the italics were meant for just the "might" word in might just about make it!

Ron.

[Taxi_Driver]

Let's say you want to water heated to 60 degrees C and incoming water is worst case at 5 C.

Water has a heat capacity of 4200j/kg^oC and you need 10 litres, which is 10kg.

Heat input needs to be 10 X 4200 X (60-5) = 2.31Mj

A 2kW element gives you 2kj per second. In 10 minutes, that's 2000x60x10 = 1.2 Mj

So no, 2kW is not enough. What's more, you'll need something that stores at least 10 litres of water so you can draw it off in one go, and most under counter ones only have a capacity of a couple of litres.

I'm certainly not putting my hands in water thats 60C....45C is nearer.....my combi is set to 43C for hot water, and that gives a 'toastie' shower  But I suspect a 2kw heater wouldn't be enough....How about an electric shower heater ... 8 or 10 kw that could give that sort temp continuously 

[Kevin Wood]

Let's say you want to water heated to 60 degrees C and incoming water is worst case at 5 C.

Water has a heat capacity of 4200j/kg^oC and you need 10 litres, which is 10kg.

Heat input needs to be 10 X 4200 X (60-5) = 2.31Mj

A 2kW element gives you 2kj per second. In 10 minutes, that's 2000x60x10 = 1.2 Mj

So no, 2kW is not enough. What's more, you'll need something that stores at least 10 litres of water so you can draw it off in one go, and most under counter ones only have a capacity of a couple of litres.

I'm certainly not putting my hands in water thats 60C....45C is nearer.....my combi is set to 43C for hot water, and that gives a 'toastie' shower  But I suspect a 2kw heater wouldn't be enough....3kw? 

Agreed, but HSE (legionella) requirements in commercial premises require it to be at at least 60 degrees C.

[powerslinky]

Let's say you want to water heated to 60 degrees C and incoming water is worst case at 5 C.

Water has a heat capacity of 4200j/kg^oC and you need 10 litres, which is 10kg.

Heat input needs to be 10 X 4200 X (60-5) = 2.31Mj

A 2kW element gives you 2kj per second. In 10 minutes, that's 2000x60x10 = 1.2 Mj

So no, 2kW is not enough. What's more, you'll need something that stores at least 10 litres of water so you can draw it off in one go, and most under counter ones only have a capacity of a couple of litres.

I'm certainly not putting my hands in water thats 60C....45C is nearer.....my combi is set to 43C for hot water, and that gives a 'toastie' shower  But I suspect a 2kw heater wouldn't be enough....How about an electric shower heater ... 8 or 10 kw that could give that sort temp continuously 

Redring Powerstreams come in 9.5   10.5  or even 12KW   I think  . . .  but don't know if they will do 60 c

[Taxi_Driver]

Let's say you want to water heated to 60 degrees C and incoming water is worst case at 5 C.

Water has a heat capacity of 4200j/kg^oC and you need 10 litres, which is 10kg.

Heat input needs to be 10 X 4200 X (60-5) = 2.31Mj

A 2kW element gives you 2kj per second. In 10 minutes, that's 2000x60x10 = 1.2 Mj

So no, 2kW is not enough. What's more, you'll need something that stores at least 10 litres of water so you can draw it off in one go, and most under counter ones only have a capacity of a couple of litres.

I'm certainly not putting my hands in water thats 60C....45C is nearer.....my combi is set to 43C for hot water, and that gives a 'toastie' shower  But I suspect a 2kw heater wouldn't be enough....3kw? 

Agreed, but HSE (legionella) requirements in commercial premises require it to be at at least 60 degrees C.

Ah...ok ...now I understand...why my boiler controller has a setting for legionella....its set to off 

[Andy H]

Two more points
How much does your gas cost you at the moment? I haven't done a cost comparison recently but electric heating will cost more to run than gas (about 3 times more IIRC)

Also how big is the electricity supply? 12kW on a single phase supply will draw 50 Amps. Even assuming that your distribution board is man enough you may find that you spend most of the cost saving on the electrical supply.

[Tony H]

Hi everyone thanks for the replies especially yours Kevin very thorough  you've all  given me plenty of "food for thought" sorry for the pun "I'll get my coat"