High volume water heating

[bcraig]

Can someone please tell me, what would be the cheapest method of heating 36oC water to 45oC at the rate of 80 Litres per minute for 15 minutes and then maintaining this temperature for an hour? All to be repeated every hour.

I will have multiple 1200 Litre baths that will fill within 15 minutes then drain after an hour session.
The baths will bet set to be either 36, 40 or 45 degrees but the majority will be 36 degrees. A 10,000L storage tank will maintain 36 degrees with a heat pump. So the majority of the bath refills will simply use the stored, 36 degree water. But I need to top up the temperature for the two other temperature settings.
Solar is not an option.

 

[snowhead]

You can't store water at 36 deg,

 

[Riley]

Legionella???? What're the baths for

 

[chris watkins]

FASTflo
Maybe something like this ? but there are so many other things to be considered not least as snowhead has said you shouldn't store hot water at under 60 deg C without additional protection from Legionella.
Recommend you seek specialist design advise on this one.

Welcome to the forum bcraig, the job it sounds an interesting one.

 

[snowhead]

It's got to be Horses with that volume of water?

Dropping water at 36 deg into a bath will result in a significantly lower temperature once it's heated the bath up and contents and will drop temperature quickly over the hour.

 

[bcraig]

FASTflo
Maybe something like this ? but there are so many other things to be considered not least as snowhead has said you shouldn't store hot water at under 60 deg C without additional protection from Legionella.
Recommend you seek specialist design advise on this one.

Welcome to the forum bcraig, the job it sounds an interesting one.

The large storage tank will be similar to one large spa running constantly that feeds smaller baths on demand. So the water will be treated. I am hoping to work out running costs roughly at the moment before I approach a specialist.

This is a clearer breakdown of what I am planning and what I think is the best solution...

- 10,000L insulated storage tank containing 36 degree water.
- 8x spa baths draw 1200L each from this tank.
- Natural gas heaters located on each spa will bring the 36 degree water (which may have lost 10% in piping so now 32.4) up to desired temps(36,40,45 degrees)
- The natural gas heaters continue to circulate the bath water locally maintaining the desired temp.
- Once 1 hour session is complete then the water is pumped back to the storage tank through a natural gas heater located on the tank to bring the water, after piping heat loss, to 36 degrees again.
- Within the tank, a solar powered heat pump pool heater maintains the water at 36 degrees.
- Ventilation pumps warm air from the spa rooms into the heat pump as well as the storage tank to fill the empty space when water is drawn from it.
- This will be a commercial system providing private spas.


Will gas heaters be the best for "topping up" the heat and for maintaining the heat?
I haven't been able to read up clearly on how much energy input->output a range of gas heaters I have looked at have. That link you posted has units that specify their flow-rate at an increase of 25 degrees. What I have seen so far is that the rates shown there are the units maximum physical flow rate which the highest on that chart is 32 L/min. So I assume I would need 3 units coupled together to get 80L/min.. or does it not work like that?. I need a maximum temp rise of 9 degrees so that is 64% lower than the specification on that chart of 25 degrees. Would that mean I would be using 64% less energy to achieve my goal?

 

[gasmanrob]

Something like an Andrews heater, hamworthy or lochinvar. May give you what you need if it's a dead cert job you can call them in and they will design something for your needs. You'll need to store the water at 60 degrees but a blending valve at the bath will get you down to your required temperature.

If as suggested this is for equine use ie solarium and physio of the animals make sure you've had the water meter removed I certainly wouldn't fancy that bill.

 

[gasmanrob]

Coupling 3 units together wouldn't give you the higher flow rate as it is dependant on your supply pressure and flow.

Sounds like this really is a job for a designers consultation they'll be best placed to provide the correct information and set up

 

[snowhead]

This is a Specialist job from the start.

There are too many costs/ risks involved to be able to guess at any running costs.

 

[bcraig]

Basically at this stage in hoping someone can lead me in the direction of a range of products that can provide me 80L/min at a rise of 9 degrees at the cheapest efficiency.

Just a thought now.. The goal is to fill baths and be at temperature within 15-20minutes. Could I instead get a very high water pump to get the water to the bath as quick as possible then just use a high speed heat pump spa heater to top up the temp and then maintain?