Home made Hybrid Oil and ASHP

[Fly100]

Hello all,

 

Id appreciate your toughts on the following.

 

We will be changing our car soon to a Plug in Hybrid which will enable us to make use of a 4.5p per unit electricty through the night.With this in mind im looking to install an ASHP in addition to the exsisting oil boiler for use in the colder months. House is a selfbuild 3 years old with underfloor downstaris and rads upstairs (oversized rads for future proof).

All the above world allow me to run the ASHP for 5 hours through the night for a small amount of money. Going on from that is how to merge the 2 sytems? I have 2 spare ports on my buffer vessel so the plumbing part is easy, its the control methods that I fall down on.

Has anyone completed such a task ?

 

Thanks,

Fly

[JohnMo]

Daikin do a hybrid solution.  They do two versions, a split and mono block.  You need the mono block version.  Basically you can have their solution of ASHP and gas boiler, or their ASHP and any other boiler.  The heat pump does heating only.  You boiler does hot water and or heating.

 

Think Vaillant and others also do a similar solution.

 

The heating system will run in bivalent mode, for heating which is either or not both together.

[joth]

Not a specific recommendation, but as another datapoint the Ecodan supports this out of the box in the standard controller too.

Search the FTC6 install manual for "boiler" for schematics and setup instructions (Dip switch SW 1-1, inputs IN4 & IN5, output OUT10, thermistors THWB1 THW10)

 

https://library.mitsubishielectric.co.uk/pdf/book/Ecodan_FTC6_PAC-IF071-3B-E_Installation_Manual_BH79D843H03

[Wil]

The cool energy ASHPs have a contact pair that allow you to choose a time to bring in a backup heating source. You run the ASHP as lead until it decides it can't cope and then bring the Oil burner in behind it. You could also use the ASHP to 'pre heat' the water going into the oil burner so that it doesn't have to work so hard but I have no idea of the efficiencies and was persuaded to just drop the oil burner altogether and run the ASHPs only.

 

If you've already oversized the rads, you could run the oil burner at a really low temp too.

 

It's a tough combo and would need a bit of fettling to run an ASHP in parallel with an existing Oil burner rather than buy a hybrid.

[JamesPa]

You could crudely just switch between the two so you use oil on the coldest days and ASHP on the warmer days (or ASHP at night and Oil during the colder days).  A couple of three way valves and either a manual switchover or one which is somehow temperature-controlled would do this.  Essentially arranging the plumbing such that either the oil is connected or the ASHP is connected but never the two together.  Not as efficient but far less complicated.  Im thinking about doing exactly this (in preference to anything complex/expensive involving buffer tanks etc) so that I can retain my existing gas boiler as a backup to the ASHP I intend to install, just to cover failures.

 

Bear in mind that the ASHP might take some time for the compressor to 'warm up' though (see the thread about ecodan standby consumption to understand why).