Flow rate needed

[jamesdiyer]

I do seem to have two issue. 

 

The exterior temperature sensor seems to have been placed in a microclimate as it's 2C above exterior (real) currently. 

 

Also the DHW is reading 23C as the sensor is quite low down, as on photo. Maybe this needs be higher. Or mains water arrives around 12C. The tank isn't 23C as it's coming out nice and hot. Suggestions on this one and where it should be would be helpful. 

I've set the DHW that it can heat in two windows per day (cheap off peak) so perhaps it's not an issue as it won't be constantly trying to heat. 

 

 

Thanks 

 

 

 

 

Edited Thursday at 17:30 by jamesdiyer

[jamesdiyer]

Also I realise I can reduce the target DHW temp. I should be less worried about temps as actual temps and treat them as a tool to adjust based on if we have enough hot water. 

Edited Thursday at 19:17 by jamesdiyer

[JamesPa]

2 hours ago, jamesdiyer said:

The exterior temperature sensor seems to have been placed in a microclimate as it's 2C above exterior (real) currently. 

This should be located in the shade where the air is free flowing.  If the offset is constant it wont matter much, if its not constant it will and should be relocated.

 

2 hours ago, jamesdiyer said:

Also the DHW is reading 23C as the sensor is quite low down, as on photo. Maybe this needs be higher.

Fairly normal.  DHW manufacturers assume people want something close to a full tank or at least half a tank and locate sensors accordingly.  Putting it at the top would mean that reheat is triggered only when its empty, meaning that there is a period when DHW is unavailable, which the majority of punters will complain about.  Just adjust your schedule/hysterisis to get what you are comfortable with

[jamesdiyer]

The sensor is located near the heat pump in the shade but under a lean too roof, so it's a microclimate. I'll ask the installer to move it to a North wall. 

 

And thanks for confirming the tank situation, makes sense. It is actually a good location thinking about it, it's a 200L tank and some family members like scalding huge baths. 

[jamesdiyer]

Another question. 

 

I noticed the flow return pipe between the 3way valve / volumiser and radiator input is done in 25mm plastic, so 20mm internal. It's about 3m of pipe overall. From A to B. After point B, the copper pipe splits immediately into two 22mm coppers one for upstairs on for down, so it is a restriction. 

 

The pipe between diverter is 32mm external. If on DHW cycle we get 2000l/h but 1700l/h heating circuit. 

 

Could this short stretch of reduced pipe be reducing flow so much? Before I ask installer to change. 

 

 

Edited yesterday at 05:26 by jamesdiyer

[JamesPa]

2 hours ago, jamesdiyer said:

The pipe between diverter is 32mm external. If on DHW cycle we get 2000l/h but 1700l/h heating circuit. 

 

Could this short stretch of reduced pipe be reducing flow so much? Before I ask installer to change

Possibly.  1700l/h is a bit low for 12kW (12000/4200/5*3600)=2000l/h.  I would describe this as sloppy plumbing.

 

Why is what appears to be the sensocomfort in what appears to be the plant room/garage.  This should be in your house so the heat pump knows the OAT and control the heat pump.  Its normally wireless so you can put it somewhere convenient.  Maybe Ive misinterpreted the photo.  I hope you arent using third party controls/thermostats.

Edited yesterday at 07:53 by JamesPa

[jamesdiyer]

27 minutes ago, JamesPa said:

Possibly.  1700l/h is a bit low for 12kW (12000/4200/5*3600)=2000l/h.  I would describe this as sloppy plumbing.

 

Why is what appears to be the sensocomfort in what appears to be the plant room/garage.  This should be in your house so the heat pump knows the OAT and control the heat pump.  Its normally wireless so you can put it somewhere convenient.  Maybe Ive misinterpreted the photo.  I hope you arent using third party controls/thermostats.

 

The sensor comfort is there temporarily, it's wired and I couldn't decide where to put it - walls are 80cm think. I'm running pure weather compensation. 

