ASHP (Valliant?) + Sunamp + PV w/ battery queries.

[ReedRichards]

1 hour ago, I wish I was a Trex said:

Interesting about the LG re: target temp for UFH / Rads as the ability to do this was one of the reasons it was recommended. 

 

I could be wrong but I've familiarised myself with the controller and read the Product and Installation Training Material and I don't remember seeing anything on how you would set different flow temperatures for different zones.  Now my system overrides the LG controller with a third party controller which means I don't get all the features that LG controller could do on its own (such as the poorly-documented Load Compensation).  So possibly the capability you need is there but not visible to me.

 

You can read the Training Material here (bottom of page 11): 

 

[JamesPa]

2 minutes ago, ReedRichards said:

 

I could be wrong but I've familiarised myself with the controller and read the Product and Installation Training Material and I don't remember seeing anything on how you would set different flow temperatures for different zones.  Now my system overrides the LG controller with a third party controller which means I don't get all the features that LG controller could do on its own (such as the poorly-documented Load Compensation).  So possibly the capability you need is there but not visible to me.

 

You can read the Training Material here (bottom of page 11): 

 

Maybe Im being thick, but I cant see how any ASHP can, on its own, set different flow temps for different zones to be delivered simultaneously, since there is only one flow pipe coming out of the unit.  Different flow temps at different times is possible (eg setback and for DHW) but two flow temps at the same time is not.  The only way to achieve the latter is some sort of mixing valve which is what is commonly put in where there is a combo of rads and UFH.  In  principle this could be controlled by the ASHP, I dont know if any do this.

 

Others may comment on how a rad/ufh combo could best be set up, or it may be in the manual.

[Dan F]

17 minutes ago, JamesPa said:

Maybe Im being thick, but I cant see how any ASHP can, on its own, set different flow temps for different zones to be delivered simultaneously, since there is only one flow pipe coming out of the unit.  Different flow temps at different times is possible (eg setback and for DHW) but two flow temps at the same time is not.  The only way to achieve the latter is some sort of mixing valve which is what is commonly put in where there is a combo of rads and UFH.  In  principle this could be controlled by the ASHP, I dont know if any do this.

I have two different flow temperatures for different circuits all controlled by the Vaillant ASHP controller. You need:

- Buffer

- Mixing valve and temperature sensor on each circuit
- Controller that supports this.

 

If the two circuits are for two different zones in the house, then you can assign them to zones with each zone having its own thermostat, min/max flow temperatures, schedule, set-back and even its own heat curve.

 

The ASHP will deliver the flow temperature (to the buffer) that is equal to the maximum flow required by the different circuits.  The circuit(s) that needs lower flow temperature will then mix down.

Edited March 16, 2023 by Dan F

[ReedRichards]

9 minutes ago, JamesPa said:

Maybe Im being thick, but I cant see how any ASHP can, on its own, set different flow temps for different zones to be delivered simultaneously, since there is only one flow pipe coming out of the unit. 

No, you're absolutely correct.  What you want is an ASHP that reduces its flow temperature when the radiator zone is not calling for heat.  Given the different response speeds of UFH and radiators there could be quite a lot of time when the UFH needs a bit of warmth but the radiators don't need any.  

[JamesPa]

11 minutes ago, Dan F said:

I have two different flow temperatures for different circuits all controlled by the Vaillant ASHP controller. You need:

- Buffer

- Mixing valve and temperature sensor on each circuit
- Controller that supports this.

 

If the two circuits are for two different zones in the house, then you can assign them to zones with each zone having its own thermostat, min/max flow temperatures, schedule, set-back and even its own heat curve.

 

The ASHP will deliver the flow temperature (to the buffer) that is equal to the maximum flow required by the different circuits.  The circuit(s) that needs lower flow temperature will then mix down.

As. I surmised, a mixing valve is required and there is at least one controller that will deal with it.

 

However does this not mean that the CoP is governed by the higher of the two flow temps, thus losing the principal efficiency advantage of ufh, unless, as @ReedRichardssuggests, the ashp somehow reduces the flow temp when there is no demand from the rads.  

