How to measure the remaining HW in an unvented cylinder

[marshian]

20 minutes ago, Adsibob said:

Any idea how I find that info? Playing around in the display, I found readings for burner modulation, flow temp and flue gas temp, but not return temp. 

 

Put a K-type Thermocouple on the pipe???

 

No idea how to get it out of the boiler menus - if you had a glow worm I could tell you without even looking at the manual

[Lofty718]

13 hours ago, Adsibob said:

Re the comments on weather or compensation rather than room stats, I’ve mentioned this elsewhere on this forum, but I don’t see how that is meant to work in a house which has some rooms which are east facing, other rooms which are west facing and one fairly large room which is neither. Solar gain, even in winter means that our east facing room is warmer in the morning and cooler in the evening than the west facing room. Yet each of two rooms on opposite sides of the house is used as a bedroom for each of our kids. They don’t have the same temperatures without heating on, and we require heating at slightly different times because they have different schedules. So having each room on its own zone with its own stat and timer is very helpful. Similar issues at play in respect of many other rooms in the house. Each room, without heating has its own micro climate - apart from the different orientations, the house is a mixture of constructions, with some of it built in the 1930s and upgraded now, and some of it built from scratch now. The house is on three floors to make matters slightly more complex too. I’m not sure how one could retain the control we have now, without individual room stats and timers in each room.

 

 Maybe the answer is load compensation, I’m not sure what that is???

@Adsibob  no offence pal but just because something doesn't seem logical in your mind does not mean it doesn't work. plenty of people run heat pumps on boilers on pure weather compensation with no room influence at all. The only time you might have a bit of trouble is on mild days but anything can be over come. Your system is all UFH so it would be perfect for weather comp, the circuits are easy to balance on the manifolds simply provide more flow to the rooms that don't get as hot.

 

Vaillant controls allow room influence and weather compensation at the same time which is what I use because sometimes when cooking in the open plan area it heats up  a lot so it's good to have some room influence, you can do the same on Viessmann they have a stat for room influence, but using third party room stats is a mistake unless it's only as a high temperature limiter and not turning boiler on/off

 

I think a good engineer could get you a 20% reduction in your yearly gas bill compared to the setup you have now. You spent a fortune doing up your house why settle for an outdated heating system that just 'works'

 

Load compensation will allow your boiler to modulate down to the 1:19 ratio that it can and the burner will acheive longer burn times, some people I know with Viessmann can have single burns lasting hours. Longer burns and less cycling = constant condensing which means less gas usage, the house would also be more comfortable too. As someone mentioned previously without weather comp or load compensation your boiler is not currently doing what you think it's doing

Edited January 31 by Lofty718

[Adsibob]

Thanks @Lofty718. Following your and @SimonD’s recommendations I’ve reached out to an engineer that specialises in Veissman. Had a chat with him this morning and his preliminary view was that weather compensation and covering to a 4 pipe system would be worthwhile as it would save me money, significantly more than the cost of the upgrade. The only thing that he said against weather compensation was that it would only not be of benefit in a house that only needs heating for a couple of hours in the evening and a couple of hours in the morning. In those circumstances, he said an on/off system MIGHT make sense. He emphasised that he would still err on the side of weather compensation, but I do find this interesting given four days a week the house is empty from 830 to 5ish and we don’t run the heating at all between 10pm and 5am. Maybe that’s enough is to justify weather compensation though.

 

 I am slowly coming around to the idea of removing all/most zoning, and converting to weather compensation. Still hampered by my own ignorance.
 

I think what’s still holding me back is:

 

1) what is load compensation ?

2) I need to understand this further:

20 minutes ago, Lofty718 said:

Vaillant controls allow room influence and weather compensation at the same time which is what I use because sometimes when cooking in the open plan area it heats up  a lot so it's good to have some room influence, you can do the same on Viessmann they have a stat for room influence,

 

particularly in light of the two matters below:
 

First, we have a daily situation where it makes sense to have very different temps in different rooms: our master bedroom, has slightly more heat loss than our other bedrooms, because it is more exposed/has greater surface area ratio of external walls to volume of room storage. We like this about the master bedroom, because it keeps it nice and cool at night, usually around 18C. We would only turn the heating on if it falls below 17.8C and that only happens in very cold winter weather that lasts for more than a day or two. You mention balancing allows different temperatures in different rooms, so presumably I could still keep this room really cool because it’s on a separate loop.

 

Second, about once or twice a week in winter we run a wood burning stove. How would we switch off the heating in the rooms that benefit from the stove without zoning and thermostats?

