Plumbing heating design etc

[bassanclan]

I am looking for feedback and comments on the design of this heating system.

5/6 bedroom - 2 ensuites with showers, 1 bathroom with a bath, 1 bathroom with a bath and a shower, 1 ground floor shower room

 

Boiler - mains gas - Ideal Mexico 28Kw (already insitu fitted in boiler room circa 2012)

PV - 4KW facing SSW

Wood burning stove - Dunsley Yorkshire multifuel with back boiler (up to 7.9KW to water) (to be located in lounge)

Thermal Store - Xcel heat bank 500litre (to be located in airing cupboard) with external heat plate exchanger. Tappings for UFH for ground floor and first floor (yellow areas)

Cold water accumulator - 500litre to be fitted in the loft

 

system design.pdf

 

Incoming water is approx 2.5bar static and 18 litres per minute.

The desire is to be able to run 3 showers @ 10-12 litres p/m each simultaneously.

 

Ideally in the winter the wood burner will be a lot, heating up the thermal store and during the summer the PV will be diverted to heat the thermal store

[MikeSharp01]

Hi @bassanclan looks very interesting. First observation is that you only have 18l/min from the mains but are asking for 30-36 if you are running three showers at 10-12 l/min. To achieve that you either need to beef up the feed or perhaps have some intermediate storage and a pump. 

[Nickfromwales]

16 minutes ago, MikeSharp01 said:

Hi @bassanclan looks very interesting. First observation is that you only have 18l/min from the mains but are asking for 30-36 if you are running three showers at 10-12 l/min. To achieve that you either need to beef up the feed or perhaps have some intermediate storage and a pump. 

?

Thats what the above mentioned accumulator is for me old China mug. . 

 

@bassanclan

The major ( possible ) flaw here is the plate heat exchanger. Is it 15mm in and 15mm out for DHW?  

[MikeSharp01]

@Nickfromwales Ok I get it.

[bassanclan]

Yes the cold water accumulator is to help boost the flow rate.

I don't know about the size of the plate heat exchanger connections, it is not detailed on the spec sheet, I will ring up and find out tomorrow, but it says it is capable of 45 litres per minute.

 

I'm also looking at the Joule Cyclone Thermal Store 2.0 which can get flow rates up to 33 litres per minute.

 

Apparently you can fit two plate heat exchangers if you want to increase flow rates.

[PeterW]

I don't think 500 litres will be enough - you will have to watch the shower length as despite the boiler kicking in, a 28Kw boiler isn't going to keep that tank hot for long. 

 

Any chance of putting the accumulator on the ground floor as that's a lot of weight in an attic. 

[bassanclan]

I've already put some steels up in the loft which will carry the weight of the accumulator.

I am going to have to stick in another steel at first floor level to take the weight of the thermal store

 

I am looking at a few other manufacturers with a view to getting a 700 litre store, but I am restricted by a diameter of approx 750mm

[PeterW]

What about a UVC with a preheat buffer..?? 

[AliG]

Depending on the size of the heat exchanger 500l should be more than enough. A 20kW heat exchanger could heat 5-600l of water by 30C every hour. It's unlikely that you use hot water at more than that rate. @PeterW is right though, a larger boiler might help if you want to run the heating and generate hot water at the same time.

 

Does the boiler heat the thermal store in the same way as an indirect cylinder or is there a coil in the store as indirect heating will struggle to keep up with the hot water output of the store?

 

Also the hotter you store the water the more equivalent capacity you will have although it will modestly increase standing losses.

 

 

Edited June 5, 2017 by AliG

[bassanclan]

The wood burning stove manufacturers give this layout with their "neutraliser" to connect a wood burner to an unvented cylinder, which was my initial starting point, but the thermal store seemed like a "proper" solution.

 

I don't really have room for a decent sized buffer tank and seperate uvc unless they make them stackable?

layout2.pdf

[Nickfromwales]

The acc'r @ 350kg when loaded ( 50-60% water + vessel ) is a lump, agreed. Better off in the corner of the garage if there is one? Or, can you slice that corner of the study so the boiler room is bigger?

Tbh, even with the 500l accumulator your borderline due to the number of hot AND cold outlets. Last job I did on this scale had a pair of 500l acc'rs ( so about 500l actual stored water combined ) which is what I'd recommend here if you wish to just use the dynamic of the cold mains, ie a passive install ( no pumps and break tanks ). 

To do preheated you'll need at least an additional 300l TS with 46kw coil to give any meaningful uplift, so agree with @PeterW, the boiler needs binning ( sell it off ) and upgrading, as you still couldn't match demand even with the preheat with only 28kw on tap. 

