How to measure the remaining HW in an unvented cylinder

[marshian]

1 hour ago, JohnMo said:

Makes you wonder if you could simply strap an external pump on the DHW pipes and charge a cylinder. Use a heat pump cylinder at 14 to 16l/min - same as 6kW heat pump. Then leave the CH on WC.

 

Where does the water go after the cylinder?

[JohnMo]

27 minutes ago, marshian said:

 

Where does the water go after the cylinder?

Back to the boiler, where the cold water would go in.

 

So a closed loop with an external pump, into the boiler where cold water normally goes in and out where hot water comes out, pumped through a cylinder coil. Almost the same as a 4 pipe system boiler?

[marshian]

19 minutes ago, JohnMo said:

Back to the boiler, where the cold water would go in.

 

So a closed loop with an external pump, into the boiler where cold water normally goes in and out where hot water comes out, pumped through a cylinder coil. Almost the same as a 4 pipe system boiler?

 

Ahhh gotcha - Boiler would modulate down based on a much higher return temp than the normal mains temp

 

I guess with a closed circuit you could treat the water - what about expansion of water in the circuit?

[JohnMo]

3 minutes ago, marshian said:

guess with a closed circuit you could treat the water - what about expansion of water in the circuit?

Pressure safety group and an expansion vessel. Inhibit the water with a corrosion inhibitor and Y type strainer. Take out any flow restrictors in the normal cold feed.

[marshian]

Adsibob How far from your HW tank is your Boiler?

Edited January 29 by marshian
Trying to get to grips with tagging

[Adsibob]

3 hours ago, marshian said:

Adsibob How far from your HW tank is your Boiler?

Far. Boiler is in utility room on ground floor. Tank is in the converted loft on second floor (although pretty much directly above it, so maybe 6m away.

Edited January 29 by Adsibob

[Lofty718]

I've told you about this in previous threads before but you thought I was talking nonsense setting up a Viessmann like that should be a crime and the plumber is 1000% a cowboy

 

-No weather compensation

-No PDHW

-Boiler sending high temperature water down to UFH manifolds (inefficient) ufh should be controlled by weather compensation and electronic mixing valves wired directly into the boiler

 

There should also be temperature sensors on the flow pipes, one for before the low loss header and one for every other zone and another in the hot water cylinder.

 

Viesmmann has all of this stuff built into it out of the box, I had to pay £300 extra to add this all to my boiler.

 

 

 

With PDHW on my Vaillant I leave my hot water cylinder constantly set to 44c and whenever it drops below the boiler will ramp up to 75c to heat the cylinder, then back down to 38-45c flow temp to heat the rads/ufh.

 

You have the best boiler on the market but the way it's been setup he might aswell have slung in a crappy baxi boiler because you are not actually using any of the tech that you paid for that makes the boiler so good.

 

I had a similar issue with my 'plumber' who wanted to install my Vaillant ecotec with heatmiser stats zoned into tiny little bits with a nest for radiators and hot water but I stopped him in his tracks and got it done properly. In my case installing a Vaillant with anything but Vaillant controls means the boiler cannot modulate and is simply an on/off dumb stat - yours must be too if it's controlled by Tado

Edited January 30 by Lofty718

[Lofty718]

 

 

This is an example of how it should be setup, 4 pipe with the mixing valves. I have the same electronic valves in the video controlling my UFH.

 

[Lofty718]

7 hours ago, JohnMo said:

Makes you wonder if you could simply strap an external pump on the DHW pipes and charge a cylinder. Use a heat pump cylinder at 14 to 16l/min - same as 6kW heat pump. Then leave the CH on WC.

This is almost how mine is setup, I have cct's they go to 1 pump for radiators which is piped to two seperate zone valves one for radiators and one for pdhw then the other branch of the CCT goes to an esbe valve and UFH pump.

 

All pumps and zone valves/esbe valve is wired into Vaillant wiring centre. When cylinder calls for heat the heating shuts totally off and the boiler ramps up to 75 and uses the same external pump used for the radiators to heat the cylinder. Once the cylinder is satisfied (which is very quickly) it goes back to heating mode with all zones open

[joth]

10 hours ago, Adsibob said:

Far. Boiler is in utility room on ground floor. Tank is in the converted loft on second floor (although pretty much directly above it, so maybe 6m away.

(Sorry dipping in haven't read all the pages)

Do you know where the 3 port diverter valve is, that switches from UFH to DHW? If that' near the boiler, there should be a dedicated flow/return pair from boiler to tank so easy to switch to 4 pipe.

