Central Heating Questions

Hi,
Is it OK to replace a Honeywell three port valve with one from another manufacturer, say, Danfoss?
Danfoss make three port valves in a paddle type and a shoe type, what is the difference and is one preferable to the other? I believe that the Honeywell is a paddle type.
Finally, I was searching uk.diy from google for references (which I have just failed to find again) to descaling boilers and I found a couple of posts that suggested that conventional boilers don't really scale up, why is this?
Thanks, BraileTrail
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Because there's no fresh water circulating round them, unless something is leaking. And once the scale from the re-circulating water is deposited, that's it.
--
*Horn broken. - Watch for finger.

Dave Plowman snipped-for-privacy@argonet.co.uk London SW 12
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OK, thanks. I have a very noisy Ideal Elan 2 boiler of about 1989 / 1990 vintage and my first thought was that it had scaled up as we live in a very hard water area. I have just moved in to the house and there is some signs of historical leakage from a joint near the three port valve but that seems to have sealed itself. I think I will clean away the green grime and keep an eye on it.
I think it was one of your posts that I found yesterday, I can't seem to find it again today!
Thanks, BraileTrail
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In an earlier contribution to this discussion,

Yes.
There are 2 basic types of 3-port valves. One type switches between hot water and central heating, and can't run both at the same time. The other type has a mid position and so can provide just hot water, just central heating or both together. Make sure you replace like with like - function-wise.

The primary circuit keeps circulating the same water rather than drawing in fresh - so there's only a limited amount of limescale in it - and once that's been deposited, that's that!
--
Cheers,
Set Square
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Thanks for the information.

Great.
Yep, I understand that. I was just curious about the difference between the "paddle valve" and the "shoe valve". I know that a "paddle valve" is the one with the offset "rubber" ball on a stick, but I can't imagine what a "shoe valve" is. They are both three port mid position valves by the way.
Thanks again, BraileTrail
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Yes. Certainly Danfoss themselves claim this, but make sure that you order a valve with the correct wiring/microswitches. You might also want to check that the body length is the same.

One difference is that with the shoe type the motor body is directly above the centre line of the pipe, whereas with the paddle type the motor body is offset.
No harm in phoning Danfoss themselves.
Michael Chare
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