Daikin Hydrobox

[terminator]

Excuse me fellas if my questions appear dense...

I'm working on a site where they are using vrv iv's for space heating / cooling, but they are also connected to hydroboxes for hot water (showers & taps - not heating)

I've never actually worked on such a system before (or any Altherma for that matter) which has these hydroboxes.
I managed to take the covers off and have a very brief look inside one today.

The first thing I could not understand is why this hydrobox has a secondary system on 134a with it's own rotary compressor. I would have assumed it's using mainly discharge gas from the outdoor unit to heat the water in the primary circuit?

Unless I've been looking in the wrong places, I've struggled to find anything that shows exactly how these things work with a decent schematic.

Could anyone explain how these work, or point me in the right direction?

Any help appreciated.

Cheers

[The Viking]

OK,
What you are looking at is a cascade system.
Using just the discharge from the VRV outdoor unit you could reach water temps of around 50ºC.
Using the discharge from the VRV to instead heat the evaporator of a secondary circuit you can now reach temperatures of around 85ºC.

Assuming the hydrobox is feeding an immersion type storage tank then to comply with Legionella legislation the temperature of the water in that tank needs to once per week be raised above 75ºC(?) and the cascade hydrobox can do that without having to use immersion heaters.

:cool:

[terminator]

Nice one buddy.

Yep, that makes total sense now.

Cheers for that - appreciated..

[terminator]

Another question if you don't mind.
This hydrobox has the optional 200ltr domestic hot water tank fitted.

There were complaints of the water at the outlets being too high (68c)
Now, the leaving water temp adjustment on the controller seems to have zero effect.

In the sub menu's, the storage temp was set to 70c (default). I reduced this to 60c, which changed the outlet temps accordingly. The manuals seem to infer that the lwt adjustment on the controller should in fact control the lwt setpoint, but it doesn't. However, I can't see how it can without some kind of mixer valve to add cold to the hot to control the lwt?
Problem is, there are still complaints that 60c is still too hot. I don't want to lower the storage temp to less than 60c due to legionella.

Any ideas guy's?

Cheers

[frank]

You can set the stored water temperature to whatever level you want. The heating circuit water is separate to the stored water.
The electronics will have a weekly setting to deal with legionella by raising the water temperature in the tank to 70C. Usually around 11pm on a Friday night (default from the factory)

[hyperion]

Once you set the domestic water temperature to a lower limit, most people find between 50 and 55 deg C to be satisfactory, please advise your client that after the anti-legionella disinfection cycle, the stored domestic water temperature will be considerably higher than the normal setting until they have drawn off some hot water.
The normal water temperature controls will then take over and maintain the domestic hot water at the set-point.
The disinfection cycle is adjustable for day and time and duration. If the disinfection temperature is set at 60 deg C, then the duration should be 1 hour. If the temperature is set at 70 deg C, then the duration can be reduced to 15 minutes, but you will end up with a tank full of very hot water, which is why it is recommended to go for 60 deg C.

[terminator]

Cheers fellas

[Kev The Tool]

I fitted a Mitsi system in Brighton about 6 years ago with a Cascade type system, quite an interesting set up, had fun commissioning it all!!