Help needed to design energy efficient solution

[mandm65]

Guys looking at energy efficient CH/HW/Wet-UFH would you consider below mentioned items as part of efficient system? The items required for a 3 bed house with one bath and 3 shower units, ideally mains fed. We have used Vaillant boiler before and are happy with that so we would like to stay with Vaillant, unless there a better energy efficient solution available?

Our proposed solution consist of:

Vaillant ecoTEC plus 630 system boiler
Vaillant uniSTOR indirect unvented cylinder
Additional Expansion Vessel
Digital weather compensator
Some sort of Control centre?
Low Loss Header for combining Rad/UFH zones
Naturally the UFH (multi zones) would be on a separate loop.

I am not clear on how many programmable thermostats would we need. Do we need multiple programmable thermostats for each UFH zone plus CH and HW? I am sure there must be a better option?
Can anyone help me or suggest a suitable solution which can help us to meet our requirements?
Thanks in advance
Cheers

 

[Dan Robinson]

Start at the start.

Why do you want a 30kW boiler?


I would suggest 2 zones with bathroom/towel rail on the hot water primary circuit.

 

[mandm65]

Thanks fo your response/help

Start at the start.

Why do you want a 30kW boiler?

Well thats what Vaillant website suggested, no prefrence really.

I would suggest 2 zones with bathroom/towel rail on the hot water primary circuit.

Yep, that would have been ideal, i checked the zone limit and realised that its best to opt for 3 zones as the coverage is approx 6x5.5 so it would be best to split that zone.

Any thoughts on control unit/ thermostats?

 

[88v8]

If you check your summer/winter gas usage, you may deduce that despite having a well insulated cylinder, a significant portion of your bill goes on water heating.

We saved a good amount by having two stats on our cylinder; one about a third the way from the top, the other a third up from the bottom. In the kitchen we had a switch to swap between them.
We found that nearly all the time we could run on the top stat, so we weren't heating the whole cylinder. The only time we needed the bottom stat was if we intended to take two baths back-to-back.

A cheap feature to install and a good saving.

Ivor

 

[mandm65]

If you check your summer/winter gas usage, you may deduce that despite having a well insulated cylinder, a significant portion of your bill goes on water heating.

We saved a good amount by having two stats on our cylinder; one about a third the way from the top, the other a third up from the bottom. In the kitchen we had a switch to swap between them.
We found that nearly all the time we could run on the top stat, so we weren't heating the whole cylinder. The only time we needed the bottom stat was if we intended to take two baths back-to-back.

A cheap feature to install and a good saving.

Ivor

Thanks Ivor your post, wow what a shrewd yet simple solution, i would like to take a look at that, can we have this dual stats on Vaillant unvented cylinder or this option is specific to a cylinder?
Secondly can i know more about this swap switch/installation etc?
Cheers

 

[Dan Robinson]

Not really possible on the unistorwithout cutting into the shell. Which may void the warranty.


Easy enough to do with a twin coil cylinder. Bit pointless imho in this situation. Much better to size the cylinder and boiler properly.


3 bed semi? 18kw will be plenty with a 180 or 210 litre cylinder.

My 4 bed detached only has a 15kw boiler and soon to be either a 150 or 180 litre cylinder.

 

[88v8]

.....can we have this dual stats on Vaillant unvented cylinder or this option is specific to a cylinder?

Secondly can i know more about this swap switch/installation etc?

The switch was a double-pole which swapped the live feed from one stat to the other. For convenience, the switch was in the kitchen but could be anywhere.

We had a standard indirect cylinder with sprayed foam insulation, we just cut two pockets in the insulation for the stats.

Whether it's pointless as Dan says, depends on your household situation. With just the two of us it made complete sense as we didn't often need a full cylinder of hot water - if you have a bigger household and constantly need lashings of hot water it may not be worth bothering.
But I do think that when it comes to economy, the heating side receives overmuch attention, while the hot water tends to be pretty much ignored.

Cheapest save on heating costs is well-fitting curtains, and shutting them at night, yet one only has to walk down any street of an evening to see it doesn't often happen :}

Ivor

 

[mandm65]

Thanks Dan/Ivor for your input.
I guess i rule out the switch option, like Dan said you would not want to void the cylinder warranty.
Does it make sense to have over size boiler now knowing that within couple of years we have loft conversion planned?
Does it cost lot more if you have over size cylinder, Dan suggested that 210L would be fine for 3 beds, i was thinking around 310L as we all have tendency to take showers frequntly and sometime twice daily, specially after a workout.

 

[Dan Robinson]

Size the boiler for the heating/planned heating.

Cylinders will reheat in 20 minutes.

310 litres is crazy.

Over sizing the boiler is counter productive.

Running costs of an oversized cylinder are negligible, but space and capital costs are the consideration.

 

[mandm65]

Running costs of an oversized cylinder are negligible, but space and capital costs are the consideration.

If the Running costs are negligible then i can overcome the space and initial cost.

While you appear quite knowledge with the subject so let me ask you something which making me go round in circles.
As you can see from the above setup that I will have cluster of thermostats (3 zones UFH, HW and CH) so do I have to have thermostats for all controls or there is better option?
Appreciate your input.
Cheers

 

[Dan Robinson]

Vaillants own in house control kits will do what you... can't remember off the top of my head is you need remote sensors of if the boiler module will do it all - Alec1 here is better in thei department than I.

 

[mandm65]

Thanks Dan, awaiting eagerly for Alec1’ response.

 

[tiptoptrump]

Have a look for a control system like Danfoss Link. Together with electronic trv's (Living Connect) & Hydronic controllers for wet ufh. All controlled from one small control unit. Not cheap but a very neat package and user friendly.

 

[gazdaz36]

Is this a new build?

 

[mandm65]

Have a look for a control system like Danfoss Link. Together with electronic trv's (Living Connect) & Hydronic controllers for wet ufh. All controlled from one small control unit. Not cheap but a very neat package and user friendly.

Thanks, will take a look.