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Green Building Bible, Fourth Edition
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  1.  
    Posted By: Jeff BIf I do remove or by-pass Pump 2, would Pump 1 be man enough to do the job of circulating water all the way to the TS? I assumed Pump 2 acted like a second locomotive on a long freight train!

    From the comfort of my armchair, some miles distant it is difficult to be absolutely sure that the pump will cope - however often the pumps in shunt valves are are standard CH pumps ('cos they are plentiful off the shelf items and why invent something new to do a standard job) so have a look to see what pump you have. The design is for this pump to run the system from the boiler to the TS and one diagram in the user manual shows the boiler connected to a CH system with out a TS so if it can cope with a CH system I would expect it to cope with TS supply.

    My main thoughts at the moment are centering about the pump 2 and the effect of this in the circuit whether it is either running or stationary (or both)
    • CommentAuthorJeff B
    • CommentTimeDec 8th 2020
     
    Green Paddy - some answers to your questions:

    (a) Is the boiler purely based on a timer for permission to run, ie. there is no stat on the DHW cyl or TS that asks the boiler to fire up? Yes.

    (b) The temperature taken at the TS sensor near the top (what you labelled on the graph as TSmid, but is actually high up, just below the CH flow), is that taken with the same IR thermometer, or are you reading a sensor? Can you check that temp is reasonably accurate?

    I am using a probe thermometer inserted into the pocket where a temperature sensor would be placed. The thermometer has been calibrated in ice, boiling water and water at 50C (as measured with a standard alcohol in glass thermometer) and is within +/-1C. The IR thermometer has not been properly calibrated by me, but it compares well at room temperature against the same alcohol in glass thermometer and also with the boiler temperature, comparing the figure on the LCD screen with the boiler flow pipe immediately at the outlet of the boiler, so covers the range that I am likely to encounter.

    (c) Pump2 starts once the boiler has got up to a reasonable temp output, it seems. What is that pump2 start set point? (I think I'd relocate that pump, if it is really necessary now the LLHeader has been removed, beside the one at the boiler, so you've got the pressure lift, but not yet another bit of logic in a messy system. Again a can of worms for later).

    Pump 2 is started by a pipe thermostat located on the boiler flow pipe at the back of the boiler. The flow temperature needs to be 70C to start the pump.

    (d) The 3 way diverter near the TS, what is the temp set point for that to operate? (seems a bit unusual to have the 2port valve at the DHW cyl, and then the 3port to divert if the boiler flow isn't hot enough cause it's coming from the DHW coil, but let's not open another can of worms).

    70C. The boiler flow water splits just before the 2 way valve.

    (e) Regarding the temperature difference between the TS and the C/H flow.

    There was a loft mounted F&E with the “old” system when the boiler flow to TS was direct but when it was changed to indirect the loft F&E tank was removed. There is an F&E tank directly on top of the TS and there is about 10cm of water in there so unlikely to be any air in the TS as it as an open vented system?

    I will try opening the AAV which is mounted at the highest point on the C/H flow where it leaves the TS – it may be faulty and trapped air is not escaping? There is a "London Loop" where the C/H flow leaves the TS to prevent thermo-syphoning overnight - could that be causing a problem?

    Latest data/graphs to follow later!
    • CommentAuthorJeff B
    • CommentTimeDec 8th 2020
     
    Reply to Philedge's comment:
    Jeff. The boiler flow temp and the boiler power both started to drop at 70 mins into the data logging. Do you know why the boiler started to reduce its output? Without any external sensors and only the internal timer to control the boiler it shouldnt have throttled back??

    I agree it seems odd. I think what must happen is that as the boiler temperature approaches the set temperature, the boiler automatically starts to throttle back presumably only if the heat output is sufficient to balance the load requirement. In the graph you can see that the TS temperature reached a peak at 70 minutes and then only drops slightly for the next 50 minutes (same for the C/H flow).
    • CommentAuthorphiledge
    • CommentTimeDec 8th 2020
     
    Unless you changed the flow setpoint, the flow temp should stay the same. The power could drop with reduced demand, but the flow temp should stay at the set point whilst the boiler is running.

    I would monitor that scenario again as youre not going to get far if the boiler is doing its own thing!!
    • CommentAuthorJeff B
    • CommentTimeDec 8th 2020
     
    Herewith the latest data. The graph shows the 5 main parameters as before but this time with the boiler power data included. The boiler had been on for 30 minutes before hand and the C/H kicked in 6 minutes after that.

