In a post a few days ago, off-topic I mentioned (in Jest!) using an old 23KW
gas multipoint water heater to heat a thermal store for a new CH system. It
ended with me thinking I'd ditch the multipoint to make way for the
cylinder. Err, well... see below.

First, a question relating to thermal stores. To promote a cool return
temperature I'm contemplating that I may (or may not!) need to run my
1300mm/210L store at a lower temperature - say 70 degr rather than 80. To
compensate, I was going to get Newarkcyl to add one or two alternative
tappings a bit higher up the cyl for the space heating take-off. But I'm
working blind, I don't have the foggiest what the existing return
temperatures will be, or where to ask for the extra holes to be. Any ideas?

And one other thing, what is the difference between a 'vented' CH boiler and
a multipoint - both just heat water don't they (:-).

I just couln't let go of the idea of a free (installed) CH boiler. There
*will* be a thermal store - the only issue now is what & where the boiler
will be. If the council don't object on Part L (It's an existing boiler)
then I'll hook up the multipoint. I now plan to put the store on the ground
floor, under the stairs in the middle of the house. The primary pipes will
run to the multipoint boiler along a path that will run close to the (ground
floor) siting of any new Condenser boiler - if and when that happens. F&E
tanks in the loft. Pumps near to the store (maybe).

At the moment I'm now planning on doing it as Dr Evil suggested - integrated
with common primary water to boiler, store and radiators. There might be
risk of the Fernoxified, sludgy brown water affecting the multipoit's
rubbery flow sensors? but I'll take a chance. And as the store is now
downstairs, in the event of a catastrophic leak upstairs at least the
cylinder contents wouldn't add to the flood.

One thing that occurred to me is that the water in the multipoint would
generally be hotter than if heating from the cold mains. And as the pressure
via the F&E will be relatively low this might risk 'kettling"? For this
reason I'd like the return temperature to the boiler to be cool. On the
other hand, if fitting a condensing boiler (now or in future) then again I'd
like the ruturn temperature to be cool to promote condensing. So, I've gone
for a somewhat oversized 1300mm, 210L thermal store, Newarkcyl, to aid
'stratification'. Two stats as well - external as these give positioning
flexibility.

And if the above is completely mad let me know!.

Thanks DIYSOS.

Well no news is hopefully good news, as it might mean this plan isn't
completely mad.

I can see I'm probably barking up the wrong tree trying to recalculate a
position for hotter radiator take-off. Even so I'll ask for an extra tapping
about 200mm above the normal take-off - gives me an option just in case.

Cheers - DIYSOS

"DIYSOS" wrote in message
...
Well no news is hopefully good news, as it might mean this plan isn't
completely mad.

I can see I'm probably barking up the wrong tree trying to recalculate a
position for hotter radiator take-off. Even so I'll ask for an extra
tapping
about 200mm above the normal take-off - gives me an option just in case.

Cheers - DIYSOS

I'll get back. First, does your multipoint have temperature control? If so
what is the highest temp it supports?



_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

It doesn't have a thermostat, and by implication I assume no temperature
control (unless there is a cutout), other than indirect via the cylinder
stats. This probably means it could have steam coming out it's ears if the
cylinder stat mechanism were to fail... anyway I'd thought perhaps to
maximise (within reason) the speed/volume of water through it, to minimise
the temperature rise on each pass.

Following taken from an earlier post...

Heat input 30.27KW, heat output 22.7KW, raises 12.5L/min by 25C. Minimum
operating head if connected to static tank 2.29M, max pressure 13 bar.

Installation guide is on bax/partsarena...then go Main... goWater heaters...
goMedway... go Basic later production... go Installation instructions... go
Mersey, Medway automatic & Trent... and there it is (Medway).

DIYSOS

"DIYSOS" wrote in message
...
It doesn't have a thermostat, and by implication I assume no temperature
control (unless there is a cutout), other than indirect via the cylinder
stats. This probably means it could have steam coming out it's ears if the
cylinder stat mechanism were to fail... anyway I'd thought perhaps to
maximise (within reason) the speed/volume of water through it, to minimise
the temperature rise on each pass.

