Buffer tank and Alpha

Tristan

This a revised drawing for the system that I want to build. Knowing that I have a Burnham RV5, with internal circulator, do I need another circulator between boiler and buffer tank?

The Alpha would be between buffer tank and manifold and would run constantly.

SWEI

circs and piping

Internal boiler circ will handle flow to and from the tank on that side, but may be oversized given the low head loss it will see, so check your delta-T.  If it's a 3-speed, the low setting might work out OK.



Add a motorized mixing valve (what is that ODR controlling?) and you're off and running.



If budget is tight, TRVs on the rads can be added later.  Don't skip the mixing valve.

ColoradoDave

RV5 Primary Loop

Actually, I believe the RV5's Primary Pump ONLY pumps a primary loop built into the boiler.  It's been a couple of years since my last RV.  I don't have the manual handy, but I'm pretty sure the primary boiler pump kicks on until the boiler comes up to minimum operating temperature BEFORE it will energize the secondary pump.  So I don't think the boiler pump will provide ANY flow to the buffer tank. 

If the purpose of the buffer tank is to keep the boiler from short cycling, I'd consider putting it in series on the return.  That way, the hot water will go straight to your heat emitters and the tank will allow the boiler to have a longer initial run cycle.

If the purpose is to act as a low loss header, I believe it will be unnecessary. 

ColoradoDave

ODR & Mix Valve

I missed the first respondants comment about the mixing valve... but if that's part of the reason for the tank, get rid of the buffer tank.

Install the 3 way mix and ODR and you're all set with an alpha pump.

SWEI

RV5 Primary Loop

Never would have guessed - so the hydraulic separation is inside the box?

Tristan

Buffer tank

Yes, reason for buffer tank is short cycling due to micro zones andn overzized boiler.

What is the reason for buffer tanks to have 4 ports if puting it il line would be better for short cycling (longer firing times)? Can anyone explain what is low loss header?

Thanks,

Tristran

SWEI

buffer tanks and hydraulic separation

Four ports on a buffer tank in the configuration your drawing shows make the buffer tank into a low-loss header while also adding some thermal mass (think flywheel) into the system.  Closely-spaced tees perform the same function as a low-loss header, which is to hydraulically separate each loop (whether there are two or twenty of them) so its circulator does not 'fight' with the one(s) on the other loops.



http://www.flickr.com/photos/magicfoundry/1764196037/ explains the concept pretty well.

Tristan

Boiler Buddy

Great! But I still doesn't get if this should apply to my system.

Should I pipe the Boiler Buddy via the 4 ports, or should I use only two ports and pipe in line on the return pipe?  I'm being a bit confused.

Tristan

SWEI

Had to go look at the manual

They call the internal LLH an "Internal Manifold."  Page 74 shows the "Internal Primary/Secondary Piping" which page 82 describes (1L)  as "Water Manifold."  Strange design.



So piping in series as ColoradoDave suggested looks like your best bet.  A 4-way mixing valve may be in your future as well.

Gerry Alder

redundancy on air vent

No need to have an air separator on the system loop if you use a Boiler Buddy you put a cheap vent on top center of Boiler Buddy Buffer tank and definitely use all four ports to get full use of this buffer tank. The Boiler Buddy has it all in one as hydraulic separator buffering and air / dirt separation. Can you tell I am a huge fan of these!



Next issue is to use the outdoor reset control with an injection pump and put the injection pump on the supply between boiler and buffer tank . Dont fret about the system supply temperature it will be fine.



Ok in this certain case with the RV 5 boiler since it has its own primary pump for boiler protection and its high mass cast iron boiler you could argue not to even use a buffer tank eliminate it and just do the two closely spaced tees injection to system loop. If your injection control is smart (like tekmar) you could set an auto Diferential and it helps reduce short cycling. I really love buffer tanks and they have a justified use on copperfin and low mass boilers. So you choose if you want to use it here. You could go all out and do the math to see how much a buffer tank helps in cycling.



One quick TIP put your own temperature and pressure gauge on the supply pipe cause the one inside the boiler is annoyingly hard to see.

ColoradoDave

Boiler Buddy

Yes... the boiler buddy will act like a Low Loss Header, but then you'd need a secondary pump coming from the boiler feeding the tank AND your Alpha Pump on the OTHER side of the boiler buddy feeding your zones.

The GV has a built in Primary Loop which will interrupt the secondary pump output until the boiler gets up to minimum operating temp before energizing the secondary pump.

You either need to add a 3rd pump (UPS15-58) to feed the boiler buddy or remove the boiler buddy all together and do straight Primary Secondary.

The use of a LLH in this installation is redundant because of the Pri/Sec piping built into the boiler.

The use of the outdoor reset would impede the boilers function... for instance.. if the ODR says the boiler only needs to fire to 120 but the Burnham doesn't enable the secondary pump until it reaches a minimum of 140, then the secondary pump would never fire.

If you're using an Alpha plugged into a 24/7 hot outlet, you'll avoid this issue, but the boiler has the potential to run cold (condensing).  I'd seriously consider removing the boiler buddy and going straight to a 3 way mixing valve.

Boiler out into the hot, boiler return into the cold shared with the system return, and the alpha on the mix output.

Gerry Alder

This Boiler feature is it not supposed to condense.

This boiler can accept any return temperature down to 55°f and it does not condense . It has boiler protection built in. The secondary pump runs the entire time you have a call for heat and the boiler pump inside the boiler runs minimum speed injecting heat to the built in secondary loop until boiler is 160°f hot then boiler pump runs normal . Pretty neat feature on this RV5 cast iron boiler.