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Author Topic: New Boiler fitted  (Read 2832 times)
Iain
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« on: March 27, 2012, 08:34:14 PM »

Hi
After previous discussions
Quote
on boiler replacement, I have now taken the plunge. Some of this info might be usefull for someone in the same position.


Finally decided to go for a new boiler for various reasons. The old boiler was a combi but since fitting a cylinder for my thermal a few years ago I have only used it as a system boiler.

I had a few requirements:-

Needed to modulate to a lower level than my existing boiler (<9Kw)

Only needed 18Kw Max (Combi was 25Kw on the CH side)

Weather compensation

Ability to link in to  my HW Cylinder to control the top up of the solar heated water.

High efficiency

I spent ages looking around and finally decided on the Remeha Avanta 18S for various reasons.(modulates down to 6kW)

I believed that in order to control all I needed I would need the Isense controller to make it all work.

Whilst the kitchen was being done I helped my mate fit the boiler.
It was very simple and easy  to fit. Redundant pipework removed and all plumbed in, condensate pipe inside to stop it freezing in the winter.. I decided to start off using my existing 2 channel programmer just to get it all working.

All worked well and is very quiet in operation.

I then started to learn:-

Wired in the external temp sensor and found the boiler PCB then activated the weather compensation settings. The 4 set points are adjustable. I have set the flow temp to 60deg C at 0 deg outside temp, and 35degC at 20deg C outside temp. I will tweek these settings over the next year to optimise it all.

Wired up the cylinder temperature sensor and found the boiler then is able to control the set temp of the cylinder.
Have set the hysteresis to 2degC and all works well. There is an option to activate “anti legionella”. Either, ON, cylinder taken to 65degC every time. AUTO, takes the cylinder to 65degC once a week.
Or OFF.

Whilst doing the radiators the flow/return temps are controlled by the weather compensation and the return is always below the 55degC required for condensing. When the boiler heats the cylinder the return temp can obviously be higher(than 55 deg C) due to the cylinder temp.

I have used the boiler PCB output to operate a relay to deactivate the CH zone valve when calling for HW, so as to make the system HW priority. This allows the boiler to be on HW for the shortest time so the higher return temp is also there for the shortest time.

There is an inhibit circuit on the boiler PCB, so have used this, so when my heat dump is operating the boiler is inhibited. The old boiler was used for the heat dump circuit. With the new boiler I am reluctant to modify the boiler to use the boiler pump for heat dump. All I have done is to fit a Zone valve and circ pump (controlled by the Resol) that links the HW supply pipes to the CH supply pipes. The boiler is inhibited and the HW and CH zone valves shut automatically during heat dump.

The installation book is translated from Dutch and something is lost in the translation. Some technical guys at Remeha don't understand what all the adjustable parameters of the boiler do exactly so it took quite a while to get all the information to understand how to set up the boiler to do what I wanted.
It does seem a very flexible and good control system on the boiler and does all I want of it.(now I have set it all up!)

When it is “commissioned “ it should have a 5 year guarantee so seems quite good when compared with other boilers.
If anything does go wrong in the boiler it all appears very accessible. Any item could litterally be changed within 10 minutes. It does seem a very well designed boiler.
Iain


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dimengineer
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« Reply #1 on: March 27, 2012, 09:45:57 PM »

Now that it what I call a proper control system. Given how primitive most CH controllers are, it will be really interesting to hear how you get on. Can you give us an update from time to time?

Tim
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Iain
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« Reply #2 on: March 31, 2012, 05:15:16 PM »

Hi Tim
Finally all the wiring is done and all is working. Heat dump tested but just waiting for the real event.  On the old system the programmer controlled the valves/relays which then controlled the boiler. Now I have had to change it all round the other way.
On the HW side:- the programmer sends a call to the boiler via the safety stat in the cylinder (unvented cylinder). The boiler will then fire up and opens the HW zone valve (CH zone valve shuts) for the boiler coil and fires up, if the HW temp set on the boiler is not satisfied.
On the CH side, the programmer sends a call to the boiler and it fires up. (CH valve already open)
If both the CH & HW are called for, the boiler will prioritise the HW and shut the CH zone valve until the HW is satisfied.

