Gravity Buffer

[marshian]

@Nickfromwales any chance you can fix the replies within quotes by @Ann D Mann - makes it hard to read…..

 

@Ann D Mann reply outside/below the quoted box please or your replies get buried in the quotes and they need to be expanded to read

[SteamyTea]

31 minutes ago, Ann D Mann said:

If I could stress the content of the OP. 

https://en.m.wikipedia.org/wiki/Rube_Goldberg_machine

 

 

 

[marshian]

36 minutes ago, Ann D Mann said:

 

If i could stress the content of the OP. 

The Stove is decorative.  We never intended it to be a primary heat source.  We are "waste not want not " people and it seemed silly  NOT to try and capture some heat with a back boiler.

 

so as “waste not want not” people surely you can see that adding

 

1. A boat load of extra cost

2. A shed load of complexity

 

and probably

 

3. A bucket of safety risk (kettling a HE behind a stove leading to steam which considerably ramps up the pressure in a circuit and that would be “sub oprimal” 

 

Would not be a “waste not want not” solution 

 

Treat the stove as a stove and let another heat source do what it should be good at

 

all in my opinion of course you will do what you want at the end of the day but remember one thing - you came on here asking for advice  If you came on here asking for your options to be validated you should have said so at the start - no-one would have responded

[marshian]

9 minutes ago, SteamyTea said:

https://en.m.wikipedia.org/wiki/Rube_Goldberg_machine

 

 

 

much better reply than mine - said it all so well 

 

bravo @SteamyTea

[marshian]

On the plus side @Ann D Mann credit is due for the choice of user name - did make me chuckle a liitle

[Nickfromwales]

@Ann D Mann

 

The responses here are constructive criticism, just honest opinions shared here as you’ve asked the question(s).

 

“Waste not” is fine, every single person on here is of exactly the same mindset, but you wouldn’t spend £1 to earn 30p would you?

 

The shear cost and complexity, upheaval, maintenance for life, and inconvenience of burning wood routinely to then have this make ANY kind of sense, makes no sense at all.

 

The money you’ll put into this, just put that into a glass jar and label it “GAS” and spend the money more wisely.

 

When the WBS is lit, try and maximise the benefit by opening doors up and using the convection fans to get heat shifted about the property.

 

I'm a fan of crazy ideas, but not when the cost outweighs the benefit.   

[Ann D Mann]

Dear members

 

We hoped to get frank responses and they have been very thought provoking. Thank you all.

We haven't ruled anything in or out yet, but before you launch another tirade of why we shouldn't install this system..  In the OP I said "if this seems mad to you, I have to admit it's an experiment and probably quite costly"

 

We're still hoping to get advice on the three questions posed in the OP if anyone wants to have a go..?

 

The PDHW proposal is not something we'd previously discussed. Our preferred Boiler (ATAG) supports the tech so we can explore it.

From what was said, the benefit seems to be in the flow/return DeltaT and condensing process. Is that right?

Is this a more compelling or contrary reason for us to install the buffer?

 

If I understood correctly,  its better to keep the condensing boiler return as close to the temp of the flow,

If that's so and water in our buffer is warmer that the boiler return

then referring to the schematic: 

V3 swings to V4 and the return to boiler is via the warmer buffer.

 

Thanks ADM

 

[marshian]

3 hours ago, Ann D Mann said:

The PDHW proposal is not something we'd previously discussed. Our preferred Boiler (ATAG) supports the tech so we can explore it.

1. From what was said, the benefit seems to be in the flow/return DeltaT and condensing process. Is that right?

 

2. Is this a more compelling or contrary reason for us to install the buffer?

 

3. If I understood correctly,  its better to keep the condensing boiler return as close to the temp of the flow,

 

4. If that's so and water in our buffer is warmer that the boiler return

then referring to the schematic: 

V3 swings to V4 and the return to boiler is via the warmer buffer.

 

Thanks ADM

1. yes lower the return temp (below 54 deg C) the better the condensing and efficiency improvements

 

@JohnMo has experience with atag - I don’t

 

2. Circuit size and volume of water in the rads normally drives the need for a volumiser @JohnMo is your man for discussion around that

 

3. No you will always have a difference between flow and return unless your room and rad temps are equal
 

4. You really want to make A, B or C work don’t you????

 

I’ve no further comments on any of those schemes

[JohnMo]

2 hours ago, marshian said:

(ATAG) supports the tech so we can explore it.