Following taken from an earlier post...

Heat input 30.27KW, heat output 22.7KW, raises 12.5L/min by 25C. Minimum
operating head if connected to static tank 2.29M, max pressure 13 bar.

Installation guide is on bax/partsarena...then go Main... goWater
heaters...
goMedway... go Basic later production... go Installation instructions...
go
Mersey, Medway automatic & Trent... and there it is (Medway).

DIYSOS



If it's a Medway or Mersey it does not have a temperature control. If it's a
Medway Super or Thame then it has a temperature control on the front lower
panel.

"Doctor Evil" wrote in message
...

"DIYSOS" wrote in message
...
Well no news is hopefully good news, as it might mean this plan isn't
completely mad.

I can see I'm probably barking up the wrong tree trying to recalculate a
position for hotter radiator take-off. Even so I'll ask for an extra
tapping
about 200mm above the normal take-off - gives me an option just in case.

Cheers - DIYSOS

I'll get back. First, does your multipoint have temperature control? If
so
what is the highest temp it supports?


6.5 litres per minute @ 50C.

If it's a Medway or Mersey it does not have a temperature control. If it's
a
Medway Super or Thame then it has a temperature control on the front lower
panel.

Oh I see a 'temperature control' as in 'knob' (;-)... well it doesn't have
a variable temperature control as such though it does have a Winter/Summer
knob in the bottom right corner (two modes only, "winter" = less but hotter
water flow). It says it's a Medway Automatic on the lower panel. It doesn't
have a Thermostat (BTW that would be the "Trent"?), and it doesn't seem to
modulate - burners just seem to go on & off.

I believe it would have been installed mid 1980's - one clue is a reference
to British Gas (ie post-privatisation) inside. And thankfully it's room
sealed with a 12x12 inch hole behind that is the back flue.

DIYSOS

[BTW no relation to TV program of same name!]

In article , "DIYSOS"
says...
snip

DIYSOS

[BTW no relation to TV program of same name!]

AFAIK no relation to me either - so why are you using my email
address?

6.5 litres per minute @ 50C.

.... or to put it another way will heat 12.5L pm @ 25C like I said before.
But I repeat not a Medway Super, no temperature selector, nor I believe a
cutout.

DIYSOS

"DIYSOS" wrote in message
...
In a post a few days ago, off-topic I mentioned (in Jest!) using an old
23KW
gas multipoint water heater to heat a thermal store for a new CH system.
It
ended with me thinking I'd ditch the multipoint to make way for the
cylinder. Err, well... see below.

First, a question relating to thermal stores. To promote a cool return
temperature I'm contemplating that I may (or may not!) need to run my
1300mm/210L store at a lower temperature - say 70 degr rather than 80. To
compensate, I was going to get Newarkcyl to add one or two alternative
tappings a bit higher up the cyl for the space heating take-off. But I'm
working blind, I don't have the foggiest what the existing return
temperatures will be, or where to ask for the extra holes to be. Any
ideas?

And one other thing, what is the difference between a 'vented' CH boiler
and
a multipoint - both just heat water don't they (:-).

I just couln't let go of the idea of a free (installed) CH boiler. There
*will* be a thermal store - the only issue now is what & where the boiler
will be. If the council don't object on Part L (It's an existing boiler)
then I'll hook up the multipoint. I now plan to put the store on the
ground
floor, under the stairs in the middle of the house. The primary pipes will
run to the multipoint boiler along a path that will run close to the
(ground
floor) siting of any new Condenser boiler - if and when that happens. F&E
tanks in the loft. Pumps near to the store (maybe).

At the moment I'm now planning on doing it as Dr Evil suggested -
integrated
with common primary water to boiler, store and radiators. There might be
risk of the Fernoxified, sludgy brown water affecting the multipoit's
rubbery flow sensors? but I'll take a chance. And as the store is now
downstairs, in the event of a catastrophic leak upstairs at least the
cylinder contents wouldn't add to the flood.

