Can too much antifreeze effect radiator valves

[Renewable Heat]

Hi there,

we are having issues with Mitsubishi ASHP Pre Plumbed cylinder.

we have 2 zones. UFH and radiators on the first floor. Feeds come off the low loss header at the tank. Both pumped.

UFH works fine. It’s the rads that struggle. We always seem to get loads of heat to the rad valves but it really struggles to flow properly around the radiators. SO FRUSTRATING

System balancing has been done over and over. Pipe sizing is all really good. Pump speeds are equal, bypass are only cracked open.

the only thing that has changed in the most recent installs are the levels of anti freeze. Systems used to be protected to 10% -5c and are now 10% -20c

I’m not sure if the extra anti freeze is causing problems with the thermostatic radiator valves??? I may be clutching at straws but I’m not sure what to try next. The anti freeze was pumped straight into the UFH manifold. Would it have been better to mix with water first and check with refractometer then pump in?? Is the fluid thick at the valves if not mixed correctly???

Any ideas would be great

 

[Chuck]

UFH works fine. It’s the rads that struggle. We always seem to get loads of heat to the rad valves but it really struggles to flow properly around the radiators.

Are both valves on each radiator geting hot without the radiator itself getting hot? If so, you might have a plumbing mistake, such as shunt between the CH flow and return. If just the flow valve on each radiator is getting hot check the zone valve is opening properly.

 

[king of pipes]

Use a buffer vessel separate the systems antifreeze only needs to be in the ashp primaries then , all the heating will come off the buffer vessel treated as normal with a quality inhibitor and biocide thats what I would have done ? . Kop

 

[Brambles]

Two points:

Put the system into open flow - when it is operating properly, then and only then introduce the minimum number of controls. A heat pump will be at its most efficient with no restrictions on flow. The majority of thermostatic controls respond too slowly (when opening) for a single speed heat pump to operate properly. Even inverter pumps can struggle if there is too much downstream control.

Second point, check the size of your buffer tank with respect ti ASH secondary flow - most flow issues on small air source rad systems are a result of either no buffer or too small a buffer.