All very standard and basic.
For my heat dump on the solar thermal:-
The Resol sends a dump signal to 2 relays 1 upstairs and one downstairs. The relays Inhibit the boiler, open the zone valve for the heat dump which then starts the heat dump pump when open. I have also had to have the relay contacts wired in the circuit to the CH zone valve as I have found the boiler, even in the inhibit mode still powers the Zone valve for CH and would keep it open. (the CH/HW boiler electrical output is obviously fed via a change over relay so stays in the deenergised state when inhibited ie CH output live)
On the front of the boiler you can scroll through the temp readings, T1-Flow temp, T2-Return temp, T3-Cylinder temp etc. So very useful.
The boiler recognises whatever sensor/programmer is wired in automatically.
ie I fitted a temp sensor to the cylinder,the boiler recognises it and allows the temp reading to be displayed and the temp control to work. If I had wired a thermostat to the same terminals it would have just worked as an on/off circuit. Same with the programmer, I have fitted standard 2 channel on/of programmer and all works well,same terminals would accept an open therm programmer and recognise automatically. Same for the outside sensor, connect and it recognises and activates the weather compensation. Very simple really looking back but has taken a lot of phone calls as experimenting to get it all working as the manual could be clearer. A simple rewrite of the installation manual would make life so simple. Will keep you updated of any changes/problems
Iain

 
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1.98kWp PV  (11 x Sharp 180 and SB1700)
20 x 65mm Thermal and 180ltr unvented
9000ltr rainwater storage   Plymouth
http://www.bdpv.com/fiche_utilisateur_en.php?util=iain
http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?plant=cba8d47f-bf09-4533-a105-4303b353f20f&splang=en-US
Alec Morrow
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« Reply #3 on: April 08, 2012, 08:12:36 AM »

Iain My I sense has a screen to count the solar contribution to the cylinder ( I dont have solar though)..I would be sure yours does too..which rather indicates there is a solar functionality there...

These are great systems, and it is very sad that compensation controls are not universally adopted in the UK..

out of interest what control strategy are you using?
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Iain
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« Reply #4 on: April 08, 2012, 12:16:32 PM »

Hi Alec
When I fitted the boiler the weather compensation didn't seem right so I contacted Remeha and they sugested the following settings as the factory set ones were not correct for UK
P1=70degC
P27=35degC
P28=20degC
P29=0degC

Since then I have set P27=40degC and P1=60degC

I dont have the ISense so my weather compensation is boiler controlled. I believe the ISense has it's own weather compensation curves you can choose from.
I have set P2 cylinder temp to 43degC with P26 (Hysterysis) set to 2degC (works well for us)
Solar during the day and hot water topped up at 0600-0700 in the morning for the morning showers.
Iain
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20 x 65mm Thermal and 180ltr unvented
9000ltr rainwater storage   Plymouth
http://www.bdpv.com/fiche_utilisateur_en.php?util=iain
http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?plant=cba8d47f-bf09-4533-a105-4303b353f20f&splang=en-US
Alec Morrow
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« Reply #5 on: April 09, 2012, 10:39:46 AM »

Are you just running the boiler on a time clock, or do you have a room stat as well...


I am glad you pointed out the issues Remeha have with their own equipment...I hope people can begin to understand why some installers struggle to some degree....

a sad reflection on the way we do engineering in this country...
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Iain
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« Reply #6 on: April 09, 2012, 02:08:24 PM »

Hi Alec
The boiler on the CH side is just running on a time clock with all the room rads on TRV's. The U/F in the sitting room is on its own thermostat. So far all seems good but I have a wire run just in case I fit a room stat or initially I was going to fit an ISense. Will wait and see how it runs. My mate has the Remeha software on his laptop and the lead, It was quite interesting/useful to see how all the temps were behaving and how the control system were working (all comes up in graph form).The settings can be altered and then you can see how the changes affect the boiler control loop. So far very pleased. I think some of the problems are because I think it is Baxi that have taken them over and some of the Baxi technical are not quite up to speed on it all. If you can get the Ex Remeha Technical they have a lot more info.
Most plumbers just fit a boiler and leave it set up with factory settings and just have the CH temp up to 75/80degC!!,probably why most condensing boilers are running too hot to condense. If you are lucky you might get an engineer that fits the boiler and sets it up properly. I think it is the exception rather than the rule to have it set up properly.
Iain
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20 x 65mm Thermal and 180ltr unvented
9000ltr rainwater storage   Plymouth
http://www.bdpv.com/fiche_utilisateur_en.php?util=iain
http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?plant=cba8d47f-bf09-4533-a105-4303b353f20f&splang=en-US
Alec Morrow
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« Reply #7 on: April 09, 2012, 06:03:43 PM »

normally with your system design you would use a low loss header and a second  variable sped pump for the heating circuit to avoid the pump dead heading leaving all TRVs open...the trick is to tweak the curve not the trvs you don't want the boiler producing more heat than  is necessary.

The advantage of the I sense is that you can select different controls strategies...on the main screen, and you get to add the room influence for quicker heat up times if thats the way you run it.