[JohnMo]

5 minutes ago, Adsibob said:

what is load compensation ?

Load compensation is flow temp altered with respect internal temperature, (quite immediate changes), where weather compensation is with respect outside temperature (more an average outside temperature). Load compensation and UFH is not a match made in heaven - tried it it was awful, temperature yo-yo.

[JohnMo]

The main difference between operating in weather comp mode and timed heating mode is floor temperature. WC floor will be cooler, this does several things itself.

 

It self modulates output - the closer the floor surface to room temperature the quicker and more immediate the change in heat output.

 

Heat output is a calculation of surface area and difference in room temp to floor temperature. The smaller the differing temperature the less the output. So room gets solar gain, floor gives off less kW of heat. This in turn gives the boiler a higher return temperature so it modulates heat output down to match. The opposite is also true, room cools, boiler gives a higher output, because return temp to boiler is lower.

 

Setting the correct WC curve will automatically switch off and on the heating also, as return temp remains too high once you get to a given flow temperature - this point is adjusted house by house and is curve dependant.

 

Radiators cannot do this nor can high flow temp UFH.

 

[Adsibob]

34 minutes ago, JohnMo said:

Radiators cannot do this nor can high flow temp UFH.

Thanks. What  is high flow temp ufh? I installed slightly thicker ufh pipes (I think they are 15mm diameter) at 150mm distance from each other. Is that high flow?

[JohnMo]

Flow temp is related to pipe centres and output required. Timed heating is never low flow temperature, weather compensation can be and most likely.

[Adsibob]

I still find it incredible that I spent so much money on a complete lie. This is from a shop specialising in Veissman kit:

 

[TonyT]

And they aren’t lying, they aren’t telling you it’s the best way to control your equipment though, just sell you more stuff like any good retailer.

[JohnMo]

9 hours ago, Adsibob said:

spent so much money on a complete lie.

What lie they don't say anything really except it smart - smart just means internet connected. Highlighted bit says a radiator valve doesn't takk to anything.

[JohnMo]

Before you go the road of making mods

 

Check your summer gas usage, add 10% to that usage, to account for the colder mains water coming in during the winter. That is your DHW usage, convert to a month usage.

 

Any changes you make, will not change this figure.

 

Now subtract the calculated monthly DHW usage from your winter gas usage. That figure is how much your heating is costing you. You could save between 10 and 20% on that gas cost, but if you don't like the feel of the house on WC you will save nothing.

 

Do you maths. Is it worth it to you?

[marshian]

1 hour ago, JohnMo said:

Before you go the road of making mods

 

Check your summer gas usage, add 10% to that usage, to account for the colder mains water coming in during the winter. That is your DHW usage, convert to a month usage.

 

Any changes you make, will not change this figure.

 

Interesting to state 10% - historical data for my house gas usage is 35% more in winter - water usage pattern and temp its heated to is unchanged All year round.

 

My Summer gas usage is consistently 3.7 kW per day

My Winter gas usage is 5.0 kW per day

 

However we have cold water tank in the loft so get some solar gain in the stored water in late spring, summer and autumn

 

And I do think I have a thermosyphon issue that probably hurts more in winter than warmer periods

[SimonD]

@Adsibob can you describe the zone setup you have in more detail please? I'm particularly interested in the UFH setup and zoning, where this is and how you manage the spaces with UFH, but also the radiator circuits. I haven't kept up with your retrofit but generally speaking, I'm guessing you have brick walls with added insulation (where? IWI, EWI cavity?), upgraded floor insulation and roof insulation.  What I'd like to understand is the level of heat loss in relation to the thermal mass of the building. (Yes, I've used dreaded thermal mass, and in terms of figures, thermal mass = Building element volume x Volumetric Heat Capacity). Also, which rooms experience significant solar gain and how are those rooms generally used?

 

Your stove will also play a role here as you don't want that interfering too much with heating through the rest of the house, as you've mentioned.

 

What I'm getting at here is that I don't always think that whole house weather compensation is the right answer for everyone and every house. With well planned zoning, you can get good results. The problem is the control of this, especially with a mixture of UFH and radiators because they'll behave so differently, particularly where you've got thick coverings.

 

But in terms of controls, I do think that using load compensating combined with weather compensating controls can be used to good effect for improved efficiencies in a zoned situation. In this instance we need to figure out the best way to approach this, and as you've mentioned, whether it it is more efficient than the existing Tado arrangement without modulation.

