heat pump water heater

[Lc_shi]

Hi dear sirs
THere is one hotel with 132 rooms which need 30 tons 45C hot water for shower daily. And it's supplied by electric heating boiler and consumes lot of KWh. I suggest to use heat pump water heater to decrease the electricity bill and the saved money can make up the investment in about 2~3years.
The existing system is : two parellel electric boiler +circulation pump which runs all the time +3 cubic meter hot water tank ,temperature control: if temp>=45C,stop heating, if temp <=40C, start heating.
If use hp water heater, is it directly parellel connected to the existing system or add a water tank for hp water heater to prevent frequent on-off?
Would you give me some suggestions?
Any body who is familiar with hot water system design ,pls teach me. Thanks!

best regards
LC

[Lowrider]

First off all, I would never keep such a large amount of water, or any water at all, at 45 dgr C.

All water for showers etc. should be kept at at least 60 dgr C to prevent legionella from forming!

A heat pump to heat the water is an option, but on a normal water cooled chiller, used as an heat pump, most systems won't work. A specially build one, for this purpose can be done, but it doesn't come cheap!!

An other option is to use a heat pump to preheat the water, via a plate heat exchanger and then heat the rest with the excisting boilers.

[squil]

Heat pump have a poor COP when used for water heating. The best option would be to use the heat pump for water preheating... There is also the problem of the heat source for such an amount of water (forget about geothermy).
I am not sure it is worth the investment.

What about solar collectors?

[Lc_shi]

Hi sirs
It's good comments. Thanks anyway.

regards
LC

[Pooh]

Lc Shi
sounds like a nice project, as long as you have a good heat source, ground loop or lake 45C should be no problem. From my experience it would be better to split the load over several heat pumps rather than one large unit this gives flexibility and a safety net if a unit fails. COP should be at those temperatures around 4.6 to 5.0 so payback would take some time depending on the cost of energy.

Ian

[Peter_1]

Lc, see you're still busy with nice projects.
Thanks for the postcard, it's standing om my desk.

[star882]

First off all, I would never keep such a large amount of water, or any water at all, at 45 dgr C.

All water for showers etc. should be kept at at least 60 dgr C to prevent legionella from forming!

A heat pump to heat the water is an option, but on a normal water cooled chiller, used as an heat pump, most systems won't work. A specially build one, for this purpose can be done, but it doesn't come cheap!!

An other option is to use a heat pump to preheat the water, via a plate heat exchanger and then heat the rest with the excisting boilers.

Couldn't you use some UV lamps to stop bacteria and fungus growth?

[Abby Normal]

will run the risk of scalding old people at 60C, would have to use anit-scald valves. Typical home on the west side of the atlantic will be keeping water heaters set cooler than 60C.

[Abby Normal]

preheat the water with the heat pump, use electric on top to get the final desired temperature.

[WINJA]

preheat the water with the heat pump, use electric on top to get the final desired temperature.

I have installed a few of these on smaller systems,they worked great.

I did note however that one of our larger york chillers turned up with a plate hx on the discharge fitted in the factory , we never used it and never ordered it like that

[Lc_shi]

Thanks for all of your excellent comment

rgds
LC

[Tesla]

Minumise the waste first. Preheating is ecconomical prefeerably from waste heat from chiller. I have calculated a shower and the biggest bang for my buck was to install a gravity feed heatexchanger to the shower waste pipe and run the cold water supply through heatexchanger. They are expensive to buy but cheep to make - a coil of 1/2 or 5/8 cu tube coiled 600mm long and 100mm id welded or sleeved. Spiral clockwise in southern hemisphere or anti clockwise in northern hemisphere. In cold regions this is very ecconomical as the waste temp is about 35C and supply temp 10C - 15C. Saved more than 25% once installed in NZ.

[Lc_shi]

Hi Tesla
It's real a good idea!
Have you any picture or sketch for it ?

regards
LC

[Peter_1]

look once hear on this site of a colleague of me.
http://www.nemegeer.com/html/wist_u_dit_.html and click on the first green Volgende Pagina
It's in Dutch of course

[yangchenchen]

I don't know Dutch, so i can not get the meaning.
anyway, thanks!

Best regards from
yangchenchen

[Peter_1]

Sorry, this is the one, also in Dutch but with schematics where you don't need more words.
http://www.nemegeer.com/html/body_requperatie.html