After another 6 days with no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but thinking
it's time to look at replacing .... becoming pretty unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected to a
pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as thermal
store control need to manage pump)


Want to replace with 'similar' .... I did like idea of Vaillant boilers
with SS heat exchangers - but only offer these in System boilers.

Couple of heatings guys advised that current range of Baxi is now vastly
improved ..... so could use Baxi Heat 800
Though only with aluminium heat exchanger (but with 10 yr warranty)

I did ask on another forum .. the answer there is to use the Dutch
boilers by Intergas, but there are no local Intergas approved installers
When I have asked British Gas/SSE and independent GasSafe guys they have
never come across one.

Thoughts on the Baxi Heat ? or other Heat only models to consider

On Wednesday, 3 March 2021 at 11:00:09 UTC, rick wrote:
After another 6 days with no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but thinking
it's time to look at replacing .... becoming pretty unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected to a
pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as thermal
store control need to manage pump)


You can get system boilers without a pump, we had a Bosch Greenstar at the last house and the pump was separate, in fact sited some distance from the boiler. It is Combi boilers that usually come with an integrated pump. A friend of mine who had a thermal store had a very similar arrangement to yours with a Bosch boiler.

Richard

In article ,
rick wrote:
After another 6 days with no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but thinking
it's time to look at replacing .... becoming pretty unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected to a
pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as thermal
store control need to manage pump)

Is that the case today? No thermal store can be used with a system boiler?
When I did a self install quite a few years ago, Viessmann had an
incredibly helpful technical advice guy in the UK. Seemed to know
everything.

Just that system boilers being the norm, may be far better value due to
economy of scale.

--
*My dog can lick anyone

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

On 03/03/2021 10:59, rick wrote:
After another 6 days withÂ* no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but thinking
it's time to look at replacing .... becoming pretty unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected to a
pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as thermal
store control need to manage pump)


Want to replace with 'similar' .... I did like idea of Vaillant boilers
with SS heat exchangers - but only offer these in System boilers.

They do the 400 series heating only models (mostly open vented, but some
also suitable for sealed system).

The newer ones seem to be Ali HX though.

Couple of heatings guys advised that current range of Baxi is now vastly
improved ..... so could use Baxi Heat 800
Though only with aluminium heat exchanger (but with 10 yr warranty)

I did ask on another forum .. the answer there is to use the Dutch
boilers by Intergas, but there are no local Intergas approved installers
When I have asked British Gas/SSE and independent GasSafe guys they have
never come across one.

Thoughts on the Baxi Heat ?

No experience of them, so can't comment.

or other Heat only models to consider

Worcester Bosh have a few as well like the Greenstar 24Ri features



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 03/03/2021 11:31, Tricky Dicky wrote:
On Wednesday, 3 March 2021 at 11:00:09 UTC, rick wrote:
After another 6 days with no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but thinking
it's time to look at replacing .... becoming pretty unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected to a
pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as thermal
store control need to manage pump)


You can get system boilers without a pump, we had a Bosch Greenstar at the last house and the pump was separate, in fact sited some distance from the boiler. It is Combi boilers that usually come with an integrated pump. A friend of mine who had a thermal store had a very similar arrangement to yours with a Bosch boiler.

Richard

OK ... I thought all System boilers had expansion vessel & pump built in
..... my misunderstanding.

On 03/03/2021 13:58, Dave Plowman (News) wrote:
In article ,
rick wrote:
After another 6 days with no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but thinking
it's time to look at replacing .... becoming pretty unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected to a
pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as thermal
store control need to manage pump)

Is that the case today? No thermal store can be used with a system boiler?
When I did a self install quite a few years ago, Viessmann had an
incredibly helpful technical advice guy in the UK. Seemed to know
everything.

Just that system boilers being the norm, may be far better value due to
economy of scale.



Not tried Viessman .. if you have a name to contact be happy to try them.

The reason I can't see how to use System boiler is that thermal store
operates the pump to 'stir' the store when you are drawing off DHW .....
otherwise heat exchanger gets cool quickly and you lose hot water.

