We've had this debate before as well. While this approach reduces boiler cycling, it does not allow the boiler to modulate down to lower temperatures where it can be even more efficient.
It is better to run the CH directly from the boiler and allow downward modulation to occur and then to have a heat bank or other energy store such as a DHW cylinder with an effective coil to transfer heat quickly from the boiler.
.andy
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Does a multipoint have a secondary heat exchanger, or does the main heat exchanger directly heat the incoming DHW?
Christian.
It is not the same. A combi "combines" DHW and CH. The operational principles of some combi's is similar to a multipoint, but few are the same. A multipoint has one large gas to water heat exchanger and a water diaphragm operated gas valve (not 3-way). Most are modulating these days.
The current plume is a mere wisp which dissipates within 30cm of the terminal. It is barely visible. If it is installed within the allowed limits from windows, it would be fine.
Christian.
Very good point. Also in flats, where small combis are very popular, I've seen several combis installed where there it would be extremely difficult to get a drain connection for a condenser.
My guess the new regs won't apply to anything solely used to heat water ... Maybe lead to some possible getouts by manufacturers claiming their products are "water heaters".
I think you're exaggerating the extent and impact of this.
.andy
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I was being facetious. The problem is the concept of heating water directly from the cold mains considering the provisioning of a domestic gas supply.
.andy
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Directly heats the incoming DHW.
In general I don't think this will be such a restriction since 90%+ are installed in kitchens (IME) and the bulk of those are near the sink (so they can access the cold main and DHW pipe work. I'd reckon on at least
75% being straight forward to get a condensate drain connection.
Not so. many flue face onto landing with overhangs from the landing above.
This a multipoint heating potable water directly. This is a cheap to install system (multipoints can be had for £350) that eliminates boiler (or mutipoint) cycling and a good pressure shower and fills a bath zippo. The total cost of the main componenst is low:
- mutipoint
- 2-port valve
- flowswitch
- high head bronze pump (the only expensive item)
- cheap CH pump
- cyl stat(s)
- room stat
- 200 litre cylinder or thereabouts, part L, or above,
Most multipoint have simple mechanical controls with no electric and no electronic board. Chaffeteux made a similar CH boiler about 25 years ago. It was an adapted multipoint with temperature control. The Ascots never had temperature control, but some Main's did. The pump pressure opened a gas valve. No flow no gas, as in all multipoints. They had a 30,000 btu/hr model that was an adapted sink heater with a conventional flue adaptor on the top. They were used in flats. It was strange to see what looked like a small sink heater in a kitchen with a flue off the top and no swivel spout. They worked very well.
As is the conventional water heater in the USA.
The main heat exchanger. Go to the Worcester Bosch site, they have a piccie of one showing the heat exchanger.
OK, so for people living in places like that, perhaps there may be a problem. However this is not the majority of housing and for the typical house it is not going to be an issue.
If you think it's a big deal, why don't you write to your friend jag+=2 and tell him about it - see whether he thinks it's a nuisance for his modest properties.
.andy
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remarkable,
I would say in London 10% of existing properties converted to condensers would give problems. That is a lot of homes.
< snip babbling >
No multipoint I have ever seen fills a bath zippo unless you're talking about a bird bath.
.. and a lifetime of the rubber diaphragm of about 2 years max.
.andy
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Have you seen a typical American water heater?
Complete junk.
.andy
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Yes. As described above.
Depends on the maker. Some are well made and condensing.
Read the original explanation and draw it out. The bath would be filled by the cylinder, only the shower directly from the multipoint. The CH via a coil in the cylinder.
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