If it's far away then you're stuck with what you got (unless you fancy pulling 2x new pipes from boiler to tank)

 

[ProDave]

What does this "4 pipe" system do to improve efficiency?

 

My ASHP is only 2 pipe (as I think they all are) and it only ever does DHW or Heating (with priority DHW) and runs both at different temperatures.  It can be plumbed with a 3 port 2 position valve (not mid position) or as I have, with individual 2 port valves.

 

The only disadvantage of the 2 pipe I can see is when it switched from DHW to heating, there can be a slug of water in the pipe at DHW temperature sent to the UFH (but the mixing valve on the manifold stops that being a problem)

 

I fail to see what magic improvement a 4 pipe system can bring and why a heat only 2 pipe boiler cannot be set up to only do DHW or heating with priority DHW.  That is more how you wire the controls than how you plumb it (as long as you avoid using a 3 port mid position valve)

[SimonD]

50 minutes ago, ProDave said:

What does this "4 pipe" system do to improve efficiency?

 

My ASHP is only 2 pipe (as I think they all are) and it only ever does DHW or Heating (with priority DHW) and runs both at different temperatures.  It can be plumbed with a 3 port 2 position valve (not mid position) or as I have, with individual 2 port valves.

 

The only disadvantage of the 2 pipe I can see is when it switched from DHW to heating, there can be a slug of water in the pipe at DHW temperature sent to the UFH (but the mixing valve on the manifold stops that being a problem)

 

I fail to see what magic improvement a 4 pipe system can bring and why a heat only 2 pipe boiler cannot be set up to only do DHW or heating with priority DHW.  That is more how you wire the controls than how you plumb it (as long as you avoid using a 3 port mid position valve)

 

A two pipe boiler can of course be set up to do this and you can still gain the benefits from PDHW. The problem with 2 pipe is that many boilers don't provide the functionality to output two difference temperatures as it's all based on CH flow temp. I just installed a Vokera for a customer which seem to be flying off the shelf because the company isn't affected by the CHMM and this boiler had single wire switched live only, not even modulation capability, but the customer just wanted a cheap boiler. Those that do have separate temperature capability, like many Worcester's need an additional diverter valve assembly to be installed into the boiler -not a great issue but most installers just don't bother - and then you need specific manufacturer controls. Likewise with Ideal, there is a switched live you can use for PDHW but Ideal will say that this can only be used if weather comp has been connected, although I do use it for PDHW installs and it does actually work. The Ideal Halo Heat & System controller is set up for priority hot water as is the Honeywell Evohome control that uses opentherm to increase flow temps. This, I think highlights the problem - it becomes quite messy unless the boiler manufacturer specifically supports and promotes the solution.

 

The difference with the Viessmann 4 pipe system is that you do away with the need to install separate diverter valves and pump (except for a cut-out 2 port valve to the cylinder on some unvented cylinders). You can also use the boiler expansion vessel & prv for the unvented cylinder. Controls also get wired directly into the boiler such as the cylinder temp sensor so you can in many cases get away without having to use a wiring centre at all. It all works in an integrated way and less time to install.

 

Control wise, you can simly use weather compensation or if load compensation if preferred, you can use Viessmann Vicare which, because the system boilers have wifi installed, you connect straight to the boiler. But if I want to, I can still use any other controller I want and still have the means to get priority hot water, even if the controller itself doesn't support it.

Edited January 30 by SimonD

[Lofty718]

Vaillant also released a 4-pipe boiler the ecotec exclusive but I don't think it's as good as the standard ecotec

 

Most Viessmann installs I see from good installers who have done the Viessmann courses generally don't ever install their systems with room stats and the boiler is run fully on weather compensation, this is what Viessmann generally recommend unless the property is not suitable

 

I beleive weather compensation is mandatory in Germany and Holland, it seems we are way behind when it comes to heating in this country and our installers are generally very poorly trained.

[SimonD]

16 minutes ago, Lofty718 said:

our installers are generally very poorly trained.

 

Yes, to become an installer all you need is a Gas Safe certificate, or if employed ACS qualification. None of this training covers efficiency in systems and only recently has low temperature system design and wiring controls been included, but at a basic level for sizing boilers only. It's on the installer to train themselves as few of the bigger companies invest the money.

 

But then there is the issue of the marketplace. If I quote for a boiler to be properly sized, set up and controlled, it will cost more than the installer who chucks it in over a few hours and runs off to the next job, all booked online through one of those fixed price cheapo websites that are cropping up everywhere. I was contacted by one of them offering me a fixed rate of £900 for install of boiler and the installation of 9 radiators all while I have to provide vanof minimum age, equipment, insurance etc. - yeah, right!

