Draining BM2000 to Replave the HW Sensor

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Draining BM2000 to Replave the HW Sensor

Post  davejwebb on Wed Feb 18, 2009 5:19 am

Any recommended sequence to drain the system to replace the HW sensor ? I noticed a number of drain plugs + isolating valves on the pump. There appears to be drain valves on both sides of the right hand pump coming from the heat exchanger.
Is is simply a matter of securing the header tank so it doesn't refill or is this element fed by the cold water mains (I'm assuming it is). Hence turn off the mains and then use one or other of these drain plugs to empty ?

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Re: Draining BM2000 to Replave the HW Sensor

Post  Hogthrob on Thu Feb 19, 2009 2:26 am

The advice on David Angier's blog (which I believe is what the plumber who fixed his system did) is:

* Remove power from the system.
* Pull the edge connector that the DHW sensor is connected to from the main board.
* Using a very small screwdriver, open the jaws on the edge connector and remove the sensor wires from it (make a note of what goes where).
* Shut down the stopcock feeding the cold water main into the heat exchanger. Verify by running a hot tap, the pressure should fall off to nothing very quickly.
* Unscrew the DHW sensor and replace (using PTFE tape to seal the joint).
* Open up stopcock.
* Reconnect sensor wires to connector.
* Plug in edge connector and power up.
* Hope that your issue was correctly diagnosed.

http://www.angier.co.uk/david/2005-12-22-boilermate-conclusion#comment-137

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HW Sensor Changed

Post  davejwebb on Thu Feb 19, 2009 11:53 am

I've changed the HW sensor and the next morning still had the same issue with the shower going cold. I did turn the shower control slightly and it recovered which points to the shower thermostat but then it occurs elsewhere in the house.

Should I change the PHE Return sensor as well ???

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Re: Draining BM2000 to Replave the HW Sensor

Post  Hogthrob on Fri Feb 20, 2009 4:26 am

Sorry it didn't work :-( I did read somewhere that it's best to change both of them.

How did the swap of the DHW sensor go? Any unexpected problems?

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Change of HW Sensor

Post  davejwebb on Fri Feb 20, 2009 4:36 am

The change out went OK. I attempted it before I had the info on how, so applied common sense. I had the mains off which was all I needed to do (as it turned out) but did try and drain it from the bottom drain valve but after several buckets of HW gave up and just tried removing the sensor aiming to simply plug the hole while I inseretd the new one all ready. Of course having the mains off nothing came out anyway.
problem I might have with the other sensor is that the recommended drain point above the pump doesn't drain. I suspect the washer is stuck as the brass insert comes right out but no water from the drain point, so it could be a bit messy when I do it !

Also didn't need to pull the wire connecting plug out. there was a strange plastic clip sitting on a spare terminal, which when aplied to the ones I needed to remove, with a simply press down on the plastic released the wire grip and they came out. Instlation of the new wires was simply the same.

I might hold off ordereing another sensor until some more replies come on here as the draining is also required for the Heat Exchanger and I'd rather just do it the once. If only it was easy to confirm the problem and relace just the necessary parts !!

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Changing the Other Sensor

Post  davejwebb on Fri Feb 20, 2009 4:43 am

I did consider replacing the other sensor with the one I've just removed on the assumption it isn't faulty given its made no difference with the new one ?? Might be false economy but would at least confirm the problem.
Also given the one replaced went back in fairly quick, I also thought whether I could simply unscrew it and hold the water with thumb/cloth etc. and shove the replacement straight back in with minimal water loss/mess ??

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Re: Draining BM2000 to Replave the HW Sensor

Post  Mike the Boilerman on Sat Feb 21, 2009 5:59 am

Right, this is one of those interesting ones with a number of possible reasons for the fault.

You say the shower goes cold. Does it do this reliably, every time, or just once in a while? How long does it run hot before going cold?

You've replaced the DHW sensor so we can (more or less) rule that out. Run the shower until it goes cold and leave it running. Now go to the Boilermate and feel to see if the pipe feeding the hot water taps is hot. (It should be.)