 

Yes your comment alludes to my first question, I felt 1700l/h is low - and I have a 15kw machine. But others here said running 32mm external 26mm internal plastic pipe over 11m isn't enough bore. 

[JamesPa]

41 minutes ago, jamesdiyer said:

Yes your comment alludes to my first question, I felt 1700l/h is low - and I have a 15kw machine. But others here said running 32mm external 26mm internal plastic pipe over 11m isn't enough bore. 

What the plumber has done with the plastic pipe is just lazy.  It's the 'never time to do it right, always time to do it twice mentality'. 

[jamesdiyer]

8 hours ago, JamesPa said:

What the plumber has done with the plastic pipe is just lazy.  It's the 'never time to do it right, always time to do it twice mentality'. 

 

Yes sadly that's so, and parts on the install weren't discussed with me. 

 

 

 

On another note, my monitor says basic circuit diagram 8. However if I am just with a volumiser and DHW tank, radiators only 1 circuit, should this be 7? 

 

Edited 19 hours ago by jamesdiyer

[marshian]

13 hours ago, jamesdiyer said:

Another question. 

 

I noticed the flow return pipe between the 3way valve / volumiser and radiator input is done in 25mm plastic, so 20mm internal. It's about 3m of pipe overall. From A to B. After point B, the copper pipe splits immediately into two 22mm coppers one for upstairs on for down, so it is a restriction. 

 

The pipe between diverter is 32mm external. If on DHW cycle we get 2000l/h but 1700l/h heating circuit. 

 

Could this short stretch of reduced pipe be reducing flow so much? Before I ask installer to change. 

 

 

 

Just a random thought from me - those valves are full bore ones and not the restrictive types?

[jamesdiyer]

1 hour ago, marshian said:

 

Just a random thought from me - those valves are full bore ones and not the restrictive types?

 

Good question. The red ones yes. The blue ones on the heating pipes should have come out during the install but we're left. They were only placed there so I could pressurise the system prior to installer coming to check some repairing I'd done was fine. So they'll come out when he's back. 

[JamesPa]

1 hour ago, marshian said:

Just a random thought from me - those valves are full bore ones and not the restrictive types?

I think you can guess!, and I fear you will guess correctly!

 

2 hours ago, jamesdiyer said:

On another note, my monitor says basic circuit diagram 8. However if I am just with a volumiser and DHW tank, radiators only 1 circuit, should this be 7? 

 

Not sure what 7 and 8 refer to here.  In my set of schematics from a year ago 

 

7. No modules

8. uniTOWER, Buffer

 

So 7.  Not sure if it actually makes a difference though to the settings, it could, it might, but it might not!

[jamesdiyer]

34 minutes ago, JamesPa said:

I think you can guess!, and I fear you will guess correctly!

 

Not sure what 7 and 8 refer to here.  In my set of schematics from a year ago 

 

7. No modules

8. uniTOWER, Buffer

 

So 7.  Not sure if it actually makes a difference though to the settings, it could, it might, but it might not!

 

Actually looking the part manual they seem to be full bore and they're 1" so 22 internal but will know when off. 

 

If we're talking restrictions, then the plastic 25mm pipe fittings are internal of that. The pipe id is 20 and so you're looking at 15mm inside of the fitting id. But that's a very tiny distance, so I'm not sure it matters? (Everything matters in totality) 

 

Annoyingly vaillant Spain seem to be useless, which isn't good. I got some answers from vaillant UK very easily - flow should be targeted at 2000l/h, and send me their installer handbook with figures. Not surprising. 

[SimonD]

What delta T are you measuring between the flow and return of your heatpump when it is running on CH? 

[jamesdiyer]

2 hours ago, SimonD said:

What delta T are you measuring between the flow and return of your heatpump when it is running on CH? 

Well 5. But the heat demand is very low currently. 

 

I'm not sure how to force the highest heat demand from the hestpump to see what the delta t and max kW produced is.