commercial hot water! lots of questions!

D

daniely87

Hello!
Basically we have just been granted planning permission for a brand new facility block on our campsite. It includes about 11 showers and 15 basins / sinks.
We plan to use eco shower heads / taps to cut down on water usage
our water pressure is LOW, about 1.5bar.
We are getting another supply for this building, greater than 32mm also, although on the existing block, when too much is on at once the water coming out of the taps and showers just drops so low
We have contacted numerous solar / renewable energy people, every single person has a different idea!
Everytime i search on google, there seems to be a good thread on here! so here i am!
from this forum and google i have gathered unvented cylinders won't work unless the mains pressure is good? although accumulators overcome this?
we have calculated our expected water usage at approximately 1500 litres per hour at maximum times.
we are worried about legionella, although may be only 50 litres an hour at times in the winter
we are worried about the water re heat time!
we have found these tank, http://www.acv-uk.com/slme.htm
possibly get 2 or 3, this also reduces the risk of legionella?
we defintely plan to use solar panels
we also require underfloor heating, but only to stop pipe work from freezing and dry floor
the site can have from 5 people to 600 people on, so another issue is stagnant water?
we have looked into heat pumps but have been told differing opinions, although most say our water volume is too much for a heat pump.
we know we require a back up to the solar, possibly just emersions? although we look like to avoid an oil boiler, although we may have no choice?
how do you calculate what size accumulator you would need if you had a 600 litre tank (3 of them)? and used 3 full tanks per hour? and then what happens if hardly any of that water is used for a few weeks? can it be bypassed at lower times? or can it be stored as its going to be heated over 55 degrees
some people have mentioned heat extractors above the showers too?
even which type of solar panel? evacuated or flat panel? any brands to stay away from?
basically anyyyy advice on anything would be appreciated, but mainly, how to lower the legionella risk / suggestions for a back up to the solar fot hot water / underfloor / stagnant water problem when site has low numbers (shutting down tanks) / low water pressure - accumulators?

i hope some of that makes sense to someone, sorry to have raised so many points in one thread. We have contacted many companies, and it seems only the large ones are interested, but still their ideas are so different! part of our problem is the usage is not constant, it varies so much, although during the summer is our busiest time and also the sunniest time! thanks in advance to anyone! any thing else you want to know or i haven't mentioned, please ask! thanks again, Daniel
 
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Hi Daniel
I am pushed for time at the moment but will have a think about your shower block and post a reply as soon as I can so keep checking the forum.
Brian- Plumber
 
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Forget accumulators; whoever suggested them is misinformed.

Install a cold water storage tank with a variable speed booster pump set on the outlet, supplying both the hot and cold water.

The hot water should be generated by plate heat exchangers, with the pumped secondary side taken from, and flowing to an insulated hot water storage cylinder(s). You need two (at least) plate heat exchangers piped up to allow a set to be serviced.

You need to monitor and control the hot and cold water temperatures, as required by the HSE's L8 document.

You may need TMV (thermostatic mixing valves) on every outlet if anyone who is infirm (very young, very old, disabled) can get to them.

If you want a commercial system, I'd suggest you employ a CIBSE consultantcy, rather than rely on advice on a DIY forum.
 
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We have installed alot of shower blocks for MOD army camps and have found rinnai water heaters with thermal store for solar collection to be very good
http://www.rinnaiuk.com/5_Downloads/Solar_Brochure_09.pdf

As said dont bother with accumaltors, fit breaktank and booster set, at times of low usage a flushing programme maybe required to cover Acop L8 legionella requirements

Additional coil can be fitted to thermal store to give UFH buffer.
 
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D

daniely87

thanks everyone for your replies!