1. From what was said, the benefit seems to be in the flow/return DeltaT and condensing process. Is that right?

Atag, great boilers. Return temp drives condensing. Most Atag boilers have modulating output and have modulation of circulation pump, so almost manages dT itself. They work very differently depends on running against a thermostat or weather compensation. On WC the flow temp is almost rock solid, on thermostat operation it will keep adding to flow temp approx 10 mins after starting and will go up to max temperature set in the controller

 

3 hours ago, Ann D Mann said:

If I understood correctly,  its better to keep the condensing boiler return as close to the temp of the flow

 Poor advice, flow temperature does not directly affect condensing, return temp only does. 

 

3 hours ago, Ann D Mann said:

buffer

Avoid if you can. One big zone or two large ones are the way to go. The bigger volume the better, you also need good flow, so a nice open system give the boiler plenty of opportunities to move the heat and it be absorbed. 

 

With an Atag you just need the Atag controller, and TRVs on the radiators.

 

Just keep everything simple

[Ann D Mann]

On WC the flow temp is almost rock solid, on thermostat operation it will keep adding to flow temp approx 10 mins after starting and will go up to max temperature set in the controller

 

JohnMo 

Re, ATAG... Does this work alongside PDHW that was discussed in thread.  None of the plumbers that I've spoken to have mentioned any if this so I'm trying to get a handle on the questions I should be asking 

 

 

[JohnMo]

The on off thermostat and temperature ramping up is discussed here on page 5.Hints Tips & Fault Codes.pdf

PDHW will work with any configuration for heating, so on/off thermostat, Opentherm controller (Atag controller for example) or load compensation (same as weather compensation but using inside temperature for reference)

 

Another read h too big to upload 

https://www.google.com/url?sa=t&source=web&rct=j&opi=89978449&url=https://www.atagheating.co.uk/wp-content/themes/atag/hubfs/Appliance%20Technical%20Guide%20Pre%202019.pdf&ved=2ahUKEwi1xfGl4biLAxVkVEEAHQFyBAwQFnoECB8QAQ&usg=AOvVaw1gl0y29TTeKTIoqVVZ3xGC

 

[marshian]

To get your head around all aspects of boiler sizing, efficiency optimisation etc etc have a watch of this

 

 

[Ann D Mann]

Hey Marshian

Thanks for linking this video. Very clear presentation. Learned a lot

I was still very much in the dark ages and unaware that condensing boilers function best with Delta T at 20C

 

The blogger's advice suggested we’re all buying boilers about 2x bigger than necessary 

 

I'm being lazy now cos my next post is not really thread related. 

If the question's been covered elsewhere, - any pointers welcome.

I had a closer look at our heat losses (at -2C)

GF calculated by UFH supplier (OMNIE) = 6.5kW

1 F calc'd by me and hubby = 6kW  (it'll be rads )

 

Not sure what to allow for DHW especially if we go PDHW 

ATAG Boiler proposed. ATAG claim a turndown ratio of 10:1
We have Family bathroom with shower and a 2nd proper bathroom,  WC , Kitchen  & Utility

We think 250Ltr tank required..?

 

How do we decide what size boiler to get?

 

Blogger also talked about load sensing thermostats and the inconsistencies between them and boiler systems

Our intention was to buy stats from OMNIE But now I'm concerned about compatibility with ATAG

Duh!

 

 

 

[JohnMo]

1 hour ago, Ann D Mann said:

ATAG claim a turndown ratio of 10:1

Very dependant on flow temp. 6kW is nearer to what they modulate to at low temps.

 

PDHW allows t 2 hrs per day, that will be loads. So 22 hrs to supply all your heating instead of 24 hrs.

 

As said previously use a heat pump cylinder heat to 50 degs. 210 to 250L would be ok for 3 to 4 bed house.

 

Size boiler the same as a heat pump. Say your heat demand is 6kW, (24 x 6)/22. So 6.5kW.

 

UFH gives you quite a bit of leeway on sizing. As the floor will take all the heat you can though at it. I found mixer and additional pump a hinder rather than a gain.

