Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.
Vitodens SuperStor
Mike T., Swampeast MO
Member Posts: 6,928
Peak demand from a large Jacuzzi tub. 80 gallons minimum, about 95 when utterly full. Fills in about 10 minutes.
So with a 50°F rise (50°F to 100°F) that's 95 * 8.33 = 791# * 50 = 39,500 BTUs.
At 80 mbh (1,333.33 btu/minute) heat transfer to the indirect (shouldn't be any problem) that means right at 30 minutes to recover. Hard for me to believe that a standing iron system where daily setback is rarely (if ever) used would have much fall in space temperature in 30 minutes. The "car wash" shower can possibly be a larger load, but if you've used up a 120-gallon indirect, I'd say you've had <I>more</I> than enough shower...
The wild bathroom has been my problem all along. I hate to say how many thousands it has cost do do things properly--and that's when I do the work myself! There's an electric steam generator and hydronic towel warmer as well. Everything from the water service entrance through to the ventilation of the room was affected.
The Victorians had their "follies" in the garden. Mine is a bathroom. Never again! I love to design baths, but this one has taken me three years and I'm still short the $$$ to buy an L-shaped soapstone vanity top as the price of soapstone has nearly doubled since I bought it for the other (much simpler) baths in the house.
So with a 50°F rise (50°F to 100°F) that's 95 * 8.33 = 791# * 50 = 39,500 BTUs.
At 80 mbh (1,333.33 btu/minute) heat transfer to the indirect (shouldn't be any problem) that means right at 30 minutes to recover. Hard for me to believe that a standing iron system where daily setback is rarely (if ever) used would have much fall in space temperature in 30 minutes. The "car wash" shower can possibly be a larger load, but if you've used up a 120-gallon indirect, I'd say you've had <I>more</I> than enough shower...
The wild bathroom has been my problem all along. I hate to say how many thousands it has cost do do things properly--and that's when I do the work myself! There's an electric steam generator and hydronic towel warmer as well. Everything from the water service entrance through to the ventilation of the room was affected.
The Victorians had their "follies" in the garden. Mine is a bathroom. Never again! I love to design baths, but this one has taken me three years and I'm still short the $$$ to buy an L-shaped soapstone vanity top as the price of soapstone has nearly doubled since I bought it for the other (much simpler) baths in the house.
0
Comments
-
Answers Please
I have a problem which I am sure is not uncommon.
I have a very small mechanical room and was constrained to using a HTP SuperStor 60Gl indirect with a Vitodens 8-32. I just could not get the Vitocell in, although that is naturally my first choice.
Now I have the boiler short cycling every 15 seconds. I have the water temp maxed at 176° and the pump speed at 100% (though I think coding addresses 45 and 46 are just for the heating circuit anyway)
The way I see it -- one of two things is happening.
1) The Superstor heat exchanger coil just is not transfering the BTU's (could the coil be that lame?) and I have no Delta T.
or
2) The coil head pressure is such that the water is barely getting out of the boiler in the first place and trips the high limit.
Now I've spoken to some knowledgable people but I'd like to submit this problem to the Council of Elders for a definitive resolution. (And please don't just tell me to but a Vitocell next time -- I KNOW that.)
Is the solution?
A) Treat the indirect as a high temp heating zone, use a mixing valve and actuator, and install the loop downstream of the Low Loss Header so the boiler can modulate...
or
Add a pump and move more water out of the Boiler and overcome the head in the heat exchanger loop.
I'd appreciate hearing from someone who has actually overcome this problem in one of those ways (or some other way). It would sure save me a lot of time and $.
Thanks in advance for your pearls of wisdom.
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
Delta T
With no delta you might have a build up on the coil. I have had this happen with Amtrol a few times, mostly on commercial with high domestic water temperatures. (160 plus)
Marc0 -
High Head
I have been told that when using the small Vitodens units and are not using a Viessmann tank you probably will need to use a second in series on the domestic return. Most tank use smaller diameter HX. Another great reason to use Viessmann. I have used a Crown tank once and had no problems, but I have heard Superstores will have problems
Good Luck Jeffrey0 -
A) Treat the indirect as a high temp heating zone, use a mixing valve and actuator, and install the loop downstream of the Low Loss Header so the boiler can modulate...
Is probably your better solution.
Viessmann will frown upon adding a pump. I asked about adding a TINY (think ounces per minutes) for a system component with slightly higher delta-p and was told, "Don't do it."
A third option that might be possible is using the "external call for heat function". You provide a DRY contact closure and the boiler will heat to a fixed (but adjustable for max) temperature. Hook up the indirect as just another "zone" off the LLH side with its own circulator. Obviously you'll loose weather responsive operation during a call from the indirect and every other zone will have access to the same high, fixed temperature. May or may not work, but if possible would certainly save some $$$ in components. You could "lock out" all other zones during your "external call" if high temp is a problem for the space heating circuits. Done this way you'll still have DHW priority, but time required to replenish the indirect during a period of high consumption may become excessive.
