ASHP any good for hot water

[Jeremy Harris]

21 minutes ago, PeterW said:

I’m looking at using an ozone generator for a rainwater tank but struggling because the air pumps don’t seem powerful enough to reach 8-900mm depth needed to get the air stones into the bottom of the tanks. Other thought is to change the design and allow it to recirculate between the tanks and put an ozone Venturi injection in the recirculating loop. 

 

 

I can let you have details of my ozone injection system, as I spent a fair bit of time experimenting to find what would and would not work, and also which ozone generators are reliable and which aren't (they all lie about their ozone output, though!).

 

The main problem is that pumping ozone is damned challenging, as it will seriously attack many materials that might be in any pump (particularly rubbers and elastomers, Viton is just about the only sealing material that works).  I use a venturi/eductor injector, home made, but easy to machine up from 15mm brass bar and normal compression fittings:

 

 

The ozone supply into the injection tee is via a 1/4" BSP VUP4.VM NRV, selected because it has Viton seals and a very low opening pressure.  The ozone is supplied from a tubular ozone generator, fitted in a fan-cooled enclosure (it has a finned heat sink around it) that is fed with dry air from a modified 10" water filter housing.  The water filter housing has a refillable filter cartridge, filled with silica gel.  Air is supplied to the filter from a small pond aeration diaphragm pump, at around 3 psi.  Any more than this and the ozone generator stops working.  To prevent ozone flowing back when the system is off (bleaches the indicating silica gel and buggers op the pump) there are PTFE/Viton NRVs in the supply pipes.  All the ozone piping is PTFE, I tried silicone, as used in milking machines, and it rotted out within a month or so.

 

I can let you have a list of all the bits, plus better drawings, if they might be useful.  The venturi/eductor flows water at around 12 litres/minute, with a pressure drop of around 3 or 4 bar, which is plenty to draw in ozone well.  The long mixing section in the eductor, before the pressure recovery flare, is essential to get ozone to be dissolved well in the incoming water.  In practice, the oxidation effect in the first few inches after the mixing zone is pretty high, with a lot of our ferrous iron being precipitated out as ferric oxide before it gets to the 22mm pipe section.  This also works pretty well at killing off any bugs in the water, I suspect.

[ProDave]

21 minutes ago, scottishjohn said:

the mitsubishi system i has and anti  baceriaa function built in and every now and then it lifts water temp high to kill anything without nay input from me 

Mine has that feature but I have turned it off.

[scottishjohn]

21 minutes ago, ProDave said:

Mine has that feature but I have turned it off.

typical tight highlnder  LOL

[ProDave]

43 minutes ago, scottishjohn said:

typical tight highlnder  LOL

Yes. But mainly because I want the solar PV to be free to top it up, rather than have some time clock deciding when to top it up which probably does not coincide with surplus solar PV being available.

 

And I doubt it's software has the built in logic to say "oh it heated to 65 degrees yesterday by some unknown means so I don't need to do it manually"

[scottishjohn]

3 hours ago, ProDave said:

Yes. But mainly because I want the solar PV to be free to top it up, rather than have some time clock deciding when to top it up which probably does not coincide with surplus solar PV being available.

 

And I doubt it's software has the built in logic to say "oh it heated to 65 degrees yesterday by some unknown means so I don't need to do it manually"

I suspect your summation of the software is coorect--lot easier just to do a clock/number of days  base protcol

[joe90]

6 hours ago, Adam2 said:

If the main risk is water in shower heads due to contamination through air exposure then I don't see how heating the tank periodically will make any difference at all to mitigate that risk as by the time the "fresh" hot water arrives at the shower head the bacteria is already in your eyes, ears and nose. If this is correct then hard to see any point in heating the tank to 65.

 

Yes, if the beasties are in the shower head then “hot” water in the tank won’t effect it, plus, who gets under a shower when the cold water is still flowing?, you wait till the “clean” hot water is flowing.