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JamesI
JamesI, Developer
Category: Home Improvement
Satisfied Customers: 2026
Experience:  I have a portfolio of renovated houses, including DIY projects from installing bathrooms and new heating systems to rewiring.
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I want to install a Grasslin OP-Duostatbm to Potterton

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Hi,
I want to install a Grasslin OP-Duostatbm to Potterton Performa 28i. Can I just replace the fitted timer with the new one or does it require any wiring?
Thanks
Mike

Hi Mike,

The answer is that it depends if the current timer is Integral or External. If its integral then you would need to connect to the Graddlin receiver using the external timer wiring which is shown on 23 here, as its will pull more current than the traditional integral timers are designed to. However as per building regulations this would need to be carried out by a boiler engineer as you have to strip the boiler down to get to the PCB where the terminal block is located to connect into your proposed timer.

With regard to an external timer its just a case of taking the wires going to the legacy external timer and wiring them on to the new Grasslin receiver.

Please let me know if I can be of any further assistance.

Customer: replied 1 month ago.
Thank, the only problem I have is the fact that the existing timer has 4 connectors and the gosling replacement unit has 5. Am I correct to assume that on the gosling I need to connect to connector 3 and 5 and leave 4 open?
What version\model is the rf receiver?
Customer: replied 1 month ago.
Sorry I have been away. The receiver is called OP-DUOSTATBM (Rx)
Thats all i can see

It sounds like a Grasslin T55, which is the receiver for the RF205 thermostat/timer range.

When looking at the 5 connections from current timer in place where do the wires go, are they terminated in a terminal block as shown on page 23 of the manual above or are they connected somewhere else?

Assuming this is a T55 your installing 4 wires should be as follows:

1 – Neutral input

2 – Live input

3 – Common input

4 – Normally open output

Which based on the boiler wiring diagram should be terminal 1 goes to Neutral (blue) wire on the terminal block, terminal 2 to the Live (brown) wire on the terminal block, terminal 3 goes to that marked 1 on the diagram and 4 goes to position 2 on the diagram.

Regards

James

JamesI and other Home Improvement Specialists are ready to help you
Customer: replied 1 month ago.
Thanks for your help. I will try to connect this as you suggested when I'm off work again (Thursday).
May I come back to you if i need further help with the same item?
Kind regards
Mike

Sure will await to hear back from you.