    There is still an approx 10C difference between the TS temperature and the CH flow temperature which is difficult to explain when both are measured at practically the same point in the TS. However I can live with this - the two rads in the lounge, which are at the end of the longest run, are achieving over 50C(up to 63 even!) which is much better than previously. I think the combination of upping the boiler set temperature from 75 to 80C combined with speed 3 on the boiler-to-TS pump (pump 2) has done the trick.
    • CommentAuthorJeff B
    • CommentTimeDec 8th 2020 edited
     
    <blockquote><cite>Posted By: philedge</cite>Unless you changed the flow setpoint, the flow temp should stay the same. The power could drop with reduced demand, but the flow temp should stay at the set point whilst the boiler is running.

    I would monitor that scenario again as youre not going to get far if the boiler is doing its own thing!!</blockquote>

    I did a little experiment by turning off Pump2 to observe what would happen. The boiler temperature started to rise almost immediately presumably because Pump2 restricts the boiler flow when it is off. I turned the pump back on smartly because if I didn't then the boiler would exceed the set temperature and would switch off. What happened next was interesting as the situation simulated what happens when the boiler temperature approaches the set temperature. See attached graph.

    This graph was plotted from some data generated to study this effect and this test started at the end of the test run which produced the graph in my last post a few minutes ago. Pump 2 was turned back on at the 10 minute mark. The maximum power output mirrors the minimum in the boiler temperature curve and as the latter starts to increase again, so the power decreases. The variation is small however with the boiler temperature in the range 81 +/- 3C
    • CommentAuthorphiledge
    • CommentTimeDec 9th 2020
     
    The 8 Dec power temp graph is fine with the power ramping up as the flow temp drops, but that doent seem to be what happened on the 6 Dec. Maybe worth keeping an eye on that to make sure the boiler hasnt got an intermittent fault??
  2.  
    Jeff B The data looks much better now. The 10 deg difference between the TS and the CH flow is IMO because you are taking the heat out of the TS with a coil. It is very difficult (= almost impossible) to get a heat exchanger to give out the same temp. as the source temp. there will always be a lower temp. out unless the coil is oversized which is not generally practical. You will note that the TS temp is 8 deg lower than the boiler flow - for the same reasons. If you go back to my first post I said that it is usual to take the output of the CH directly from the TS / here you are seeing why.

    Putting up the boiler temp to 80 should have only lifted the flow and TS temps by 10 deg. IMO increasing the pump 2 speed was the majority of the fix. I still thing pump 2 is probable messing with the flows by confusing the pressures when running in conjunction with pump 1. Increasing the speed probable hid this phenomena.
    • CommentAuthorJeff B
    • CommentTimeDec 9th 2020
     
    <blockquote><cite>Posted By: philedge</cite>The 8 Dec power temp graph is fine with the power ramping up as the flow temp drops, but that doent seem to be what happened on the 6 Dec. Maybe worth keeping an eye on that to make sure the boiler hasnt got an intermittent fault??</blockquote>

    Phil - attached please see the graph from 6 Dec which I have updated to include the power data. I am content in as much as the the TS and CH flow temperatures are being maintained whilst the boiler flow and boiler power are decreasing and my financial director is happy that the property is warmer with no further capital outlay. (Don't mention the increased pellet consumption though!).:wink:
  3.  
    Posted By: Jeff Band my financial director is happy that the property is warmer with no further capital outlay. (Don't mention the increased pellet consumption though!).

    The increased pellet consumption is because the house is warmer ! Easy to justify (or remedy by turning down the heating)
    • CommentAuthorJeff B
    • CommentTimeDec 9th 2020
     
    Posted By: Peter_in_HungaryJeff B The data looks much better now. The 10 deg difference between the TS and the CH flow is IMO because you are taking the heat out of the TS with a coil. It is very difficult (= almost impossible) to get a heat exchanger to give out the same temp. as the source temp. there will always be a lower temp. out unless the coil is oversized which is not generally practical. You will note that the TS temp is 8 deg lower than the boiler flow - for the same reasons. If you go back to my first post I said that it is usual to take the output of the CH directly from the TS / here you are seeing why.

    Putting up the boiler temp to 80 should have only lifted the flow and TS temps by 10 deg. IMO increasing the pump 2 speed was the majority of the fix. I still thing pump 2 is probable messing with the flows by confusing the pressures when running in conjunction with pump 1. Increasing the speed probable hid this phenomena.