Check the shower is still running cold. Feel a piep to see if you have hot water coming out of the boilermate feeding the hot water taps and shower. You probably don't you don't. Now see if the DHW pump is running. (It should be.) If it is, feel the pipe coming out of the store feeding stored water into the DHE. Is it scaldingly hot? (It should be.) Now feel the pipe with the DHW pump in it returning water back to the store for re-heating. Is it luke warm or cold? (it should be.)

Report back with your results.

If you have HOT water coming out of the boilermate but the shower is still running cold, then the prob is probably with a second shower mixer in the property having non-return valves jammed in the open position. This can be a perverse fault to diagnose, but allows cold mains water to flow into the hot distribution pipework feeding the shower that is running cold, and I'm wondering if this is happening to yours.

Cheers, Mike

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Hot & Cold Shower Info

Post  davejwebb on Sat Feb 21, 2009 10:40 am

Mike,
Have run the shower. FYI it doesn't go cold for long (apologies may have given that impresssion) only about 15 secs or so about 3 maybe 4 times during the average time for a shower.

Wife ran the shower while I checked the BM. Before she noticed the shower going cold the temp of the pipe from the BM feeding taps/shower was getting less warm (maybe going cold but the pipe retains some heat anyway- certainly doesn't go stone cold like the mains but a noticeable drop). After 10-20 secs both the feed from the BM and the shower get hot again. On this occasion it reoccurred (got cold) a few seconds later and then stayed OK for several minutes before doing the same again.
During this time the DHW pump was running and the pipe from it to the PHE was cold (not as cold as the mains-sort of room temp). Mains feed was stone cold (as expected).

Not sure which is which on the PHE as regards flow/return but I'm guessing the flow from the BM into the PHE is the top one (nearest the BM where it joins the PHE) as this was red hot throughout, couldn't leave my fingers on it.

The pipe at the front of the PHE at the top was also hot but not red hot i.e. could leave my fingers on it for 5 -10 secs unlike the one at the back).

Once the shower was turned off the pipe with the DHW pump on it also got hot after a short while.

So to confirm the answers to your questions:

You say the shower goes cold. Does it do this reliably, every time, or just once in a while? How long does it run hot before going cold? Happens every shower, and on others in the house including ones on the bath mixers. This time once it got hot it went cold after 20 secs, then recovered and again went cold a few secs later, then settled down before going cold about 3 mins later. each time it goes cold for about 15-20 secs ish.
You've replaced the DHW sensor so we can (more or less) rule that out. Run the shower until it goes cold and leave it running. Now go to the Boilermate and feel to see if the pipe feeding the hot water taps is hot. (It should be.) It is until just before wife reports shower going cold, it goes luke warm in time with the shower going cold.

Check the shower is still running cold. Feel a piep to see if you have hot water coming out of the boilermate feeding the hot water taps and shower. You probably don't you don't. As above the temp coming out the BM goes luke warm (possibly cold but over 10-15 secs the pipe still luke warm) and the shower goes cold.

Now see if the DHW pump is running. (It should be.) Yes

If it is, feel the pipe coming out of the store feeding stored water into the DHE. Is it scaldingly hot? (It should be.) I'm assuming this is the top pipe from the PHE, the one at the back nearest the BM. Red Hot throughout.


Now feel the pipe with the DHW pump in it returning water back to the store for re-heating. Is it luke warm or cold? (it should be.) Yes until just after showers was turned off when it got quite hot.

Report back with your results.

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Re: Draining BM2000 to Replave the HW Sensor

Post  Mike the Boilerman on Sat Feb 21, 2009 12:07 pm

Hi Dave,

Have to say this sounds as though the new sensor you fitted is not working.

The cool(ish) water being returned to the store from the HE suggests the HE is not suffering form water scale contamination. (Return water comes out HOT when this is the problem, the PHE sensor senses the rise, tells the board which then thinks you've turned the hot tap OFF even though you haven't, and stops the pump....)

The intermittent behaviour suggests a DHW sensor problem. Check the electrical connections into the control board plug. These are a clumsy design to say the least, especially when two wires go into one connector hole. Ultimately, having ruled out scale in the HE, and made sure the store water is hot enough, the only components controlling the temp of the water to the hot taps are the DHW sensor, the control board itself, and the pump. If I were on site I'd change the DHW sensor again, and then the control board. If the behaviour remains I'd then change the pump and put the old control board back again. (Pumps can get sticky and stop spinning when the control board lowers the supply voltage.)