[Dan F]

7 minutes ago, JamesPa said:

However does this not mean that the CoP is governed by the higher of the two flow temps, thus losing the principal efficiency advantage of ufh, unless, as @ReedRichardssuggests, the ashp somehow reduces the flow temp when there is no demand from the rads.  

Yes, it only uses the highest flow temperature of enabled circuits.  That's how the Valiant controller works anyway.

[sharpener]

  

1 hour ago, JamesPa said:

As. I surmised, a mixing valve is required and there is at least one controller that will deal with it.

 

However does this not mean that the CoP is governed by the higher of the two flow temps, thus losing the principal efficiency advantage of ufh, unless, as @ReedRichardssuggests, the ashp somehow reduces the flow temp when there is no demand from the rads.  

 

A workaround would be to wire it so the rads and DHW both call for heat at the DHW temp e.g. they have their own motorised valves and you connect the microswitches in parallel to the HP.

 

From the efficiency point of view this is not perfect but you do not suffer from the inefficiency of mixing the flow down from a higher temp when you need only the UFH, which might be for much of the daytime.

Edited March 16, 2023 by sharpener

[DanDee]

Just now, sharpener said:

 

A workaround would be to wire it so the rads and DHW both call for heat at the DHW temp e.g. they have their own motorised valves and you connect the microswitches in parallel to the HP.

 

From the efficiency point of view this is not perfect but you do not suffer from the inefficiency of mixing the flow down from a higher temp when you need only the UFH, which might be for much of the daytime.

 

Use the higher temp return as a flow for the lower temp

[sharpener]

1 minute ago, DanDee said:

 

Use the higher temp return as a flow for the lower temp

 

Indeed possible. Would need complicated pipework, you would need to connect the DHW & rads in parallel and then the UFH zones in series, with shunt valves and/or bypass valves to control and balance the flows.

 

And in the end the UFH flow might still be hotter than ideal.

[JohnMo]

17 minutes ago, sharpener said:

Would need complicated pipework, you would need to connect the DHW & rads in parallel and then the UFH zones in series, with shunt valves and/or bypass valves to control and balance the flows.

CoP would be rubbish most of the time pump 50+deg water around. Think things are being made more complicated than they need to be and would result in something that cost a small fortune to run.

 

Just had a look at my ASHP controller, it can set two flow temps controlled by a open/closed contact, as well as another temp for DHW.  But it would only flow either a high or low temp, not both at the same time. It can also control a mixer valve if required.  

 

Best CoP and simplest design would come from running UFH and Rads at as low temp as possible (i.e. big radiators).

[DanDee]

2 minutes ago, JohnMo said:

(i.e. big radiators).

With fans

[JohnMo]

1 minute ago, DanDee said:

With fans

If you wanted

[sharpener]

30 minutes ago, JohnMo said:

CoP would be rubbish most of the time pump 50+deg water around. Think things are being made more complicated than they need to be and would result in something that cost a small fortune to run.

 

Just had a look at my ASHP controller, it can set two flow temps controlled by a open/closed contact, as well as another temp for DHW.  But it would only flow either a high or low temp, not both at the same time. It can also control a mixer valve if required.  

 

Best CoP and simplest design would come from running UFH and Rads at as low temp as possible (i.e. big radiators).

 

Yes I know, bad idea, I was not advocating @DanDee's suggestion just trying to point out the practical difficulties of implementing it! Mostly I don't think either DIYers or professionals would want to plumb up an arrangement like that.

 

If you have the flexibility your controller provides, the pipework is conventional and it is a lot easier. The eternal trade-off between the optimal CoP and the costs of a retrofit. (In my case the rads are not required simultaneously with the UFH as posted here.)

 

Have forgotten what you have, is it a third party controller?

[JohnMo]

It's a Maxa ASHP, with its own inbuilt controller.  The only third party bit is a limit stop thermostat, one in the house and one in the summer house.

 

Just need to finish the install, work and weather keep getting in the way.