I've got a 15 year-old non-condensing combi boiler in a 2-bed semi,
which has developed a controller fault.

I can replace the PCB or replace the boiler. If it was a condensing
boiler, I'd replace it. But I'm wondering if replacing a
non-condensing with condensing will cause additional work.

Obviously, I'll need to add a condensate pipe. But it's in the
kitchen, so I expect that won't be too difficult.

But I believe the CH water temperature will be lower, so might I need
to re-size the rads? Is this something that can be worked out with a
rule of thumb, or is it generally not a problem? Is it possible to
run with the water temperature at the same temperature as the old
boiler and accept that it won't actually condense?

On 11/07/2016 18:50, Caecilius wrote:
I've got a 15 year-old non-condensing combi boiler in a 2-bed semi,
which has developed a controller fault.

I can replace the PCB or replace the boiler. If it was a condensing
boiler, I'd replace it. But I'm wondering if replacing a
non-condensing with condensing will cause additional work.

Obviously, I'll need to add a condensate pipe. But it's in the
kitchen, so I expect that won't be too difficult.

But I believe the CH water temperature will be lower, so might I need
to re-size the rads?

It does not have to be lower (you can set it to whatever you like
basically), however you get higher efficiency gains if you can keep the
*return* temperature low ish (you see most boost with the return below
54 degrees). You may be able to achieve that with balancing alone.

Is this something that can be worked out with a
rule of thumb, or is it generally not a problem? Is it possible to
run with the water temperature at the same temperature as the old
boiler and accept that it won't actually condense?

Yup, that is an option. You may well find that a modern boiler will
modulate anyway, and be able to condense much of the year as it is. You
may lose a little efficiency during the coldest months.

--
Cheers,

John.

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On Monday, 11 July 2016 18:50:46 UTC+1, Caecilius wrote:
I've got a 15 year-old non-condensing combi boiler in a 2-bed semi,
which has developed a controller fault.

I can replace the PCB or replace the boiler. If it was a condensing
boiler, I'd replace it. But I'm wondering if replacing a
non-condensing with condensing will cause additional work.

standards change, so extra work may be required.

Obviously, I'll need to add a condensate pipe. But it's in the
kitchen, so I expect that won't be too difficult.

But I believe the CH water temperature will be lower, so might I need
to re-size the rads? Is this something that can be worked out with a
rule of thumb, or is it generally not a problem? Is it possible to
run with the water temperature at the same temperature as the old
boiler and accept that it won't actually condense?

If using it on existing rads they should be well cleaned out & a magnetic cyclonic filter added.


NT