Cooling the slab

[dogman]

Now i have a few days off from the build i am looking at the heating again.

 

Those who have looked at cooling the slab, have you bypassed the buffer tank when cooling.

 

Obviously this only applies to tanks where you are using the coil to preheat your incoming cold.

 

I remember some time ago i was told (don't remember who told me) that cooling 70-90 lt buffer tank hits the cooling efficiency and to build a bypass into the system.

 

Any thoughts or experience?

[IanR]

I'm going with an off-the-shelf solution from Nibe, which does cool the buffer.

 

I'm having a 200ltr buffer which will hold about one third of the fluid in my system, requiring additional energy to cool initially. After that it's just the energy losses (heat gain from environment) of the buffer that would drop the efficiency I would have thought.  But, it may help reduce short cycling when cooling requirements are low.

 

If it proves to not require the buffer for cooling then I may look to re-plumb and bypass the buffer in cooling mode. 

Edited April 1, 2017 by IanR

[Jeremy Harris]

I turn the buffer off when cooling, as I use the buffer to pre-heat the DHW, so need to keep it warm in summer.  Also, the ASHP doesn't seem to need the buffer in cooling mode, perhaps because the temperature differential between the outside air temperature and the flow temperature is a fair bit lower.  I have mine set to deliver 40 deg C flow temp in heating mode and 12 deg C flow temp in cooling mode, which seems to be just about right, with the floor surface temperature not getting below about 18 deg C in cooling mode and above about 22.5 to 23 deg C in heating mode.

[dogman]

I am thinking the same as JSH. Also if you have a buffer tank that has a bypass fitted, you can divert any excess pv to the tank to preheat the water(after all the other items needing PV as my diverter has two outputs)