 

In terms of the difference between load compensation and weather compensation, it is just a different approach to ensuring the heat input to the house matches its heat loss. With weather compensation, it uses outdoor temp (and sometimes other inputs) matched to a curve a closely matched to corresponding heat loss of the house.With load compensation, it does this by measuring actual reference room temperature to target temperature and the better load compensating controls will learn how the room responds to heat input/loss over to time to control heat output of the boiler.

 

As I've been thinking about your system and earlier comments about the low loss header, I wonder whether your installer confused the use of low loss header versus a buffer. Their functions can be the same but from a control perspective, they are different. If you're running a system with lots of zoning, then you use a buffer, not a low loss header and the low loss header can't replace it, because its function is different.

 

So my thoughts are drawn to thinking about whether a buffer can be installed in place of the LLH together with a 4 pipe system for DHW and then turn down your flow temperature on the the boiler. Then, only if necessary look at replacing the tado which I'm guessing has lots of smart TRVs installed through your house too? Just a strawman though at the mo.

 

 

Edited February 1 by SimonD

[Adsibob]

10 hours ago, TonyT said:

And they aren’t lying, they aren’t telling you it’s the best way to control your equipment though, just sell you more stuff like any good retailer.

Well, I think they are stretching the interpretation of “compatible”. I’d hardly describe it as “compatible with all Veissman boilers” when there is actually very limited functionality compared with other fully functional thermostats.

[Adsibob]

1 hour ago, JohnMo said:

Do you maths. Is it worth it to you?

Thanks, I will do this and report back.

[JohnMo]

38 minutes ago, marshian said:

Interesting to state 10% - historical data for my house gas usage is 35% more in winter - water usage pattern and temp its heated to is unchanged All year round

 

4 minutes ago, Adsibob said:

Thanks, I will do this and report back.

10% is a little low, just had a look at my EPC and 20 to 25% is a better value for the increased heating requirements for DHW in the 6 winter months, as an average, compared to 6 summer months, as an average.

[SimonD]

56 minutes ago, Adsibob said:

Well, I think they are stretching the interpretation of “compatible”. I’d hardly describe it as “compatible with all Veissman boilers” when there is actually very limited functionality compared with other fully functional thermostats.

 

Froma slightly nerdy perspective, I have yet to find an Erp certificate for the Tado controllers. Erp of controllers is important because their functionality determines the overall energy efficiency of the boiler over 89% - therefore if you're installing a brand new system and need to provide 94% efficiency you haven't got the info, you can't actually provide that guarantee whereas with other controllers I've got the certificate to back up the install.

[Adsibob]

1 hour ago, SimonD said:

can you describe the zone setup you have in more detail please? I'm particularly interested in the UFH setup and zoning, where this is and how you manage the spaces with UFH, but also the radiator circuits. I haven't kept up with your retrofit but generally speaking, I'm guessing you have brick walls with added insulation (where? IWI, EWI cavity?), upgraded floor insulation and roof insulation.

I have pasted below the plans of my house which show the different zones. Under each plan I have noted details of the construction, as these aren't always accurately set out on the diagram.

 

GROUND FLOOR (4 zones)

There are 4 zones on the ground floor shown above, each with its own overpriced and misrepresented piece of junk tado thermostat. When you look at the above ground floor plan, the two thirds of the ground floor to the right is original construction, solid brick walls, upgraded externally with 40mm of EWI Kingspan Kooltherm K7 and a layer of silicone render on top of that (shown in green). There is a mistake in the plan in that the rear extension forming the third of floorspace to the left of the plan, show the EWI extending all along the flank wall, but in actual fact only about half of that extension wall is covered in EWI and render, the rest is brick.

We have 2G windows throughout. The rear extension has large sliding doors which are West facing, and there is also a large 2G window above the kitchen sink that is west facing, so plenty of afternoon/evening sunshine. Whereas the front of the house is east facing so gets morning sun. The original house was a 1930s semi, with the Northern side (top of diagram) being attached to the adjacent building. Funnily enough, they have had their front elevation done with the same EWI we have, using our builder after they saw ours. But only the front. Our front room (UFH zone 03) rarely needs any heating. I think part of the reason is the neighbour's EWI, but the other reason is that room, as well as UFH zone 00 is raised upper ground floor (about 210mm higher), with much more concrete under the 100mm PIR floor insulation, onto which the UFH pipes are tacked.

 

 

FIRST FLOOR (5 zones)

 

The hallway and family bathroom are the same zone. Orientation is same as described above, so UFH zone 7 is getting morning solar gain, whereas zones 04 and 05 are getting evening solar gain. Zone 04 also has a fairly large skylight. Not much solar gain for the ensuite bathroom or family bathroom, as windows are small. The entirety of the external walls of the first floor are covered with the same EWI buildup as described above, despite this not being shown on the drawing.

