Do i Need Primary Loop ?

Walter_3

Hello Proffesionals.

Please help me in the following.
I'm gonna use a buffer tank for the radiant heat. I will try to charge the buffer tank from the boiler and then use the buffer tank as a source of heat for the radiant pipes.
As i've seen on many aplications you guys use primary loop from the boiler like a heat distributor, and then you use secondary loops for zoning. In my situation, do I also need to use a primary loop from the buffer tank or can I connect an injection pump dirrectly from the outlet of the buffer tank ?? Like is shown in the picture.. Please comment and correct me.

Thank You,

Brad White_2

To my thinking

the Buffer Tank is part of your primary loop if properly applied. Normally I see a buffer tank as a way to take the spikes out of a limited-modulating or non-modulating boiler in a low water content system. Basically a "bulge" in your primary loop.

Personally, I would need more information such as flow arrows, how the pumps are controlled (variable speed, other valves those sorts of things). I would think that the primary pump would be variable. Is that correct? I can see the buffer tank being diluted with radiation return water and no distinction to what goes back to the primary circulator -direct from system or from tank in an unknown proportion.

I know it is a basic diagram, so no criticism is intended. Just trying to complete the picture is all.

The check valves kind of threw me (no arrows so had to figure the logical flow).

It would appear that the two upper circuits are higher-temperature radiation and the radiant has the 3-way valve, correct?

The second-from bottom leg looks like it could flow both ways depending on damand. Is that correct? The primary pump could flow down and then right, then return to the buffer tank, but the secondary circulators (which may have high heads what do I know) could force flow back to their secondary pump suctions, fighting the primary pump all the way.

hr

A couple things

In your drawing the buffer would need to heat up before you could cover any loads. Slow and cumbersome depending on the buffer size.

Also you could keep that boiler in the condensing mode for long periods. I'd only use that piping with a condensing boiler.

It nice to be able to supply hot to the load ASAP, from the boiler. Then purge off excessive into the buffer as the load allows. At design possibly the boiler would run non stop. Below design, as loads (zones)shut down you start building buffer. this should provide a nice long efficient burner on cycle. When all loads are satisfied the buffer could run up to set point and be available to supply loads without firing the boiler, come next call. Size the buffer for optimun run times with the smallest load calling.

Here is another of many ways to pipe this. With a non condensing boiler use a Grundfos MixiMiser as the boiler loop to primary loop pump and this will give you boiler protection. The sensor mounts on the boiler return and watches that temperature and responds by varing the pump speed.

Loads come and go as they please off the primary and buffer storage.

A workable control system will be a head scratcher. Maybe some differantial controls to control buffer pump cycling.

How many and how high are your temperature requirements? I'd like to see a smart control, weather responsive instead of a three way thermostatic for better comfort control. You could use a tekmar dual VS control, the 363 I believe and handle the VS pump on both the boiler to primary pump and a mix pump for the distribution mix devise.


hot rod

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