Altherma bivalent

[icecube51]

Hi everyone,

I have been teaching the installing, using and working with heat-pumps, and have a couple of models at school in labo set-up. One of them is a Daikin Altherma second generation.

We are playing with the fact of using a gas heating system instead of the build in electric coil, to become a bivalent heat pump. I think it will improve the temperature on the anti-legionella cycle, and also for somewhat bigger families, the hot water supply.
Has anyone ever did this already and what was the outcome?

Did you had problems with the bivalent point? Was the alternatief heating working to long/short?
Problems with the display/regulator and so on.

Love to hear it,
Ice

[frank]

Are you talking about the High Temperature or Low Temperature Altherma?

[mikeref]

I see Frank is next in line to shout a round of cupcakes and/or do-nuts
I'll have to be quick to get in this time as Stufus and company pinched em off Brian's shout.

[icecube51]

Are you talking about the High Temperature or Low Temperature Altherma?

Hi Frank,

Early second generation is still low temp, that's why i am worried about the high temps from the gas boiler.

[MikeHolm]

Does the tank sensor for the Altherma have an upper limit where it generates a fault should the tank temp go higher than the programming expected?

[hyperion]

Don't believe that it does. It relies on the sensor to switch off the booster heater when the sterilisation process is completed. The two safety cut-outs are preset to break the control circuit to the booster heater contactor and the second one breaks the power circuit to the heater element. These are both manual reset.
If you had the solar capable conversion for the storage tank, then you could use the associated controls to prevent the storage cylinder form over heating which woild also prevent the over 55degC water returning to the Altherma unit.
If you wish to go bi-valent, you will have to install a pipe thermostat to sense the water temperature returning to the Altherma along with a two port valve which will need to close if the water temperature is above 55degC. You will probably need a check valve in the flow from the Altherma to prevent migration of hot water into the Altherma when the gas boiler is operating.
You will end up with a low efficiency system utilising both gas and electricity.
As this is only and experimental demonstration system, you will have the opportunity to monitor the performance.

[frank]

As it's the Low Temp unit, you have got to be careful back-feeding high temp water into the BPHE within the Hydrobox. The refrigerant won't like it (high pressure) and the outlet water sensor will generate a 8H fault when the water temperature exceeds +65C.

The better way to do it would be to use a buffer vessel and install an electrical interface between the Boiler and Hydrobox (terminals 1 + 4 on X2M) If you do this, set Dip Switch SS2 (3) to 'ON' and reset the power. The Hydrobox will only run now when terminals 1 + 4 are Closed.

The configuration of your shunt pipework from the Hydrobox to the Buffer will have to be configured to ensure that you don't get gravitation or fit an NRV to the flow and a Solenoid valve to the return.

Does the tank sensor for the Altherma have an upper limit where it generates a fault should the tank temp go higher than the programming expected?

The tank sensor will generate an EC error when the tank temperature exceeds +89C. Even with a primary flow temp of +80C, I wouldn't expect the DHW to be stored above +60C so this shouldn't be a problem.

Doughnuts....Cupcakes......I'm not that tight.

It will be virtual PINTS all round

[icecube51]

Thnx for this info guys.
They have started yesterday with the plumbing, so they still have time to make it wright. I am going to tell them this and give some feed back with results later on. Because they only have lessons once a week, it will be somewhere start November.

Cheers Frank,
Ice