post purge of system using zone valves

clammy

Just wondering if anyone has given much thought to when they are using the post purge cycle on a mod con which also is controlling there system pump.Usually the boiler pump is either just pumping through P/S tees or a hydro seperator and the system pump is pumping out eo the emitters or through a DBVif zone valves are used ,i was wondewring if anyone has a control which would let you leave the valve open in concert with the boiler post purge cycle and dump the btus into the system instead of just pump through a DPV and also not enable the burner circuit unless there was a call for heat.Been thinking about that one for years .It really isn't a issue with single zone systems but multi zone with higher temps makes me think i like to run the post cycles usually 3 to 5 minutes on central heat and about the same for indirects .On mod cons i like for the boiler to shed some btus at the end of any cycle espically when used for high temp just a pet pev. Thanks peace and good luck clammy 

Plumdog_2

I was just thinking the same thing.....

Nowhere to shed some heat except what dissipates from the manifold piping. Need to open the 'best' zone (like basement concrete) during post purge.   

Jean-David Beyer

using the post purge cycle on a mod con

If I understand you, my W-M Ultra 3 runs both the boiler circulator and the appropriate system circulator during the post-purge portion of things; i.e., during the time after the thermostat stopped calling for heat. The fire goes out, and the circulators continue to run (for 30 seconds default, but programmable). This dumps the leftover heat in the boiler into the load. If using a zone valve, you would need a relay to grab the system circulator signal and use that to run the zone valve.

Plumdog_2

well, yes, but...

Yer gonna hafta have a way to trigger it ONLY during post-purge, or else it remains open any time the system pump runs. This should be incorporated into the boiler hookups. Maybe it is and I missed it?

Tom_133

Baxi

Baxi 380HT has an internal bypass to allow the post purge to do its thing when you pipe with zone valves. I like that better than when I see a 1/2" bypass at the end of the supply and return header tied together with a 1/2" ball valve to control it.

CMadatMe

Zone Valve

How about a zone valve designed to stay open for 1:30 once the zone is satisfied. Take a Taco Zone Sentry that uses stored power to close and give it a delay. Make the time adjustable via a dip switch..

clammy

how about taco controls

To bad taco did not offer one of there plug ins  for there expandable relays that would be a great options for either there circ or zone valve multi relay center .Be even nicer if it had a set able timer and possible a pre and post especially with a small buffer tank and micro zones ,btu required  wise to lowest modulation of the boiler would really be able to ride some systems of short cycling plus rid the boiler of excess btus .Would really like to see some one have a  indoor door sensor that communicates with the boiler water temp and gives the control indoor feedback and i know buderus has this but how about one that can be used with a any brand of mod con .I really have not looked at tekmar as of late but i image they would have something up there sleeve Thanks peace and goodluck clammy  

CMadatMe

0-10VDC

Most mod/cons have 0-10VDC so you could do it with a Tekmar control. Viessmann also has this function when using a Vitotrol or RTU.. On Vitodens 200 the boiler looks at outdoor temp, indoor feedback from the Vitotrol and supply water temp to adjust on the fly to meet the need. On the Vitodens 100 with a Como-Ot does the same but only looking at boiler temp not system supply temp. There's a difference because of the temp drop across the LLH so it's more effective with the 200 then the 100..