@justme Even the condensing gas boilers were sometimes incapable of running well but carried the badge ‘Condensing’. We had a BG badged Glow Worm boiler that was well oversized and could not condense as it heated the hot water as well as heating BUT ONLY HAD ONE TEMPERATURE DIAL for DHW and Heating. You want condensing and cooler hot water or to hell with condensing! (In addition, BG had slapped the boiler in just set to its’ maximum capacity rating!) Who cares? We were paying BG for the fossil burning!!! Regrets, Toodles.

@toodles I got this from my new best friend (Google AI mode):

"If a condensing boiler's flow temperature (often set via a dial on the boiler itself) is too high, the return water from the radiators will be too hot to allow the boiler to enter condensing mode.  (Note the source - The Heating Hub)
 
Condensing boilers reach their maximum efficiency (90%+) by recovering latent heat from exhaust gases. This process only happens effectively if the water returning from your radiators is cool enough to turn the water vapour in those gases back into liquid."

I have the thermostat of my backup oil boiler set to minimum. In my case it just sends water to the buffer tank but does so at a rather higher temperature than the heat pump. I'd prefer that the two sources were at the same temperature but I might be able to drop the boiler water temperature by altering the pump speed on that short loop - something to experiment with in the next cold snap.

@dr_dongle Precisely! Which is why a single temperature controller on a condensing gas boiler is just a joke and (cynically) probably just claimed to be a condensing system to satisfy some regulation or grant scheme. Cynical Toodles.

@toodles I am on E.On Next Drive, no I don't have an EV.

I have compared other tariffs and even though I am pulling a small amount from the grid at the end of the day it still works out cheaper than octopus cosy tariff and other available tariffs, we already load shift the washing machine and Dishwasher to the cheap time and hardly use a tumble dryer, meaning that the house is generally on tickover for the rest of the day about 200w even when I am working from home.

At the moment on calculations its not viable to get a second battery as it will only save us about £30 a month for the winter months.

@n1ckw 200 Watts when working from home?! You are obviously not working hard enough!😉 Lovely weather today and the ASHP (keeping us at 22.5 degrees C.) is running on ~ 300 - 400 Watts when not on idle😊 Our average ‘house draw’ (without the heat pump) is `300 - 400 watts an hour. We are all electric of course and today we have harvested 18.4 kWh of solar energy so far and the sun still has a few more minutes of glory to share with us. This is the best day so far this year and very welcome after all the rain clouds of the last few months.

As you mention, a small amount of peak rate consumption is ‘cheaper’ than investment in a second Powerwall. I didn’t fancy changing my allegiance away from Octopus as I have previously had bad experience with other suppliers but don’t have a vehicle at all. Whether an EV tariff would be cheaper in my circumstances, I am unsure but I like Octopus’s ethos and straight dealings so will stick with them. The IOF tariff is possibly my next move though (just for the summer months) then back to Cosy if it is still available. Regards, Toodles.

Posted by: @jamespa

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The other difference is that boilers with weather compensation are generally European, whereas heat pumps are frequently far eastern.  The European manufacturers, because they were forced to do it for boilers (it is mandatory in some enlightened EU countries), have sometimes developed a better, albeit still not perfect, interface to WC than the far eastern manufacturers.

For a heatpump system that cannot respond as quickly to heat loss as a gas boiler, some would need some sort of weather anticipation feature. 😁

I remember that my previous bosch/worcester boiler also had an external sensor that would enable it to have warmed the solid brick home to the target temperature by the set time..

Posted by: @toodles

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We had a BG badged Glow Worm boiler that was well oversized and could not condense as it heated the hot water as well as heating BUT ONLY HAD ONE TEMPERATURE DIAL for DHW and Heating. You want condensing and cooler hot water or to hell with condensing! 

I find it almost incredible that they could get away with it.. 🤔Probably when a customer is desperate, after the breakdown of a previous boiler.. Was it not BG that had some warranty that would at some point allow them to choose any boiler they wanted? 

Posted by: @batpred

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For a heatpump system that cannot respond as quickly to heat loss as a gas boiler, some would need some sort of weather anticipation feature.

 

That's not necessary so far as I can see.  Measuring the current weather tells the heat pump or boiler whats currently happening to the outside of house.  The inside of the house will respond much slower than the heat pump or boiler can.  

What we don't have at present is heating systems that take into account solar gain or wind factors.  Neither is that dramatic in most cases, but it is a refinement that some here have experimented with on here.  However its quite plausible that mild auto adapt of the sort featured by many boilers and heat pumps is sufficient to deal with this and if so it should probably be left at that.  Boiler/Heat pump control systems are already too complex for many, perhaps most, ordinary people to cope with, adding additional factors needs to be carefully considered!  

Anticipation might be useful for tariff optimisation, but do we really want another level of internet-driven complexity to an already complex control system.  Personally I think heat pump manufacturers should leave this sort of thing to the geeks, and instead optimise the basic controls and function for ease of use.

Has anyone heard of or had a survey/design done by Apex?

A company I'm currently in talks with has used them for the heat loss survey + design and there are some very questionable things in there.

One example is a hallway area (4.75m x 1.3m, 2.4m high with 1 standard size external door and roughly 2m² window area) having a supposed 1290W heat loss (all other surveys I had averaged out to about 700W).

For context they, and most others, considered a ground floor extension of 2.5m x 3.8m with 4 standard-sized velux windows, a high vaulted ceiling, fully-glazed double french doors and in addition to the velux windows another 3.64m² of windows being around 1310W heat loss. Clearly these 2 rooms are absolutely nowhere close in terms of heat loss, and yet they've got a very similar number according to Apex. 

They also disregarded some of my criteria (vertical radiator in the hallway due to size limitations) and instead listed 2 horizontal radiators. If I didn't have room for 1 horizontal radiator, where is this second one going to go??? And similarly for a bedroom I'm using as an office I requested it to be designed for 21c, they did it at 18c like all the other bedrooms.

They also seem to be really overestimating the output of my existing radiators and their proposed radiators. At a design flow of 47.5c in a room targeting 18c they've got down a P+ 600x1100 outputting 700W, but if I run the numbers (which I could be doing wrong) I only get 600W. 

Can't say I'm thrilled from what they've given and I'll be speaking to the installer about my concerns and maybe question if they should find another company to do their surveys for them? It's a small operation so I don't blame them for outsourcing the heat loss and design, but I wouldn't be happy to proceed with it myself. 

Posted by: @petch

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Has anyone heard of or had a survey/design done by Apex?

There are quite a few installers I know that are called 'Apex' - can you please give me the full name? 

@editor I'm fairly certain it's this company but I'll have to check with the installer https://www.apex-surveys.co.uk/

@petch, nope, never came across these guys. I’ll look into them later this week.