Odd behavior after SAC replacement

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Odd behavior after SAC replacement

Post  Eserim on Sat Sep 28, 2013 6:51 am

OK - we've lived with a Boilermate III for 10 years now, and I think I understand it.

Recently the thing stopped sending water down to the boiler.  The SAC had lights on, but no-one was home.  Sometimes the pump to boiler came on when there was a heat store demand, but then failed if the demand was for heating.

Anyway, we have Home Emergency insurance (a well spent £19) and the insurers classed as one, so it was all covered.  The chap who came out had never seen a Boilermate before, and between us we (correctly) diagnosed a SAC board failure.  New one ordered and fitted a few days later by another Boilermate virgin.

All seems fine.  Apart from now I get a bit odd behavior.

For starters the heat store demand was going on longer than the boiler could meet it - so I ran the commisioning setup to get the BM to recognize the maximum heat the boiler could produce.

Next, a few times a day, it goes into a weird mode.  All LEDs on SAV flash on/off at about a second interval, which sends pulse do main boiler pump.  This goes on for a few minutes.

Also, when there in no demand for heat store, the boiler doe fire for 10 seconds or so.  When it is doing this LED 1 on the SAC is flickering.

Is this all "behaviour as designed" that I simply missed before?  Or is this something else?

Cheers

Eserim

Edit - two more facts - when the boiler is doing its 10 second stop/starts there is no action on the pump. So I guess it is firing, hitting a preset temp with what is inside it, then stopping.

Also, I have just noticed the old SAV only had jumper one set. The new one, as per the manual has 1,3 and 4 set.

Eserim

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Re: Odd behavior after SAC replacement

Post  mike on Mon Sep 30, 2013 5:23 pm

Well I would check your manual.
Or download one from Gledhill (free)
Page 22 onwards.
And check the jumper settings.
As they do not seem to compare to yours.
There may be more than one model.
As in your was an earlier one.
Then the units changed later.
Hence the board / jumper settings.
At the very least start at page 22 and commission again.
Mike

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Re: Odd behavior after SAC replacement

Post  Eserim on Tue Oct 01, 2013 1:44 am

Mike

:-) you mean, as we in ICT say, RTFM?

Anyway, did all that. The manual says jumpers 1,3 & 4, but only describes what 4 is (180s over run)

We had the actual boiler serviced yesterday (a potterton) and the local chap, who has had to deal with a lot of boilermates took a look. AS far as we can see the Potterton is delivering to spec.

However at times the BM is sending demand down, even with all green LEDs on (and last one flashing)

Then at other times the SAC LED 1 & 4 do this fast flicker and occasionally fire off the boiler even through the system pump isn't going.

Removing jumper 3 (as the old SAC had) drops the measured temp, so if all LEDs were on with it in place, removing it drops the all off. And with it removed the commissioning routine doesn't work.

The one thing our local engineer suggested is that the tank may be sludged up - he's had to de-sludge a few around here. AS the temp sensor is in the bottom then if there is sludge there it could be effecting the readouts. Which sort of makes sense, as when there is a store drop caused by a sudden hot water demand, it seems happy - this means the store has been mixed up well. When the demand is due to ambient heat loss, it isn't so happy.

Any other ideas welcome.

Many thanks

Eserim

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Re: Odd behavior after SAC replacement

Post  Eserim on Tue Nov 05, 2013 3:38 am

OK - still got the initial issue, which I think is either sensor related or sludge related. However, I have a new one.

The SAC will, several times a day get stuck in a bad thing - LEDs 1 and 3 flicker - mainly on, but not totally - and these two being on should never be a good combo, as it is the power to the boiler and power to the 3 way, but not power to the pumps. So when this happens the 3 way opens and we get short (10 second ) bursts at the boiler.

Killing the power clears this, as does a radiator demand. A demand for the main heat store doesn't seem to.

In the manual it says you can do a reset of the SAC to factory conditions, but contact Gledhil - this was when such contact was free - anyone know how to do this - I'm guessing it is by powering up with a differnt jumper combo

Cheers
Eserim

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