Any benefit to draining down ??

Hi I had an original post where we were experiencing problems with heating / hot water etc.

Had emergency cover on bank account and engineer came out and suspected problem with thermostat sensor in boiler. This has been replaced now and the same symptoms exist.

With CH OFF on the room stat or programmer, BM2000 heats up to indicated 72 deg stored.

Turn on CH and after approx. 3 mins the temp. steadily drops to 59 deg where CH turns off. Boiler then continues to cycle normally and temp fluctuates between 60/61 deg (CH turns ON) and back to 59 deg (CH turns OFF). So we only have 'trickle heating' through the day. Providing the store is at a good temperature the DHW is not really affected.

The engineer now suspects restricted flow through the boiler but reckons the boiler pump is OK (tried stopping impeller with screwdriver).

Now my question is - is there any benefit to me draining the system down and trying to flush with clean water. If so what is the best procedure for this ?

I was thinking;
1) Turn OFF boiler
2) Close valve to cold feed on F&E tank
3) Turn OFF BM2000
4) Connect hose to lowest point - radiator in hallway and open bleed valve
5) Open bleed valves on upstairs rads
6) When upstairs drained, open bleed valves on downstairs rads
7) Continue until system empty

Then could I re-open valve on F&E tank to allow fresh water into the system to run through and out of the drain point ?

If I was to follow this draining procedure, I take it this would completely empty the system ie Boiler pipework, Radiators and pipework and BM2000 unit ?

I am also aware of closing off the bleed valves when refilling and then having to bleed off radiators as required when the heating is re-instated.

Thanks in advance for any advice.

Be wise to do all that.
After you have put in some sludge remover 1 litres to every 100 litres.
10 rads max 1 litre plus the unit volume.
If it works out to 3.5 put 4 in not 3.
Run it for at least a week or a month if need be.
Then do what you have said.
Mike

Hi Mike

Thanks for quick reply. I actually drained F&E tank down yesterday and put in 2 litres of the stuff (Sentinel X400) as it says for older systems including thermal stores.

One thing I have noticed after 24 hours, my store temp is now reaching 75 deg whereas previously it was reaching 70 deg or sometimes 72 at best.

Also now when I run hot water and the temp on the store drops, it seems much quicker to return to its intended temp as if the boiler is working better. And the hot water temp is now indicated as H65 whereas before it was probably more like H52 or less.

Perhaps the cleaner is starting to work its magic ??

Could well be.
2 litres enough?

Dunno - it says 1litre treats a normal hot water cylinder with 10 rads. Larger systems should be dosed with 2 litres.

My BM2000 holds 125 litres so I thought add another bottle ??

Yes not far out.
When done / completed.
Need to put X100 in at the same rate.

Mike

Hi Mike

Had a thought yesterday that maybe pump performance could be root cause. Isolated BM2000 and physically swapped Boiler and CH pumps over. Refitted and connected up and powered unit back up.

No noticeable improvement in CH although boiler pump now feels much hotter when circulating water through the boiler. Not got any thermometers to check but I think it is better. However BM2000 still has same symptoms, with CH switched OFF store heats up to > 72 deg. Turn CH on and store holds temp for around 3 minutes then quickly drops down to 58/59 deg and CH turns OFF. Boiler heats store back to 60 deg and CH comes ON - this cycle repeats throughout the day and of course means we are just getting 'trickle' heating.

Any more ideas or have you seen this before on a unit ??

Boiler on MAX ?
You do know that;
A BM 2000 when it drops below 60c the heating will NOT work.
It is giving DHW priority.

And also.
Your unit being a 125 litre is the smallest in the range.

Mike, we have lived in the house from new (11 years now). This is the first time the CH has struggled to cope.

The boiler is on max, always has been. Engineer thought it was a problem with the boiler thermostat and replaced this last week. Boiler is firing correctly.

When the engineer visited he put temp clamps on the pipework at the BM2000. Boiler flow and return only measured around 48-52 deg. He wasn't sure he could get an accurate reading though as the BM2000 was installed with the use of push fittings and flexible hoses.

Through this forum and my own curiosity I have learnt more and more about the BM2000. The ACB is doing what it should, the pumps are working as and when they should. It's just the poor heating performance that is driving me mad.

If we turn the CH off on the room stat or programmer the store heats up ok. If we turn the CH on and don't use the DHW, as I said previously within minutes the CH turns off again as the store drops nearly 20 deg.

If the store is up to temp then the DHW is perfect, no complaints with this.

Mike, just a thought. This may be the problem that I have ??

https://gledhill-repairs.forumotion.net/t1324-replacing-pipes-to-the-boilmate-2000

Right Basics / simple.
Your unit is not hot enough.
Yes you will / are getting DHW
Heating No.
1;
Heat water up and the heat rises.
2'
The DHW / plate heat exchanger take off from the unit is high and the unit water temperature is hot at the top.
3;
The heating flow and return is / are taking off low on the unit and the heated water is where? At the top.

The BM 2000 is not just one tank inside.
It is 2 tanks. Both are linked together.
I would think that in 11 years you may have a sludge problem.
Perhaps the right hand tank inside is ok
And the left hand one is not. Or both.
The are linked / joined together with pipes. Top and bottom.
All doing there various jobs etc.
You have 3 choices.
1; New unit.
2; Drain down unit remove pumps etc and check all pipe / connections.
3; Put a good amount of sludge remover in. Run boiler and DHW as normal. But not the heating too much.
As you want to clean the unit and the boiler flow and return.

2 and 3 are easy but labour intensive.
As your unit is the smallest one you are most likely running at a reduced rate etc.

And check the flexible hoses as they can / are know to collapse inside.

I can not add or think of anything else to say.
Mike

Thanks Mike,

I will leave the cleaner in until the next Bank Holiday weekend. I will then have time to drain the unit down and inspect various components. I will certainly give consideration to inspecting the flexible hoses !!

feebet wrote:Mike, just a thought. This may be the problem that I have ??

https://gledhill-repairs.forumotion.net/t1324-replacing-pipes-to-the-boilmate-2000

This is EXACTLY the problem I had, 4 hoses nearly completely blocked with the rubber insides collapsing

Well done
You got there.
Easy !
Mike

Thanks Mike,

Not quite, seen my Airlock thread ??

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