I would agree with you so long as the pipe work isn’t going to be changed. 

Swapping a radiator or two isn’t expensive and well within the scope of a competent diyer. 

Have you checked for any extras on the Octopus side? For example I had to either get artex removed or lift floorboards for an alternative pipe route - both at my own cost above their fixed quote.

@gunboatdiplomat Yes when I have had the survey and report I will check. The BG one was pretty perfunctory with little detail except that it is up to me to provide piping and cabling under the path.

@jancold since you’re choosing between BG or Octopus, basing your decision on price makes sense if they’re both offering similar installations. However, design remains the most crucial component. I’d definitely evaluate this and see if either is proposing a buffer tank. BG is supposed to be phasing these out from their designs and proposals, which could result in hardware savings as well as long-term running cost savings.

@editor Yes my BG quote includes a buffer maybe as a thermostat or TRV was suggested downstairs (which I did not want had it been explained). I am questioning whether my BG man was an installer as he did not seem to be able to suggest, for instance, what I needed to provide for running the services under the path. He talked of piping but no mention of cables which are also rather necessary! I don't know if BG will produce a more detailed report after paying my deposit but anyway OE will not be surveying till 31st July. I wish I had started this process so much earlier as time is rushing by.

@jancold Just a thought, when you say the Octopus quote was half BG, what are we talking about here? Not £500 v £1000 I take it 🙂 If it was then of that order then the system designs would need to be scrutinised closely.

@bontwoody It is £2300 for OE (assuming they do not alter it in the survey) and £4200 for BG which was down from £5900 initially. As you say I have to wait for the OE Survey and detailed report.

However if the boiler flow temp reading was reasonably accurate: I ran it 24/7 for the last two winters at an indicated 40C and only on the coldest days it fell below 19C. I know the Kitchen /Diner rad  and Bathroom towel rail is far too small and maybe I need a rad at the top landing (according to the MCS rule book).

Since no piping changes were suggested the only changes can be the radiator output/size? and the system setup. About which I need to learn to understand before I even think about fiddling with it. 

@jancold To me its a no-brainer then, a max 40C flow temp should give you a very pleasing SCOP. You seem aware that a buffer tank isnt usually a good idea so its not a plus point for BG.

What I managed to do in my house to keep costs down was change the largest radiator I needed to and then shuffle the others down to the next smallest room so pretty much everywhere got an upgrade.

I used 15mm plastic pipe to feed the rads which made for a very easy install and they have a large enough diameter to allow 1.89 kW at DT5 at 0.9mps flow (versus 2.75 kW for 15mm copper pipe)

Octopus have now surveyed. He was very thorough and for instance felt the need to contact his electrical expert on a possible problem with my supply: thankfully all was good. All his measurements and photos are then passed to chair jockey designers so he suggested that if I am in disagreement with something to say no and make a counter proposal they want to please the customer.

I now await the detailed report but his heat loss was a lot higher than BG at 5.25 (BG 3.46) my heat punk result was 4.9 which agreed more closely. Also the radiator changes on the ground floor are closer to my Heatpunk predictions but as they require two new radiators they may want to charge me for them. So I guess it will be a 6kW Daikin.

They will also supply a larger towel rail though it has not got the required output. I may query this as I am not against a radiator and like a warm bathroom.

They will lay a gravel base for the Heatpump BG won't. I provide a trench for the pipework they do the rest. Surely If I made up an insulated pipe there could be problems with the warranty? BG made no mention of how to route the electrical supply or data cable.

I could have gone for the Cosy6 but he admitted it was not quite as efficient so I'm sticking with Daikin. It was suggested using the immersion in the summer and switch the heat pump off, that does not make sense to me.

Has anyone had a bathroom towel rail on the DHW circuit to dry towels all year round? Is this a bad idea?

I mentioned I would like a design temp of 45 and it was noted and, if necessary taken up with sales. 

There will be a volumiser which he sometimes calls a buffer "to help with the defrost cycle" is this bull**It?

The property is about 2 meters above the road and he was concerned about lifting the heat monster up! I said I could rig a derrick (no not Derek M) or rent a Telehandler or platform surely that can be overcome fairly easily!

So now it is another wait...

@jancold The only reason i can think of to suggest using the immersion in summer would be to turn the heat pump off completely to avoid its standby losses, but I would be very surprised if they were large enough to make it profitable to do given the extra energy needed by the immersion.

Re the towel rail, do you mean just have the towel radiator heated when the DHW cycle is on, which would only be for an hour or two a day? The rest of the day it would be cold, so it doesnt seem like a good idea to me.

My understanding of a volumiser is to ensure that there is always enough volume of water in the system for the heat pumps minimum requirement to smooth out cycling and provide energy for defrosts. I dont have one as I know I have sufficient volume in my pipes and always open radiators

@jancold We have an ‘oversized’ radiator in the bathroom as we wanted an elevated temperature compared with MCS guidelines. We achieve the 25 - 26 degrees C. - our installers took note of my requirements on this matter. We also have a towel rail above the radiator; we have a ‘dual fuel’ fitting and use the immersion element in it during the summer (approx. 300 watt consumption per hour) I close one of the towel rail valves if we want to heat the rail to the higher temperature in the winter. The element heats the rail to a higher temperature than the ASHP circuit would. I close the valve so that I am not returning hotter water to the ASHP system than it would expect to see as this I feel, would cause confusion to the control circuitry. The electrical element is controlled via a Myenergi Eddi; we use the relay board and I programme that to give power to the rail for 3 hours in the evenings. Anything else I can tell you - please ask! Regards, Toodles.