    PiH - thanks for your comments again. Yes I'm sure that's right - the two coils is one coil too many! That's why I thought about a PHE in the beginning. I still wonder if I could run my system without the TS (as described in the Ekoheat manual), reducing the boiler set temperature significantly say down to 60C - 65C in such a way that after the initial surge to get the rads up to temperature, then modulate down to the 4 kW minimum and tick over for the whole time period maintaining the desired room temperature without turning itself off.
    • CommentAuthorJeff B
    • CommentTimeDec 9th 2020
     
    Posted By: Peter_in_Hungary
    Posted By: Jeff Band my financial director is happy that the property is warmer with no further capital outlay. (Don't mention the increased pellet consumption though!).

    The increased pellet consumption is because the house is warmer ! Easy to justify (or remedy by turning down the heating)


    Exactly! I am pleasantly surprised that the pellet consumption has not increased hugely despite the recent drop in the outside temperature. I'll continue to monitor that every day as I have done for years (what a geek :wink:)
  4.  
    Jeff B, looking much better. Agree with what PiH has said;

    - you now have a decent flow rate from boiler to TS. The modulation of the boiler I suggest was due to the flow temp very quickly being at set point, so the boiler assumes it's done its job, and throttles back, only to realise it hasn't done its job, and ramps up again (hunting). Now you are getting a decent flow rate, that volatility has reduced.

    - agree with PiH about pump2 location, and would mention again about moving it adjacent to pump1, and run both together, as it seems you need that oomph to get the decent boiler flow rate, but don't want interference from pump2 low pressure side.

    - the initial drop in TS temp but recovery and subsequent increase, suggests that the input from the boiler is easily man enough for the radiator demand even starting from cold (20oC CH return). I would still be interested to see the effect of slightly throttling the CH flow rate, giving you warmer rads, but over 50oC may well be acceptable. That could lead to you being able to lower the boiler set point a little too, and just having a much more stable burn cycle, at slightly lower temperatures, but a test run with these really useful graphs would help clarify that - tune the system a bit.

    - I still think that the temp set point for the load valve at 60oC is too high, and would suggest you at least try it at 50oC, to understand any impact. I know you understand the boiler to be non-condensing, but the manual does briefly mention about the removal of condensate. Also I'd be surprised if RHI would have accept a non-condensing boiler, and the stated efficiency is over 90%, which to me says you have a condensing boiler. Future thoughts may be to consider how to improve efficiencies, if it is a condenser (eg lower return boiler temps for quite a portion of the cycle, hence my comment about reducing the load valve set to 50oC).

    - I don't think there's a any issue with the boiler shutting down at the end of the first test. It's just doing its job. It is programmed to get to set point, then modulate back till it hits its lowest power point, still keeping to set point, then shutting off. It may also have a minimum run time also pre-programmed, to avoid short cycling, but the previous low flow rate made it easy to maintain set point, and so shut itself down.

    - I don't really like your control set up, which is purely time based, with no link to the temperatures in either the DHW cyl or TS, but I don't suppose you're interested in changing stuff, when you're comfortable how it works now. When the boiler shuts down, having maintained temperature for a period of time, what initiates a re-start?

    Keep doing what you're doing Jeff, use logic, make a single change, measure and review the data, improve with each step. Don't be tempted to jump to apply technology in a hope that it will magically solve a problem you haven't fully identified. Plus your finance director will be happier too.
    • CommentAuthorJeff B
    • CommentTimeDec 9th 2020 edited
     
    Posted By: GreenPaddyJeff B, looking much better. Agree with what PiH has said;

    - you now have a decent flow rate from boiler to TS. The modulation of the boiler I suggest was due to the flow temp very quickly being at set point, so the boiler assumes it's done its job, and throttles back, only to realise it hasn't done its job, and ramps up again (hunting). Now you are getting a decent flow rate, that volatility has reduced.

    - agree with PiH about pump2 location, and would mention again about moving it adjacent to pump1, and run both together, as it seems you need that oomph to get the decent boiler flow rate, but don't want interference from pump2 low pressure side.

    When you say adjacent, do you mean in parallel?



    - the initial drop in TS temp but recovery and subsequent increase, suggests that the input from the boiler is easily man enough for the radiator demand even starting from cold (20oC CH return). I would still be interested to see the effect of slightly throttling the CH flow rate, giving you warmer rads, but over 50oC may well be acceptable. That could lead to you being able to lower the boiler set point a little too, and just having a much more stable burn cycle, at slightly lower temperatures, but a test run with these really useful graphs would help clarify that - tune the system a bit.

    OK, I'll give that a try.



