new build domestic hot water design

esox28

if you were designing a hot water system for your own new house as a blank sheet...

with optional heat inputs at your desposal of solar thermal, oil or gas or a combanation of any of them to generate the heated water.

would you.....store the heated water in stainless steel high density insulated and enameled cylinder.

would you.....use an instantainious boiler but with the inclusion of solar thermal.

or would you....?

dodgyknees

i dont have much expierience with solar ,but any of the solars i fitted [3] i always used a stainless steel one about 6 foot high so they take up your whole hot press.i fitted a booster pump last week and the customer had solar and new copper cylinder installed height 46 * 18 width and customer was very happy .but if it was me i would go for stainless steel in a utility room.

dodgyknees

dodgyknees wrote: »

i dont have much expierience with solar ,but any of the solars i fitted [3] i always used a stainless steel one about 6 foot high so they take up your whole hot press.i fitted a booster pump last week and the customer had solar and new copper cylinder installed height 46 * 18 width and customer was very happy .but if it was me i would go for stainless steel in a utility room.

sorry forgot to say wouldnt use an instanoeous water heater unless it was a small apartment or out house

heinbloed

I would check out the thermal demand first.

And then check out what others are doing, the most common solutions for covering DHW with ST energy look usually like this:

http://www.sunshore.cn/en/Products_Page.asp?id=9

Tank and collector delivered for around €1,000. Installed for maybe another €500 .


Maintenance free. No glycol involved.

Well, for the idiots of clients a slogan like " It works also at night " can be used (smiley).

Outkast_IRE

You have gone about this backwards and asked the wrong first question.

How much hot water do you need, what are its uses how many showers and baths etc. If you want power showers you need more stored hot water etc.

No problem in looking for the best solution when you are missing the question .


But in a very general way in a large family home i like the idea of multiple heat sources linked to a buffer/ accumulator tank and then heat the hot water cylinder from this accumulator tank.

I would also like to size the solar panels or tube to contribute to the buffer rather than the cylinder , or perhaps bypass the cylinder to the buffer once the cylinder is heated.

esox28

yea I know what you are saying outkast about using the buffer to store ch water then transfer to a dhw via coil, great system..... 12 mtrs * of solar thermal with 1000 ltr buffer and oil or wood to top up the tank

but do you think it is necessary to store 200 to 300 ltrs of dhw ?

surely there are gas instant boilers with the capacity of delivering any amount of 47*c heated water even to satisfy a shower head with 30ltr / min capacity

andy2die4

esox28 wrote: »

surely there are gas instant boilers with the capacity of delivering any amount of 47*c heated water even to satisfy a shower head with 30ltr / min capacity

Yes there are gas boilers that will, if this is the way you want to go then maby solar is not the system you need. Solar is slow and takes a few years to pay for itself.

Outkast_IRE

esox28 wrote: »

yea I know what you are saying outkast about using the buffer to store ch water then transfer to a dhw via coil, great system..... 12 mtrs * of solar thermal with 1000 ltr buffer and oil or wood to top up the tank

but do you think it is necessary to store 200 to 300 ltrs of dhw ?

surely there are gas instant boilers with the capacity of delivering any amount of 47*c heated water even to satisfy a shower head with 30ltr / min capacity

Yes there is systems like this usually need to be ordered in etc, im not going to get into the costs and math but in my opinion, if its a family home , where lots of showers and baths are a certainty i would like the solar with the 300 ltr cylinder. If its a home where maybe one or two showers a day are likely the instanteous is what i would go for.

The only thing with the instantaneous is if its a long pipe run from the heater to the outlet theres a lot of water wastage.

esox28

Its fair enough to say that the large storage dhw cylinder with st system is the traditional set up for many homes.

the set up I have in mind is a 150 ltr dhw cylinder which has a single st heated coil, the feed from this cyl is then run through a intaineous gas boiler,
if the dhw is at required temp then boiler wont fire also if its not it run till temp. is satified.

never seen this set up before does it or could it work?

surely its cheaper to heat water as u need it rather than storage!

Outkast_IRE

esox28 wrote: »

Its fair enough to say that the large storage dhw cylinder with st system is the traditional set up for many homes.

the set up I have in mind is a 150 ltr dhw cylinder which has a single st heated coil, the feed from this cyl is then run through a intaineous gas boiler,
if the dhw is at required temp then boiler wont fire also if its not it run till temp. is satified.

never seen this set up before does it or could it work?

surely its cheaper to heat water as u need it rather than storage!

I havent seen this set up either but , im trying to think in a real world situation of the advantages over other options.

in your sceanario , your normal heating will still heat the cylinder and then the hot supply from the cylinder passes through an instanteous heater which fires as needed.

Wouldnt you be just as well off with a properly zoned system which can heat hot water only as needed, in a new high end cylinder the heat losses can be very very small if the pipework to it is installed correctly.

