ok lets hope the insulation over the probes brings these closer otherwise its just another indicator of an issue.
following the pipes all the way from the low loss header to the heatpump outside unit, can you take some pictures? Interested to see how well they have been insulated.
Thanks Ian, I’ll take pictures in morning in daylight. Looks it be goes in a duct under utility then outside with some pipe insulation over the pipes from outside wall to ASHP. Outdoor photo I’ll send when light picks up.
essentially the ashp in pipe is one with red valve on it
@crimson insulation looks mostly ok. what you have not got is a huge long uninsulated length (that was worrying me with the temp diffs). so hopefully insulating over the top of the probes, gets us numbers that are close-ish. never seen one of those ducted pipe systems in person but I assume it is heavily insulated.
there is something uninsulated to the left of the blue valve outside, a closer-up picture in daylight would be useful.
Plumber has suggested they look at the LLH itself to rule that out before looking elsewhere. Basically a bit of trial and error.
Running pump at different speeds had zero affect on the temperature differential coming across the LLH
Try switching the secondary pump off for say 5 minutes and see what happens with the return temperature to the heat pump, and then the flow temperature to the heat emitters when the secondary pump is restarted.
I would expect the return temperature to rise until it is approximately the same as the heat pump flow temperature. If you time how long it takes for the return temperature to increase, and if you know the volume of the buffer tank, it should then be possible to calculate the approximate flowrate.
Before you start ripping your system apart, has anyone checked that the 'Y' strainer is clear. I would also suggest that you check the temperature at the pipes where they enter your home, to see if they are closer to the controller values.
Don't forget that you have quite a lot of un-insulated pipework, which will lose temperature if the flowrate is restricted.
Edit.
I forgot to ask did you look for a bypass valve in the primary pipework? If you are not certain what one looks like, just Google.
@crimson you appear to have lots of issues with your install as we did with our Grant ASHP and we've had to install it twice. There is thread on this forum with the history. I haven't read through all of the messages but resolving the primary flow if it hasn't been resolved is the first thing. On our second install we found out the heat exchanger was blocked because the system wasn't flushed by the installer and the crap in the system effectively blocked the heat exchanger and at the moment I only get 20 lpm after 4 years since first install. Despite flushing twice flow rates went up briefly only to come back to the lower rates. As yours is a retrofit, have you had your system properly flushed. Its most likely not the cause of the issue at the moment because it too new but please make sure the installers have flushed the system properly so you don't end up with the problems we faced.
Also we had one of the Grant engineers come and perform a flow test directly on the heat pump to confirm flow rates are as expected. You may want to consider also to rule out the heat pump although very unlikely if its brand new.
Happy to have a call with you to go through what we found on our journey if you want if it helps you not make some of the mistakes we made. PM me and I can send my number if its of interest. I know first hand it's not always straight forward.
Thanks both, I’ll ask about a flush of the system tomorrow.
note this isn’t really a retrofit as essentially fully new plumbing as part of the project, (I believe they replaced all pipe work pretty much). But will doubly confirm.
I also really want them to get a Grant engineer out for a second opinion on site. The architect is keen on another opinion also as currently atm can’t sign off their work for payment essentially.
in case of use context wise when I took photo ASHP was off as a log burner was run a lot today and all zones hit temp
Yes that appears to be a bypass valve. Check the the temperature of the pipes either side to try to ascertain if there is flow going through it. It looks to be at the highest pressure setting so hopefully should not be passing.
The 4 port black bypass valve in one of your previous photo's, is that across the flow and return pipes? Check the temperatures around this valve and try to ensure it is not partially open.