 

But then you also get those that charge a fortune to install a complex system that doesn't work at all, just like this one I've got to go and sort out. You can't see it in the photo but the installer has put in 3 pumps on one flow pipe from the LLH all teed off a  22mm pipe. Heating is on constantly but relay only and no timers for anything, plus none of the rads work as they should while both boilers merrily cycle away. Oh, and it's all in a garage with no pipe lagging anywhere - the garage is toasty! And  @Adsibob thinks he's got problems..😉

 

 

 

[Lofty718]

Yes that's a common thing I've seen too some installers will assume money is no object and add loads of pumps, a low loss header sometimes even a second uneccessary boiler.

 

My boiler is an oversized ecotec 30kw, unforunately I purchased it on advice of the installer before I learnt about the proper design practises. It's range rated to 10kw and heats the house perfectly so I could of probably had a 15kw ecotec and even that might of been oversized. The only advantage of my oversized boiler is that the coil in the cylinder is rated to 28kw so it provides quicker heating times, but the ideal setup would of been smaller boiler and a high recovery heat pump cylinder.

 

Oversizing is less of a problem on the Viessmans since the modulation on them is so impressive. I would advise @Adsibob at a minimum to get his boiler installed with controls that can actually modulate his boiler. His house I think is fully UFH so to actually have a boiler running at 50c+ constantly in this day and age is bonkers.

Edited January 30 by Lofty718

[SimonD]

3 hours ago, ProDave said:

What does this "4 pipe" system do to improve efficiency?

 

My ASHP is only 2 pipe (as I think they all are) and it only ever does DHW or Heating (with priority DHW) and runs both at different temperatures.  It can be plumbed with a 3 port 2 position valve (not mid position) or as I have, with individual 2 port valves.

 

The only disadvantage of the 2 pipe I can see is when it switched from DHW to heating, there can be a slug of water in the pipe at DHW temperature sent to the UFH (but the mixing valve on the manifold stops that being a problem)

 

I fail to see what magic improvement a 4 pipe system can bring and why a heat only 2 pipe boiler cannot be set up to only do DHW or heating with priority DHW.  That is more how you wire the controls than how you plumb it (as long as you avoid using a 3 port mid position valve)

 

2 hours ago, SimonD said:

 

A two pipe boiler can of course be set up to do this and you can still gain the benefits from PDHW. The problem with 2 pipe is that many boilers don't provide the functionality to output two difference temperatures as it's all based on CH flow temp. I just installed a Vokera for a customer which seem to be flying off the shelf because the company isn't affected by the CHMM and this boiler had single wire switched live only, not even modulation capability, but the customer just wanted a cheap boiler. Those that do have separate temperature capability, like many Worcester's need an additional diverter valve assembly to be installed into the boiler -not a great issue but most installers just don't bother - and then you need specific manufacturer controls. Likewise with Ideal, there is a switched live you can use for PDHW but Ideal will say that this can only be used if weather comp has been connected, although I do use it for PDHW installs and it does actually work. The Ideal Halo Heat & System controller is set up for priority hot water as is the Honeywell Evohome control that uses opentherm to increase flow temps. This, I think highlights the problem - it becomes quite messy unless the boiler manufacturer specifically supports and promotes the solution.

 

The difference with the Viessmann 4 pipe system is that you do away with the need to install separate diverter valves and pump (except for a cut-out 2 port valve to the cylinder on some unvented cylinders). You can also use the boiler expansion vessel & prv for the unvented cylinder. Controls also get wired directly into the boiler such as the cylinder temp sensor so you can in many cases get away without having to use a wiring centre at all. It all works in an integrated way and less time to install.

 

Control wise, you can simly use weather compensation or if load compensation if preferred, you can use Viessmann Vicare which, because the system boilers have wifi installed, you connect straight to the boiler. But if I want to, I can still use any other controller I want and still have the means to get priority hot water, even if the controller itself doesn't support it.

 

After saying all of that, I've spoken to technical support and found out the Worcester diverter kit I need for the above job actually converts the boiler to a 4 pipe system.

[Adsibob]

8 hours ago, SimonD said:

And  @Adsibob thinks he's got problems..😉

That’s helps put things in perspective. Thanks!

 

 Reflecting on all this, I know my situation isn’t terrible, because I imagine we use a fair bit of hot water and we like the house fairly warm, yet our bills aren’t crazy. But it remains rather disappointing because I suspect that if I’d have everything done properly, I’d be saving something on my bills, but the question is what?