    - I still think that the temp set point for the load valve at 60oC is too high, and would suggest you at least try it at 50oC, to understand any impact. I know you understand the boiler to be non-condensing, but the manual does briefly mention about the removal of condensate. Also I'd be surprised if RHI would have accept a non-condensing boiler, and the stated efficiency is over 90%, which to me says you have a condensing boiler. Future thoughts may be to consider how to improve efficiencies, if it is a condenser (eg lower return boiler temps for quite a portion of the cycle, hence my comment about reducing the load valve set to 50oC).

    OK, I'll give that a try.

    As far as I know there is no condensate drain facility on the boiler. Where would the condensate collect?






    - I don't think there's a any issue with the boiler shutting down at the end of the first test. It's just doing its job. It is programmed to get to set point, then modulate back till it hits its lowest power point, still keeping to set point, then shutting off. It may also have a minimum run time also pre-programmed, to avoid short cycling, but the previous low flow rate made it easy to maintain set point, and so shut itself down.

    - I don't really like your control set up, which is purely time based, with no link to the temperatures in either the DHW cyl or TS, but I don't suppose you're interested in changing stuff, when you're comfortable how it works now. When the boiler shuts down, having maintained temperature for a period of time, what initiates a re-start?



    I don’t like it either! We were sold a “pup” with this boiler. When we bought it the supplier/installer promised that the Ekopower company were working on a retro-fit which we would be able to have FOC within a few months; this would enable the boiler to be restarted remotely when there was a demand for heat. This never materialised and the company went bust some time after. With hindsight I suppose we should have followed this up with the supplier/installer under the Trade Description Act. Hence we are lumbered with a time-based control mechanism. In the manual you will see that there are two modes of operation – either summertime on or summertime off. With “summertime on” you have the ability to set several on/off periods (which is what we use) and with “summertime off” the boiler will run 24/7 which apparently is how the boiler is used on the continent. By carefully setting the C/H on/off times it is possible to operate the system reasonably well but it is far from ideal.

    The boiler restarts when the boiler temperature reaches a preset lower limit but I don't know what this is. When the boiler gets too hot i.e. about 4C above the set temperature the boiler switches off and the LCD display will show "Awaiting temperature drop" but I am never around when that point is reached!



    Keep doing what you're doing Jeff, use logic, make a single change, measure and review the data, improve with each step. Don't be tempted to jump to apply technology in a hope that it will magically solve a problem you haven't fully identified. Plus your finance director will be happier too.


    Many thanks for your help with all this!
    • CommentAuthorGreenPaddy
    • CommentTimeDec 10th 2020
     
    Jeff, pumps in series, so you're adding more pressure rather than more flow rate (not quite that straight froward as there is an inter-dependence).

    You could remove pump2 first, and insert the spool piece (bit of pipe), and run the boiler. It may not need the second pump, which would give you a handy spare, and one fewer thing to go wrong. If you do that, you want to see the boiler flow and return temp difference around the number you were getting after you boosted the pump speed, think it was about 10oC.

    If that delta T has increased again to the 30oC odds as originally, then you need the second pump. Just daisy chain the power feed, so both run as one.

    I'm never that keen running equipment on a high temp cutout. For me that's a failsafe to prevent damage. I remember rectifying a clients GSHP which was set up to run continuously, and cut out on high pressure (high temp), so it just cycled on/off repeatedly when the cylinder was hot, and then wouldn't start when the cyl was cold, cause it had locked out on too many starts. Control logic is everything, but the kit gets the blame all too often. There may be an opportunity to put a stat control on the DHW (maybe TS too??) and tie it in to the boiler control. Would save guessing what time your DHW needed reheating, but let's get some stability with the above items first :cool:
  5.  
    Posted By: GreenPaddyYou could remove pump2 first, and insert the spool piece (bit of pipe), and run the boiler. It may not need the second pump, which would give you a handy spare, and one fewer thing to go wrong. If you do that, you want to see the boiler flow and return temp difference around the number you were getting after you boosted the pump speed, think it was about 10oC.

    +1
    • CommentAuthorArtiglio
    • CommentTimeDec 10th 2020
     
    Hi Jeff, in the bits about a condensate drain and as to wether the boiler is a condensing model. The boiler we have is rated at over 90% and rhi approved but is not a condensing boiler . The condensate (if there is any in the flue gases) is collected at the bottom of the exhaust flue and drains away through 22mm copper pipe. I’ve never seen any condensate and when cleaned out what ash there is in this part of the flue is dry.

