Indirect Unvented cylinder, Combi Boiler and Nest Thermostat

[Chris1012]

We have just had an indirect unvented cylinder (250l Vertical Telford Tempest) installed along with a nest v3 thermostat.
The plumber was able to modify our existing combi boiler, so it runs like a system boiler.

I am trying to understand how it works as currently the plumber has set it to come on for 2 hours each day (1hour between 5am-6am and 5pm-6pm).
During these times, the boiler remains continuously on and only switches off after the hour mark.
Is this right?
I would have thought during the set times that the boiler should come on, it would work in connection with the cylinders thermostat so once the waters heat got to a set level, the boiler will shut off.

The cylinders booklet states it takes 28min for it to heat up.

Could someone please advise on how this setup should be working and if there is anything I could do to make it more efficient, then it currently is?

Thank you

 

[ShaunCorbs]

Any pictures of the set up ?

 

[Chris1012]

Any pictures of the set up ?

I can take some but the boiler is located in the kitchen and there is shelf above the pipes, so wont be able to see anything and the cylinder in the basement.

 

[Chris1012]

Another potential issue is that it takes 45-60seconds to get hot water from the taps.
The route for the mains water supply enter the kitchen, goes through a water softener then travels 5 meters to the cylinder and then is routed to the rest of the house...

 

[sparkie30]

You are correct the boiler should turn off when cylinder stat satisfied.

Should be wired like this from nest to cyl stat,
Stat to 2 or 3 port valve and then to boiler.

Sounds like plumber has wired straight from nest to boiler thats the reason is on for full hour.

Good luck

 

[Chris1012]

Looks like the gas light comes on the boiler during the schedule to heat the tank but once it reaches the correct temp, the gas light goes off (so does the flame) but the boiler continues to run with the rad light on until the scheduled time is over.
Does this sound right?

Also does the 45sec heat up time to each tap and shower, sound right?
Length to each service is no more than 6meters, using a 22mm flexi pipe

 

[Scott_D]

Pictures needed

 

[Bibbs118]

Combi on an invented, I've scene these sort of installs before and your asking for trouble in my opinion.

If I where you, I'd ring the boiler manufacturers and ask them if their combi can be installed on a invented, I very much doubt they will say yes.

And if they do say yes, ask them to email you a wiring and piping diagram, if they are unable to provide you with a drawing, then, despite the tech help line saying it is "possible", without a drawing it is NOT approved. And probably dangerous.

 

[ShaunCorbs]

Combi on an invented, I've scene these sort of installs before and your asking for trouble in my opinion.

If I where you, I'd ring the boiler manufacturers and ask them if their combi can be installed on a invented, I very much doubt they will say yes.

And if they do say yes, ask them to email you a wiring and piping diagram, if they are unable to provide you with a drawing, then, despite the tech help line saying it is "possible", without a drawing it is NOT approved. And probably dangerous.

Why it's just another heat load prividing you have a draw off eg a tap off the combi your fine

 

[Bibbs118]

Why it's just another heat load prividing you have a draw off eg a tap off the combi your fine

Because without a drawing, it not installed to manufacturers instructions.

Min AR.

Always say on first page, MUST BE INSTALLED TO MANUFACTURERS INSTRUCTIONS.

 

[ShaunCorbs]

Because without a drawing, it not installed to manufacturers instructions.

Min AR.

Always say on first page, MUST BE INSTALLED TO MANUFACTURERS INSTRUCTIONS.

Your joking right nothing to do with gsiur/p

 

[Bibbs118]

Your joking right nothing to do with gsiur

No, if it say, MUST BE INSTALLED TO MANUFACTURERS INSTRUCTIONS, and the manufacturers can't provide INSTRUCTIONS how to install an invented on a combi then you are NOT REPEAT NOT installing it to MIs.

If it says MUST BE INSTALLED TO MANUFACTURERS INSTRUCTIONS unless your bolting a invented cylinder to combi, in that case you can just make it as you go along, or ask your mate how to do it. Then it's fine.

 

[Bibbs118]

Ask yourself this question.

Has it been installed to MIs?

If MIs don't give you INSTRUCTIONS how to do a invented combi install.......Then it's not been installed to MIs has it.

 

[ShaunCorbs]

How is any of that ar

guess they tell you what brand / type of rads to install as well

 

[Bibbs118]

You are correct the boiler should turn off when cylinder stat satisfied.

Should be wired like this from nest to cyl stat,
Stat to 2 or 3 port valve and then to boiler.

Sounds like plumber has wired straight from nest to boiler thats the reason is on for full hour.

Good luck

So thats no temperature control or safety shut off on an invented cylinder!!!! What could possibly go wrong?

 

[ShaunCorbs]

So thats no temperature control or safety shut off on an invented cylinder!!!! What could possibly go wrong?

And how does that make it a nono to install with a combi boiler

Ffs

 

[Bibbs118]

How is any of that ar

guess they tell you what brand / type of rads to install as well

All boilers are designed to be installed as per MIs, if it's not installed to MIs and it's ncs are no longer applicable then it's AR.

SERIOUSLY..........THERE IS A REASON WHY ON THE FIRST PAGE OF EVERY INSTRUCTION MANUAL IT SAYS MUST BE INSTALLED AS PER INSTRUCTIONS. Never say, if you think you know better than us ( manufacturers) just crack on, do what want, install it how you think.

Do you not remember being constantly told during training ALWAYS FOLLOW MIs?