ok,
1. how worried should i be about legionella?
2. http://www.thermsaver.co.uk/media/pdf/cylinder/smartline-slme-brochure.pdf thoughts anyone? i am unsure about these heat plate exchangers? says on google basically lots of pipes....surely a coil like in a worcester bosch cylinder at the bottom of the tank that the solar fluid goes through is an exchanger? someone please explain! the reason we like that tank is because of the legionella thing.
3. storing the cold water, so presumably drinking water. is there any rough guide on how long it can be stored without being used? say we have a 500 litre storage tank and 5 people on site, 90% of that water will be left each day...i suppose if its in darkness it won't go green, one person also mentions controlling the temperature of the water, i believe as long as the water is heated over 55 / 60, the legionella in showers will not be an issue / will use blender valves too, but if the cold water was to say be refrigerated / stored well below legionellas breeding temperature? if possible we would rather not have to drain down / store the cold drinking water. Technically the basin water is only for cleaning teeth / washing face anyway, so its not like they will drink, but there will always be someone who drinks it and tries to sue?
4. thanks for that rinnai link. At the moment we have schuco and bosch designing possible systems, will have to try them too!
5. say we were to have 2 cylinders / thermal stores, is it best to link all the solar panels together, or split the panels between them?
6. is there any rough rough guide on the maximum water a solar panel can produce on a good summers day? i know its like asking how long a piece of string is, but i have been trying to think of it as a 1.7kw solar panel, you would need 10 of them to match a 17kw boiler? wrong?
7. what back up would you use? just emersion heaters? we would rather stay away from oil, but some people have said no, don't let anyone else tell you otherwise? we require underfloor heating too, yet have been told air source heat pumps dont produce enough hot water?
sorry to be such a pain. thanks again so much!
 
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thanks everyone for your replies!!


1. how worried should i be about legionella?

Not much, if you keep coldwater at less than 20 degC, hot stored at 60 degC and have a monitoring regime ( see the L8 document, too much to detail here). If you don't do that, you should lie awake and worry at night.

2. i am unsure about these heat plate exchangers? says on google basically lots of pipes....surely a coil like in a worcester bosch cylinder at the bottom of the tank that the solar fluid goes through is an exchanger? someone please explain! the reason we like that tank is because of the legionella thing.

A pipe in a cylinder is a heat exchanger. Plate heat exchangers are metal plates with waterways stamped into them. They have a huge heat transfer surface area but narrow waterways which can clog up with limescale, so you need to be able to swap and service them. They generate a lot of hot water quickly. Re tube type heat exchangers; do you know how much copper costs nowadays?

3. storing the cold water, so presumably drinking water. is there any rough guide on how long it can be stored without being used?

L8 again. The stored water must turn over once every 24 hours. You're not trying to store a 24 hour supply, the tank will be refilling constantly. You're trying to get the highest possible input rate from your low pressure supply. The tank is a break tank, required to feed the pressurization pumps.

but if the cold water was to say be refrigerated / stored well below legionellas breeding temperature?

L8 again,must be below 20 degC. The tank must be insulated, you must get the right kit of parts installed by a tank specialist. Refrigerating isn't usually necessary.You must record H&C temperatures regularly.

Technically the basin water is only for cleaning teeth / washing face anyway, so its not like they will drink, but there will always be someone who drinks it and tries to sue?

Forget that, it must all be good potable quality. The days of minging loft tanks is over for commercial premises. People have got legionella by drinking contaminated water, coughing up droplets and inhaling them. It won't be 'someone trying to sue'; the HSE will trace the source of an outbreak with DNA analysis. The owners of a contaminated system will be prosecuted in a criminal court. The victims will sue in the civil courts and the insurer's barrister will agree a settlement because they'll know they'd lose.

5. say we were to have 2 cylinders / thermal stores, is it best to link all the solar panels together, or split the panels between them?

Link the lot,unless they're widely separated.

6. is there any rough rough guide on the maximum water a solar panel can produce on a good summers day? i know its like asking how long a piece of string is, but i have been trying to think of it as a 1.7kw solar panel, you would need 10 of them to match a 17kw boiler? wrong?

No, as much solar as you can afford, the boilers top up the heat on cloudy days. 1.7 kW is peak summer performance.

7. what back up would you use? just emersion heaters?

Oil boilers. Avoid immersion, electric is usually most expensive.
 
D

daniely87

thanks yet again! couple more questions! i think we are getting there!

regarding point 5, yes, they will all be side by side, so linked, just if one day we have hardly anyone on using the water, then the next day busy, then a few days later back to a low number, if there were say 15 solar panels heating 3 tanks, and some tanks were to be turned off / if they were turned off, 15 solar panels on one tank....would it not overheat? what if the water isn't used at all and the solar panels are all on? does the water just get hotter and hotter? (hope that question makes some sense!)

anyone have any links to ANY tanks with heat plate exchangers in? everywhere i look they are just coils, i would have though worcester bosch would make some with plates in? can you just switch a coil for a heat plate? :S regarding the tanks with coils in, i take it the solar coil can only scale up, nothing else can go wrong with it!?

