Everyday is a school day and fitting a heat pump offers load of opportunities.

[MikeSharp01]

Today's learning point is this. The heat meter arrived yesterday and very smart the OpenEnergyMonitor.org Level 3 system is!  However pasted across the flowmeter port is a sticker that says '1.5bar minimum pressure' which gave me cause for concern because our system only has a 9m head pump and in normal operation we will be using only 2.7m of that at 5^oC delta T  (5.57m at 3^oC delta T) which is only about .25bar. So I called the suppliers and asked how this would work and got a simple, but not obvious to me, answer that you need to pressurise the system first. Reflecting on this news I think I get why the system might need a base load pressure.

 

• To ensure positive flow to each circuit giving the pump a stable operating point.
• Stop cavitation in the pump
• Remove the possibility of negative pressure sucking air into the the system.

 

If that make sense the only question now is what pressure to set it at? 1.5, 3 bar or some other value?

[Bramco]

1.6 bar?  😉

 

be very interested in how you get on - think one of the kits will be next summers project.

[JohnMo]

35 minutes ago, MikeSharp01 said:

1.5bar minimum pressure

This is nothing to do with pump and it's output, just the static set pressure of the system. So set pre charge pressure at an appropriate setting prior to filling to system and fill until to 1.5 bar on the gauge on you fill loop gauge. Bleed system and then top up. Run system for a week and you will have to top up again as air is removed.

 

But I am operating mine at a pressure of 0.5 bar without issue. The pressure is set that high to make sure you have no air bubbles which render the flow meter useless.

Edited Wednesday at 16:18 by JohnMo