Here's the scenario:

At the moment by CH and HW is heated by a gas powered Rayburn (with a
thermostatically controlled boiler). It runs on LPG which isn't cheap
and isn't helped by having a rather inefficient Rayburn on the other end
of the pipe from the tank.

So...

I was wondering of the possiblities of linking in a separate (modern,
efficient) gas boiler to provide and alternative heat source whilst
still keeping the Rayburn in the system.

I'm aware of the problems of people's attempts to link in solid fuel
devices (stoves, Rayburns, Agas etc.) into existing CH systems and the
risks and pitfalls (boiling the back boiler, problems in event of
power/pump failure etc. etc.). I'm also aware of the Dunsley heat
exchanger device thingy.

I am trying to find reasons why a system with dual boilers would not
work and also the possible setup (boilers in parallel? boilers in
series?). Since both heat sources are controllable thermostatically I
cannot see any major issues as per using solid fuel devices.

Anyone seen/installed/experienced a 2 boiler setup?

Thanks in advance

Andy

On 25 Mar, 15:35, Andy Kirkland wrote:

Anyone seen/installed/experienced a 2 boiler setup?
Yes, just about every commercial installation and many large domestic
ones. 10 or 12 modular boilers (large domestic types) is common, 15
years ago it would have been 2 or 3 commercial boilers handling the
same load.

You'd need some custom controller if boiler selection is to be
automatic but fairly simple switching with thermostats should be
adequate, e.g., the new boiler is the lead boiler, the Rayburn is held
off by a pipe thermostat so only operates if the lead boiler fails.

Have a Google for primary/secondary pumping. The heating circuit
would have its own pump and the boilers would be on secondary circuits
which would only draw water from the primary when the boiler &
secondary pump runs.

You need to ensure that hot water isn't circulated through a non-
firing boiler unless it has a fanned flue, or else it will be acting
as a heat dump. You also need to consider some device to keep an
elevted return temperature to a non-condensing boiler.


..

"Andy Kirkland" wrote in message
...
Here's the scenario:

At the moment by CH and HW is heated by a gas powered Rayburn (with a
thermostatically controlled boiler). It runs on LPG which isn't cheap and
isn't helped by having a rather inefficient Rayburn on the other end of
the pipe from the tank.

So...

I was wondering of the possiblities of linking in a separate (modern,
efficient) gas boiler to provide and alternative heat source whilst still
keeping the Rayburn in the system.

I'm aware of the problems of people's attempts to link in solid fuel
devices (stoves, Rayburns, Agas etc.) into existing CH systems and the
risks and pitfalls (boiling the back boiler, problems in event of
power/pump failure etc. etc.). I'm also aware of the Dunsley heat
exchanger device thingy.

I am trying to find reasons why a system with dual boilers would not work
and also the possible setup (boilers in parallel? boilers in series?).
Since both heat sources are controllable thermostatically I cannot see any
major issues as per using solid fuel devices.

Anyone seen/installed/experienced a 2 boiler setup?

Thanks in advance

Don't bother with Dunsleys, a waste of time. Use a vented thermal
store/heat bank to couple the two boilers up directly to the cylinder. The
DHW and CH comes from the store. No headers or primary/secondary pumps,
etc. Simple. Both can operate independently. Just turn one off if not
needed.

Look at http://www.heatweb.com They have good diagrams on how to connect.

Doctor Drivel wrote:

"Andy Kirkland" wrote in message
...
Here's the scenario:

At the moment by CH and HW is heated by a gas powered Rayburn (with a
thermostatically controlled boiler). It runs on LPG which isn't cheap
and isn't helped by having a rather inefficient Rayburn on the other
end of the pipe from the tank.

So...

I was wondering of the possiblities of linking in a separate (modern,
efficient) gas boiler to provide and alternative heat source whilst
still keeping the Rayburn in the system.

I'm aware of the problems of people's attempts to link in solid fuel
devices (stoves, Rayburns, Agas etc.) into existing CH systems and the
risks and pitfalls (boiling the back boiler, problems in event of
power/pump failure etc. etc.). I'm also aware of the Dunsley heat
exchanger device thingy.

I am trying to find reasons why a system with dual boilers would not
work and also the possible setup (boilers in parallel? boilers in
series?). Since both heat sources are controllable thermostatically I
cannot see any major issues as per using solid fuel devices.

Anyone seen/installed/experienced a 2 boiler setup?

