Indirect water heater, sensor or thermostat?

CBRob

I installed a new cardinal indirect from tri tube.
It's got a thermowell built in and is made to work with the boiler by way of a temperature sensor or a basic on /off thermostat.

My experience with indirects has always been using a thermostat.
A boiler runs full power and sends out 186f water until the call for heat is met.
The sensor seems to allow the boiler to modulate and does not run at full blast much if at all.
I imagine that it's far more efficient to modulate the dhw output, but will it heat up the indirect as quickly?
What do you guys do when you have the option? The new indirect came with a thermostat I can use instead of the sensor.

hot_rod

The control on the boiler should have different settings and should allow full flow 180 to the indirect

Sounds like it is in a mode  and RWT low for higher boiler efficiency, condensing mode

using the boiler control would give you more data to look at, run times, cycles temperatures, maybe even a post purge option

CBRob

I turned this up from 25 to 50 and it's cranking out 186f from the boiler.
Still shutting off when the dhw temp is met.

New problem, when the snow melt system is next to get demand the boiler does not like the Delta T being so hi even momentarily.

hot_rod

What is kicking off the snowmelt? The boiler temperature too high? If you post purge the DHW the boiler should not be warmer than the indirect temperature?
What type of snowmelt control?

CBRob

It's a modulating control.
I think I have a 2 minute post pump purge.
I'm not sure what the supply temp was but the return temp from the snow melt was probably 40 ft or so.
Boiler gives the warning that the Delta T is too high.

I can try a longer post pump purge, or maybe have both the boiler pump and the dhw running during a dhw call.
Right now the snow melt is run though a hydraulic separator and the dhw pump bypasses it and goes straight through the boiler.

clammy

I’m not familiar w that boiler but can the post pump run time be extended for the indirect tank ? Personally I would check that first and if so it would set for a 3 min post ,I have it set that way for my munchkin and it usually drop the supply temp from 176 down to my what my tank ends up at after post purge ,I usually gain about 7 to 10 degrees above my tank temp . Personally I The a sensor worked into the boiler ,if using aquastat I tend to use a ranco etc extremely accurate over a bi metal aquastat and in this day and age it cheaper then a 4006 so it’s a win win plus I ve yet to see one dies accept for maybe a extreme surge but I de say maybe 2 replaced in over 30 years .on another’s note you could check the program for hi limit and temp differential setting before re firing at worst a 25 to 30 degree below limit temp before re firing should lower your supply temp and help you out on to high temp differential . Is your snow melt going through a heat exchanger ? Hope this helps
Peace and good luck clammy

hot_rod

CBRob said:

It's a modulating control.
I think I have a 2 minute post pump purge.
I'm not sure what the supply temp was but the return temp from the snow melt was probably 40 ft or so.
Boiler gives the warning that the Delta T is too high.

I can try a longer post pump purge, or maybe have both the boiler pump and the dhw running during a dhw call.
Right now the snow melt is run though a hydraulic separator and the dhw pump bypasses it and goes straight through the boiler.

Maybe the post purge to the zones is not possible, without holding a ZV open. Or in the delta P circ mode?

CBRob

clammy said:

I’m not familiar w that boiler but can the post pump run time be extended for the indirect tank ? Personally I would check that first and if so it would set for a 3 min post ,I have it set that way for my munchkin and it usually drop the supply temp from 176 down to my what my tank ends up at after post purge ,I usually gain about 7 to 10 degrees above my tank temp . Personally I The a sensor worked into the boiler ,if using aquastat I tend to use a ranco etc extremely accurate over a bi metal aquastat and in this day and age it cheaper then a 4006 so it’s a win win plus I ve yet to see one dies accept for maybe a extreme surge but I de say maybe 2 replaced in over 30 years .on another’s note you could check the program for hi limit and temp differential setting before re firing at worst a 25 to 30 degree below limit temp before re firing should lower your supply temp and help you out on to high temp differential . Is your snow melt going through a heat exchanger ? Hope this helps Peace and good luck clammy

I'll try extending the post pump purge, I found that setting easily.
The snow melt is running direct to the boiler, primary secondary and a hydraulic separator.