Gas heat recovery

[anonymous]

I have this boiler:

https://www.mrcentralheating.co.uk/vokera-easi-heat-i-29c-combi-boiler-only

It's 93% efficient. I've also seen this:

https://www.toolstation.com/vokera-fuelsaver-gas-heat-recovery-unit/p13232?utm_source=googleshopping&utm_medium=feed&utm_campaign=googleshoppingfeed&mkwid=_dm&pcrid=&pkw=&pmt=&gclid=Cj0KCQjwz8emBhDrARIsANNJjS7vYqZxRNxEqmDhWd952ps_Unl0AYZqsRdh4OWB7KH9S_URzioesVkaAiloEALw_wcB&gclsrc=aw.ds

Is it worth buying such a thing? Or are these heat recovery thingies basically redundant with newer boilers? I've never heard of them before but it appears that the technology is at least 10 years old, so I wonder if it's something that's "built in" these days 

Also fwiw, I wouldn't ordinarily have installed a Vokera but the people before me did, so now I'm effectively stuck with it for a while

[Big Jimbo]

The first thing i notice is that the item is on clearance. I have no idea, but i wonder how long it would take to save you the £400 quid ?  I tried to have a look at the waste water recovery things currently, it seems in fashion. I didn't think that they were worth the money either. Obviously they are other good reasons to do things, like saving the planet etc. It's all a bit of a balancing act. Cost verses reward + making you feel good.

[markc]

If heat recovery units were viable the boiler manufacturers would be incorporating them into their boilers to increase efficiency.

on a similar topic I remember when the new gas fired station at Cleethorpes was being commissioned… big song and dance about how much heat they could recover from the chimney gasses …. After weeks of problems they realised the exhaust gasses were too cold to go up the chimney and kept falling back chocking the combustion chambers

[anonymous]

30 minutes ago, Big Jimbo said:

The first thing i notice is that the item is on clearance. I have no idea, but i wonder how long it would take to save you the £400 quid ?  I tried to have a look at the waste water recovery things currently, it seems in fashion. I didn't think that they were worth the money either. Obviously they are other good reasons to do things, like saving the planet etc. It's all a bit of a balancing act. Cost verses reward + making you feel good.

I've certainly seen those, and the ROI isn't as big an issue as it does simply using less heat 

 

Equally, one thing I'll do at the very end of all my refurbishments is to have a waste water recycling system given I don't need fresh drinking water for most of the things I use water for, and tbh, ditto for most people 

 

 

[JohnMo]

They are part of efficiency measures brought in about 10 years ago. 93% isn't really that good. There are much better out there, 93% eff is the minimum allowed I believe.

 

 

[SteamyTea]

Two things have crossed my mind.

If you have a long flue, around the manufacturers limit, the gas will be cooler to start with, recovering the extra (say 5% wasted energy) will be harder. May pose other problems as well.

Will only work on a combi, plumbed in as an instantaneous water heater, and you really need all your pipework in a suitable place, and insulated.

 

So probably cheaper to add an extra 50mm of loft insulation.

Or fix a draught.