Posted by: @jancold

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@broadsman Unfortunately this does not seem to have trickled down to the surveyor who still added one to my quote even though I mentioned I did not want one.

But do you have room thermostats? You can only delete the buffer if you ditch the room thermostats and most TRVs (keep bedrooms only) as well.

@broadsman I think there may be a few old buffers on the board…

Toodles.

@johnmo Ah yes he did say something about a TRV downstairs not a room thermostat but why would I need that? I want the most economic system controlled by the heatpump and WC don't I?

Posted by: @jancold

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TRV downstairs not a room thermostat but why would I need that? I want the most economic system controlled by the heatpump and WC don't I?

You do.

Are your bedrooms downstairs? TRVs will strangle flow just as easily as a zone valve. If your normal living space needs TRVs your flow temp is too high and the TRVs could easily close of big bits of the circuit and flow. You only have them in bedrooms to act as a limit stop - to stop bedrooms getting too warm.

State you want a fully open system in all living spaces, TRVs only in bedrooms and no buffer.

@johnmo Thanks , bedrooms upstairs. A fully open system is what I want, I must specify that to Octopus surveyor.

Posted by: @jancold

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@johnmo Thanks , bedrooms upstairs. A fully open system is what I want, I must specify that to Octopus surveyor.

The only time that you may wish to have a TRV in the living area is in a room or rooms that suffer from high solar gain. While in an open system, the temperature in each room would be set by adjustment of the lockshield valves, because the effect of solar gain is not consistent it is quite possible that the temperature in certain rooms may increase on cold, but sunny, days. This can unbalance the temperatures around your home which you may not find desirable.

If a TRV was installed in such a room, it should be set as a temperature limiter so that during normal system operation the TRV is fully open so does not limit overall flow rates.

@jancold Hi, I think you need a separate thread for this. My phone has been going off all morning... 🙉 🙂

@lucia Yes agreed I have started one now. It has been a very helpful thread

OK! An update from 🐙 I'd be very interested in your opinions please.

They are now proposing a Daikin 6kw but were going to leave everything else the same.

My response - I agreed that it was a borderline HP size case but emphasised that my focus was on running costs and efficiency as well as heating output.

I pushed back on design flow temp and made a formal request for 45º noting that Octopus has designed this way for other clients.

I also pushed back on the hallway design heating temp of 18º pointing out it was a CIBSE box tick but my hallway is a square central room that is used for multiple reasons including kids play area and yoga. 

I did the same for my bedroom office and noted it was a workspace and needed to be designed to be warmer. 

Sales first tried saying 'turn the heating up' [🤦🏻‍♀️] and then asked what I thought it needed. My response: higher design room temp & rad upgrade.

I thus requested 2 x rad upgrades - hall & bedroom/office.

I am supplying and fitting the bathroom radiator. 

Dunno about the 4kw v 6 kw bit - and I made that clear in my response. 

What do you all think? 

They are, in theory, coming back to me on this later today after meeting with the installations 'big boss'. 

@lucia Sounds to me as though you have made great progress (and I suspect, Octopus staff have learnt a few things about customer’s want and needs and heeding them!). Did you manage to get them to design out a LLH or buffer tank? Though I could not employ Octopus to install my system (as relayed ad nauseam elsewhere), I still think they will install a good system at a good price - and at least they are a company that listen and have the resources behind them to rectify any problems. Regards, Toodles.

Posted by: @toodles

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@lucia Sounds to me as though you have made great progress (and I suspect, Octopus staff have learnt a few things about customer’s want and needs and heeding them!). Did you manage to get them to design out a LLH or buffer tank? Though I could not employ Octopus to install my system (as relayed ad nauseam elsewhere), I still think they will install a good system at a good price - and at least they are a company that listen and have the resources behind them to rectify any problems. Regards, Toodles.

Quite agree, @toodles.

Posted by: @toodles

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@lucia Sounds to me as though you have made great progress (and I suspect, Octopus staff have learnt a few things about customer’s want and needs and heeding them!). Did you manage to get them to design out a LLH or buffer tank? Though I could not employ Octopus to install my system (as relayed ad nauseam elsewhere), I still think they will install a good system at a good price - and at least they are a company that listen and have the resources behind them to rectify any problems. Regards, Toodles.

I agree @toodles that for me with limited resources they are the best deal - plus I really liked the lead installer (who may not be my installer -dunno yet). 

But I don't know if I have made great progress ... that's the problem. 6kw is the result BG came up with if designing for no cavity wall insulation.

4kw was borderline for Octopus. 

My question - brain knot - is am I better going 4KW with more /bigger rads or 6kw with more/bigger rads (hall/bedroom as identified by me above)? 

I need to keep running costs as low as possible without getting cold. 🤔 

It hasn't got a buffer it has a volumiser and I'm not pushing back on that. 

I don't want the short cycling probs of a too big heat pump but I don't want a too small one working flat out when it's cold or wet.