Works really well ..... but with a System boiler the Boiler controls the
pump, and therefore the Thermal Store controls can't operate a 'stir'

When I put in the system teh company specified a HEAT only boiler for
this reason.
The thermal store installed is not changing, and heating company state I
should still use a HEAT only boiler.

I had thought of installing Vaillant but they advise only their system
boilers can be connected to a pressurised Thermal store not Heat only.
When I asked them how do I get the pump to stir the store - that was
beyond their experience and could offer no solution.

On 03/03/2021 14:27, John Rumm wrote:
On 03/03/2021 10:59, rick wrote:
After another 6 days withÂ* no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but
thinking it's time to look at replacing .... becoming pretty unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected to
a pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as
thermal store control need to manage pump)


Want to replace with 'similar' .... I did like idea of Vaillant
boilers with SS heat exchangers - but only offer these in System boilers.

They do the 400 series heating only models (mostly open vented, but some
also suitable for sealed system).



I contacted Vaillant support they were very clear that Heat only boilers
cannot be connected to a pressurised thermal store, they have to be used
open vented.
Pity as they are supposed to be god boilers.

In article ,
rick wrote:
Not tried Viessman .. if you have a name to contact be happy to try them

It was many years ago. The number I have is 01952 675000

--
*I don't feel old. I don't feel anything until noon. Then it's time for my nap.

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

On Wed, 3 Mar 2021 17:12:01 +0000, rick
wrote:


Pity as they are supposed to be god boilers.

I thought god's boilers were that big bright things in the sky?

--
AnthonyL

Why ever wait to finish a job before starting the next?

On 03/03/2021 17:12, rick wrote:
On 03/03/2021 14:27, John Rumm wrote:
On 03/03/2021 10:59, rick wrote:
After another 6 days withÂ* no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but
thinking it's time to look at replacing .... becoming pretty unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected
to a pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as
thermal store control need to manage pump)


Want to replace with 'similar' .... I did like idea of Vaillant
boilers with SS heat exchangers - but only offer these in System
boilers.

They do the 400 series heating only models (mostly open vented, but
some also suitable for sealed system).



I contacted Vaillant support they were very clear that Heat only boilers
cannot be connected to a pressurised thermal store, they have to be used
open vented.

Be careful with your terminology here though. Since cylinders can be
vented and unvented, and they can be connected to primary systems that
are also vented and unvented.

So there is nothing stopping you having an unvented cylinder (i.e. mains
pressure cold feed), heated via an indirect coil connected to an
unvented primary heating circuit.

Much as the (more common) sealed system primary heating a vented
cylinder is also ok.

The time you may have a problem is with a sealed system thermal store[1]
connected in a "direct cylinder" setup connected directly to a boiler
(i.e. the CH primary water also fills and mixes with that in the store,
and it uses a coil or external plate Hx to extract the energy from the
water stored water).

For the latter case you will need a boiler that can be used with a
sealed primary system. Vaillant claim[1] that some of the 400 series
*can* be used in sealed systems (although obviously you would need to
provide an external expansion vessel, filling loop and over pressure
relief valve)

[1] and to be fair, many traditional vented boilers can be used in a
sealed system with the addition of the right external bits.

[2] And even then it not uncommon for people to build heatbanks and
thermal stores using unvented cylinders - but they don't have to be used
that way.


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 03/03/2021 18:24, Dave Plowman (News) wrote:
In article ,
rick wrote:
Not tried Viessman .. if you have a name to contact be happy to try them

It was many years ago. The number I have is 01952 675000


You able to find the name of the guy in any old emails ? finding
someone at a Boiler manufacturer who understands needs of Under Floor
Heating is not easy.
Their standard answer is go talk to Heat Safe engineer - never come
across one who has any clue about such systems, and had a great many
from SSE, Baxi & British Gas at my place over the years.