One manufacturer did some experiments and found that the addition of the modulating sensor saved a few percentage points but that was with boiler's considerably bigger than 19kws



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Iain
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« Reply #8 on: April 09, 2012, 10:45:17 PM »

Hi Alec
Quote
normally with your system design you would use a low loss header and a second  variable sped pump for the heating circuit to avoid the pump dead heading leaving all TRVs open
There is a radiator always fully open in the airing cupboard and the boiler has a built in bypass pipe so the low loss header is not needed, the control on the boiler seems to work well with the TRV's so far. I will monitor for a while and might possibly get the ISense in the future. Trying to keep it simple. I know a couple of people with the ISense and they don't really understand what it can do as it seems too complicated to them. Even Remeha couldn't answer all my questions on it first time round. So far the system does all I need with the boiler controls and is very easy for others to adjust and use.
Iain
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1.98kWp PV  (11 x Sharp 180 and SB1700)
20 x 65mm Thermal and 180ltr unvented
9000ltr rainwater storage   Plymouth
http://www.bdpv.com/fiche_utilisateur_en.php?util=iain
http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?plant=cba8d47f-bf09-4533-a105-4303b353f20f&splang=en-US
Alec Morrow
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« Reply #9 on: April 10, 2012, 08:02:24 AM »

I am not so sure that the boiler does have a by pass...one of my installs dead headed when the trvs shut down but the pump kept running...Broag changed the pump three times but it took me to spot the fact that it was dead heading..

I think in the UK we have a Neanderthal approach to heating...and as you have pointed out no one is really up to speed...and the boiler manufacturers have no interest in sharing information about controllers...

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Iain
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« Reply #10 on: April 10, 2012, 08:28:54 AM »

Hi  Alec
It has a bypass pipe inside the boiler(looks about 10mm) between the pump suction and heat exchanger.
Quote
one of my installs dead headed when the trvs shut down but the pump kept running...Broag changed the pump three times but it took me to spot the fact that it was dead heading..
Was it a system boiler or combi? I have a system boiler but assume the combi has the same bypass, unless it is a recent addition to the boilers
Iain
« Last Edit: April 10, 2012, 08:30:58 AM by Iain » Logged

1.98kWp PV  (11 x Sharp 180 and SB1700)
20 x 65mm Thermal and 180ltr unvented
9000ltr rainwater storage   Plymouth
http://www.bdpv.com/fiche_utilisateur_en.php?util=iain
http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?plant=cba8d47f-bf09-4533-a105-4303b353f20f&splang=en-US
Alec Morrow
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« Reply #11 on: April 10, 2012, 12:14:17 PM »

it was the 18kw, it must have been the OV version though...now you mention it...
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gazchaz
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« Reply #12 on: November 07, 2012, 02:34:43 PM »

I have just had the same boiler fitted with the weather comp sensor and an isense controller.

Could someone point me in the direction of a sensor that would be suitable to replace the thermostat on the cylinder so I can control and monitor the temps of the cylinder from the boiler/isense? The cylinder is a basic vented indirect foam insulated thing.

I haven't had much chance to play around with it yet, but your settings look like a good starting point!


Thanks,

Chaz
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Iain
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« Reply #13 on: November 07, 2012, 04:30:31 PM »

Hi Chaz
Quote
Hi Alec
When I fitted the boiler the weather compensation didn't seem right so I contacted Remeha and they sugested the following settings as the factory set ones were not correct for UK
P1=70degC
P27=35degC
P28=20degC
P29=0degC

Since then I have set P27=40degC and P1=60degC

I have since changed them slightly. I am at work so don't have the new settings here. I will post them as soon as I have them.
I just ordered some 12K ntc surface mount

https://uk.rs-online.com/web/p/thermistors/6974626/

Soldered 2 wires on put it in some 12mm copper tube, and filled with araldite
Works well. I think Remeha sell the sensor quite cheaply anyway £20 ish
Probably easier to get the proper one.
Or just use the NTC sensor from an outside sensor if it fits in the pocket.
I just used 2 core data cable to extend the wire.
Really well thought out system.

Just found it:- I have dropped P1 down to 55 deg, Ensures boiler will always be in condensing mode and temps are ok for us.
Iain
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1.98kWp PV  (11 x Sharp 180 and SB1700)
20 x 65mm Thermal and 180ltr unvented
9000ltr rainwater storage   Plymouth
http://www.bdpv.com/fiche_utilisateur_en.php?util=iain
http://www.sunnyportal.com/Templates/PublicPageOverview.aspx?plant=cba8d47f-bf09-4533-a105-4303b353f20f&splang=en-US
gazchaz
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« Reply #14 on: November 08, 2012, 09:05:48 AM »

Excellent, thanks Iain.

I cant seem to find the Remeha sensor in the UK. According to the remeha pdf it should be part number S43946.

Do you think this would work?

http://www.navitron.org.uk/product_detail.php?proID=239&catID=74#

I dont have any pockets on my cylinder so would I just wedge it between the cylinder wall and insulation?

8 degrees outside at the moment and t2 is showing is 50 degrees  Smiley
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