condensing boiler thermostat setting

Hi.

i have a vaillant ecomax 613 condensing boiler with indirect cylinder.

at the moment the boiler thermostat is set to 65 deg and the cylinder to 58 deg.

my question is it better to set up to boiler thermostat to max ? will the boiler still work in condensing mode ?

my gas engineer told my that the boiler is very efficient so it is OK to run the hot water 24HR a day. we take 3 baths a day 2 in the morning and one in the evening. should i set the programmer to run the hot water for those times or let it run all the time ? what it cheaper.

Reply to
Golan
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Run at the lowest temperature you can get away with. If 65 is OK for DHW and heating then leave it. Time the DHW. The cylinder may lose heat during the night and it is reheated unnecessarily during the night.

Reply to
Doctor Drivel

It will condense better if you keep it at the lowest setting consistent with getting the heat you require.

Well, no matter how efficient ist is, it's always going to be cheaper NOT to run it 24 hours a day.

Think about it. Rate of heat loss from the cylinder is proportional to the temperature difference between it and its surroundings. As the cylinder cools, its heat loss slows. If you keep it hot all the time, its heat loss will be greater. Keeping it hot thus costs more than letting it cool, and just putting the lost heat back.

So, run the boiler only when you need to heat the cylinder. Don't heat it at night, or during the working day when you're not there.

Reply to
Bob Eager

Golan wrote in news:ec4690a8-b340-4d8e-987c-732b73ac3732 @y5g2000hsf.googlegroups.com:

cylinder.

cylinder

max ? will

The boiler would be running at its most efficient when the return water temp to the boiler is 54c Whether that will be sufficient in cold weather depends on your rad sizes and how much water you like in your bath.

it is OK

the

to run the

it

No timed twice daily would be better.

Reply to
John

It still gets even more efficient at lower temperatures than that. My condensing boiler runs at 40C return temperature for heating, but the radiators were sized for low temperature operation.

A fast recovery cylinder will return the water to the boiler at not much above the water temperature of the cylinder at the base of the coil, so even if heating to 65C, much of the reheat time will operate in condensing mode, until the return temperature gets above 55C. With a standard (non-fast recovery) cylinder, the return water is usually much hotter than the cylinder water as the heat transfer to the cylinder water is not as effective.

If the same boiler does heating and hot water and doesn't have independant temperature controls for each, then it's not possible to reap the most efficient operation of the heating, as that will be too cold for the hot water.

It's a shame how few heating installers actually understand the physics behind their trade.

Reply to
Andrew Gabriel

snipped-for-privacy@cucumber.demon.co.uk (Andrew Gabriel) wrote in news:474db632$0$511$ snipped-for-privacy@news.aaisp.net.uk:

the cylinder

max ? will

that.

heating,

True but I was replying to OP and making some assumptions based on his plumbers comments I.e. I would be surprised if radiators have been replaced and resized to allow such a low return temp. And I think it's only the ecomax combi that has a separate HW temp setting.

Reply to
John

I believe AG may have done that for himself. I doubt that serviceable radiators are worth replacing with oversized units on fuel efficiency grounds. But with a new system you would try to design/guesstimate for cooler return temps.

Many many combis have seperate controls for heating and the MAXIMUM HW temp, even really low end units.

There are only a few quite high end models for non combis which have different setting for HW mode and heating mode, and then only in the larger units.

Reply to
Ed Sirett

Ed Sirett wrote in news:finevc$1ej $1$ snipped-for-privacy@news.demon.co.uk:

to

the return

than

based on his

and resized to

ecomax combi

serviceable

efficiency

design/guesstimate for

Yes that was the assumption I was making in my reply to the OP

MAXIMUM HW

I wasn't suggesting that the ecomax combi was the only one with a separate HW control, more that the OPs ecomax system or heatonly boiler did not have this facility whereas the combi variant does.

which have

only in the

Yes like Vaillants own EcoTec plus 415, although hardly classified as large at 15Kw. Unless you were referring to case dimensions :P

John.

Reply to
John

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