I had a right numpty last week ... (boiler broken again) repair contract
company sent a guy, who decided pressure gauge of thermal store were too
low and started pumping them up with water from filling loops - luckily
I walked in as he wa doing this .... Explained basic science to him, and
then he agreed to release the pressure .... watched him for several
minutes trying to drop pressure in underfloor heating circuits by
tripping Thermal store pressure ..... explained again the basics, he
could not comprehend.
declared boiler had PCB fault .... would report it to service company.

Luckily they engaged 'Baxi' to do the re-visit as they do some form of
fixed price repair ..... in only few minutes the guy identified boiler
overheating inside casing ... found burner box door seal disintegrated
in corner, and burner inside all broken.
Replaced both - boiler fine

In article ,
rick wrote:
On 03/03/2021 18:24, Dave Plowman (News) wrote:
In article ,
rick wrote:
Not tried Viessman .. if you have a name to contact be happy to try them

It was many years ago. The number I have is 01952 675000


You able to find the name of the guy in any old emails ?

Did it all by phone. He was the one I got put through to when asking for
technical help. Of course it's likely just a robot now.


finding
someone at a Boiler manufacturer who understands needs of Under Floor
Heating is not easy.
Their standard answer is go talk to Heat Safe engineer - never come
across one who has any clue about such systems, and had a great many
from SSE, Baxi & British Gas at my place over the years.

He was an expert on Viessmann boiler related stuff. So would likely know
about using a system boiler with a heat store. Even my now quite old
Viessmann can communicate with other devices. So it's possible they do a
pump controller for a heat store. But just musing.

--
*I didn't like my beard at first. Then it grew on me.*

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

On 04/03/2021 13:59, Dave Plowman (News) wrote:

He was an expert on Viessmann boiler related stuff. So would likely know
about using a system boiler with a heat store. Even my now quite old
Viessmann can communicate with other devices. So it's possible they do a
pump controller for a heat store. But just musing.



The issue is I can't use an external controller .. I have a full
controller for Underfloor Heating (17 zones) so that needs to stay.
It needs to control the pump .....
Its mains pressure HW through a heat exchanger in the Thermal store ...
once you start running HW after a couple of minutes the water around
heat exchanger will cool
The control start the boiler pump - so it 'stirs' the store without
powering up boiler, meaning you can get loads of DHW before it needs to
start boiler and replenish the Thermal store.
Added advantage is that I have my Solar panels on roof dumping any
excess electricity into the Thermal store .. in Summer boiler never
fires up at all.


I found Tech Help email address for Viessman so will ping them a mail

On 03/03/2021 21:25, John Rumm wrote:
On 03/03/2021 17:12, rick wrote:
On 03/03/2021 14:27, John Rumm wrote:
On 03/03/2021 10:59, rick wrote:
After another 6 days withÂ* no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but
thinking it's time to look at replacing .... becoming pretty
unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected
to a pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as
thermal store control need to manage pump)


Want to replace with 'similar' .... I did like idea of Vaillant
boilers with SS heat exchangers - but only offer these in System
boilers.

They do the 400 series heating only models (mostly open vented, but
some also suitable for sealed system).



I contacted Vaillant support they were very clear that Heat only
boilers cannot be connected to a pressurised thermal store, they have
to be used open vented.

Be careful with your terminology here though. Since cylinders can be
vented and unvented, and they can be connected to primary systems that
are also vented and unvented.

So there is nothing stopping you having an unvented cylinder (i.e. mains
pressure cold feed), heated via an indirect coil connected to an
unvented primary heating circuit.

Much as the (more common) sealed system primary heating a vented
cylinder is also ok.

The time you may have a problem is with a sealed system thermal store[1]
connected in a "direct cylinder" setup connected directly to a boiler
(i.e. the CH primary water also fills and mixes with that in the store,
and it uses a coil or external plate Hx to extract the energy from the
water stored water).

For the latter case you will need a boiler that can be used with a
sealed primary system. Vaillant claim[1] that some of the 400 series
*can* be used in sealed systems (although obviously you would need to
provide an external expansion vessel, filling loop and over pressure
relief valve)

[1] and to be fair, many traditional vented boilers can be used in a
sealed system with the addition of the right external bits.

