Vaillant ecotec green iq 843 or unvented?

[robwelsh458]

Hello all. ..first post so please forgive the lack of technical knowledge.

I'm looking at replacing an old potterton 100e regular boiler connected to a unvented traditional system.

Can't decide between the above high powered combi or going unvented with a ecotec 637 system boiler and 210 glendhill cylinder.

It seems most heating engineers prefer the unvented but I'm not sure it's a great fit for our place.

20 litres per min mains flow
Engineer said that there was 3 bar with the outside and kitchen tap running.

We have a large 15 rad house but well insulated. Current 100e which is 100000btu/ 30kw does the rads fine so I'm concerned that the 37kw system boiler may be overkill.

2 bathroom house and will want to run a decent shower in both.

However, at the moment there is only 2 of us living here. It is rare that both of us use the existing electric showers daily due to showering at the gym etc.

I guess I'm wondering if it's a waste of time heating and storing the water when it won't even be used daily, let alone 2 showers at the same time.

Also, if my incoming is 20 lpm am I really going to get the full benefit of an unvented system when the 843 combi can do 17.8 lpm anyway!

Anyone got any experience of the new ecotec 843?


Oh. .and 3600 for the combi. ..4320 for the system (both with vsmart)

Any views greatly appreciated

 

[robwelsh458]

*traditional vented system.

 

[ShaunCorbs]

I would go unvented all day long , as if you run a hot tap while someone is in the shower either yours will run cold or there shower will be reduced,

If you have the space look at a storage combi Viessmann 222f

 

[robwelsh458]

Hi Shaun. . Thanks for the speedy reply.

Would the reduction not happen with an unvented system? That was something I wanted to ask in the original post but it was already pretty long!

Funny you should mention the 222f.. I did like the look of that when I was searching


Can you believe I emailed 2 installers from the viessmann site and neither responded!

Majority of the local fitters don't do them but might try again.

 

[muggles]

Go unvented, I think you'll have a rather better incoming flow rate than 20l/min if you've still got 3 bar with two taps running. I suspect your chap doesn't quite know how to test flow rate properly. Personally I'd go with an Intergas ECO RF 30 coupled to a Joule unvented cylinder, wired for hot water priority, which will give you an excellent system with super-fast reheat times on the cylinder at a substantial discount over the 637 (which I agree is likely to be overkill) and Gledhill. You can get away with a smaller cylinder with the Intergas as well, and less hot water stored is less wasted. Alternatively, you could use it as a combi and run a split system - combi side can heat the water for the taps you use regularly, and you have a hot water cylinder to run your showers which is just heated when you need it. This does depend a bit on the layout of your house though

 

[ShaunCorbs]

Hi Shaun. . Thanks for the speedy reply.

Would the reduction not happen with an unvented system? That was something I wanted to ask in the original post but it was already pretty long!

Funny you should mention the 222f.. I did like the look of that when I was searching


Can you believe I emailed 2 installers from the viessmann site and neither responded!

Majority of the local fitters don't do them but might try again.

yep wont happen with an unvented system as it can supply more than one outlet

where are you located?

 

[robwelsh458]

yep wont happen with an unvented system as it can supply more than one outlet

where are you located?

Staffordshire

 

[robwelsh458]

Go unvented, I think you'll have a rather better incoming flow rate than 20l/min if you've still got 3 bar with two taps running. I suspect your chap doesn't quite know how to test flow rate properly. Personally I'd go with an Intergas ECO RF 30 coupled to a Joule unvented cylinder, wired for hot water priority, which will give you an excellent system with super-fast reheat times on the cylinder at a substantial discount over the 637 (which I agree is likely to be overkill) and Gledhill. You can get away with a smaller cylinder with the Intergas as well, and less hot water stored is less wasted. Alternatively, you could use it as a combi and run a split system - combi side can heat the water for the taps you use regularly, and you have a hot water cylinder to run your showers which is just heated when you need it. This does depend a bit on the layout of your house though

Very interesting..didn't realise they were so flexible. .