One thing that occurred to me is that the water in the multipoint would
generally be hotter than if heating from the cold mains. And as the
pressure
via the F&E will be relatively low this might risk 'kettling"? For this
reason I'd like the return temperature to the boiler to be cool. On the
other hand, if fitting a condensing boiler (now or in future) then again
I'd
like the ruturn temperature to be cool to promote condensing. So, I've
gone
for a somewhat oversized 1300mm, 210L thermal store, Newarkcyl, to aid
'stratification'. Two stats as well - external as these give positioning
flexibility.

And if the above is completely mad let me know!.

Thanks DIYSOS.

If you want a lower store temperature go for a larger store, as you are
doing, but have a plate heat exchanger for DHW take off. These are so
efficient they can run with a thermal store at 60-65C.

You are wanting the store below the boiler position and below the highest CH
rad. This will mean two coils in the store. One for CH and one for the
boiler. Both boiler and CH circuits will need to be pressurised. A system
boiler comes complete with vessel. A separate vessel is needed for the CH
circuit. The store needs is own F&E tank. Look at:
http://www.rangecylinders.co.uk/prod..._combi/index.h
tml
They can install another coil for you. Have two stats on the cylinder to
prevent boiler cycling. Or get a cheaper quote for a defined spec.

To use the multi-point with the store, a temporary measure by you I believe.
You will need a temporary F&E tank for the boiler flow and return primaries.
Run the primaries in 28mm. Have the pump on the boiler return to apply
pressure to lift the diaphragm. Have a clamp on pipe stat on the boiler
flow set to 80C, this cuts off the pump when 80C is reached. This will
prevent boiler temperature overshoot. Have the cold feed from the F&E
between the pump and boiler and the open vent teed off the flow pipe.



_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

I've just had a quick glance before going out and I just wanted to check
back...

True the store would be downstairs and the boiler upstairs... all very
upside down. However the cold tanks would be in the loft, the small F&E tank
could be raised if necessary. The store is not a combination and no
radiators will be in the loft.

Is it still the case I need a pressurised system or wouldn't 100%
integrated/vented be OK?.

Thanks again,

DIYSOS

"DIYSOS" wrote in message
...

I've just had a quick glance before going out and I just wanted to check
back...

True the store would be downstairs and the boiler upstairs... all very
upside down. However the cold tanks would be in the loft, the small F&E
tank
could be raised if necessary. The store is not a combination and no
radiators will be in the loft.

Is it still the case I need a pressurised system or wouldn't 100%
integrated/vented be OK?.

That changes matters a little. The store will be open vented and direct CH
and boiler primaries. No coils inside at all. The flow/return primaries is
still the same as I explained except no separate F&E tank. Have a full bore
isolation valve on the flow and the return pipes to the boiler to isolate
when the condensing boiler goes in. Have an auto air vent on the boiler
flow near the boiler to remove any air. Also have an auto air vent on the
highest point on the rad circuit if possible.

One F&E tank in the loft, above the highest rad, feeding the store on the
ground floor. As you want the store at around 65C, best have the CH return
at the bottom and flow tapping taken off about 2/3 of the way up. You have
two tappings. One 2/3 of the way up and one near the flow at the bottom.
This gives you leeway. With high a temperature store you use the two bottom
tappings for CH. With a low temp the top. You could connect both and tee
into the CH flow. Have an isolation valve on each. Just turn one off and
the other on. Then you are covered if things don't turn out as you thought.
Simple and cheap.

If you have TRVs on all rads then fit a Grundfos Alpha pump on the CH
circuit - no need for a flow switch. A normal pump on the boiler primaries.




_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

In article ,
"DIYSOS" writes:
6.5 litres per minute @ 50C.

... or to put it another way will heat 12.5L pm @ 25C like I said before.
But I repeat not a Medway Super, no temperature selector, nor I believe a
cutout.

Main added a cutout to heaters later on (not sure which model it
first turned up in). It is a standard self-resetting electrical
disc type thermal cutout, connected in series with the thermocouple
and flame failure solenoid, and positioned on the heat exchanger
pipework at the top of the heat exchanger. (The heater itself won't
self reset, as the pilot light would need manual relighting after
the thermal cutout self-resets.) The earlier units use a bimetalic
flame failure sensor, which couldn't have such an electrical cutout
added. (Also, the bimetalic flame failure sensor just stops the main
burner coming on, it doesn't cut the gas supply to the extinguished
pilot light.)

