Vitodens Short Cycling [Personal] Solution

Solarstar

Ok Mike: now I get it...so let me know when your ready for the omron temp controller/Rtd and Maybe an SSR for the higher voltage end of it..Paul

Mike T., Swampeast MO

THANKS to previous thread in the vein. YOU MADE ME RECONSIDER!!!!

Lacking solar integration, I have a VERY SIMPLE solution.

I'll wrap the near boiler return piping with "heat tape"!!! A sensor, relay and contactor will cost MUCH less than a tank and three-way valve!!!!!!!!

jp_2

what are you talking

about?

Brad White

Mike- Please Come Back

You are scaring me. Your use of exclamation points and capitals is symptomatic of ....

jp_2

better solution!!!!!!!!!

you could wrap ALL the pipes with heat tape and get rid of the BOILER!!!!!!!!!!!!!!!!!!

hey you could hook the heat tape up to an inverter and PV panels and get "FREE" heat!!!!!!!!!!!!!

Mark Hunt

hehehehe


haha hahaha HAHAHAHAHAHAHAHAH BWAAAAAAAAHAHAHAHAHAHA!!!!!

YOU ARE KILLING ME!!!!!! STOP IT!!!!!!!

I copied and saved that one J-p.

I'm sure that is not what Mike meant and I HOPE Brad is wrong.

Mark H

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Mike T., Swampeast MO

I told you I was dangerous when I'm thinking...

By everything I've observed and measured I only have to add a few thousand BTU/hr to the system to prevent the vast majority of the "pulsing". With only one temperature sensor in the Vitodens it could care less where (supply or return) those BTUs are added in a directly connected TRVd system.

Glen

STOP!!!!!!!

my sides hurt - :-)

joel_19

real solution

If you want a real answer I have it for you. I'll make you guys all the 20 gallon stainless buffer tanks you want. All top taps with air vent on top and sensor well. much better than the low loss header just email me. Bigger custom sizes if you want too.

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Perry_3

Have you considered a RS Sensor in the house

That would allow feedback of the actual house temperature.

I have not experienced the short cycling "pulsing" operation that you mention. Yes, the boiler does cycle on and off during fall - and now some spring days. But nothing like "pulsing".

Perry

Mike T., Swampeast MO

Seriously--Have I Lost It?

Sure looks like something here would be suitable.

Certainly plenty of near-boiler return piping to wrap and I could insulate such VERY heavily. Not enough of the 1 1/4" common piping, but once it goes to 3" it doesn't take much pipe length for a LOT of single-layer wrapping space.

About 11A @ 220V should suffice.

Turn the tape on once temp drops below 55F and off when it drops below 38 or so. Many of those heat tapes are "self-regulating" so I might even get lucky and find proportional control in the temperature range I need.

Mike T., Swampeast MO

Really no good place for a "room temperature" sensor in my house and I seriously doubt the usefulness of such in a fully TRVd system. My reset curve is not the problem.

ALH_4

How about....

Essentially you are adding a small first stage?

What about pulling the heat off of the domestic hot water tank when the outdoor temperature is in the 38°F to 55°F range and letting the boiler simply work on the tank? It would probably require a dual coil tank. That way the indirect water heater works as a buffer tank during periods of low heat load.

jp_2

but you said

pulsing is efficient, so why worry.....:)

unless you can modulate to zero, every system in the world short cycles, unless it has a buffer.

Mike T., Swampeast MO

I've seriously considered buffering, but in a directly connected Vitodens system with TRVs and constant circulation there's no simple way to "charge" the buffer once it is depleted and it will be fully depleted before the "pulsing" ever begins!

I could be very wrong here, but it [seems] the only way I could use a buffer is to alternate the buffer exclusively between a load to the boiler and a heat source to the system. My solar integration system was simpler...

Remember--no low-loss header in my system. No form of primary/secondary. The built-in circulator is the ONLY circulator used in the system. Due to the huge (original gravity) pipes and TRV flow control I'm essentially driving the rads via a 50-gallon or so buffer.

The Vitodens [seems] to have determined that the most efficient way to deliver heat when load is less than about 1/4 minimum modulation is via the "pulses".

My previous boiler (a simple cast iron W/M CGM-6) operated the EXACT same secondary system. In similar weather when the Vitodens is typically "pulsing" the efficiency difference is nearly a complete flip-flop. I'd swear that the W/M was loosing about 80% of its input while the Vitodens is retaining at least 80% of its input.

Uni R_3

Is there any chance...

Mike is there any chance of you firing your Vito manually (when you're there)? Is there a button combination that is used for combustion testing? If there is and you can somehow use a pushbutton to generate a test fire, you could get away from the pulsing by controlling the controller. ;-)

Not sure how it goes on the Vito, but on a Prestige if you hold both the Mode and Plus buttons in at the same time, it goes to high fire for 10 minutes (unless it temps out). Likewise Mode and Minus at the same time makes it test fire ten minutes on minimum fire. If you do a test fire from a remote switch wired to the Vito somewhere handy upstairs you could give it big blips -- multi-minute floored blips. Do Italian tune-ups help modulating condensing boilers?

I'd love to have a switch for my boiler because I'm frequently doing that to keep balance without changing the t-stat and overheating on cloudy days. When we have a sudden warm day, the southwestern front of my house warms up incredibly compared to the back.

A 10 minute shot of maybe 50 MBU or so... my max is capped lower than factory because the smallest model is still big (very nice though on noise and electrical consumption basis - if you want a quieter boiler in luxury environments with big domestic requirements size for the domestic - there are small gas losses vs significant gains in recovery, noise reduction and electrical consumption depending on pump activity. Probably far less cycle stress as well).

Anyway, I frequently grab a 8000 BTU injection to warm up the back of the house. I can even cheat and use low distribution circ speed when doing this which bypasses most branches and effectively heats the house from the bottom up with more rear exposure. Okay that's sounding Bradish. This would be easier if the circ wasn't inside the boiler. If the Prestige didn't have the internal circ, it could be almost half as wide as it is. I might be unique however in changing speeds. I use low speed when valved primary secondary but need medium speed when valved direct. The low speed helps increase the ΔT which suffers low ΔT from being a 1¼" diameter monoflo system (minimum GPMs to heat the branches are higher than low speed on a 15-58).

I should really move the t-stat from to the family room and allow the outdoor reset sensor to get insolation exposure. Then, during unbalanced weather, the house will heat to where the lived in part of the house needs it. The overshoot in the front will be minimized during the daytime and that's the part used during the daytime anyhow. That would be cheaper than zoning...

Mike T., Swampeast MO

Conondrum

From everything I measure the pulsing is fantastically efficient compared to a traditional cast iron boiler operating under nearly identical (including cut-in and cut-out points) circumstances.

BUT, I'm seeing an equally fantastic cycle rate--granted I keep the 1903 home cool but I suspect it can't be that much different that energy-conscious new home of similar size at "normal" temperatures. And this is the SMALLEST Vitodens available...

Maybe it's just this crazy Swampeast MO climate. I've checked and average temps are similar to non-mountainous Northwestern Europe but the standard deviation is MUCH higher here. Easy to heat a building in Berlin with a 6-24.

I WANT TO MAKE THE SUN ACT AS MY BUFFER!!!!!!!!!!!!!