And appear to condense full time in CH and DHW mode. How does it manage that! ?

 

[AMGasServices]

I'm pretty sure the new worcester I system boiler has 2 returns. You could connect an unvented hot water cylinder to that without zone valve etc.... You can control everything from the boiler.

 

[Gasmk1]

viessmann 100 4 pipe no 2 port needed for the hot water has integral diverter valve.

 

[muggles]

Very interesting..didn't realise they were so flexible. .

And appear to condense full time in CH and DHW mode. How does it manage that! ?

A well designed heat exchanger coupled to some very good software

 

[Scott_D]

Combi if you want to gain some space and save some money
Unvented if you don't want to compromise on hot water

 

[robwelsh458]

Thank you all for your input.

I'm leaning towards an unvented set up but I'm a bit concerned about the flow.

Had a look and I've got an old lead pipe which looks like 22mm but likely to be much smaller inside.

It also immediately goes to 15mm for the meter and all pipes after that seem to be 15 mm as do the ones in the loft to the existing set up. .

I think most unvented need 22mm?

I'm going to get a quote for upgrading the mains as I suspect that will massively increase the flow and give be the full benefit from an unvented set up.

Most threads seem to suggest not to bother if you haven't got 25lts dynamic flow?

Anyone got a ballpark per metre figure for a pipe upgrade? ... it's a free connection service from the road to the edge of the boundary with seven trent.

 

[ShaunCorbs]

Depends it's like a poke in the dark 300-2k

But if your whiling to do the digging it won't be that much but as that's where most of the labour goes

 

[muggles]

Sounds like a pipe upgrade could be a great idea if you're on old lead pipe, you should see a significant improvement. Cost-wise, MDPE is about 50p per metre. You need to dig a trench 3 feet deep from your boundary to your house. If you do this yourself it's a cheap job. You then need to find a way of getting the pipe inside your house to an acceptable (to you) location for your internal stopcock and oncoming pipework.

 

[robwelsh458]

Thanks guys.
It's going to be a pain to do but I might as well get a quote.

The plumber mentioned an accumulator. ..
I'm assuming that would also help. ..just only for the amount of water in it?

Anyone got any idea how much a 300ltr one might improve the flow or is there no real way of knowing?

Might be considerably cheaper!

 

[Chuck]

The plumber mentioned an accumulator. ..
I'm assuming that would also help. ..just only for the amount of water in it?
Anyone got any idea how much a 300ltr one might improve the flow or is there no real way of knowing?

Roughly speaking, it would deliver its specified boost (typically half the nominal size) at a very high flow rate and then you'd have to wait for it to refill. A modest bath needs say 75 litres. A shower can range from 25 litres (the person who pays the bills) to 150 litres (teenager )

I'd recommend upgrading the incoming main if you have the choice. An accumumlator is a last resort IMO. Expensive, big and heavy and space is at a premium in most UK homes.

 

[muggles]

I agree with Chuck - an accumulator will take up a lot of room and is quite expensive. If upgrading the mains is a viable option, do that

 

[Ant Parkes]

We are basing this off hot water output, however the OP mentions they have electric showers in each bathroom, not mixers.

I know they have kitchen taps among other hot water outlets however, the main concern is usually shower or bath?

Still fairly new so apologies if missing something out here.

 

[robwelsh458]

Yes still have electric at the moment but both will be going and being replaced by mixers in due course.

I just want to avoid the situation where we can't viably use both at the same time with a half decent flow. ..or where it cuts out if the washing machine comes on.

Plumber very helpful and is going to look at a quote for the pipe.

It might all be OK with no pipe upgrade and no accumulator but who knows!

Thanks all for the input on the accumulator. ..

It would be in the loft so space not an issue. ...but the weight added to the unvented is certainly something to think about!

 

[Ant Parkes]

@robwelsh458, noted. If that is the case and you will be moving from electric showers to mixers then the above recommendations stand firm.