@allyfish I am not sure on the calculations as they were never given to me. I have just dug out all the paperwork left with me after the install. I will attach what I think answers some of your questions. House was built in 2006. Seems to be differing system temp numbers in their paperwork but was defo 55c. I also have only the pump in the unit itself and there are no flow gauges installed. Pump is set to the highest flow setting as per the manual. There are a total of 17 rads fitted. It has 22mm copper that branches off to 15mm to the rads themselves. I have been in the the void of the first floor and checked as wanted to fit wet underfloor heating in the bathrooms upstairs. 

Right now it is set to 18c all day and comes on and off as needed. It was set previously to 20c during the day and 18c in the night. Currently has Taco controlling it all as that was what was on my oil boiler and they left it installed.

Valves and outdoor unit:

@daniel nothing wrong with those parameters for HW generation. 4degC over flow and return is about what I see. ASHP is pulling quite a high power in HW generation, as it will for water at 50degC. My 10kW tops out around 2.7kW consumed power, so pro rata that for a 17kW unit = 4.6kW.

Your rads should not be getting warm when this is happening of course, if CH has not been called for, and the Grant controller always prioritises HW over CH. I suspect you may have a sticking or faulty 2 port motorised CH control valve. Could be debris causing the ball not to seat and seal, could be faulty. The valve has a manual opening lever on it, which you can operate to latch open. When the valve cycles next under auto control (to open), the manual lever will disengage and revert to auto control. If the lever isn't showing fully closed under spring return (compare with your HW valve lever position) something may be wrong. When did you last check & clean the Grant MAG magnetic filter? It's condition might indicate if debris is present in the circuit.

@daniel nothing wrong with the pics of the outdoor unit. Grant say 'over 300mm' clearance to the wall behind the coil inlet face. Yours looks a little close. 300mm is their minimum, more is better but only to help with access for maintenance, such as coil cleaning, it won't impact performance provided the minimum is achieved.

@allyfish @allyfish I manually operated the valve after I took the reading and the pipework past the valve become hot fairly quickly. So would presume it was sealing good. I had thought that the way the HW return was piped might be causing a reverse flow situation. I have had it maintained annually for the 10 year warranty that greener energy offered with Grant. They had some deal for this. Guy showed me the filter.

I would have thought the tank would have reached temp well under an hour and presumably it does when it isn't trying to heat all the radiators at the same time.

Will check the standoff distance but it looks around 300mm to me. Thinking of complaining to Greener Energy but don't know how that will go since it was fitted in 2019. Only really noticed after the electric price went to high and was costing over a grand a month to run in the winter. 

@daniel

I would suggest that you check the position of the manual lever on the CH valve. If it is in the valve closed position then try moving it manually to the open position. You should feel some resistance as you push the lever against the return spring, if the lever moves freely then the valve may be stuck in the open position. If this appears to be the case then try tapping the valve body with a rubber mallet or piece of wood.

@daniel 55degC is your HW max storage temp. That makes sense as Grant ASHP can provide up to 60degC. 50degC is the system heating design temp. A touch high, and if running slow and slow and continuously, (maybe with a few hours off at night) should be adjustable down to around 45ddegC. Supplying heating for longer at 45degC will consume less energy and be cheaper than supplying in shorter bursts at 50degC. You've probably trimmed the top end max LWT on your weather compensation anyway to 45degC?

Taco controller or Tado? If there is a digital on/off room thermostat, ensure it's not cycling the central heating on and off. That's not efficient. Use weather compensation and radiator manual balancing. The heating should run for long periods uninterrupted. The compressor will never modulate down to stable control otherwise, and you'll be spending a fortune in electricity. There's a bit of trial and error involved in this. My HIVE room stat is set to 24degC, purely to prevent overheating. The house balances out at around 20degC on pure weather compensation. Last thing you want is a thermostat switching the ASHP on and off multiple times an hour, but that's exactly how Grant sets them up. They've now recently partnered with Homely and I think have woken up and smelled the coffee realising that how they  commission ASHPs with WC disabled and cycling on room stats is incredibly inefficient and bad practise. 

@derek-m took the actuators of and checked the valves manually and they are definitely closing. I originally thought they weren’t closing all the way but the actuator seems to keep a bit of tension on the actual valve itself. Wondering if it would be worth putting some non return valves in the CH returns. Will get in the crawl space tomorrow and check the upstairs CH pipes and see which one gets hot first.

@allyfish I can’t remember what the WC settings are believe I just turned it on as it was off. And set the flow to 45c if I remember correctly. Will go through it and have a look. Have noticed that with the WC on the rads are much cooler than the previous years. 

Yes, Tado not taco guess auto correct got me there! Yes believe it is only calling for heat when it thinks it needs it. I used to have all smart TRVs but got rid of them all and just opened all the TRVs wide open. Though going by what you say to manually balance the system to you mean control the temperature with the TRVs and basically have it running nonstop? As tried setting it to 25c the other day just to see how the compressor was going to behave and it was probably the first time I have ever seen the pump running without the compressor going all the time. So presumably my system temperature got to temp and it only put the compressor back on once the temperature dropped too much in the circuit. Going to go have a look through all the settings just now and see where I am at. 

@daniel

If you measure the size, and check the type of each radiator, you should be able to obtain their heating capacity on the Screwfix or similar website. Note how many radiators are on the downstairs loop and how many on the upstairs, then total the heating capacity of each group.

It would appear that the pipework is 28mm at the CH control valve, where does it reduce to 22mm feeding the radiators?

@daniel

There appears to be plenty of 'cooks' today so I will go back to the movie I was watching.

One final suggestion, when you have time carryout your own heat loss calculations, which should be useful in deciding if the heat pump, emitters and pipework are correctly sized.

@derek-m will have a look at that tomorrow. I do know they were all replaced with Purmo ones I believe as had column cast iron sort of ones before. I know some of them were replaced with larger and in the case of my second sitting room they added another one. Basically all windows in there. 

Directly after the valves it goes down to 22mm copper as they just basically cut the boiler out and put this in exactly how the oil boiler was piped. Guy who built the house was apparently a plumber but to be honest I have done better work myself haha. At some point I plan on doing the whole ground floor in underfloor and replacing the glass wool in the joists with kingspan type insulation. Though want to do that in tandem with a new kitchen as the ground floor pipes start in the kitchen. So figure that would be a good time to do it. Looking at the Nuheat pre routed floor boards that just came out. May go with screed as well. Plenty of time to decide though. 

Is there a guide on here for doing your own heat loss calculations?