 

SECOND FLOOR (three zones)

This is a loft conversion so largely a modern construction, but the side walls and front wall (top and botoom and right) are mostly original construction from the 1930s, with only the dormer cheeks being new. There is a combination of wood fibre insulation and PIR backed plasterboard in the roof build-up, but it still only just passed building regs as we didn't have space to put more in. We went for wood fibre to increase decrement delay. The three skylights in the roof give quite a bit of solar gain.  

Our adjoining neighbour has also done a loft conversion, so we get protection along the northern wall, which is all adjoined by their house. On the eastern wall (right) and parts of the southern wall (bottom) we have the same EWI.

 

The house is VERY airtight. I haven't done a test, but the detailing was pretty good and builder was good about using Tescon Vana tape on all windows and doors.

 

CONTROL/ZONING

 

So as you can see, I have a whopping 12 UFH zones, each with their own Tado. Then there is a 13th zone, just to control the two towel rads we have on the first floor. These are simply switched on and off by a command to alexa to switch on a smart plug.

 

I have the Tado extension kit to control the HW cylinder in the attic space.

 

There are four UFH manifolds in total:

1. two on the ground floor (one for zones 00 and 03 which are on the upper ground floor; and one for lower ground zones 01 and 02)
2. one on the first floor
3. one on the second floor

Edited February 1 by Adsibob

[marshian]

1 hour ago, JohnMo said:

 

10% is a little low, just had a look at my EPC and 20 to 25% is a better value for the increased heating requirements for DHW in the 6 winter months, as an average, compared to 6 summer months, as an average.

 

Ahhh so I just need to find a 10% reduction not 25% - much relief - thanks

[Adsibob]

21 minutes ago, SimonD said:

 

Froma slightly nerdy perspective, I have yet to find an Erp certificate for the Tado controllers. Erp of controllers is important because their functionality determines the overall energy efficiency of the boiler over 89% - therefore if you're installing a brand new system and need to provide 94% efficiency you haven't got the info, you can't actually provide that guarantee whereas with other controllers I've got the certificate to back up the install.

Are you saying it's possible they do modulate Veissmans after all, they are just not certified as such?

[SimonD]

2 minutes ago, Adsibob said:

Are you saying it's possible they do modulate Veissmans after all, they are just not certified as such?

 

No, I'm saying that every other manufacturer of controls publishes their ErP certification class so as a system designer and installer I can certify the installation properly - with Tado I can't and couldn't without this data and frankly their report supporting efficiency savings they publish on their website is worthless.

[SteamyTea]

3 hours ago, JohnMo said:

Do you maths. Is it worth it to you?

 

1 hour ago, Adsibob said:

Thanks, I will do this and report back.

You can also use heating degree days.

Where the line intersects the y-axis is your non spacing usage.

 

https://www.degreedays.net/

 

 

[Lofty718]

@Adsibob Don't rush into getting an installer yet until you figure out what you want and then crucially make sure you choose someone who knows what they are talking about and knows about low temperature heating and proper controls.

 

@SimonD can I ask why you think he needs a buffer? it's quite unusual. It's my understanding that a LLH is installed to hydraulically seperate the circuits so a multi pump heating system can run at different flow rates without the pumps fighting against eachother.

 

since he has only UFH in his house it seems to me the most efficient way of setting up his system would be to run two different flow temperatures one on hot water priority for the DHW and then the boiler at all other times providing flow direct to the UFH circuits.  This would mean boiler always condensing 100% of the time in CH mode

 

Is it possible he could even go as far as removing every mixing valve and pump from the manifold and running all off the boiler pump? this could of potentially been a much cheaper install with much less equipment needed.

[joth]

2 hours ago, SimonD said:

 

No, I'm saying that every other manufacturer of controls publishes their ErP certification class so as a system designer and installer I can certify the installation properly - with Tado I can't and couldn't without this data and frankly their report supporting efficiency savings they publish on their website is worthless.

Interesting I hadn't heard of this before. Seems like something Homely will need to provide for their products

 

[SimonD]

51 minutes ago, joth said:

Interesting I hadn't heard of this before. Seems like something Homely will need to provide for their products

 

 

You'd certainly hope so. Here's a link about controls and ErP from the Worcester website: https://www.worcester-bosch.co.uk/professional/support/troubleshooting/faqs/erp-faqs/how-do-controls-affect-erp