Posted by: @alec-morrow

@mike-patrick it might seem to you there are choices of approach, but for for optimum performance of the heat pump and vrc700 you really should select and install the components as they indicate in vaillants schematics.

 

I don’t know why installers and specifiers think they know better that vaillant design engineers!

@alec-morrow I wondered this too, a Vaillant rep suggested to me it normally comes down to cost (or value engineering as it is often referred).

Posted by: @derek-m

Hi @webcmg 

Check to see if any of the valves are partially closed on any of the radiators.

Check that your water pump is producing adequate pressure and flow to get the water up to the radiators. Try measuring the temperature of your radiators and then shutdown your UFH so that all the flow is going to the radiators. If the temperature of the radiators starts to increase then you have a pressure or flow problem. Try increasing the pump speed.

@derek-m thanks. This is starting to go beyond my technical capability so think I'll need to await the developers heating engineer to investigate, but very helpful to make some suggestions when discussing the issue with them. 

@webcmg 

I’m using the same control equipment as you and designed the system (installers didn’t have a clue).

The VRC location is critical as it is the reference for the compensation, I went for wireless so I could be sure of the best location. I’m also using the full ambisense system and have done a review of it.

Fundamentally the VRC allows for a mixing valve which is essential when combining radiators and underfloor heating. Split the zones one underfloor and the other radiators which will allow different compensation curves to be used and the system optimised. 

Posted by: @mattengineer

@webcmg 

I’m using the same control equipment as you and designed the system (installers didn’t have a clue).

The VRC location is critical as it is the reference for the compensation, I went for wireless so I could be sure of the best location. I’m also using the full ambisense system and have done a review of it.

Fundamentally the VRC allows for a mixing valve which is essential when combining radiators and underfloor heating. Split the zones one underfloor and the other radiators which will allow different compensation curves to be used and the system optimised. 

@mattengineer Interesting, I read the manual and there is a setting to basically tell the vrc 700 to ignore the internal temp from the unit. I guess that way it just uses the external temperature sensor and bases the temp control on the current flow rate? 

@webcmg yes you are right internal reference is optional

if you get the heat input right relative to the outside temp you don’t need indoor reference

Several other parameters achieve this

@webcmg you’re absolutely correct. I was purely referencing my own experience with the improved effectiveness / efficiency of the control system. Depending on the requested temperature the VRC will vary the flow rate from c40c to 75c and if the interior delta is 0.5c or 2c makes a difference of c6c in flow rate. 

Personally, I am a huge fan of vaillant equipment, it just takes a little trial and error of each installation to optimise depending on the individuals requirements.

@mattengineer I’ve probably installed 200 of the vaillant and 100 of the Viessmann equivalent

I can talk you through the parameters if you like…

of course the gold standard is vaillant monitoring your equipment…getting to the  fault codes before you know

Interestingly once you pay for the monitoring the equipment doesn’t seem to generated faults..

@alec-morrow 

That's what I meant, every system is different. These are the instructions for my Grant Aerona³:

Heating System Controls
Your Grant Aerona³ heat pump is NOT controlled by the remote
controller but will usually be controlled by a normal domestic heating
control system.
This control system will typically consist of the following controls:
A heating timer or programmer
This device allows you to set the ON and OFF times for your heating
and (if it is a programmer) the ON and OFF times for your hot water
heating also.
With the Grant Aerona³ heat pump, Grant recommends that
the hot water heating periods should be set to occur when the
heat pump is NOT operating to provide heating, i.e. when the
programmer is set to OFF for heating.

Mike

@alec-morrow @mattengineer @mike-patrick @derek-m

How appropriate are these types of valves on a ASHP heating system installation? I don't fully understand how they work, but it kooks like they might mix cold water into the hot water to achieve a temperature between 30 and 50 deg. This doesn't seem efficient if it cools down comparatively cool ASHP outputs, pptentially reducing efficiency. I could understand using them on a gas boiler installation given the water output is significantly hotter.

Here are some other pictures, if anything looks odd for ASHP system installations please let me know.

@mike-patrick 

this is all that is required by British regulations, it would not be installed this way in any number of countries where heating skills are more prevalent 

@webcmg 

It looks like you have a thermostatic blending valve which should reduce the flow in the underfloor to a predetermined level by mixing the cold return in the underfloor with the hot flow. I would buy some clip on temp sensors from a local merchant and track what is happening before making changes. 

I presume you have an outdoor temp sensor on a north facing wall with the VRC700?

I’ve included an image of the heating curves below, using the indoor reference allows the system to vary the flow temp depending on the delta between current room temp and desired room temp this will reduce as you get closer to the desired so you don’t overshoot.

The image on right shows the vaillant schematic for combining underfloor with two other radiator zones. By separating the zones you can use different curves for the radiators upstairs (I.e. hotter flow) and the underfloor (blended colder flow) provided that the vaillant mixer ref 67 is wired in to a vr71 wiring centre. 

An electronic mixer and a pump can be supplied for about £240..to replace the manual mixer and pump and with that you will have a system that complies with the way vaillant design engineers intended the system to work..

you can keep a few on off stats and actuators but these left open should be a fairly big zone where a vr91 can be located