Thanks in advance

Don't bother with Dunsleys, a waste of time. Use a vented thermal
store/heat bank to couple the two boilers up directly to the cylinder.
The DHW and CH comes from the store. No headers or primary/secondary
pumps, etc. Simple. Both can operate independently. Just turn one off
if not needed.

Look at http://www.heatweb.com They have good diagrams on how to connect.

Don't bother with drivel, he's a waste of time.
I forgot new installation=new killfile.

Out you go drivel!

"The Natural Philosopher" wrote in message
...

Out you go drivel!

Put me on your killfile. You are a complete snotty uni plantpot.

On 25 Mar, 23:25, "Doctor Drivel" wrote:

Don't bother with Dunsleys, a waste of time. *Use a vented thermal
store/heat bank to couple the two boilers up directly to the cylinder. *The
DHW and CH comes from the store. *No headers or primary/secondary pumps,
etc. *Simple. *Both can operate independently. Just turn one off if not
needed.


Beware of Drivel, he is the resident moron.

For an example of his incompetent ramblings see above.

The point of the Dunsley neutraliser is that it provides hydraulic
disconnection between the primary and secondary pumped systems. All
flow and return pipes connect to the Dunsley device and so there is no
pressure difference between the flow and return pipes causing nuisance
flows. Boiler A's pump running does not cause flow through Boiler B or
through the heating system since they are hydraulically disconnected.

The heat store does the same job, but with some thermal storage
capacity; connecting boilers to it will require primary (usually heat
sources) and secondary pumps (usually heat distribution devices).

I wouldn't use the Dunsley device because I can get better for less.

Hi,

Onetap wrote:
The point of the Dunsley neutraliser is that it provides hydraulic
disconnection between the primary and secondary pumped systems. All
flow and return pipes connect to the Dunsley device and so there is no
pressure difference between the flow and return pipes causing nuisance
flows. Boiler A's pump running does not cause flow through Boiler B or
through the heating system since they are hydraulically disconnected.

The heat store does the same job, but with some thermal storage
capacity; connecting boilers to it will require primary (usually heat
sources) and secondary pumps (usually heat distribution devices).

I wouldn't use the Dunsley device because I can get better for less.

Thanks everyone for their input.....

COuld you explain further on "better for less" vs the Dunsley? The
Dunsley does seem pricey for a block of steel (albeit researched and
engineered)....

Alternatively to the above, can anyone point me in the direction of a
good heating engineer who can, paid, give me some good design pointers
and/or installation advice and/or actual installation - I am after
someone with specific multi-source experience. I live in North
Derbyshire (30 mins from Manchester and Sheffield).

Cheers

Andy

"Doctor Drivel" wrote in message
...

"The Natural Philosopher" wrote in message
...

Out you go drivel!

Put me on your killfile. You are a complete snotty uni plantpot.


You forgot to tag him. Is your nurse on holiday?

Adam

"Doctor Drivel" wrote

Put me on your killfile.

Good idea. Thanks.

On 26 Mar, 18:35, Andy Kirkland wrote:

COuld you explain further on "better for less" vs the Dunsley? The
Dunsley does seem pricey for a block of steel (albeit researched and
engineered)....

The Dunsley things are about 6" x 18" diameter. If you need some
thermal storage, most cylinder manufacturerers would braze additional
tappings onto a direct cylinder. They're usually required for solid
fuel (open vented systems); you have to ensure that it is rated for
the system pressure and a suitable presure relief valve is fitted.
Buffer vessels were used on heating and chilled water systems long
before Dunsley marketed their product.

If you do not need thermal storage, you can get a low loss header
fabricated from steel or copper pipework. This will provide hydraulic
disconnection of the various primary secondary circuits.

"Onetap" wrote in message
...
On 26 Mar, 18:35, Andy Kirkland wrote:

COuld you explain further on "better for less" vs the Dunsley? The
Dunsley does seem pricey for a block of steel (albeit researched and
engineered)....

The Dunsley things are about 6" x 18" diameter. If you need some
thermal storage, most cylinder manufacturerers would braze additional
tappings onto a direct cylinder. They're usually required for solid
fuel (open vented systems); you have to ensure that it is rated for
the system pressure and a suitable presure relief valve is fitted.
Buffer vessels were used on heating and chilled water systems long
before Dunsley marketed their product.

If you do not need thermal storage, you can get a low loss header
fabricated from steel or copper pipework. This will provide hydraulic
disconnection of the various primary secondary circuits.

The Dunsley is a waste of expensive time offering little at all. Thermal
store/heat banks offer CH buffering and instant mains pressure DHW, and
simplicity which an expensive header will not.

