Water heater and QUIET sidewall venter?

I am about to replace my 18-year old sidewall venter (for the furnace and water heater).
This replacement was imposed on me since when the plumber replaced an 18-year old leaking water heater, he replaced it with a water heater that _probably_ requires a venter stronger than the existing TJERNLUND HSUL-1. I say "probably", because the plumber himself admits that he doesn't know why the water heater keeps shutting off by the safety thermocouple switchs next to the "draft hood".
So, is it true that all new water heaters require more powerful venters? (one hint that I received was that the vent in the new heater is WIDER the vent in the old heater - 4" diameter vs. 3").
If so (which means I have no choice but shell out extra $$$ to buy a new venter), could someone recommend a QUIET sidewall venter? What about an EXTERNAL venter that can withstand extreme weather (New England winters...)
If not, could someone please suggest brands/models that can work with the TJERNLUND HSUL-1 (http://www.tjernlund.com/gassidewall.htm ) ?
Please reply to this newsgroup, as my email address is not valid (to block spammers).
Many thanks in advance, Daniel
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Please help. Thanks! Daniel
snipped-for-privacy@my-deja.com (Daniel) wrote in message

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Please call a qualified professional.

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That is exactly the problem. The person who installed the water heater _is_ a "qualified professional", but he is clueless regarding this problem.
I called another "qualified professional" but he, too, was baffled by the problem and could not suggest any solution other than calling the water heater manufacturer (AO Smith FSGL-40) and hoping for the best...
In the meanwhile, my entire family is left without hot water...
Believe me, I have no intention of handling this myself (too dangerous). But in this situation, where the "qualified professionals" are clueless about the problem as much as I am, ANY idea would be appreciated.
Except for the "idea" of calling a "qualified professional", that is.
Thanks anyway for your effort.
Daniel

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