    If you whisper an email address i have a picture of the drain , too large for posting.
    • CommentAuthorJeff B
    • CommentTimeDec 10th 2020
     
    Green Paddy - thanks for your further response. Firstly I think I'll try your idea of restricting the flow via the C/H pump and see what happens. Secondly maybe crank the boiler set temperature back a bit as the rads are more than adequately hot now. I think I will leave Pump 2 alone for the time being, that's maybe a job for the Spring rather than at the start of the heating season, I'll see how it goes!

    I quite fancy the idea of having the boiler controlled by a thermostat on the TS. IIRC you previously spotted in the Ekoheat manual that it is possible to connect a thermal probe in the DHW tank to control the boiler and so it might be possible to do the same with the TS instead. I'll need to check the manual for details.
    • CommentAuthorJeff B
    • CommentTimeDec 10th 2020 edited
     
    Posted By: ArtiglioHi Jeff, in the bits about a condensate drain and as to wether the boiler is a condensing model. The boiler we have is rated at over 90% and rhi approved but is not a condensing boiler . The condensate (if there is any in the flue gases) is collected at the bottom of the exhaust flue and drains away through 22mm copper pipe. I’ve never seen any condensate and when cleaned out what ash there is in this part of the flue is dry.

    If you whisper an email address i have a picture of the drain , too large for posting.


    I do not have any condensate drain with my boiler, that's why I assume it is not a condensing boiler. It is also rated at >90%. There is a removable base at the bottom of the flue pipe but that is always bone dry with only a very small amount of soot in it (it gets checked once or twice a year).
    • CommentAuthorJeff B
    • CommentTimeDec 11th 2020 edited
     
    Posted By: Jeff BI quite fancy the idea of having the boiler controlled by a thermostat on the TS. IIRC you previously spotted in the Ekoheat manual that it is possible to connect a thermal probe in the DHW tank to control the boiler and so it might be possible to do the same with the TS instead. I'll need to check the manual for details.


    I checked the manual. If I am correct then my understanding is that an optional temperature probe in the DHW tank can trigger the microprocessor in the boiler to control the 3 way valve so as to divert the boiler flow to the DHW tank when necessary. It doesn't mean that that same probe can instruct the boiler to fire up. I think if it were that simple then there would have been no need for the supplier to promise us the ill-fated "retro fix" which never materialised!
    • CommentAuthorphiledge
    • CommentTimeDec 11th 2020
     
    If you look at the boiler PCB connection diagram there are connections shown for "air thermostat" and "indoor temp sensor". The thermostat seems to used to inhibit the circulation pump and is bypassed when DHW is required. Not sure this would be of much use as just stopping the pump will likely stop the boiler on high temp and it will just restart once the boiler has cooled.

    The indoor sensor seems to be an option that is enabled via the control screen. Once enabled this may give access to an air temp setpoint?? Worth getting a sensor simulation resistor, wiring it in and enable the option to see what happens??
    • CommentAuthorJeff B
    • CommentTimeDec 11th 2020
     
    Posted By: philedgeIf you look at the boiler PCB connection diagram there are connections shown for "air thermostat" and "indoor temp sensor". The thermostat seems to used to inhibit the circulation pump and is bypassed when DHW is required. Not sure this would be of much use as just stopping the pump will likely stop the boiler on high temp and it will just restart once the boiler has cooled.

    The indoor sensor seems to be an option that is enabled via the control screen. Once enabled this may give access to an air temp setpoint?? Worth getting a sensor simulation resistor, wiring it in and enable the option to see what happens??


    OK, thanks, I'll take a look.
    • CommentAuthorJeff B
    • CommentTimeDec 16th 2020 edited
     
    .
    • CommentAuthorGreenPaddy
    • CommentTimeDec 20th 2020
     
    No. The live feeds to both the grey and white wires, which drives it to open the port to the CH.
    • CommentAuthorphiledge
    • CommentTimeDec 20th 2020
     
    Posted By: GreenPaddyNo. The live feeds to both the grey and white wires, which drives it to open the port to the CH.


    If this is commenting on what I wrote, Im not sure its correct, unless we're looking at different wiring diagrams. The grey and white wires are not connected together. The white wire carries the pump run signal after the air thermostat/DHW valve open relay contact. The grey wire carries the DHW valve open signal. The grey wire alone opens the DHW valve.

    Is the diagram youre looking at different??
    • CommentAuthorGreenPaddy
    • CommentTimeDec 21st 2020 edited
     
    separate conversation, sorry.
    • CommentAuthorJeff B
    • CommentTimeJan 21st 2021 edited
     
    .
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