modern boilers

Jan 04, 2009 4 Replies
D

While reclining in my bath the other day (I do all my best thinking there) I realised that our boiler, installed a few short years ago was designed to pump on for 15 minutes after the flame went out. The Corgi plumber wired it wrongly, so that the pump ran all the time the central heating timer said give me heat. I can live with this, as he said that a pump that runs all the time, is far better than one that starts and stops all day.



Now to my question.



As I am now using the timer to optimise the running time of the boiler, it may prevent the boiler from running the pump for the 15 minutes it needs after the flame goes out. Will this do any harm?



Boiler is a Baxi Solo PFL 30/80



Dave


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R

Read the installation guide for the boiler. If it requires the pump to run-on, then let it.

This will require 2 supplies to the boiler:

1) a constant mains supply to run the pump for the required time; 2) a 'demand' signal to fire the burner.

The pump does not need to run the whole time - just the run-on time required by the boiler. The boiler will normally handle this. Simply provide the necessary supplies and let the boiler get on with it.

( I've not read the details of your boiler, just general advice.. )

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D

Are you sure it's 15 minutes? The actual 'need' is to equalise the heat exchanger temperature to prevent boiling when the pump stops. Efficiency would demand you get all useful heat out of it - I suppose. But neither would take 15 minutes.

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G

In message , "Dave Plowman (News)" writes

The Baxi Solo 2 has about a 10 min o/run, the Potterton Suprima has 20 mins

15 mins sits in the middle
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D

I'm amazed. I fitted a home made one to my old Potterton Kingfisher which had a massive cast iron heat exchanger - and 5 minutes did it. Of course this was dumping the heat into the rads not fitted with TRVs - thinking on, it would be different if just using a bypass circuit.

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