Balancing radiators with an ASHP

[Marvin]

When balancing my radiators using water from the ASHP, set at 40C, what temperature difference should I expect across the radiator when aiming for a room temperature of 21C? Is 11 degrees too much?

 

[dpmiller]

IIRC the iVT will throttle it's power back if the delta exceeds 10c. I can't recall- are you directly connected or is there a buffer tank involved?

[Marvin]

1 hour ago, dpmiller said:

IIRC the iVT will throttle it's power back if the delta exceeds 10c. I can't recall- are you directly connected or is there a buffer tank involved?

Hi @dpmiller 

 

Thank you for your kind response. 

 

We have a 60 litre buffer tank. and about 85 litres in the pipework and radiators.

Having little knowledge, I assume iVT means inverter, which we have.

IIRC I had to look up ?

 

So do I ignore the temperature drop between the inlet and out let from each radiator because the temp drop will happen in the buffer tank?

But would that not mean losing high temperature heat unnecessarily through the flow return pipes?

 

Should not the water temperature in the buffer tank slowly reduce until the ASHP kicks in? I notice that the sensor for the Heating water is in the buffer tank?

 

All opinions greatly appreciated.

 

[dpmiller]

At 40c you'll need all the heat you can I'd guess, but yes the buffer will slowly drop until the ASHP comes back on.

[Marvin]

If the buffer tank is to increase the volume of the water in the system, why is the hot from the ASHP going directly into the buffer tank instead of directly to the heat emitters (ours are radiators) before the temperature drops?

 

Why not return the cooler water in to the buffer tank and draw off for the ASHP?

 

 

[Olf]

I think the answer is controls: with a buffer between source (boiler, heat pump) and heaters you demand heat from the source using buffer temperature. Simple.

With buffer on the return you'd have to use flow measurement to shut off the source when demand (=flow) reduces, but getting there means more and more struggle for the source (on both modulation and pressure). With the only benefit being lower buffer standing losses, you pick a buffer on supply side every time.

[Marvin]

14 minutes ago, Olf said:

I think the answer is controls: with a buffer between source (boiler, heat pump) and heaters you demand heat from the source using buffer temperature. Simple.

With buffer on the return you'd have to use flow measurement to shut off the source when demand (=flow) reduces, but getting there means more and more struggle for the source (on both modulation and pressure). With the only benefit being lower buffer standing losses, you pick a buffer on supply side every time.

Thanks for this info.

 

In order to stop the flow reducing would not a bypass valve overcome this issue?

[dpmiller]

A bypass valve is my strategy, but it's a wee bit noisy at the flow rates the ASHP wants to see.

[Marvin]

1 hour ago, dpmiller said:

A bypass valve is my strategy, but it's a wee bit noisy at the flow rates the ASHP wants to see.

@dpmillerI will look into this. Thanks.

[markocosic]

Look for the target deltaT and minimum flow in the heat pump manual.

 

Mine wants 5-7C for example. 11C is high. (old school non condensing gas boiler high)

[Marvin]

33 minutes ago, markocosic said:

Look for the target deltaT and minimum flow in the heat pump manual.

 

Mine wants 5-7C for example. 11C is high. (old school non condensing gas boiler high)

Yes I thought as much