 

I did look into a professional design, but it was quite expensive, circa £2k, and the two companies I spoke to seemed to be wedded to the idea that I should get a Veissman storage combi boiler which didn’t sound right for our usage case and in circumstances where we had space for a 300L cylinder in the loft. So I thought I would just do as much research myself and then specify the model of the boiler I wanted, and the size of the cylinder and the heating zones, and that I’d leave the detail of how to set that up to the professional. I can’t now remember how the low loss header came into the equation. I think it was an alternative to buffer tanks as (a) I wasn’t sure we had space for a buffer tank; and (b) the installer didn’t think a buffer tank was necessary, but I was worried about short cycling.

 

I am not really sure how I feel about raising this with the installer. I could make an argument that he was incompetent in that he did not install according to best practice, but I never told him I wanted a specific set up. I just assumed he would install it in accordance with best practice. On the other hand, the following analogy appears apt:

 

When I get in a black cab in London (as opposed to a clueless Uber) and I give the cabbie an address, I expect him to take a reasonable route. If he doesn’t know the route, I expect him to ask or to look it up in an authoritative source. Within my fare, I’m paying for the petrol consumed as well as for the cabbie’s time, and so I’m entitled to get a reasonable route that is reasonably quick and reasonably petrol efficient. Am I not entitled to the same in respect of my boiler and UWC install? 
 

In that case, whether it’s his fault or mine, probably comes down to how inefficient the system is compared to a 4 pipe system. If significantly less efficient, then it’s probably not a “reasonable” install. But if it’s costing me no more than £75 extra a year in gas, it’s probably not terrible. 

 

 

[Adsibob]

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???

Edited January 30 by Adsibob

[marshian]

2 minutes ago, Adsibob said:

In that case, whether it’s his fault or mine, probably comes down to how inefficient the system is compared to a 4 pipe system. If significantly less efficient, then it’s probably not a “reasonable” install. But if it’s costing me no more than £75 extra a year in gas, it’s probably not terrible. 

 

 

 

If you think it's only going to be 1000 kW or £75 then as you say not worth worrying about the payback for changing the system about

 

I think I asked earlier - what is your flow temp and what's the return

 

Return is the one that matters but with UFH you should have a fairly narrow delta

 

An indication of the benefits of condensing and the efficiency as a result are below

 

Return Temp	Boiler % Eff
65	88%
60	88%
55	88%
50	91%
45	93%
40	94%
35	95%
30	96%
25	97%

 

[Adsibob]

4 minutes ago, marshian said:

think I asked earlier - what is your flow temp and what's the return

 

Return is the one that matters but with UFH you should have a fairly narrow delta

I presume you mean at the boiler, rather than at each of our four UFH manifolds?

[marshian]

23 hours ago, Adsibob said:

Far. Boiler is in utility room on ground floor. Tank is in the converted loft on second floor (although pretty much directly above it, so maybe 6m away.

 

Actually that was a stupid question - I was think how much effort would it be to run a flow and return to the tank from the boiler - it was stupid because you've already got a flow and return running to the tank.....

 

The question is really how far away from the boiler is the LLH I assume that shares it's feed with the flow and return for the tank!!!

Potentially you can split the system at that point

[marshian]

7 minutes ago, Adsibob said:

I presume you mean at the boiler, rather than at each of our four UFH manifolds?

Absolutely I mean at the boiler

[Adsibob]

3 minutes ago, marshian said:

The question is really how far away from the boiler is the LLH I assume that shares it's feed with the flow and return for the tank!!!

Potentially you can split the system at that point

Right next to each other. Here is a as photo, boiler on the right, LLH is the anthracite polystyrene clad box immediately to the left of the magma clean, which is immediately to the left of the boiler. 

Edited January 30 by Adsibob

[Adsibob]

4 minutes ago, marshian said:

Absolutely I mean at the boiler

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. 

[marshian]

1 minute ago, Adsibob said:

Right next to each other. Here is a as photo, boiler on the right, LLH is the anthracite polystyrene clad box immediately to the left of the magma clean, which is immediately to the left of the boiler. 

 

So the two vertical 22mm copper pipes that are together and uninsulated go to your HW tank?

 

If that is the case then as @SimonD said you can convert to separate feed for HW and CH pipework wise relatively easily

 

Control wise I'm not in a position to advise but you are in London right? I'd be asking "Urban Plumber" to quote for the changes