Dodgy Bypass Preventing Condensing

gpbeck · Oct 31, 2018

I am always surprised that Boilers don't display return temperatures. I manually adjust flow temps to achieve a return of about 53 as a form of weather compensation. Last time the best flow temp was 62 with return 54 and as you can see my solid walled home couldn't get there.

A hand on the return pre and post bypass showed the problem. Radiator returns were in the 40s. I estimate 50% of boiler flow was heading straight back. Interestingly the valve stayed jammed open even after the foreign body was out, presumably due to wear. It is a big aperture, so even a slight opening has a large curtain area.

Quick swap, Boiler temps now 70 - 50 and boiler output up from 10kw to 16kw.

I know this is not rare, but the lesson for me is to check return temps before and after the bypass regularly, when the system has recently started up.

Rob Foster · Oct 31, 2018

gpbeck said:
View attachment 35187 View attachment 35189
I am always surprised that Boilers don't display return temperatures. I manually adjust flow temps to achieve a return of about 53 as a form of weather compensation. Last time the best flow temp was 62 with return 54 and as you can see my solid walled home couldn't get there.

A hand on the return pre and post bypass showed the problem. Radiator returns were in the 40s. I estimate 50% of boiler flow was heading straight back. Interestingly the valve stayed jammed open even after the foreign body was out, presumably due to wear. It is a big aperture, so even a slight opening has a large curtain area.

Quick swap, Boiler temps now 70 - 50 and boiler output up from 10kw to 16kw.

I know this is not rare, but the lesson for me is to check return temps before and after the bypass regularly, when the system has recently started up.

I love stuff like this , it’s very informative thank you
Rob Foster aka centralheatking

gpbeck · Oct 31, 2018

There is very little about this out there when I searched. So I posted this. I wondered how many boilers out there fail to condense for this reason, and how many are checked for this.

A man of great esteem and intellect such as Robert perhaps feels this stuff beneath them, their advice being to fit a leaky filter thingy I suppose.

dancinplumba · Oct 31, 2018

gpbeck said:
View attachment 35187 View attachment 35189
I am always surprised that Boilers don't display return temperatures. I manually adjust flow temps to achieve a return of about 53 as a form of weather compensation. Last time the best flow temp was 62 with return 54 and as you can see my solid walled home couldn't get there.

A hand on the return pre and post bypass showed the problem. Radiator returns were in the 40s. I estimate 50% of boiler flow was heading straight back. Interestingly the valve stayed jammed open even after the foreign body was out, presumably due to wear. It is a big aperture, so even a slight opening has a large curtain area.

Quick swap, Boiler temps now 70 - 50 and boiler output up from 10kw to 16kw.

I know this is not rare, but the lesson for me is to check return temps before and after the bypass regularly, when the system has recently started up.

some do, good ones

Dodgy Bypass Preventing Condensing

gpbeck

Rob Foster

gpbeck

dancinplumba

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