back to the cylinders / thermal store, providing the water is kept above 60 degrees, it doesnt matter how many hours i store it for / if it is all used the day it is heated.

regarding the legionella, there are a couple of companies who i have been in contact with providing special filters! (shower-safe.com) is one, they also provide special replacable filters for taps, which completely eliminate the legionalla! they sound wonderful! even found one company with UV bulbs that go in the shower unit, but i would rather change a filter or copper and silver beads yearly, than a bulb!

accumulators / pressure vessels. is there any reason why a booster pump and a buffer tank are better?

one final question to anyone!
if you were asked to calculate the maximum hot water requirement for 11 showers / 15 basins per hour, 7 litre per minute showers, aereating taps, how many litres per hour would you suggest? we have been estimating 1500 - 1800 litres per hour maximum, again, is it best to have say small 2-300 litre tanks, or 600 or even a thousand litre tank / cylinders / thermal store....any rough ideas on recovery time if the solar is at maximum efficiency??
thanks again sooo much!
 
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anyone have any links to ANY tanks with heat plate exchangers in? !

http://www.hvindex.com/pdf/RYCROFT/03_HTBREEZE.PDF

Details of typical installations on here. The plate heat exchanger (PHE) stands outside the tank/buffer vessel. You'd have a pump pushing the domestic water (secondary) being heated through the PHE. You could have several PHEs heating water in one tank. You don't have to take the tank (and hot water system) out of service to descale one PHE.

See the Rycroft site for details of other hot water installation. The storage calorifier was the usual method prior to PHEs becoming available. The coil/tube bundle would have been removable for cleaning in commercial installations.


15 solar panels on one tank....would it not overheat? what if the water isn't used at all and the solar panels are all on? does the water just get hotter and hotter? !

It would overheat during summer and low use. You'd have to have some means of dumping heat or water or shading the collectors. The solar installer would propose some means of doing that.

back to the cylinders / thermal store, providing the water is kept above 60 degrees, it doesnt matter how many hours i store it for / if it is all used the day it is heated.

No, the heat kills the bugs, so once it's hot you could keep it indefinitely until it's used. It is cold water storage tanks that should use their full capacity every 24 hours (and stay below 20 degrees).

is there any reason why a booster pump and a buffer tank are better?

If the mains pressure is adequate to supply your peak demand you could use that. If it isn't,you need a booster pump unless you're content for the showers to slow to a dribble. If you use a booster pump, you need a break tank.

It's equivalent to the traditional loft storage tank; the water can trickle in all day, but there is adequate stored water to supply peaks in demand that exceed the mains supply. They used to build water towers to achieve the same effect.
 
D

daniely87

thanks so much YET again!
just been reading about schuco solar controllers
"Schüco's solar regulators for heating systems are extremely easy to use. They feature an integrated troubleshooting system plus an LCD display that enables you to closely monitor all functions.Regulator functions:

Maximum limit on storage tank temperature

Solar panel cooling function

Safety cut-out "

running out of questions! we are going to see what supply we can get from the water company later this week, and are waiting for some quotes / designs to come back. This forum is wonderful.
 
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We've not long completed one just past Mansfield.

Owner wanted solar....cost some became an issue for commercial reasons.

Original design was 2 Vaiilant 65's,500 litre tank in tank, 300 litre solar preheat.(obviously solar got knocked on the head)

Original design thought theyd get away with a 35mm mdpe water main.

2000litre external tank later and a DAB booster set copes with the demand off peak season.

Lee
 
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I think you need to rethink your water usage!

Even if you have meagre showers with just 6 li/min each then thats 66 li/min or 4000 litres of hot water per hour if all showers are assumed to be running continually. And even thats ignoring the wash basins !!!

Wonderful idea to have solar and a small solar installation might help to save costs but they are not usually cost effective as a return on capital. To supply that demand continuously you would need about 200 m² of panels or tubes, or with 40,000 litres of solar storage then about 20 m² of panels!

My simple approach would be to consider say three Rinnai instant water heaters taking water from a preheated solar cylinder and supplied as stated from a very large break tank of about 4000 litres less whatever mains flow rate you can get in an hour.

Tony
 
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Remeber a decent shower runs 2 parts hot to 1 part cold when determining storage size.

Lee
 

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