"ARWadsworth" wrote in message
...

"Doctor Drivel" wrote in message
...

"The Natural Philosopher" wrote in message
...

Out you go drivel!

Put me on your killfile. You are a complete snotty uni plantpot.

You forgot to tag him. Is your nurse on holiday?

His nurse left him.

"Jonah" wrote in message
g.com...

"Doctor Drivel" wrote

Put me on your killfile.

Good idea. Thanks.

pleasure.

"Onetap" wrote in message
...
On 25 Mar, 23:25, "Doctor Drivel" wrote:

Don't bother with Dunsleys, a waste of time. Use a vented thermal
store/heat bank to couple the two boilers up directly to the cylinder.
The
DHW and CH comes from the store. No headers or primary/secondary pumps,
etc. Simple. Both can operate independently. Just turn one off if not
needed.

Beware of Drivel, he is the resident moron.

You are an incompetent idiotic fool. The fool goes on...

The point of the Dunsley neutraliser is that it provides hydraulic
disconnection between the primary and secondary pumped systems.

As does a thermal store. But better. He continues to drool drivel...

All flow and return pipes connect to the
Dunsley device and so there is no
pressure difference between the flow and
return pipes causing nuisance
flows.

As does a thermal store.

Boiler A's pump running does not cause
flow through Boiler B or through the heating
system since they are hydraulically disconnected.

As does a thermal store.

The heat store does the same job,

My God!! He has got it!!!!!! Has he been converted on the road to Damascus?

but with some thermal storage
capacity; connecting boilers to it will
require primary (usually heat sources)
and secondary pumps (usually heat
distribution devices).

A great advantage. The secondary pump (heat distribution devices as you call
them) can be a Smart pump on the CH circuit. Have TRV's on all rads and
then no nusisance central walls stats.

A gravity fed boiler can heat thermal store.

I wouldn't use the Dunsley device because
I can get better for less.

Like a thermal store/heat bank. Which are cheap and offer so much more.

On 28 Mar, 15:32, "Doctor Drivel" wrote:

but with some thermal storage
capacity; connecting boilers to it will
require primary (usually heat sources)
and secondary pumps (usually heat
distribution devices).

A great advantage. The secondary pump (heat distribution devices as you call
them) can be a Smart pump on the CH circuit. *Have TRV's on all rads and
then no nusisance central walls stats.


Yes Drivel, but my I just point out that in your first post you said
that vented thermal store/heat bank had " No headers or primary/
secondary pumps,"

It has both primary and secondary pumps, like the Dunsley job. My
point was that your post was bollox, as usual.

A low loss header is not expensive if you make them.

"Onetap" wrote in message
...
On 28 Mar, 15:32, "Doctor Drivel" wrote:

but with some thermal storage
capacity; connecting boilers to it will
require primary (usually heat sources)
and secondary pumps (usually heat
distribution devices).

A great advantage. The secondary pump
(heat distribution devices as you call
them) can be a Smart pump on the CH
circuit. Have TRV's on all rads and
then no nusisance central walls stats.

Yes Drivel, but my I just point out that
in your first post you said that vented thermal
store/heat bank had " No headers or primary/
secondary pumps,"

There is no expensive headers and no carefully designing primary and
secondary pump circuits. No complex, expensive, boiler sequencing
controls, as two boiler anti-cycle stats on the cylinder will just bring in
both boilers and heat up ASAP. No constant click-click of the boiler when
cycling when on headers.

Even in summer it doesn't matter, just a rapid re-heat if two boilers
switched on. In summer one boiler can be switched off by the user. Two
cheap simple boilers can be used. They don't need to modulate or have
complex boiler controls. All simple. All easy. Want waether compensation?
Well use a Broag "dual temperature" boiler with integral weather
compensation and an external 3-way diverter valve controlled from the
boiler. When the top DHW section calls for heat the boiler runs up to
maximum temperature and reheats ASAP. Then reverts to CH and weather
compensation control and heat the bottom CH section to the outside weather
dictates. All simple and easy and cheap.

Headers are a direct loop back to a boiler's return reducing condensing
efficiency. They can be complex and expensive and have to be sized right.
They do not provide CH buffering as a thermal store does. Thermal stores
are easy, just two tappings for each boiler.

A thermal stores/heat banks are easy. A flow and return tapping for each
boiler onto the cylinder. The same cylinder stat(s) switches in both
boilers. Simple. A gravity wood burner can be hitched up the same way.
Simple and easy. Even you could understand it - I hope.