Hi all...

I'm replacing the boiler and DHW system in my 3 bed semi-d that I'm
renovating.. so far so good - thanks to all the regular posters! I've
putting the boiler and DHW cylinder in the loft (attic) space to save
room downstairs. Hoisting the boiler up was fun!

Anyway, I've run into one issue which I haven't seen covered here
much. I live in Dublin, where the mains water supply / pressure can
be quite erratic, especially during summer. That pretty much rules
out a mains pressure system. The local water bye-laws also mandate
cold water storage for cisterns, showering, etc. I guess this is to
stop our mains distribution system getting overloaded at peak times.

So I can't get rid of tanks in the loft, and if I want a pressurised
(power) shower I'm going to have to use a pump. The two options seem
to be either (a) regular vented / unpressurised system where the pump
is on the appliance side of the DHW cylinder or (b) use a pump to
pressurise an unvented cylinder from a cold water storage tank.
These diagrams illustrate what I mean:

a - http://www.lycrisbyrne.com/images/combination1.jpg
b - http://www.lycrisbyrne.com/images/glasslined2.jpg

All the kit will be in the attic, so if I go with (a) I'll need to use
a combination cylinder to get a positive head to feed the cylinder.

Has anyone installed (b) the pumped unvented system?

As far as I can see the only pro is that I can have a larger DHW
cylinder as I don't need the cold water directly overhead, but with
the drawbacks that I will have pump noise on any hot water draw off,
no hot water if the pump fails, and more complicated pipework.
Advantage combi cylinder?

Thanks for any input...

Regards,
Niall

In article . com,
Niall Smart writes
Hi all...

I'm replacing the boiler and DHW system in my 3 bed semi-d that I'm
renovating.. so far so good - thanks to all the regular posters! I've
putting the boiler and DHW cylinder in the loft (attic) space to save
room downstairs. Hoisting the boiler up was fun!

Anyway, I've run into one issue which I haven't seen covered here
much. I live in Dublin, where the mains water supply / pressure can
be quite erratic, especially during summer. That pretty much rules
out a mains pressure system. The local water bye-laws also mandate
cold water storage for cisterns, showering, etc. I guess this is to
stop our mains distribution system getting overloaded at peak times.

So I can't get rid of tanks in the loft, and if I want a pressurised
(power) shower I'm going to have to use a pump. The two options seem
to be either (a) regular vented / unpressurised system where the pump
is on the appliance side of the DHW cylinder or (b) use a pump to
pressurise an unvented cylinder from a cold water storage tank.
These diagrams illustrate what I mean:

a - http://www.lycrisbyrne.com/images/combination1.jpg
b - http://www.lycrisbyrne.com/images/glasslined2.jpg

All the kit will be in the attic, so if I go with (a) I'll need to use
a combination cylinder to get a positive head to feed the cylinder.

Has anyone installed (b) the pumped unvented system?

As far as I can see the only pro is that I can have a larger DHW
cylinder as I don't need the cold water directly overhead, but with
the drawbacks that I will have pump noise on any hot water draw off,
no hot water if the pump fails, and more complicated pipework.
Advantage combi cylinder?

I suppose the advantage with b) is that the pump is simpler (single) and so
may cost less, but the twin pump is a standard retrofit for those wishing
higher pressure so economies of scale may have eliminates the price
difference.

Bear in mind that with a) you can use the cheapest (pressure) grade of
cylinder available whereas with b) you may require a more expensive one,
plus grade 3 (lowest) cylinders are on the shelf in every plumbers'
merchants.

Remember also that in a) there is no requirement for the hot and cold
tanks/cylinders to be co-located, the cold could be a coffin tank high up in
the apex of the roof or elsewhere.
--
fred
Plusnet - I hope you like vanilla

"fred" wrote in message ...
In article . com,
Niall Smart writes
Hi all...

I'm replacing the boiler and DHW system in my 3 bed semi-d that I'm
renovating.. so far so good - thanks to all the regular posters! I've
putting the boiler and DHW cylinder in the loft (attic) space to save
room downstairs. Hoisting the boiler up was fun!

Anyway, I've run into one issue which I haven't seen covered here
much. I live in Dublin, where the mains water supply / pressure can
be quite erratic, especially during summer. That pretty much rules
out a mains pressure system. The local water bye-laws also mandate
cold water storage for cisterns, showering, etc. I guess this is to
stop our mains distribution system getting overloaded at peak times.