One last possibility that can cause this - basic lack of water in the store. Is the header tank filled up above the lowest pipe connection in the side? Does the pump ever sound noisy as though part air, part water is being pumped?

Cheers, Mike

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Update

Post  davejwebb on Sun Feb 22, 2009 4:28 am

Mike,

The header tank is full and in my case in the loft. Pump appears to run smoothly i.e. no noise/air.

FYI I did also run the diagnostics as detailed in the manual using the two switches on the PCB board.

From the manual chart.

Press SW2 = 74 followed by SW1 = 68 then SW1 again = 75. I think this is OK so far. This is the line on the chart moving across from L to R.

back to start (now moving down the chart).... Press SW2 = 74, Press SW2 again (moving down the chart) gives error. Press SW2 again gives 59.

This from what I can understand gives a value of 74 for the Store_T1 value, Sensor Error for the PHE_T2 and 59 for DHW_T3.

Hence I'm getting an Error for the PHE_T2. What isn't clear from the manual is what sensor this is although it shows possible errors in 3 parts of the test, one of which the error is prefixed with an 'H' e.g. HEr. I'm assuming the H indcating the DHW sensor and as my error is the other one the PHE sensor.

My error is on the PHE_T2 test indcated by 'oEr', just to confirm the 'o' being at the lower half of the 8 grid display.

Does this suggest the PHE sensor as opposed to the DHW sensor which I'v changed.

I'll check the wiring to the board in the meantime.

Thanks

Dave

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Further Update

Post  davejwebb on Sun Feb 22, 2009 10:46 am

Mike,

Checked wiring and all seems OK. Not sure about the DHW Pump (right hand one) though.

If I hold one of the other pumps (Left hand one) when running I can it working even holding the top plastic part where the speed switch is. Also if I put a screwdriver against the large metal screw in the middle and my ear to the other end I can hear it running.

When I do the same to the DHW pump (with a hot tap running), I can't feel it through the plastic part like the others and the screwdriver/ear test I can hear just a buzzing noise (not the same as the other pump).

Holding the pumps by their metal casings (although the left one gets a bit hot) reveals that the DHW one appears to be running but not so easy to feel it.

All pumps set to full speed.

Of course this is all a bit touchy feely and doesn't prove it one way or the other and does this explainn the Diagnostic result in the earlier post re Sensor Error ?

trying to pin this down as I havn't got stock of the parts and clearly want to only buy whats needed rather than trial & error especially as the Cct Board is near £200 !

Cheers

Dave

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Re: Draining BM2000 to Replave the HW Sensor

Post  Mike the Boilerman on Tue Feb 24, 2009 2:30 am

Hi Dave,

Yes this PHE error will definitely be screwing up the hot water behaviour...

It is the sensor just above the DHW pump, on the outlet from the heat exchanger. Probably the same as the PHE sensor you previously changed. Do you still have the old sensor? Try connecting it to the board (electrically only) to replace the faulty PHE sensor and then interrogate the board to check the oEr error message has disappeared and you get a temperature reading returned. If you do, then fit it properly!

Cheers, Mike


davejwebb wrote:Mike,

This from what I can understand gives a value of 74 for the Store_T1 value, Sensor Error for the PHE_T2 and 59 for DHW_T3.

Hence I'm getting an Error for the PHE_T2. What isn't clear from the manual is what sensor this is although it shows possible errors in 3 parts of the test, one of which the error is prefixed with an 'H' e.g. HEr. I'm assuming the H indcating the DHW sensor and as my error is the other one the PHE sensor.

My error is on the PHE_T2 test indcated by 'oEr', just to confirm the 'o' being at the lower half of the 8 grid display.

Does this suggest the PHE sensor as opposed to the DHW sensor which I'v changed.

I'll check the wiring to the board in the meantime.

