not sure if i should insulate the 28mm flow and return that goes to the radiator circuits. they are quite a long 8m approx. L shape run with other rads coming off them. im just worried once the water runs a further 6m or so in 22mm and 15mm there wont be much heat left.

You’ve captured why heat pump installations require patience – it’s not just the technology, but the logistical hurdles that catch people out. @toodles had supply issues too, which he discussed during one of our podcast episodes. It does happen.

Remote surveys, coordinating trades and last-minute supply issues become even trickier when you’re outside an installer’s usual operating area, as you’ve found with your 72-mile gap.

It’s frustrating when even recommended companies stumble on basic execution, whether it’s missing parts or miscommunication with subcontractors. Your situation highlights a real problem: the UK market still lacks enough local specialists to make these installations smooth nationwide. Having said that, it’s better to have teething issues with a reputable installer than a flawless run with an incompetent one. At the end of the day, the quality of the install is paramount.

That said, your hands-on approach with the pipework modifications shows exactly the kind of engagement that gets the best results. I’d suggest sticking with it, even if the road tests your patience.

I would as I would like the heat to be emitted in the room primarily but there is a school of thought that thinks as long as the heat is going into the house it’s not that important. Obviously if the run is in the loft then insulate. 

As @bontwoody says, if they are inside the heated envelope of the house then it becomes a question of whether it is more beneficial for more of the heat to reach the radiators in question.

Another consideration for not insulating, is that with low temperature heating systems (e.g, ASHPs), we are trying to maximise the size of our emitters, and those pipes when uninsulated increase the amount of heat the system can emit into the property, so there are benefits there besides just the cost savings on the insulation. They probably act as an additional radiator in the system.

Is it possible to try running uninsulated to start with, and then add insulation later if the affected rooms are too cold? Or would adding insulation later not be possible due to pipe placement? Someone smarter than I will probably be able to calculate how much heat would be lost on your 28mm run to see if it's worthwhile insulating or if it's going to be insignificant.

I have not insulated mine because I'd rather maximise the emitter size, and I'm already struggling with a narrow dT so the more heat I can dissipate before the return flow makes it back to the heat pump, the better (e.g, it may help me go from a dT of 3C to 3.5C)

@old_scientist good point about increasing the size of the emitter!

@adamk

I am sorry to hear about your initial troubles.  Can just a) support what @mars says and b) add that, if you get a good installation, which with your monitoring you are hopefully on track to do, you will be pleased with the result.  My heat pump delivers a level of comfort way better than that delivered by my gas boiler (which was only about 15 years old).  The controls do everything I need (which mostly amounts to leave it alone) and the upgraded DHW system is a dream.  i dont have a full seasons cost yet but, between November and February, when heat pumps are least efficient, it was 12% cheaper than my gas boiler would have been over the same period.  

I think the principal things you need for a good installation can be summarised as:

• Do not permit the installation of a 4 port buffer tank, Plate Heat exchanger of low loss header separating the emitters from the heat pump (2 port volumiser is OK)
• Do design for the lowest practical flow temperature, 45 or less for rads, 35 or less for UFH
• Do not design in any 'smart' controls with the sole exception of Homely which is specifically designed for heat pumps (this comment should not be taken to mean that you need Homely)
• Do if you can, sense check the sizing so you dont over size
• System design matters more than choice of heat pump but some heat pumps are quieter and have better controls. 

Once its in you will need to tweak the weather compensation curve and possibly balance the emitters, please keep posting if you want any tips.

my worry is most of the 28mm and 22mm runs are in the kitchen ceiling so quite a bit of heat is going into the corner of the house where we dont sit most of the time. there is a bedroom above one half of the kitchen, but there is some fibre glass insulation in this ceiling/floor area as was once an external roof before the bedroom was built over it, the rest is under an upstairs bathroom.

@adamk I think I would insulate as much as I could then.

this is a rough diagram of the pipe runs, beyond the 28/22mm runs it drops to 15mm to rads. for scale the Kitchen is about 5.3m x 3.2m.

red is 28mm orange is 22mm.

is it ok to heat the HW tank using a plate exchanger? as they want to use one just for the HW tank.