So I can't get rid of tanks in the loft, and if I want a pressurised
(power) shower I'm going to have to use a pump. The two options seem
to be either (a) regular vented / unpressurised system where the pump
is on the appliance side of the DHW cylinder or (b) use a pump to
pressurise an unvented cylinder from a cold water storage tank.
These diagrams illustrate what I mean:

a - http://www.lycrisbyrne.com/images/combination1.jpg
b - http://www.lycrisbyrne.com/images/glasslined2.jpg

All the kit will be in the attic, so if I go with (a) I'll need to use
a combination cylinder to get a positive head to feed the cylinder.

Has anyone installed (b) the pumped unvented system?

As far as I can see the only pro is that I can have a larger DHW
cylinder as I don't need the cold water directly overhead, but with
the drawbacks that I will have pump noise on any hot water draw off,
no hot water if the pump fails, and more complicated pipework.
Advantage combi cylinder?

I suppose the advantage with b) is that the pump is simpler (single) and
so
may cost less, but the twin pump is a standard retrofit for those wishing
higher pressure so economies of scale may have eliminates the price
difference.

Bear in mind that with a) you can use the cheapest (pressure) grade of
cylinder available whereas with b) you may require a more expensive one,
plus grade 3 (lowest) cylinders are on the shelf in every plumbers'
merchants.

Remember also that in a) there is no requirement for the hot and cold
tanks/cylinders to be co-located, the cold could be a coffin tank high up
in
the apex of the roof or elsewhere.

In the attic it is best to have a combination cylinder with a large cold
water tank attached, then a pump on the oulet side for ashower. There rest
will gove and not much pressure wjich is fine.

Or use a cold water accumulator and a heat bank or combi

On Feb 12, 10:56 am, fred wrote:

Hi all...

a -http://www.lycrisbyrne.com/images/combination1.jpg
b -http://www.lycrisbyrne.com/images/glasslined2.jpg

I suppose the advantage with b) is that the pump is simpler (single) and so
may cost less, but the twin pump is a standard retrofit for those wishing
higher pressure so economies of scale may have eliminates the price
difference.

Good point, although the difference in costs between the two types
pumps is unlikely to sway the decision much either way as I'm doing
all the labour myself.

Bear in mind that with a) you can use the cheapest (pressure) grade of
cylinder available whereas with b) you may require a more expensive one,
plus grade 3 (lowest) cylinders are on the shelf in every plumbers'
merchants.

Now that is likely to be more of a cost differential. I do have to
get the combi made to order though as I need a short squat one.

Remember also that in a) there is no requirement for the hot and cold
tanks/cylinders to be co-located, the cold could be a coffin tank high up in
the apex of the roof or elsewhere.

Yeah, its probably easier to go with a combi cylinder though in my
particular scenario

Interestingly I rang Stuart Turner technical dept and they said that
even with option (b) you need some head over the pump (he said at
least 1m) to prevent cavitation, etc. So given that, I'm probably
almost definately going with option a. Until I change my mind
again. That has to be the worst bit about DIY, too many options!

Niall

In article .com
, Niall Smart writes
On Feb 12, 10:56 am, fred wrote:

Yeah, its probably easier to go with a combi cylinder though in my
particular scenario

Interestingly I rang Stuart Turner technical dept and they said that
even with option (b) you need some head over the pump (he said at
least 1m) to prevent cavitation, etc. So given that, I'm probably
almost definately going with option a. Until I change my mind
again. That has to be the worst bit about DIY, too many options!

I was thinking life is just a bit easier with a higher head, it's a bit of a pain
to have the pump operating for all water flows, it might be nice to have an
unpumped feed on say the toilet sink to avoid middle of the night pump
operation for a toilet visit.
--
fred
Plusnet - I hope you like vanilla

"Niall Smart" wrote in message
ups.com...
Hi all...

I'm replacing the boiler and DHW system in my 3 bed semi-d that I'm
renovating.. so far so good - thanks to all the regular posters! I've
putting the boiler and DHW cylinder in the loft (attic) space to save
room downstairs. Hoisting the boiler up was fun!

Anyway, I've run into one issue which I haven't seen covered here
much. I live in Dublin, where the mains water supply / pressure can
be quite erratic, especially during summer. That pretty much rules
out a mains pressure system. The local water bye-laws also mandate
cold water storage for cisterns, showering, etc. I guess this is to
stop our mains distribution system getting overloaded at peak times.

So I can't get rid of tanks in the loft, and if I want a pressurised
(power) shower I'm going to have to use a pump. The two options seem
to be either (a) regular vented / unpressurised system where the pump
is on the appliance side of the DHW cylinder or (b) use a pump to
pressurise an unvented cylinder from a cold water storage tank.
These diagrams illustrate what I mean:

a - http://www.lycrisbyrne.com/images/combination1.jpg
b - http://www.lycrisbyrne.com/images/glasslined2.jpg

All the kit will be in the attic, so if I go with (a) I'll need to use
a combination cylinder to get a positive head to feed the cylinder.