--
Andrew Gabriel

All in all I think things are taking shape. I like the idea of gating the
store between condenser and high-temp mode!.

I don't actually see the multipoint as a temporary measure, 2 years then I
would put the new condenser straight in. The sad fact is that I'm *mean*,
and upwards of £2k probably for a new condenser (installed) doesn't sit
easily with this disposition!. For now some of the savings will go to more
cost-effective ways of saving the planet, like 10" loft insulation and DG.
Though the multipoint has a few miles on the clock, to me this doesn't
necessarily mean it's on it's last legs. In fact I'm thinking it's got a
better chance of giving long, trouble free service than a condenser, with
all it's new-fangled pcbs and such.

A few things still unresolved in my mind...

RE double 'stats to prevent boiler cycling, I've come to realise I don't
understand this concept!. I thought you'd have a single 'stat to report the
current temperature (at that point) to some logic device, which would fire
the boiler up if min and off if max, with min and max some way apart. And
I thought the point of 2 'stats was to have one pick up quickly on a drop
at the bottom (CH), and the other at the top (HW). Somebody help me - I
can't see how having two 'stats in different locations on/in the store
reduces cycling?.

RE temp overshooot, using a pipe 'stat is good... however say you have the
primary pump running amok and not responding. In this situation, it would be
better to have this stat do something else, like shut off the flow or
divert from the boiler - possible?.

RE tappings, I contemplating have two zones - is the best way to have
duplicate sets of take-offs from the store or one set + valves?.

Apart from the above, I'm waiting on my BCO for his views on whether part L
is an issue...

DIYSOS

I'm fairly sure my model doesn't have the electrical cutout you describe,
didn't see anything on the HX pipes when I looked the other day*, plus it
doesn't have an electrical connection (;-).

The flavour of cutout I was on the lookout for was something to turn off the
boiler if the (water) temperature overshoots it's set limit. I think this is
the thermal cutout you describe... according to the docs on baxi/partsarena,
the Medway Super had such an "energy cut-off device". For better or worse,
my model is too primative to have one of these.

*I had the case open as I wanted to remove the HX to de-scale it, long
overdue after 20 years!. I followed my new-found instructions, undid the
unions and screws, but when it came to it the flue part of the HX is
immovably fixed into the wall-mounted flue housing - it really won't budge.
So, all I can think of is wait until if/when it gets disconnected for
replumbing. Then, connect into cold in / hot out pipes and somehow run
descalant through the whole thing - flow sensors and all (do these contain a
rubber diaphram and are they the 'weakest link'?) These will also have to
survive 'Fernox' of similar, and anything else coming out of the radiators
if my mad plan actually happens.

Wonder if you can still get spares for these things?

DIYSOS

"DIYSOS" wrote in message
...
All in all I think things are taking shape. I like the idea of gating the
store between condenser and high-temp mode!.

I don't actually see the multipoint as a temporary measure, 2 years then
I
would put the new condenser straight in. The sad fact is that I'm *mean*,
and upwards of £2k probably for a new condenser (installed) doesn't sit
easily with this disposition!. For now some of the savings will go to more
cost-effective ways of saving the planet, like 10" loft insulation and DG.
Though the multipoint has a few miles on the clock, to me this doesn't
necessarily mean it's on it's last legs. In fact I'm thinking it's got a
better chance of giving long, trouble free service than a condenser, with
all it's new-fangled pcbs and such.

When using the multi-point have the store temp 75C to avoid condensation
inside the multi-point. Adjust the stats when a condensing boiler is
fitted.

A few things still unresolved in my mind...

RE double 'stats to prevent boiler cycling,
I've come to realise I don't understand this
concept!.
I thought you'd have a single 'stat to report the
current temperature (at that point) to some logic device, which would fire
the boiler up if min and off if max, with min and max some way apart.
And
I thought the point of 2 'stats was to have one pick up quickly on a drop
at the bottom (CH), and the other at the top (HW). Somebody help me - I
can't see how having two 'stats in different locations on/in the store
reduces cycling?.

