Boilermate 2000 central heating problem (and proposed solution)

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Boilermate 2000 central heating problem (and proposed solution)

Post  Benedict* on Fri Nov 07, 2014 6:10 am

I inherited a Boliermate 2000 with the house I purchased in July this year. Up until this week we've not had to use the central heating and we've had plenty of (very) hot water.

We've discovered that the central heating doesn't always come on when it is supposed to. Occasionally it does, but sometimes this can be many minutes after the room thermostat closes, and even then it doesn't always stay on for long. So last night I did some diagnosis.......

Green LEDs 1 and 2 are both constantly on and the boiler pump is constantly running. the ST segment is also on. This indicates to me that the water in the store is not hot enough.

If I power cycle the unit when the room thermostat is closed, LED 3 is on, the HT segment is lit and the central heating pump runs and I get hot water to my radiators. However after a while LED 3 and the HT segment go out and the central heating pump stops and LEDs 1 and 2 light up and the boiler pump kicks in and the radiators cool down. This again indicates to me that the water in the store is not hot enough.

Using SW1 and SW2 I get the following....

Store_T1: No Reading
T1_ON: _|74
T1_OFF: ¬77
PHE_T2: OEr (Not relevant to this problem, but might explain why my hot water is so hot!)
DHW_T3: H54

I get no current T1 reading at all - the second and third digits just continue to display what they were previously displaying. So the first time I press SW2 I get Oon. If I press SW2 after the T1_ON reading it displays O74. If I press SW2 after the T1_OFF reading it displays O77.

I'm coming to the conclusion that the T1 sensor (or the ACB) is faulty, even though it doesn't display OEr. On one occasion it briefly displayed a reading of O34, but I don't trust this reading as I couldn't get it to repeat the reading and the temperature of the hot water suggests that the water in the tank is much hotter than 34C!

If the T1 sensor has an intermittent fault, it might explain why I can get the heating to come on with a power cycle and also why it sometimes just works OK.

I'm really just looking for some confirmation that my diagnosis makes sense from those that understand the Boilermate 200 better than me. The T1 sensor and the ACB were both replaced in January of this year by the previous owners of my property who had British Gas HomeCare cover, so I should be able to get either of them replaced under BG's 12 months parts warranty.

Benedict*

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Re: Boilermate 2000 central heating problem (and proposed solution)

Post  Benedict* on Sat Dec 06, 2014 5:30 am

Problem (eventually) solved!

After a bit of fault-finding I discovered that the expert from British Gas that replaced the ACB and store sensor stupidly connected BOTH the store sensor and the PHE sensor to the store sensor terminal on the ACB, which meant it wasn't getting accurate readings from either of them.

After a two minute job to connect the PHE sensor to the correct terminal I've happily discovered that both sensors are working fine, as is the whole system!

I also understand much better how the system works too, which means I'll be fitting my nice new Nest thermostat tomorrow!

Benedict*

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