Upsizing considerably to say a 700 or 800l TS may 1) allow you to keep the boiler and 2) run at low enough temps to keep the boiler condensing ( very important for efficient running costs ) but you still have the issue of space heating  and the property is too big to go DHW priority "w plan". 

For hot and cold water, this needs a whopper TBH. 3 decent simultaneous showers is a big remit, especially with white goods drawing water / toilets being flushed simultaneously too. Remember that at 2.5 bar you'll be VERY lucky to fill the acc'r half full. 

[Nickfromwales]

1 minute ago, bassanclan said:

The wood burning stove manufacturers give this layout with their "neutraliser" to connect a wood burner to an unvented cylinder, which was my initial starting point, but the thermal store seemed like a "proper" solution.

 

I don't really have room for a decent sized buffer tank and seperate uvc unless they make them stackable?

layout2.pdf

Whatever you do, don't put the heat loss rad in the bathroom. Anyone who's unfortunate enough to come into contact with that will need hospital treatment. 

Id put that in the attic and dump the unwanted excess ( from burning solid fuel ) to atmosphere. 

[bassanclan]

So it turned out that the fresh water module plate heat exchanger is only 22mm.

However I have found a very similar system made by Lovato distributed by www.woodboilersupplies.co.uk but with 1" connections rather than 3/4"

I will investigate more tomorrow.

[Nickfromwales]

With a bigger TS and a correctly sized boiler you'll be able to go for an integral instantaneous DHW coil and ditch the external PHE. I'd recommend that approach as it's far less complicated, no additional pumps / flow switches etc and way less standing losses from the aforementioned. 

Doubling up on PHE's will, however, give you better flow rates for DHW, but 3 showers will run off a 46kw 28mm Telford TS ( coil heat exchanger ) so think long and hard about your DHW consumption and choose wisely. . 

[Onoff]

1 hour ago, Nickfromwales said:

With a bigger TS and a correctly sized boiler you'll be able to go for an integral instantaneous DHW coil and ditch the external PHE. I'd recommend that approach as it's far less complicated, no additional pumps / flow switches etc and way less standing losses from the aforementioned. 

Doubling up on PHE's will, however, give you better flow rates for DHW, but 3 showers will run off a 46kw 28mm Telford TS ( coil heat exchanger ) so thinknling and hard about your DHW consumption and choose wisely. . 

 

This "correctly sized" boiler. My oil Bluebird is 43.7 / 48.4kw. Suitable for the same TS? Cheers.

[Nickfromwales]

24 minutes ago, Onoff said:

 

This "correctly sized" boiler. My oil Bluebird is 43.7 / 48.4kw. Suitable for the same TS? Cheers.

Yup. She's a beast...even more reason to fit a chunky buffer and UVC or a TS with DHW coil . 

A big TS will work with a smaller boiler if it's not charged via a coil. I almost always spec the TS to be wet fed so the heated water from the boiler is circulated around the TS entering at the very top and exiting via the lowest point. That way you don't suffer the constraints of the exchange rate ( dictated by the surface area of the coil ). 

[bassanclan]

I'm struggling to find thermal stores over 500l which are under 800mm wide. (unless they have no insulation and then what is the point!)

[Nickfromwales]

Let me make a call

[bassanclan]

There is the Jaspi GTV 700

http://jaspi.uk/gtv.html

 

but then the hot water in/out is in 22mm again

[le-cerveau]

The Akvaterm GEO AKVA 750 is 1050mm wide but you can specify detachable side panels (150mm thick each) so takes it down to 750mm wide.  It is class ERP class B!

 

However it only has a 22mm water connection

[Nickfromwales]

Need to narrow this down before Telford can quote. I'll bump this later. 

[PeterW]

7 hours ago, bassanclan said:

I'm struggling to find thermal stores over 500l which are under 800mm wide. (unless they have no insulation and then what is the point!)

 

Ring Newark Copper Cylinders and ask for Mark - will make you whatever you want with tappings to suit you. 

 

 http://www.newarkcoppercylinder.co.uk/thermalstore.html

 

 

[Nickfromwales]

1 hour ago, PeterW said:

 

Ring Newark Copper Cylinders and ask for Mark - will make you whatever you want with tappings to suit you. 

 

 http://www.newarkcoppercylinder.co.uk/thermalstore.html

 

 

Do they do stainless too?

[PeterW]

Just now, Nickfromwales said:

Do they do stainless too?

 

Yep - anything you want ..! Priced me a stainless 350 with a large surface area HP coil too - not that bad on price. 

[bassanclan]

Newark might be a good option.

I will ring up and find out.

I still think I prefer the idea of an external PHE though.