Replacing complete CH & DHW system advice.

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HarryW

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First post, but I have trawled through previous posts as much as I can.

I currently have a 22 year old system that’s a bit like triggers new broom… last straw was this week when I got an At Risk notice on the Ali flue corroded through, which was replaced quickly under my BG home care package.

The current system is Potterton SS 50L (14.7kw) feeding a Boiler Mate2000 BM210 thermal store. It’s been a good if not troublesome systems over the years, but the recent hikes in gas prices means the 24/7/365 of on time required to keep the store up to temperature for even the HW to work in summer means I want change to a more conventional unvented tank system that I can heat up the HW on a timed basis. Also I think the store itself is a ticking time bomb now for leaks given its age.

The house is 4 bed, 1 bath 2 shower and BG heat loss/required calcs showing that 18kw is sufficient for the house paired to an unvented 210lt indirect tank.
Layout would be similar with the boiler on the ground floor on external wall in the utility room and the tank in an airing cupboard on the first floor. Most of the existing pipe work would be repurposed after power flushing (not able to power flush currently due to thermal store!).

Currently I’ve 2 solutions both with the Gledhills SSL 210ltr unvented tank and a Hive 2 control system. One is heat only boiler Vaillant EcoTec Plus 418 the other is a system boiler EcoTec Plus 620.

It’s obviously not going to be cheap so I want to get it right and am erring to the System boiler solution.

However my biggest bug bear with BG is they don’t do Vaillant controls to fully utilise the modulation capabilities of modern boilers for heating. It’s as if they are stuck in a year 2000 mindset and want to set the boiler at one point and not utilise the modulation intelligence available or even the different temps for HW and CH. It’s very nearly a deal breaker for me.

My queries to the floor are;

1. Is the Vaillant 418 a bit old tech?
2. Is Vaillant 620 a good system boiler?
3. Can the Hive2 really properly control the system with its simple on/off logic?
4. Has anyone got BG to fit Vaillant controls to their Vaillant boiler?
5. Any alternatives?

TIA
 
If it makes any difference it’ll be an S plan configuration….
 
The industry is an absolute mess.
"Professionals" barely know anything tbh.

If you are arsed, do your research and design it yourself. You'll likely do a better job.

That is unless you can actually find a proper heating engineer to design it for you.

S plan is old hat. Xplan is a thing but really, the industry hasn't a ****ing clue in general.

A std boiler is simple and reliable and allows you to be flexible with your system design.

If it were me, do it properly.
Do research, draw the system out, show the pros here.

Control is where the sharp end of the pencil needs to be. Don't use 80's tech such as two zone thermostats and clockwork control. Look at systems such as wiser, where you can control rooms individually. Some don't like that and find the granularity to difficult. Other like the energy saving and individually it affords.

Best of luck
 
HarryW said:
However my biggest bug bear with BG
Click to expand...
Honestly, don't get BG to design and fit the system. It will be well overpriced and may be not what you need especially if the controls you prefer could not be included. Get recommended and well reviewed local independents with a good rep to come in and give a quote, get at least 3 and see what the options and approaches may be.

Don't rush it as it's not a small beer job you need.

Have a really good idea of what it is you want and/or need, get it all down on paper and go from there. If you can, do your research and don't be afraid to add suggestions or ideas you may prefer or wish to their design, if any of them have an issue with your input then bin them.
 
BlueLoo said:
The industry is an absolute mess.
"Professionals" barely know anything tbh.

If you are arsed, do your research and design it yourself. You'll likely do a better job.

That is unless you can actually find a proper heating engineer to design it for you.

S plan is old hat. Xplan is a thing but really, the industry hasn't a ****ing clue in general.

A std boiler is simple and reliable and allows you to be flexible with your system design.

If it were me, do it properly.
Do research, draw the system out, show the pros here.

Control is where the sharp end of the pencil needs to be. Don't use 80's tech such as two zone thermostats and clockwork control. Look at systems such as wiser, where you can control rooms individually. Some don't like that and find the granularity to difficult. Other like the energy saving and individually it affords.

Best of luck
Click to expand...
Not heard of X plan, did a quick google and the results are sparse, but it reads like a S plan where you have DHW priority at a higher heat to warm the tank quickly.
Any links to a diagram as I could find one.

Re controls that’s my bug bear with BG who propose using the latest modulation type boiler at a single temperature for both HW and CH it is criminal…
 
HarryW said:
Not heard of X plan, did a quick google and the results are sparse, but it reads like a S plan where you have DHW priority at a higher heat to warm the tank quickly.
Any links to a diagram as I could find one.
Click to expand...

X-plan just means priority hot water. Each boiler manufacturer achieves it in their own way. In essence, it is very similar to the standard S-plan but involves using a normally open valve or a diverter valve at some point rather than a normally closed valve. Here is a previous thread re. Vaillant:

www.diynot.com

Vaillant ecoTEC 428 plus. (VUGB286/2-OH)

Hello, Firstly please excuse my lack of knowledge with heating systems, ill Try and explain what I’m Trying to achieve the best I can. As per the description I have a 428 heat only boiler recently converted from open vent to a sealed system. This is operated by a Yplan and Hive controls. The...
www.diynot.com www.diynot.com

Here is a very useful video explaining the general principle and how to do it with Ideal boilers. The first seven minutes covers everything and has some very useful diagrams.

 
Last edited:
Many thanks for the link, I follow the urban plumber on YouTube as he’s a good watch regardless.