Thanks

Dave

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Re: Draining BM2000 to Replave the HW Sensor

Post  Mike the Boilerman on Tue Feb 24, 2009 2:38 am

Hi again Dave,

If the DHW pump feels like it is not spinning, then it probably isn't. Prove it by taking out that big silver screw, which exposes the end of the motor spindle. (Catch the resulting slight dribble of water in a towel or something.) Use a small screwdriver to spin the spindle and check it isn't seized, then use a multimeter to measure the AC voltage being fed to the pump terminals during HW demand. Voltage should start low then climb up to about 230V. Pump should spin ever faster as it climbs.

Altternatively try connecting a flylead to the pump terminals and plugging it directly into the mains to prove if pump works, or not. (Also an easy way to emergency-rig some hot water!)


Cheers, Mike




davejwebb wrote:Mike,

Checked wiring and all seems OK. Not sure about the DHW Pump (right hand one) though.

If I hold one of the other pumps (Left hand one) when running I can it working even holding the top plastic part where the speed switch is. Also if I put a screwdriver against the large metal screw in the middle and my ear to the other end I can hear it running.

When I do the same to the DHW pump (with a hot tap running), I can't feel it through the plastic part like the others and the screwdriver/ear test I can hear just a buzzing noise (not the same as the other pump).

Holding the pumps by their metal casings (although the left one gets a bit hot) reveals that the DHW one appears to be running but not so easy to feel it.

All pumps set to full speed.

Of course this is all a bit touchy feely and doesn't prove it one way or the other and does this explainn the Diagnostic result in the earlier post re Sensor Error ?

trying to pin this down as I havn't got stock of the parts and clearly want to only buy whats needed rather than trial & error especially as the Cct Board is near £200 !

Cheers

Dave

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Sensor & Pump Checked

Post  davejwebb on Tue Feb 24, 2009 6:51 am

Mike,

Good idea re the PHE sensor. I tried this and the sensor checks OK with the diagnostics i.e. no error. Not sure whether to fit the old one (the replaced HW one) or order a new.

Checked the pump too and with a hot tap running the pump starts slow then speeds up, but it the slowed and sped up and continued like this. Did this while the original sensor was in place so I guess that could be causing the pump to slow hence the same problem with the shower/HW.

Once I've changed out the sensor I'll report back.

many thanks

dave

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Re: Draining BM2000 to Replave the HW Sensor

Post  Mike the Boilerman on Tue Feb 24, 2009 11:03 am

I'd just fit the original DHW sensor in the PHE if I were you, as you know it works!

The pump speed changes to control the hot water temp at around 52 degrees C. Is it just the shower that runs cold or all the hot taps? This can be caused by water scale in the DHE.

Cheers, Mike

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PHE Sensor Changed and now OK

Post  davejwebb on Wed Feb 25, 2009 5:08 am

Mike,

Changed the PHE with the old DHW one (which we knew was OK given changing it had made no difference- should have run the diagnostics on the board first if I'd had known about it !).

Shower this morning was fine, so appears its all OK now.

I couldn't be asked to drain the system so I changed the PHE without doing it. Switched off power and ran a hot tap to cool the pipe/Heat exchanger down, as clearly that temp of water splashing about would not be good. Prepared the replacement ready, couple of towels, covered the pump, thumb over the hole and job done, minimal mess.

many thanks for all your help.

Regards

Dave

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Re: Draining BM2000 to Replave the HW Sensor

Post  Hogthrob on Thu Feb 26, 2009 9:36 am

davejwebb wrote:From the manual chart.
Press SW2 = 74 followed by SW1 = 68 then SW1 again = 75. I think this is OK so far. This is the line on the chart moving across from L to R.
back to start (now moving down the chart).... Press SW2 = 74, Press SW2 again (moving down the chart) gives error. Press SW2 again gives 59.

This from what I can understand gives a value of 74 for the Store_T1 value, Sensor Error for the PHE_T2 and 59 for DHW_T3.

Hence I'm getting an Error for the PHE_T2. What isn't clear from the manual is what sensor this is although it shows possible errors in 3 parts of the test, one of which the error is prefixed with an 'H' e.g. HEr. I'm assuming the H indcating the DHW sensor and as my error is the other one the PHE sensor.

