Optimizing Washwater Heating

hendrik42 — 2006-08-11T17:24:00Z

I have long searched for a way to make the Nibe Fighter 600P to a) stop making hot water (because my thermal Solarpanels are doing it) and/or b) make hot water only once a day because we only need it in the morning.

(I am talking washwater, water for shower, washing etc., not the water in the heating circulation)

The goal is to save energy. If there is good sunshine, my thermal solar panels are providing hot water and in the winter the heat pump can "concentrate" on heating the house instead of making hot water in the afternoon when we don't need it anymore.

At first I tried to just override only the compressor with a timer, but that is not a good solution because the Nibe controller starts compressor and pump when it wants to create hot water, so if I override only the compressor, the pump is still working.

So I tried to "trick" the Nibe controller into believing that the water is hot (when it is not) and finally, I succeeded.

Its not in the circuit diagram of the Nibe Fighter 600P handbook, but if you open up the covers and meditate a bit over the wires, you find the solution quickly:

- the temperature sensors all arrive at the controller board:
Right: White: outdoor temperature
Left: Blue?: vaporizer-, Yellow or White?:Exhaust Air-, Grey:Boiler-, Green:Heating circulation feeder- and Red:Washwater-Temperature

- if one interrupts the red cable at the plug-and-socket connection in front of the boiler, channel 8 (Washwater temperature) goes to 99°C. Perfect!

So I just got myself the right plug-and-socket connectors (since I don't want to destroy any cable) and inserted my timer there. Now 23 hours of the day my heat-pump believes that there is hot washwater and does nothing (in the summer) or does normal heating.

A positive aspect of this solution is also that I am not "overriding" the controller anywhere which could interfere with how the compressor is started or stopped. The controller is starting and stopping any activity like it would do if the water is really to cold or too hot.

Now I have to decide for the optimal time window to create hot water. From a need perspective that would be early in the morning, but in the winter the temperature is very low at that time -- not the best for a high COP. So I'll probably take a timeslot during the day (when ambient temperature is higher) and timed so that there is still enough hot water in the morning.

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Nibe Fighter 600P Tips & Tricks in English

hendrik42 — 2006-08-11T17:20:00Z

I have decided to translate some of my "tips and tricks" blog entries into English for the benefit of Nibe Fighter 600P users outside Germany.

The number of entries is going to expand over time, so have some patience.

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Weblog eines Wärmepumpen-Betreibers (Wärmepumpe Nibe Fighter 600P in einem KfW60 Haus)

Optimizing Washwater Heating

Nibe Fighter 600P Tips & Tricks in English