I have done installations where the Cylinder has been heated at 9am on a monday and , if you go for hot water on the tuesday night the water is still hot enough for shower. All down to a good high quality cylinder and pipework to it done correctly and lagged.

I just dont see the short term payback in what your proposing if your intend to have a standard boiler heating the system anyway.

Feel free to respond as im trying to think of the pros and cons of what your propsing but at the moment its mostly cons , as one of the main reasons to use instanteous heater is to remove the need for a cylinder yet you still want one.

esox28

esox28 wrote: »

the set up I have in mind is a 150 ltr dhw cylinder which has a single st heated coil, the feed from this cyl is then run through a intaineous gas boiler,
if the dhw is at required temp then boiler wont fire also if its not it run till temp. is satified.

As mentioned if you know what your hot water requirement is then things get easier.

I know of cylinders which have been used to feed a combi but normally they are solar heated and the cylinder is linked to the boiler controls and has a mixer valve on the hot water outlet rather than pushing hot water from the cylinder through the boiler, it may confuse the boilers logic if the plate heater exchanger is hotter than it is designed to be also the connections tend to be 1/2 inch impacting on hot water performance at the tap.

If it were me I'd keep it simple, store what I need in a decent unvented cylinder, you could look at getting the smallest twin coil, plumb both coils from the boiler then the reheat times would be very quick if you used up what you had stored. There are cylinder coming on to the market that might be worth looking into, they have a coil, emersion and a element connected to a heat pump giving a COP of 1/4 (ish) so on a night rate it could work out cheaper than gas.

There was a link put up recently of a nice Glowworm which stored hot water as well as working as a combi and Vissmann do a very nice system that incorporates a decent size cylinder under the boiler, can take solar, has great flow rates, reheat times etc.. The only downside is the cylinder is glass lined.

JohnnieK

esox28 wrote: »

yea I know what you are saying outkast about using the buffer to store ch water then transfer to a dhw via coil, great system..... 12 mtrs * of solar thermal with 1000 ltr buffer and oil or wood to top up the tank

but do you think it is necessary to store 200 to 300 ltrs of dhw ?

surely there are gas instant boilers with the capacity of delivering any amount of 47*c heated water even to satisfy a shower head with 30ltr / min capacity

It would be cheaper to heat the water as you use it but if you anticipate a large usage then a storage combi with solar interface is the way I would be going. Also make sure the boiler is located as close as possible to the draw off's to minimize lag times from when you turn a tap on to when you actually get the hot water at the tap. There is no point putting in a combi if the boiler is miles away from the point where you need the water, this goes for all hot water installations.

Stove Fan

If I was plumbing a house with a couple of bathrooms I would want an unvented hot water cylinder with high mains pressure hot water. It really depends on the incoming water pressure though unless you start pumping it.

We had an old worcester heatslave oil boiler with integral storage hot water in a place of ours with one bathroom. It worked fine but if the taps were turned on in the kitchen it would reduce the flow from the shower.
Both of these systems need very good mains pressure.

I'm not a fan on combi boilers for several bathrooms if tried to use at the same time. I prefer the conventional setup or unvented. A lot of UK homes have combi boilers, I think they are ok for the one bathroom home.

At our home in Ireland the group water scheme pressure isn't great into our home. We just have a standard setup with a power shower.

Stove Fan:)

esox28

in your sceanario , your normal heating will still heat the cylinder and then the hot supply from the cylinder passes through an instanteous heater which fires as needed.

Wouldnt you be just as well off with a properly zoned system which can heat hot water only as needed, in a new high end cylinder the heat losses can be very very small if the pipework to it is installed correctly

]

Ok then can I bore you with my 'wish list' for heating and plumbing of the new build

for heat dispersion there is infloor heating on ground floor and rads on first floor with the addition of heat recovery ventlation.

the heating system will be fed from 1000 ltr buffer located in purpose built guarge with 12 mtrs * solar panel and 26kw condencing oil fired boiler.

in the living will be a room sealed wood burning stove gravity feeding a 150 - 200 ltr cylinder and pumped to rads when needed. this cylinder will also have 4 mtr * solar panel connected.

because im not connecting this dhw cylinder to the central heating system connection, im trying to work out the best way of heating the dhw intaineously as can't rely on solar for 100% and can't garrante stove will be lit enough to take up slack.

so far Ive been thinking along the lines of

the set up I have in mind is a 150 ltr dhw cylinder which has a single st heated coil, the feed from this cyl is then run through a intaineous gas boiler,
if the dhw is at required temp then boiler wont fire also if its not it run till temp. is satified.

maybe Electric..

I think Gary71 has an intresting air to water system

There are cylinder coming on to the market that might be worth looking into, they have a coil, emersion and a element connected to a heat pump giving a COP of 1/4 (ish) so on a night rate it could work out cheaper than gas.

going to follow this up