My error is on the PHE_T2 test indcated by 'oEr', just to confirm the 'o' being at the lower half of the 8 grid display.
Does this suggest the PHE sensor as opposed to the DHW sensor which I'v changed.

I'll check the wiring to the board in the meantime.

Thanks

Dave

Info from the 'Design, Installation and Servicing Instructions' , which might help:

Error codes
oEr (o at top of LED) = Store_T1 sensor error
oEr (o at bottom of LED) = PHE_T2 sensor error
HEr = DHW_T3 sensor error

Parts
Plate Heat Exchanger (PHE) - Manufacturer Swep - Stock code GT107 - Gas Council Part No. E05 664
Appliance control board (A.C.B.) - Manufacturer Elok - Stock code XB255 - Gas Council Part No. E39 158
Store sensor - Manufacturer Elok - Stock code GT149 - Gas Council Part No. E26 022
PHE return sensor - Manufacturer Elok - Stock code GT153 - Gas Council Part No. E26 024
D.H.W. sensor - Manufacturer Elok - Stock code GT153 - Gas Council Part No. E26 024


Mike the Boilerman wrote:The cool(ish) water being returned to the store from the HE suggests the HE is not suffering form water scale contamination. (Return water comes out HOT when this is the problem, the PHE sensor senses the rise, tells the board which then thinks you've turned the hot tap OFF even though you haven't, and stops the pump....)
...and, it would seem, a faulty PHE return sensor results in the same effect.

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Re: Draining BM2000 to Replave the HW Sensor

Post  Mike the Boilerman on Thu Feb 26, 2009 2:49 pm

davejwebb wrote:Mike,

Changed the PHE with the old DHW one (which we knew was OK given changing it had made no difference- should have run the diagnostics on the board first if I'd had known about it !).

Shower this morning was fine, so appears its all OK now.

I couldn't be asked to drain the system so I changed the PHE without doing it. Switched off power and ran a hot tap to cool the pipe/Heat exchanger down, as clearly that temp of water splashing about would not be good. Prepared the replacement ready, couple of towels, covered the pump, thumb over the hole and job done, minimal mess.

many thanks for all your help.

Regards

Dave


You're welcome. It's pleasing to guide someone obvioulsy competent towards fixing it themselves!

I change the PHE sensors live just as you did. best to check it's an open vented system fist though. I once took one out on a sealed system pressurised to 1.0 bar without realising (i.e. I didn't check, DOH!) I lost a litre or so of water before I got the new one's thread started. I was lucky. Could easily have been a whole load more than that....! :-(

Useful info on part numbers etc from hogthrob too. Thanks.

Gledhill only supply parts to bona fide trade customers but anyone can buy them on line from www.segel.co.uk. (No connection with them other than being an occasional customer myself.)

Cheers, Mike

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Re: Draining BM2000 to Replave the HW Sensor

Post  Hogthrob on Sun Mar 01, 2009 8:30 am

Hopefully, touching wood, and with fingers crossed, I can report another successful sensor change.

Having a oEr error, I changed the PHE Return sensor. The error has gone, and the hot water has, so far, remained hot.

I used the procedure described by davejwebb. The hardest part was working out how to remove the wires from the connector block. When the old sensor came out, there a a mighty spurt of water - much more than I anticipated. Fortunately, I had plenty of towels covering things up, the new sensor went in easily enough, and the water stopped escaping after just a couple of turns of thread.

Thanks Mike & Dave.

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Sensor Wires Removal

Post  davejwebb on Sun Mar 01, 2009 10:29 am

On my BM 2000 the wire connecting block where the sensors terminate had a small plastic lever sitting in one of the spare terminations on the top of the block when looking at it. By squeezing it (pushing it down) it applies pressure via a lug into the hole nearest you. I guess a screwdriver or something similar pushed in would achieve the same to open up the pinch terminal connector, although the advantage of this plastic lever thingy is that to squeeze it you use finger and thumb, with the latter beneath the connecting block, so it doesn't force down on the block itself, which could be a bit risky with it still on the cct. board i.e. could break off.

Glad you managed it !

Regards

Dave

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