A store temp of 75C, The bottom stat is set to 75C, the top to 60-65C.
Heating from cold. The full store gets to 75C and the bottom stat cuts off
the boiler. In reality the top will be hotter than the bottom. When the
store cools the boiler will be called when the top gets to say 65C. It then
continuously heats the whole store until the bottom stat is 75C. Without
this the boiler would cycle as the temp around the bottom stat moved up and
down slightly. Some use one bottom stat but a Honeywell stat with a user
adjusted switching differential.

Go to:
http://www.heatweb,.com and down to Standard Heat Bank Options. This is a
design tool, and select twin stats on the right. Then the wiring button top
right. It gives you wiring diagram. It needs a smal cheap relay to operate
properly - £5 inc base from Maplin.

It is also a good idea to fit two stats when using a quick recovery coil
cylinder too.

RE temp overshooot, using a pipe 'stat is good...
however say you have the primary pump running
amok and not responding. In this situation, it would be
better to have this stat do something else, like shut
off the flow or
divert from the boiler - possible?.

The stats on the cylinder switch the pump. The pipe stat acts as a boiler
stat. If the pipe stat fails then the cylinder stat will cut out the pump
when the store is up to temp. If both fail and the pump is running, then it
will boil over and you will be alerted.

RE tappings, I contemplating have
two zones - is the best way to have
duplicate sets of take-offs from the
store or one set + valves?.

Two sets from the store, each with a Grundfos Alpha. and a programmer/stat
operating the pumps. The store is a wonderful neutral point.

Apart from the above, I'm waiting on my BCO
for his views on whether part L is an issue...

It shouldn't be, the water heater, that is what boilers are officially
called now (say boiler and you fail a CORGI exam), is already there, still
heating water.




_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

"DIYSOS" wrote in message
news
I'm fairly sure my model doesn't have the electrical cutout you describe,
didn't see anything on the HX pipes when I looked the other day*, plus it
doesn't have an electrical connection (;-).

The flavour of cutout I was on the lookout for was something to turn off
the
boiler if the (water) temperature overshoots it's set limit. I think this
is
the thermal cutout you describe... according to the docs on
baxi/partsarena,
the Medway Super had such an "energy cut-off device". For better or worse,
my model is too primative to have one of these.

*I had the case open as I wanted to remove the HX to de-scale it, long
overdue after 20 years!. I followed my new-found instructions, undid the
unions and screws, but when it came to it the flue part of the HX is
immovably fixed into the wall-mounted flue housing - it really won't
budge.
So, all I can think of is wait until if/when it gets disconnected for
replumbing. Then, connect into cold in / hot out pipes and somehow run
descalant through the whole thing - flow sensors and all (do these contain
a
rubber diaphram and are they the 'weakest link'?) These will also have to
survive 'Fernox' of similar, and anything else coming out of the radiators
if my mad plan actually happens.

Wonder if you can still get spares for these things?

There is no flow sensor, a rubber diaphragm that lifts when pressure is
applied under, the last time I looked. It may have changed.

Spare are easily available.


_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account

"DIYSOS" wrote in message
news
I'm fairly sure my model doesn't have the electrical cutout you describe,
didn't see anything on the HX pipes when I looked the other day*, plus it
doesn't have an electrical connection (;-).

Mine doesn't have an electrical _supply_, this is all driven off
the thermocouple. As I said, older ones don't have a thermocouple.

The flavour of cutout I was on the lookout for was something to turn off the
boiler if the (water) temperature overshoots it's set limit. I think this is
the thermal cutout you describe... according to the docs on baxi/partsarena,
the Medway Super had such an "energy cut-off device". For better or worse,
my model is too primative to have one of these.