[marshian]

6 hours ago, Ann D Mann said:

Hey Marshian

Thanks for linking this video. Very clear presentation. Learned a lot

 

No probs but you didn't learn enough 😉 

 

6 hours ago, Ann D Mann said:

I was still very much in the dark ages and unaware that condensing boilers function best with Delta T at 20C

 

It only matters that the return is as low as possible - as discussed elsewhere if you have a room temp of 20 deg and a flow temp of 35 deg you are never going to see a delta T of 20 deg c

 

6 hours ago, Ann D Mann said:

The blogger's advice suggested we’re all buying boilers about 2x bigger than necessary

 

We aren't buying boilers 2 x bigger than necessary - some (not all) gas engineers have just been lazy and thrown bigger boilers at the wall rather than do the required calcs because it was easy and required no thought

 

6 hours ago, Ann D Mann said:

How do we decide what size boiler to get?

 

One that can modulate down to as low as possible and is sized to meet the house heating demand plus HW requirements

 

 

6 hours ago, Ann D Mann said:

Blogger also talked about load sensing thermostats and the inconsistencies between them and boiler systems

Our intention was to buy stats from OMNIE But now I'm concerned about compatibility with ATAG

Duh!

 

A good rule of thumb is to always try to get boiler manufacturers own controls and avoid 3rd party controls - the manufacturers controls are designed to work with the boiler and maximise the efficiency of the boiler

 

3rd party controls can be good but most are fancy on/off controls which are dumb (even when labelled as "smart")

 

[Ann D Mann]

So..  choose boiler that can modulate down to as low as possible and is sized to meet the house heating demand plus HW requirements

Ok

Proposed boiler (ATAG) is >30kW. Turn down ratio 1:10 min modukated op =3kw? My floors require 6kW each

Not sure what to allow for dhw. But it looks to me like 30jW boiler is not too much

 

Or am I still uneducated? 

[marshian]

8 minutes ago, Ann D Mann said:

So..  choose boiler that can modulate down to as low as possible and is sized to meet the house heating demand plus HW requirements

 

Yes - just remember HW needs are occupancy driven

 

8 minutes ago, Ann D Mann said:

Proposed boiler (ATAG) is >30kW. Turn down ratio 1:10 min modukated op =3kw? My floors require 6kW each

Not sure what to allow for dhw. But it looks to me like 30jW boiler is not too much

 

I don't think the ATAG goes down to 3kW

 

I agree 30kW is too much 16kW would be plenty

 

8 minutes ago, Ann D Mann said:

Or am I still uneducated? 

 

You are on a journey - you haven't got to the destination yet.

 

My previous boiler I based the choice on existing boiler was a glow worm - it had been very reliable so get another

 

Old boiler was ~15 kW non condensing (single glazed wooden windows - 30mm of loft insulation - T11 rads and no CWI)  - house had been extended so new boiler 24kW with a 10kW min

 

Totally unsuitable for a property that now had SUDG, CWI and 70mm of loft insulation

 

I spent about 6 mths working out what boiler I should get this time.........

 

If your heat loss is 6kW at -2 deg c that situation is maybe 10 days out of 365 - rest of the winter it's going to be 4kWh at 5 deg C so I'd want a min modulation of 4kWh but 6kWh wouldn't be terrible.

 

[JohnMo]

9 hours ago, Ann D Mann said:

Not sure what to allow for dhw.

I will bow out, obviously wasting my time answering questions as this was answered previously.

Edited February 17 by JohnMo

[Ann D Mann]

Re JohnMo's link to the ATAG literature

I'm beginning to wonder if our mixture of UFH and rads will mean we wont be able to enjoy the sophistication of the ATAG In regard to gradient speed settings 

 

We'll have two types of heating system that appear to require different setings:
1 – 2 underfloor heating
4 – 5 Radiator convectors

 

Do I select setting 3?

 

and just to throw a real spanner in ... We had planned to distribute to rads via individual circuits from a UFH manifold,

Each room to have a stat controlling the corresponding actuator.

The ATAG manual suggests TRVs and one ATAG controller

 

In case it affects opinions .. we also have MVHR

 

[Nickfromwales]

Have you run this past ATAG’s tech support yet?