# Off-Topic >  EU Comfort number (1-4 stars)

## jdurand

The builder just put in the combo on-demand water heater and hydronic heat "boiler" and I was reading the manual for it. It's a pretty high quality one but I see it's EU Comfort Level 2. The plumber said he never pays attention to that, it's what gets good reviews from his clients and this was really high (verified recommendations).

Anyway, I tried to look up these levels and see you need to pay 160 EU to read the specification, I'm not THAT interested.

Anyone have a summary of what the levels are? Why is this only a "2" yet highly recommended?

Heater is a Bunderus Logamax U072-24K

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## DIYSwede

Seems like the criteria is Energy Efficiency (for Space & Water heating, NOx emission, Sound Power Level & Standing losses), 
thus a pure design consequence not easily improved by an Intrepid DIYer:
https://ec.europa.eu/energy/sites/en...ters_final.pdf

If your main goal is to get the gas consumption down for the unit already installed,
perhaps an Arduino-based OpenTherm interface for your very unit could be of interest:
Arduino OpenTherm Controller - Hobby Projects

I won't get into the considerations for other energy- & cost-saving alternatives, as it involves so many parameters: 
average temperatures thru the seasons, insulating factors for the house walls, cost of gas & electricity to name a few.

One tip though, depending of what kind of vent system you've got- a retrofit exhaust air heat pump for the winter season:
1 kW electricity in gives 3-5 kW heat out depending on model.
But perhaps your location demands AC for 10 months/ year instead?



Johan

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## jdurand

I'll have to look at OpenTherm. I'm not one to leave a system running on stock controls, if there wasn't an open protocol I'd reverse engineer one.

But the Comfort number isn't efficiency, it's based on things like washing hot water (Domestic Hot Water) output. Temperature stability over minutes of running, from one use to the next, time to get hot water, how long before you run out, things like that.

As this is a medium sized on demand gas heater (24kW of heating) there shouldn't be a problem running out of water so I'm guessing the 2* rating is because of time to start up or something. Maybe max flow. I'm thinking to get 4* for comfort you'd just have a tank heater. Not efficient, but "comfortable".

This is a dual circuit system, the other half of the heater is to keep our 240 square meter house warm. Seems small compared to the heater here in California but the California house only has R6 insulation while the new one is R30.

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## DIYSwede

-Guess you'd hack a brand-new appliance (under warranty) for improvements... :Smile: 

As it's of the "on-demand" type - an extra add-on could perhaps be pertinent for the longevity of the inhabitants:
Some kind of "emergency brake" making sure the hot water always gets above 60 °C (140 °F), just making sure avoiding:
https://en.wikipedia.org/wiki/Legionnaires%27_disease

AFAIK: Transmission of this bacteria is thru breathing in the aerosolized, infested water, 
i.e. in the shower/ bath or hot tub, thru humidifiers/ swamp coolers fed with contaminated water.
A little shot of pool shock chlorine goes a long way.

Better safe than sorry! ATB

Johan

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## jdurand

Of course I'd hack a brand new device, wouldn't be the first time. The trick is don't do anything detectable to the original device until after the warranty expires, if ever.

As for Legionaries, seems there's around 40 variations that cause various problems including pneumonia showing up with no apparent cause. Below 55 F it's killed by other things in the water. Above 130F it's killed by long term heat. Short blasts of hot water doesn't touch it, nor does chlorine.

It loves rust.

But apparently it has trouble with flowing water so something like the water pipes coming from the street main or through an on-demand heater are ok. Small amounts but not enough to bother people.

Tank type water heaters can build it up in the bottom and hydronic heating systems during summer idle times. As far as I know all hydronic systems have to be isolated from potable water by check valves, pressure difference, and heat exchangers.  This new heater has all 3 built in. The heating loop only runs at 1-2 bar.

Boiler mostly installed. The system has since been tested at pressure and heat (yesterday).





Radiator controls

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