 

[ShaunCorbs]

All boilers are designed to be installed as per MIs, if it's not installed to MIs and it's ncs are no longer applicable then it's AR.

SERIOUSLY...THERE IS A REASON WHY ON THE FIRST PAGE OF EVERY INSTRUCTION MANUAL IT SAYS MUST BE INSTALLED AS PER INSTRUCTIONS. Never say, if you think you know better than us ( manufacturers) just crack on, do what want, install it how you think.

Do you not remember being constantly told during training ALWAYS FOLLOW MIs?

Will put it this way

Does it say not to install one in combination with an unvented cylinder no it doesn't

Not everything is in the manufacturers instructions

 

[Bibbs118]

And how does that make it a nono to install with a combi boiler

Ffs

Because unless the manufacturers of the combi say it can be installed on an unvented they how can you follow the mis?

 

[ShaunCorbs]

Because unless the manufacturers of the combi say it can be installed on an unvented they how can you follow the mis?

They don't govern/ say what type of heat load you must have

I could install one to a pool still would be installed correctly and manufacturer would still warrenty it

 

[Bibbs118]

Will put it this way

Does it say not to install one in combination with an unvented cylinder no it doesn't


Not everything is in the manufacturers instructions

This is why I did write, ring them an ask for a drawing, no drawing and you can not be following MIs, and the instructions ALWAYS say MUST BE INSTALLED TO MANUFACTURERS INSTRUCTIONS.

AND NEVER SAY, unless you think you know better.

 

[ShaunCorbs]

I give up

@Harvest Fields @townfanjon @Best @sammathias @hammers4spanner @Riley @jtsplumbing

Am I wrong again ?

 

[Bibbs118]

I give up

@Harvest Fields @townfanjon @Best @sammathias @hammers4spanner @Riley @jtsplumbing

Am I wrong again ?

Yes or no?

Do you have to install to MIs?

 

[Harvest Fields]

Why it's just another heat load prividing you have a draw off eg a tap off the combi your fine

I have a regular customer who has moved house to a house with a Vaillant combi on a Vaillant unvented cylinder. He had me in to have a look but as Shaun has this this ones hot supply has just been capped off. So I am going to run a short run of pipe and a hot tap to the garage or inside the utility.

 

[Harvest Fields]

I give up

@Harvest Fields @townfanjon @Best @sammathias @hammers4spanner @Riley @jtsplumbing

Am I wrong again ?

I’m with you mate. Next he will be saying you cannot Zone a heating circuit? No difference between another zone and a zone for the cylinder. Seen it done loads. Would make sure it has a hot water draw off though. I spoke to Vaillant on the one my customer has as there is loads of work needed and they said just fix the issues and make sure it has a hot water draw off. I’m happy with that.

 

[Harvest Fields]

Yes or no?

Do you have to install to MIs?

I’m sure there is nothing in the Vaillant manual that shows you how to pipe in 2 zones for a larger house yet Vaillant say you can fit their 938 into a 4 bed semi with a bathroom and ensuite. So does that mean on a new build you would put the whole system on one zone? @Bibbs118

 

[Bibbs118]

Look, you are missing the point, one, seeing it done loads does not mean it's OK, two, vaillant will have a drawing for an s plan plus, three, doing it so it's safe in your mind is not the same as installing to MIs.

And four. Yes or No, do you have to install to MIs?????

If there is no instructions then how can you follow them, this is why I did say, get a drawing from the manufacturers .

 

[hammers4spanner]

You can put a combi on unvented have seen it done numourous times . One hot draw off to utility basin in most cases.

Even done a greenstar with a worcester enginger couple year ago.
If anyone would know about their product they would.

As said another heat source.

 

[Harvest Fields]

Look, you are missing the point, one, seeing it done loads does not mean it's OK, two, vaillant will have a drawing for an s plan plus, three, doing it so it's safe in your mind is not the same as installing to MIs.

And four. Yes or No, do you have to install to MIs?????

If there is no instructions then how can you follow them, this is why I did say, get a drawing from the manufacturers .

You’ve answered you own question. If they have a schematic for an s plan then yes you can.

 

[Bibbs118]

You can put a combi on unvented have seen it done numourous times . One hot draw off to utility basin in most cases.

Even done a greenstar with a worcester enginger couple year ago.
If anyone would know about their product they would.

As said another heat source.

Please re read what put. Seeing it loads off times does not meant it's OK, this is why I did say get a drawing.

And , s plan zones don't require temp and pressure relief of or a temp cut off do they? So not the same .

 

[Bibbs118]

Yes or no, do you have to install to MIs?

 

[ShaunCorbs]

Ffs

 

[Harvest Fields]

Think we have to just disagree on this one @ShaunCorbs @Bibbs118. I trust what Vaillant told me and that’s that.

 

[Harvest Fields]

Please re read what put. Seeing it loads off times does not meant it's OK, this is why I did say get a drawing.

And , s plan zones don't require temp and pressure relief of or a temp cut off do they? So not the same .

No idea what world you live in though mate.

 

[Bibbs118]

Think we have to just disagree on this one @ShaunCorbs @Bibbs118. I trust what Vaillant told me and that’s that.

Being told something is not the same has following the MIs, what am saying is, if you can't get a drawing then it's not ok .

Because it's impossible to follow MIs without having the MIs .


Just ask yourself the yes or no question and the answer will tell you what I'm saying is correct .

Do you have to install to MIs? Yes or NO