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?

 

[Riley]

You cannot maintain the water at 36°

 

[bcraig]

You cannot maintain the water at 36°

Sorry this in not constructive. I can maintain water at 36 degrees. I just would like some leads to the most affordable methods. Just regarding heat not water condition.

 

[Riley]

It wasn't meant to be non-constructive. You just seem to be ignoring the Point about storing water at this temperature, there are perfectly legitimate reasons why we are pointing it out Perhaps if you explain a little more what you actually need the water for ie end user, you say for a spa but that could be anything. Anyway I'm out!!

 

[bcraig]

It wasn't meant to be non-constructive. You just seem to be ignoring the Point about storing water at this temperature, there are perfectly legitimate reasons why we are pointing it out Perhaps if you explain a little more what you actually need the water for ie end user, you say for a spa but that could be anything. Anyway I'm out!!

Spa bath/hot pool/hot tub. Hot, treated water to bath in. I'm not ignoring the need to manage the water condition but I'm not here for water treatment advice. Just solely the method of heating bathable water.

 

[chris watkins]

It wasn't meant to be non-constructive. You just seem to be ignoring the Point about storing water at this temperature, there are perfectly legitimate reasons why we are pointing it out Perhaps if you explain a little more what you actually need the water for ie end user, you say for a spa but that could be anything. Anyway I'm out!!

To be fair he has & stated that the water will be treated so < 60 is not an issue.
OP
Go speak to Andrews Water Heaters Technical they are the only ones who will be able to answer your questions.
You must tell them what the water will be treated with !!! these units have copper heat exchangers but you may need something like a swimming pool boiler, to be able to handle the chemicals.

Why not keep the water in the spa, why send it back to the holding tank ?

 

[Dotty]

It's not water treatment. If you store water below 60°c you exponentially increase the risk of developing legionella contagions.

Store the water at 60°c or above. Provide a thermostatic mixer valve at each spa to give you your 36° or whatever it is you want.

 

[bcraig]

Why not keep the water in the spa, why send it back to the holding tank ?

I want to be able to wipe down the bath after every use as well as well as having one large combined treatment system. Holding the water in a sealed insulated tank I feel would be the best way to reduce heat lost during downtime and overnight. I dread the thought of constantly putting covers on and off the individual baths. But I will have to consider the setup costs against the running costs as well.

 

[chris watkins]

It's not water treatment. If you store water below 60°c you exponentially increase the risk of developing legionella contagions.

I don't understand croppie, can you explain, what is not water treatment ?

 

[chris watkins]

I want to be able to wipe down the bath after every use.

You must have very dirt clients thats all I can say !!!:wilted_rose:

 

[joni os]

Heating 80 litres X 9 Degrees C in 1 minute will require 50Kw off heat output. Allowing for efficiency and other heat losses your system needs a boiler/water heater rated at 60Kw min.

 

[Dotty]

I don't understand croppie, can you explain, what is not water treatment ?

The only time I've seen treatment for the prevention of legionella is in water towers, the amount of chlorine used would make the use of the water for bathing unviable.

We both know that the cheapest and easiest way of combatting legionella is in a properly designed and maintained system that has a storage setpoint not below 60°c.

Though I'm starting to think the op is on a wind up here.

 

[gasmanrob]

The only time I've seen treatment for the prevention of legionella is in water towers, the amount of chlorine used would make the use of the water for bathing unviable.

We both know that the cheapest and easiest way of combatting legionella is in a properly designed and maintained system that has a storage setpoint not below 60°c.

Though I'm starting to think the op is on a wind up here.

You and me both I thought I'd provided everything on page one. A list of manufacturers who build big water beasts, a solution to dropping the temperature. And a potential free of charge design service.

Just call me Mr. Cellophane

 

[chris watkins]

I took a group of plumbers / handy persons from a national chain of care homes around a year ago some of them were telling me they had a centrally blended system of hot water including secondary returns which ran at something like 42deg C in at least a couple of newly built homes.
They insisted that it was all OK as they had contracts with a water treatment company who had equipment installed to dose up the water supplies, it automatically maintained a preset level of chlorine throughout as I recall.

It would be a very elaborate if he was but I never can tell.

 

[stevetheplumber]

ive no ideas regarding the OP but can uv be used to prevent leginonella ?

 

[Chalked]

Sorry this in not constructive. I can maintain water at 36 degrees. I just would like some leads to the most affordable methods. Just regarding heat not water condition.

Yes you can physically maintain water at 36 degrees. But, if you don't want to give the occupants legionella, you will need to store it above 60 degrees.

 

[chris watkins]

Yes you can physically maintain water at 36 degrees. But, if you don't want to give the occupants legionella, you will need to store it above 60 degrees.

So how do they do it in a swimming pool, hot tub or in this case a spar ?

 

[gasmanrob]

You ever bathed in a swimming pool?

 

[bcraig]

Lol why would this be a wind up?
Ozone and chlorine will manage legionella. You all act like spa baths don't exist..
Thank you for your suggestion of Andrews water heaters. I am looking through their massive selection of units.
All I was after was an insight into what people consider would be the most efficient method to achieve a temperature rise in the required time.
If it helps then let's say the water is stored at 60 degrees. Do you have any experience or educated advice towards a specific method/unit/combination of units for heating this water by a further 9 degrees at a rate of 80L/min.

 

[lame plumber]

I just cant imagine taking a nice hot spa bath and breathing in all the chlorine as it evaporated off into my lungs, I woldnt go back for a second try

 

[Chalked]

The op knows it all!

 

[bcraig]

I just cant imagine taking a nice hot spa bath and breathing in all the chlorine as it evaporated off into my lungs, I woldnt go back for a second try

Most spa baths use chlorine and the ones that don't will use other chemicals that smell worse. There's never enough chlorine to really notice or at least irritate the user. I will also be using ozone to reduce the volume of chlorine needed which is more cost effective.

 

[Dotty]

Lol why would this be a wind up?
Ozone and chlorine will manage legionella. You all act like spa baths don't exist..
Thank you for your suggestion of Andrews water heaters. I am looking through their massive selection of units.
All I was after was an insight into what people consider would be the most efficient method to achieve a temperature rise in the required time.
If it helps then let's say the water is stored at 60 degrees. Do you have any experience or educated advice towards a specific method/unit/combination of units for heating this water by a further 9 degrees at a rate of 80L/min.

Yes. Quite a lot.

But rather than try and guess at a solution for you you'd best be getting a suitably qualified consultant in to design this properly for you.

Doing a job like this on the cheap never ends well.

 

[bcraig]

See this link regarding HotSpring Spa's water care...
hotspring.co.nz/spa-buying-guide

 

[Dotty]

That's new Zealand. Doesn't count or even come into the equation in the UK.

 

[Dotty]

Actually. I've just checked your ip.

Why are you asking a UK forum? Don't you trust kiwi plumbers?