Chuck Shaw - Munschkin Boiler Question

hydronicsmike

Howdy Chuck!

Looking forward to seeing you in Oakland next month.

Here is my question: Would your Boiler like it if we were to vary the flow through its Heat Exchanger by pulling out of it with a Variable Speed Injection Pump? Have a customer who wants to save one extra (Primary System) Pump.

I understand that you have a flow switch built in that has to proof before the Boiler is able to fire. Which is fine, as I only want to fire the boiler if the load on it is big enough to bother (Increased Injection Output). Or do you think I may cycle the Boiler to often when I do this, as the Injection Pump may (or may not) Increase and Decrease its output randomly, with the boiler firing and shutting off via the flow switch?

What do you think? I don't think we should do it this way. I would like to have the system pump on it in order to guarantee sufficient flow across your heat exchanger. But customer argues that your boiler will modulate based on deltaT across the Exchanger. What do you say? Bless using one less Pump, or not?

Thanks Bud and best regards.

Mike

hydronicsmike

In case anyone is wondering...

...Chuck says that it is not recommended and that a Boiler System Pump should be used to guarantee proper flow across the Boilers Heat Exchanger.

Mike

Dave H_2

Variable Speed

I was thinking along the same lines but a little different, but haven't spent too many brain cells on it yet.

Using a Munchkin with a mixing valve and motor for outdoor reset. Two radiant zones after the mixing valve, instead of using standard on/off circ pumps, using say something like the Grundfos Miximiser as a zone pump??

Something I thought of quickly but not explored the options or ramifications

hydronicsmike

Dave...

...sounds interesting what you have planned - Variable speed Flow through the zone with Supply Sensor in space?

Sounds interesting and feasible, but am not sure if I would recommend it. The response time might be too slow (due to mass)and we would have to expect temperature swings in the space because of it if you'd use the GMRC or even the 356 for this application. The reset water temperature would help minimize the temperature swings, but I have never tried it this way. If you do try it, let me know how it worked out for you.

Besides the fact, the GMRC uses a (pot style) dial for the setpoint temperature selection and it is pretty rough, should you try to maintain an exact 70°F (IE).

In any case, as Chuck recommended to me, still install a Boiler Pump and then Tee off the Boiler loop in primary / secondary before you go through the mixing valve. This will guarantee the flow across the heat exchanger in the boiler.

Hope this helps.

Mike

Dave H_2

Primary

Already have it piped with primary pump.

The radiant system is a low mass, extruded plate application so response time will be minimal.
What I am looking forward to is getting full modulation of the mixing valve coupled to the munchkin, but I thought I could dial it in a little closer with the variable pump.

Since everything is valved, swapping the pump will be quick and of course in my own home so I don't have to experiment in a customers home. (Aren't all of our own projects part of some wild experiments??)

hydronicsmike

Perfect Dave...

...if you wouldn't mind keeping me updated, I would love to hear about your findings.

Isn't it always better to try new things at a customers place? That way, if it doesn't work, you're still warm and comfy
Just kidding, of course!!

Best Regards,

Mike