Has anyone installed (b) the pumped unvented system?

As far as I can see the only pro is that I can have a larger DHW
cylinder as I don't need the cold water directly overhead, but with
the drawbacks that I will have pump noise on any hot water draw off,
no hot water if the pump fails, and more complicated pipework.
Advantage combi cylinder?

Thanks for any input...

Regards,
Niall


Why not conventional storage tank, shower pump and a thermal store?

On Feb 12, 11:12 pm, "James Salisbury"
wrote:

a -http://www.lycrisbyrne.com/images/combination1.jpg
b -http://www.lycrisbyrne.com/images/glasslined2.jpg

All the kit will be in the attic, so if I go with (a) I'll need to use
a combination cylinder to get a positive head to feed the cylinder.

Has anyone installed (b) the pumped unvented system?

Why not conventional storage tank, shower pump and a thermal store?

I did consider this, by using a submersible pump in the storage tank I
would even get away with having the storage tank at negative head with
respect to the cylinder. However any hot water draw-off would then
activate two pumps - the pump from storage, and the plate exchanger
pump. Even if I raised the cold water storage tank over the thermal
store I don't think I'd get enough positive head to overcome the flow
resistance of the plate heat exchanger.

I probably would have went for a thermal store if I had a sufficient
quality mains supply.

Regards,
Niall

Yeah, its probably easier to go with a combi cylinder though in my
particular scenario

Interestingly I rang Stuart Turner technical dept and they said that
even with option (b) you need some head over the pump (he said at
least 1m) to prevent cavitation, etc. So given that, I'm probably
almost definately going with option a. Until I change my mind
again. That has to be the worst bit about DIY, too many options!

I was thinking life is just a bit easier with a higher head, it's a bit of a pain
to have the pump operating for all water flows, it might be nice to have an
unpumped feed on say the toilet sink to avoid middle of the night pump
operation for a toilet visit.
--

Yeah I intend to use a separate tap off the cylinder to a secondary
circulation loop feeding the kitchen and bathroom taps. Similar for
the cold.

Regards,
Niall

In article . com,
Niall Smart wrote:
So I can't get rid of tanks in the loft, and if I want a pressurised
(power) shower I'm going to have to use a pump. The two options seem
to be either (a) regular vented / unpressurised system where the pump
is on the appliance side of the DHW cylinder or (b) use a pump to
pressurise an unvented cylinder from a cold water storage tank.

There's a lot of rubbish written about showers. You don't need high
pressure for a decent one - it's the flow that matters. And you don't need
high pressure for that - consider tipping a bucket of water over yourself
where there's no pressure and little head. ;-)

If you're rejigging the system, consider moving the header tank as high as
possible in the roof space and take special care with the pipe runs
avoiding elbows etc - bend the pipe instead. Run separate 22mm feeds from
the tanks to a proper shower designed for low pressure use - Aqualisa make
them. Whilst the extra cost of the pipework will negate the savings of the
pump cost you'll end up with a better and quieter shower.

--
*The early bird gets the worm, but the second mouse gets the cheese *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article . com,
Niall Smart wrote:
So I can't get rid of tanks in the loft, and if I want a pressurised
(power) shower I'm going to have to use a pump. The two options seem
to be either (a) regular vented / unpressurised system where the pump
is on the appliance side of the DHW cylinder or (b) use a pump to
pressurise an unvented cylinder from a cold water storage tank.

There's a lot of rubbish written about showers. You don't need high
pressure for a decent one

This man should eff off as he is a total idiot.

A shower needs "pressure". The high pressure on the skin gives the
sensation. A high pressure low flow shower is generally acceptable to most
people.

In article ews.net,
Doctor Drivel wrote:
There's a lot of rubbish written about showers. You don't need high
pressure for a decent one

This man should eff off as he is a total idiot.

A shower needs "pressure". The high pressure on the skin gives the
sensation. A high pressure low flow shower is generally acceptable to
most people.

Yes - stick with your electric one. You know it makes sense.

--
*What hair colour do they put on the driver's license of a bald man? *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ews.net,
Doctor Drivel wrote:
There's a lot of rubbish written about showers. You don't need high
pressure for a decent one

This man should eff off as he is a total idiot.

A shower needs "pressure". The high pressure on the skin gives the
sensation. A high pressure low flow shower is generally acceptable to
most people.

Yes

Please eff off as you are an idiot.