Can't recall what my model is -- it's about 5 years old and does
have thermostatic control, and was the middle range of 3 which were
sold at the time. My much older one (which did overheat and self
destruct) was a Main Medina. The rather long 15mm pipe with lots
of elbows which used to feed gas to it had 1974 stamped on it IIRC,
but that could predate the Main water heaters as the house did have
an Ascot at some point (neighbour still had one when I moved in,
and I have a matching filled in flue hole in my outside wall in the
same place).

*I had the case open as I wanted to remove the HX to de-scale it, long
overdue after 20 years!. I followed my new-found instructions, undid the
unions and screws, but when it came to it the flue part of the HX is
immovably fixed into the wall-mounted flue housing - it really won't budge.

My recollection (hazy) is there are just a couple of screws holding
the top of the HX in place in the cabinet, and the flue connection
is just a slide fit. I suspect if it won't slide out, you won't be
able to take the thing off the wall. These units have all used the
same flue for decades -- if a unit dies, the new ones are all designed
to hang on the flues of the older versions, so you don't need to
replace the flue too.

So, all I can think of is wait until if/when it gets disconnected for
replumbing. Then, connect into cold in / hot out pipes and somehow run
descalant through the whole thing - flow sensors and all (do these contain a
rubber diaphram and are they the 'weakest link'?) These will also have to
survive 'Fernox' of similar, and anything else coming out of the radiators
if my mad plan actually happens.

I descaled my old one a few times in the bath. I used kettle
descaler and rather worryingly, the liquid came out bright
blue or green (I forget), but it didn't seem to do any harm.
The new one has internally coated teflon pipes IIRC, which
is supposed to reduce the need for descaling and I haven't
had to do it in 5 years -- flow rate still fine.

Wonder if you can still get spares for these things?

I suspect so. They were very popular and around for several
decades. They still do a couple of models, although one is
quite different (electrical with fanned flue).

--
Andrew Gabriel

OK I mis-understood, mine does have a thermocouple but I didn't see anything
on the HX pipes, I'll check again sometime in case I missed it.

The flue is jointed such that the whole unit will slide out, but the joint
set back several inches from the wall bracket. The HX flue is tight into
this bracket - no scope to lift & pull. Maybe with brute force it would
give, but I'll go for pumping descaler thru the lot. Interesting to see what
colour the residue will be!.

BTW the model in my series with a thermostat was called Trent.

DIYSOS

OK now I understand how two 'stats work - thanks. What a helpful Dr Evil you
are!.

When using the multi-point have the store temp 75C to avoid condensation
inside the multi-point. .

This may well be sound advice... however by design mains water into this
boiler (sorry water heater) would be stone cold anyway?.

Thanks all for your input, I think I've got enough now to be going on with.
I'll be spending the next week or two doing the bread&butter stuff of
installing radiator circuits, by which time I should hear back from the LC.
With the pumps + immersion (new circuit) to install, I'll probably raise a
part P building notice anyway (or was there some dodge involving 3 pin
plugs?).

.... and I plan to drop my pseudonym of DIYSOS for any future topics - poor
name choice on reflection. There will be a no-prize for identifing me under
my new guise (probably my proper name!).

Bye
DIYSOS

"DIYSOS" wrote in message
...

OK now I understand how two 'stats
work - thanks. What a helpful Dr Evil you
are!.

When using the multi-point have
the store temp 75C to avoid condensation
inside the multi-point. .

This may well be sound advice... however
by design mains water into this
boiler (sorry water heater) would be stone
cold anyway?.

True, but don't help it along when you can avoid it. The innards are pretty
rustproof.

Thanks all for your input, I think I've got enough now to be going on
with.
I'll be spending the next week or two doing the bread&butter stuff of
installing radiator circuits, by which time I should hear back from the
LC.
With the pumps + immersion (new circuit) to install, I'll probably raise a
part P building notice anyway (or was there some dodge involving 3 pin
plugs?).

I think there was. Wire the lot up using a terminal box. Have "all"
components: cyl stats, programmers/stats, pumps, boiler, etc into the box.
Then take a flex to a 3-pin plug.



_________________________________________
Usenet Zone Free Binaries Usenet Server
More than 120,000 groups
Unlimited download
http://www.usenetzone.com to open account