Boiler frequently turned on when no demand from ACB

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Boiler frequently turned on when no demand from ACB

Post  jytillier on Sat Mar 01, 2014 6:38 am

Hi,

I have the boiler being turned on every 10 - 20 minutes, for burning less than 1 minute each time. The green led for boiler pump and boiler request are off.

When commissionning:

  • boiler is ideal F330 set at max th.6
  • the store reached 77-78 degC
  • interval T1off / T2on is [70-77]
  • PHE return is around 35-37 degC
  • HW is around 45ish


The store is at 75 between 70-77 (and I measured the store loses about 1 degree in 3.5 hours when nothing is in use, no HW, no SH). So at night nothing should fire until next morning.

Space Heating works OK according to electro-mechanical clock, thermostat and the myson T-S valves: no problem
How water works OK including overurn period: no problem here as well

So all is OK so far. But I have an additional behavior: boiler is being turned on for about 1 minute (or less) at frequency of 10 minute interval. There is no green led for boiler pump and boiler demand as neither space heating nor HW are being required. For example at night. This is a waste of energy...

First plumber said: boiler can only be turned on from ACB request. I believe this is true because if the boilermate 2000 is off, boiler never turns on. So boiler definitely not have mind of its own. So he concluded that there was a problem with the board.

Intervention of Gledhill response: changed the ACB board. All still working fine as above but: boiler still firing when not needed especially annoying at night. After changing the ACB frequency was less and unwanted firing lasted less but still wasted gas.

Below is how often the boiler fired without any demand/necessity before we changed the board

Time       Boiler store PHE HW  T1on T2off
20:00:00  on     68   24   35     70    77
20:21:00  off     75   35   48     70   77
21:06:00  on     75   35   48     70   77
21:07:00 off      75   35   48     70   77
21:14:00  on     75   37   47      70  77
21:15:00 off      75   37   47     70  77
21:24:00 on       75  37   46     70  77
21:25:00 off      75   37   45     70  77
21:34:00 on      75   37   45     70  77
21:35:00 off      75   37   45     70  77
21:43:00 on      75   36   44     70  77
21:44:00 off      75   36   44     70  77

So to avoid this waste and sleep: I have to turn boiler off. I am still measuring gas meter/elec meter after ACB change. There is improvement but still unexplained boiler firing without any need.  Possibly there are many people who never noticed this until using phone/tablet apps for gas meter/electricity measurement (where can I reduce my gas billl...?)

Any suggestion to look at?


  • electro mechanical clock contacts
  • earthing of the wires/connections


Any one know the software itself? something they did not anticipated?

jytillier

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Re: Boiler frequently turned on when no demand from ACB

Post  mike on Sat Mar 01, 2014 10:08 am

Try fitting a new Store sensor.
Or get a timer wired in so the BM 2000 does not work at night.
How are you measuring the unit temperature?
Mike

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Re: Boiler frequently turned on when no demand from ACB

Post  jytillier on Sat Mar 01, 2014 11:27 am

I was thinking of a new timer as well to force it.

What is bizarre is that when this happens the boiler pump is not on, so the boiler is turned on not to increase store temperature (turned on for nothing I'd say).

I wrote down the temperatures displayed from p35 of the manual
It never gave an error and from quickly touching the pipe the temperature displayed seems correct.

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Re: Boiler frequently turned on when no demand from ACB

Post  mike on Sat Mar 01, 2014 11:34 am

The timer you have on the unit is for heating only.
Additional timer I was referring to.
BUT.
If the boiler is firing and NOT the boiler pump then there is something wrong.
Where is your boiler located?
Has it a built in frost stat?
If in a garage etc and a separate frost stat. Then that could be set wrong or faulty.
I take it the unit / boiler pump do run ok.
If it is just evenings then you must look at it all again.
Mike

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Re: Boiler frequently turned on when no demand from ACB

Post  jytillier on Sun Mar 02, 2014 11:41 am

The boiler is on ground floor, the thermal store on first floor.
It seems it has settled down now. Seems OK today. I keep monitoring
I wondered if there could residual voltage or something like that.

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Re: Boiler frequently turned on when no demand from ACB

Post  jytillier on Tue Mar 04, 2014 6:32 am

Test made:

- triggers on the mechanical clock mostly off and off for long periods, HW on only when needed, ST temp on when needed, Space H on when needed according to T/STAT, but problem still happens boiler on with no pump when nothing is requested

- triggers on the mechanical clock reverse of above (long perdiod on) same happens: HW on only when needed, ST temp on when needed, Space H on when needed according to T/STAT, but problem still happens boiler on with no pump when nothing is requested

So the problem does not come from a control logic related to the position of the triggers on the mechanical clock.



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Re: Boiler frequently turned on when no demand from ACB

Post  jytillier on Fri Mar 07, 2014 5:10 pm

On the frost/stat.

There are no frost stat on the boiler.

However if I read the instruction manual p.24 about the wiring

It reads: "terminal 6 on the terminal strip (as shown p.22) should only be used if boiler requires a permanent live for another purpose".

and "For frost protection for the whole house,...a frost thermostat should be wired across plug in terminals 21 and 23 on the A.C.B."

I do not have any wire between 12 and 6 as on their diagram.

I do have a brown wire coming from the board into 6 and out of 6.

What would be those other purposes? could it be why it starts without the pump for some unclear reasons?

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Re: Boiler frequently turned on when no demand from ACB

Post  Warp_speed on Sat May 10, 2014 2:45 am

jytillier I had the same issue with my boilermate 2000. Boiler would constantly switch on every 5 - 10 minutes with no demand signal from the boilermate. Turns out the house builders didn't wire my boiler in correctly. I have an ideal classic se12FF which only has the power input coming into the boiler coming from the boilermate.

They wired it in to Neutral and permanent live and NOT the SL which is a switched live. i.e. only switch the boiler on when the boilermate needs it. So the boilers own thermostat was switching itself off and on when the boiler pipe temperature was reached because the power was permanently on to the boiler. Problem is no pump is spinning on the boilermate because its not expecting the boiler to be on. So we ended up with a massive gas bill, worn boiler fan assembly and a lot of noise coming from the pipes.

Switched the live from L to the SL and now problems are resolved. Makes me wonder how some of these house builders get away with it, no wonder the last home owners went bankrupt with the boiler on 24/7.

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Re: Boiler frequently turned on when no demand from ACB

Post  jytillier on Sat May 10, 2014 5:53 am

Thank you for your reply. What I did was to change the Ideal boiler to a Vaillant. The ideal was too noisy and not efficient anyway. Now everything works as expected. I had to make the decision because none of the three technicians who came could find the source of the problem. Some even said dry-cycles are normal. There are not too me: they burn gas and put no heat in the thermal store.

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