New boiler installation question

doozerman

So I just finished replacing my 18yr old MZ wall hung boiler due to a cracked heat exchanger. I can't complain. In 18 yrs it's the only issue I had. I replaced with a dunkirk DB165. Just fired it up tonight for first time and everything is great except 1 thing. On my old mz boiler my external circ pump was tied into the boiler circ pump so they kicked on simultaneously. After room tstat was satisfied and not calling for heat the pump would continue to run circulating the hot water till it dropped below a certain temp. With this new boiler I had to buy a single zone switching relay so the external circ pump kicks on when room tstat calls for heat but once satisfied and turns off it also turns off the circ pump which now is not circulating that excess hot water like the old system did. How can I get the pump to keep running till water cools down? Appreciate any input you can share. Thanks!

109A_5

Hello @doozerman,
Apparently the OEM of your new boiler does not think that functionality is necessary, I don't see any provisions for that function. Tapping into the boiler wiring for that purpose may cause problems and may void the warranty.

With Outdoor Reset there may not be much heat to recover.

You could add an 'Off Delay Timer' to your external circulator and set it to the time delay you want. Or a temperature (thermocouple) switch if you prefer.