vitodens: bypass needed?

Mike T., Swampeast MO

You caught me.

I can't find in the literature supplied with my Vito right now, but it's at least <I>implied</I> over and over by the minimum flow rate.

I have some Vito literature from the UK here somewhere and am nearly positive that it actually refers to TRVs and differential pressure bypass. The only place I've seen TRVs mentioned in my literature is in the <I>user</I> manual where it's something like "if too hot turn down the TRVs."

Manual definitely does not mention the built-in bypass as it's not intended to be used for the emitters--only for the boiler itself.

Unknown

pressure bypass on vitodens: is it necessary?

ok, so i'm installing a vitodens 200 6-24 piped in series to a manifold serving panel radiators with TRV's.

my question is, do i need a pressure activated bypass valve in between the supply & return mains? i usually always install them on systems with zone valves or TRV's, but is it even necessary with the vito having its own vari-speed pump & all? does the vito have a transducer that notices valves closing and ramps down accordingly like the grundfos alpha-pro or is it strictly linked to the burner/blower modulation?

i was going to ask my rep today but everyones gone for thanksgivng. (i'm in canada)

thanks!

ALH_4

Viessmann

Viessmann says yes, though I've seen them work just fine without.

-Andrew

Mike T., Swampeast MO

Vitodens literature says that you should use a differential pressure bypass valve with a fully TRVd system.

There's a small built-in differential pressure bypass, but was told that it's only there to handle the transition between space heating and DHW production.

I can verify that it's there--I've heard it.

Unknown

where would i find this info?

i've read through all the manuals several times and found no mention of a bypass (even the built in one) where did you read this?

ALH_4

dP

We asked Viessmann's engineers in Waterloo last year, and they said a separate dP bypass must be used.

It is mentioned in the Troubleshooting Guide in items 4 and 6. TRV's aren't exactly zone valves, but I suspect to maintain proper flow through the boiler, a dP valve will be recommended if not required.

-Andrew

Unknown

ok, I think that answers my question

I also found on viessmanns UK site something along those lines as well: UK installation guide "The boiler incorporates an internal bypass, however one radiator should be permanently open..."

thanks all for the replies!