I’ve ponder this all again and have reversed my first thought, thinking an open vented system might be simpler, cheaper and more reliable. I think using the Vaillant controls is still need to fully optimise the boiler in the separate DHW & CH output modes.
Am I right in thinking I’ll need a
SensoHome wireless
VR66/2 centre
VT10 thermistor for the tank
And the glow worm wireless outdoor temp sensor linked to the SensoHome?

Quick query regards ebus do I still need to hardwire the VR66 to the boiler or can I use a RF module on the VR66 to communicate with the boiler?
 
To clarify I’m talking about the Ecotec plus 418 heat only when I said open vented above…
 
I also follow the urban plumber - He is always encouraging intergas boilers and I personally am choosing one

My system has 4 bed 2 bath and is running an ideal mexico 2 on a one pipe system with a two port valve for hot water.

Why are you going with a valiant?
 
HarryW said:
Many thanks for the link, I follow the urban plumber on YouTube as he’s a good watch regardless.

I’ve ponder this all again and have reversed my first thought, thinking an open vented system might be simpler, cheaper and more reliable. I think using the Vaillant controls is still need to fully optimise the boiler in the separate DHW & CH output modes.
Am I right in thinking I’ll need a
SensoHome wireless
VR66/2 centre
VT10 thermistor for the tank
And the glow worm wireless outdoor temp sensor linked to the SensoHome?

Quick query regards ebus do I still need to hardwire the VR66 to the boiler or can I use a RF module on the VR66 to communicate with the boiler?
Click to expand...

Vaillant controls are a mystery to me, I'm afraid. I only know the very basics from reading about them on here.

It might be worth starting a new thread to discuss the most recent information about how to do priority hot water on Vaillant and also any questions about controls and EBus.
 
I thought I’d update this rather than start a similar thread.

I’ve reached an agreement with BG re the controls for system. They have agreed to not fit the Hive controls and will fit Vaillant controls that I supply and commission the system.

It’ll be open vent Ecotec Plus 418 with the Gledhills SSL 210ltr unvented cylinder. Although the 418 was based on the simple 230v controls as they add 3kw for hot water on top of their calculations. Whereas the 415 can produce 18kw for a DHW demand.
Any thoughts on dropping down to a 415, or just range rating the 418?

Now the main questions, perhaps @ScottishGasMan can help?

I think I need this package for Control; VRC720f SensoComfort. This is a package that has a remote wireless (rf) wall mounted controller/room stat, rf outside temperature sensor and an rf communication receiver unit for connecting to the boiler. Vaillant part No; 0010036820.

For wiring centre I think I need the wiring centre VR66/2. Vaillant part no; 002013585

The trade off for all of this is I own the controls hardware and hence no warranty on them via BG.
 
Another quick one, the wiring centre…. Seems that the same part number seems to cover both VR66 and VR66/2?

Plenty of VR66 at good prices out there not many VR66/2 showing up though?

Am I right in thinking for a simple single heating zone and DHW via a tank the VR66 does the same job and is compatible with the VRC720F sensoComfort?
 
Thats a shame, a Vaillant fitter would get you 10 years warranty on boiler and the controls if they supplied them.

Depends what you want. The 415 will modulate down a little bit more that the 418 (only about 300-500Watts in it), which means it will cycle on and off a little bit less. However on the vaillant controls the 418 can boost to 25kw for DHW so quick reheat of hot water tank.

Needs to be the VR66/2. And make sure cylinder has a pocket for a sensor probe.

For non-Vaillant unvented cylinders the DHW zone valves live feed from the VR66/2 should be wired through the cylinders own high limit (overheat thermostat) to complie with G3 regulations. And then the Vaillant VR10 sensor probe into a pocket so that you can read and adjust water temperature from the sensoCOMFORT and run legionella purges if you want to.

Obviously you can set different outputs for heating and hot water and also different flow temperatures.

I run the sensoCOMFORT on a 618 (System boiler) It's locked to 6kW max output and over the last two winters have adjusted the heat curve so that it runs very low flow temperatures and condenses constantly when running. Even on hot water. I keep my cylinder at 48 degrees, its heated with a flow temp of 55 degrees, and every friday the control heats the cylinder upto 65 for disinfection control.
 
Re the VR66/2 I’ve read on here a few times the part number between that and the VR66 is the same. Others have also reported that they function the same in monozone mode acting effectively as a VR65 legacy mode.
I suppose my question is if the part numbers are the same how do I know whether I’ve been supplied with a /2 or not?

Another quick query is there a web link to a S plan wiring diagram and the interaction of the VR66, specifically the 230v side, like a traditional 10 way JB but including the wiring to from the VR too?
I ask as the Vaillant information seem a bit light on integrated wiring.
The output from the VR provides the switched live for the zone valves (via the cutoffs for HW) what happens to the white SL output from the valve micro switch, is it not used? Does the neutral of the zone output from the VR just link to the other neutrals in the 10 way etc…
 
Interestingly went to the Mr Central Heating shop, the VR66 advertised and picked up is actually the VR66/2 on the box, so that’s comforting.

Also the VRC720F is now labelled the VRC720F/2 too.
I can but presume the /2 denotes in both cases it’s the updated variant despite the Vaillant part numbers being the same as previous iterations?
Anyone know the differences for the /2 variants? Updated Firmware perhaps?

Re the query about the 230v wires to the 2 port valves, can I assume the vaillant controls only use the 3 wires(LNE) and the other 2 are not used?
From a controls perspective it’s open loop and no positive feedback on the position of the valve is used, strange imhe? Anyone know why they chose to ignore these standard contacts?
 
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