[2] And even then it not uncommon for people to build heatbanks and
thermal stores using unvented cylinders - but they don't have to be used
that way.




In this instance the boiler is connected via primaries to Thermal Store
- it circulates the contents of the store around the boiler.
There is a pump, expansion vessel and 2 port anti heat-syphon valve on
the prinmaries
No direct connection to DHW or heating
The store is pressurised.
Inside the store is a horizontal baffle .... below which there is a heat
transfer coil for the Heating circuits
Above the baffle is a multi-plate heat exchanger through which is fed
mains water = providing the DHW for the house.

Vaillant advise that only their system boilers can be connected to a
pressurised thermal store.
I explained set up to them .......

They were clear that their OV boilers cannot be connected to a thermal
store.

On 10/03/2021 15:45, rick wrote:
On 03/03/2021 21:25, John Rumm wrote:
On 03/03/2021 17:12, rick wrote:
On 03/03/2021 14:27, John Rumm wrote:
On 03/03/2021 10:59, rick wrote:
After another 6 days withÂ* no heating ..... boiler repaired under
maintenance cover (burner, burner door, seal & electrodes), but
thinking it's time to look at replacing .... becoming pretty
unreliable.
Its now 22 years old.
Its a 30kW Heat only wall mounted gas condensing boiler - connected
to a pressurised thermal store.

I need a standard/Heat only ..... can't use as system boiler (as
thermal store control need to manage pump)


Want to replace with 'similar' .... I did like idea of Vaillant
boilers with SS heat exchangers - but only offer these in System
boilers.

They do the 400 series heating only models (mostly open vented, but
some also suitable for sealed system).



I contacted Vaillant support they were very clear that Heat only
boilers cannot be connected to a pressurised thermal store, they have
to be used open vented.

Be careful with your terminology here though. Since cylinders can be
vented and unvented, and they can be connected to primary systems that
are also vented and unvented.

So there is nothing stopping you having an unvented cylinder (i.e.
mains pressure cold feed), heated via an indirect coil connected to an
unvented primary heating circuit.

Much as the (more common) sealed system primary heating a vented
cylinder is also ok.

The time you may have a problem is with a sealed system thermal
store[1] connected in a "direct cylinder" setup connected directly to
a boiler (i.e. the CH primary water also fills and mixes with that in
the store, and it uses a coil or external plate Hx to extract the
energy from the water stored water).

For the latter case you will need a boiler that can be used with a
sealed primary system. Vaillant claim[1] that some of the 400 series
*can* be used in sealed systems (although obviously you would need to
provide an external expansion vessel, filling loop and over pressure
relief valve)

[1] and to be fair, many traditional vented boilers can be used in a
sealed system with the addition of the right external bits.

[2] And even then it not uncommon for people to build heatbanks and
thermal stores using unvented cylinders - but they don't have to be
used that way.




In this instance the boiler is connected via primaries to Thermal Store
- it circulates the contents of the store around the boiler.
There is a pump, expansion vessel and 2 port anti heat-syphon valve on
the prinmaries
No direct connection to DHW or heating
The store is pressurised.
Inside the store is a horizontal baffle .... below which there is a heat
transfer coil for the Heating circuits
Above the baffle is a multi-plate heat exchanger through which is fed
mains water = providing the DHW for the house.

Vaillant advise that only their system boilers can be connected to a
pressurised thermal store.
I explained set up to themÂ* .......

They were clear that their OV boilers cannot be connected to a thermal
store.

OK fair enough - not sure why they say that when they also describe how
to run the OV boilers in sealed systems... Perhaps its just a safety
"catch all" statement since going unvented requires the addition of
external components that are not part of the boiler (i.e. Over
temp/pressure relif valve, expansion vessel, filling loop and pressure
gauge etc).

(One of the difficulties I find with the Vaillant kit is getting "big
picture" documentation or information. There is tons of low level docs
describing many features, but not always so much covering whay you want
them or when to use them).


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/