0 -
Pipe sizing
Did you install 1" piping from the Vitodens to the DHWtank coil? 3/4" piping to the tank coil will cause the problem you describe. (BTW< I've overcome this problem)
The Vitodens engineer who can help you is Resa Mossavi, who can be reached at the Waterloo headquarters. 800-387-7373
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
Could you elaborate...
on one point please? When you say "I have been told that when using the small Vitodens units and are not using a Viessmann tank you probably will need to use a second in series on the domestic return."
A second what in series, circulator or heat exchanger?
Thanks0 -
Good eye Brad
You would need a second pump in series. I want to say Viessmann Has a Vitotalk(newsletter) atricle about this subject you might want to contact them direct.
Jeffrey0 -
Viessmann secondary relay
Viessmann provides a secondary DHW relay switch. The part # is a 7134-599. I can send you the installation instructions. Hope this helps.
0 -
It may or may not.....................
.......make much of a difference. Just because you can pump the coil does not mean it will stop short cycling. The problem is more of a transfer and water volume issue than anything else.
Having had a few issues with the 8-32 has led me to sell the Vitodens as a complete package, only. Buy a Vitodens, you get a 53 gallon V300 (or larger).
hb
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"There was an error rendering this rich post.
0 -
Thanks!
I have a Vito going in with the DHW production kit. Not at that point yet and I do have a Super-Stor already. It is my intended... so this thread has my interest.
Appreciate the response. You are not just simply Rad but like, dude, you are like, ah totally rad, dude.
0 -
another solution
The problem as I understand is heat transfer.
One thing you can do is to install a flat plate heat exchanger in series with the DHW coil, and pipe a bronze circ through the domestic side so as to take hot water from the domestic outlet, and pump into the inlet. Power the bronze circ in parallel with the DHW pump. This will increase heat transfer, and is cheaper than ripping out the Superstor, making the room bigger, and installing a Vitocell.
I don't have time to draw a diagram, late for my Master Plumber's Meeting...maybe someone else can elaborate.
Cosmo0 -
60GL
That 60GL is a glass lined tank with an epoxy coated coil that is so stretched out, I would have difficulty believing fouling. What are the temps going to and coming from the HX coil? If there isn't enough flow, the temp in will be high, while out will be painfully low. A delta of 20 is the MINIMUM that you should expect, 30 being not unusual. If you have something like 50 degrees difference, there is a flow issue.0 -
Actually, I always use 1 1/4", even on the 8/32. Is that overkill? I figure, why not minimize pressure drop. Plus it makes the whole installation look SERIOUS. But with the price of copper these days...
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
There is very little Delta T, which leads me to believe that water is flowing, but the coil is not transferring the heat.
I'm wondering if the pipe is just hot from hot water radiating back fom the boiler connection.
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
Yes...
it's overkill. Only the 120g coil needs a 11/4" supply.
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
temps
What temp are you supplying versus what temp DHW you are trying to attain?0 -
a few more things
> There is very little Delta T, which leads me to
> believe that water is flowing, but the coil is
> not transferring the heat.
>
> I'm wondering if
> the pipe is just hot from hot water radiating
> back fom the boiler connection.
>
> _A
> HREF="http://www.heatinghelp.com/getListed.cfm?id=
> 350&Step=30"_To Learn More About This
> Professional, Click Here to Visit Their Ad in
> "Find A Professional"_/A_
0 -
a few more things
Maybe coil is air bound
could be a issue with Vitodens,
check gas pressure
check inlet screen at gas valve
ensure solenoid valve for dhw is installed straight into the diverting valve against seat.
how long in has hwt been in service?
marc0 -
a few more things
Maybe coil is air bound
could be a issue with Vitodens,
check gas pressure
check inlet screen at gas valve
ensure solenoid valve for dhw is installed straight into the diverting valve against seat.
how long in has hwt been in service?
marc0 -
Something else
is going on here. The Super-Stor tank is a good product with a fine HX. Allthought I use the Ultra tank the coil is the same I belive and I have never heard of this bad a problem. At low speed with that pump you should have SOME transfer. I think its air bound or a problem with the circulators impellor, maybe a piece of solder ??
Scott
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
Let me reiterate.
The heat exchanger of a Super Stor, Amtrol, Etc. does not hold very much water. When the Vitodens comes on, it is at high fire then modulates down. With that little amount of water circulating, it heats up too fast and the Comfortrol is unable to react quick enough to roll back the input before it reaches whatever limit temp (be it fixed or variable) then starts the process of short cycling every 15 seconds or so.
Brad, do yourself a favor and use the stainless Viessmann tank.
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"There was an error rendering this rich post.
0 -
I can't find the 60GL model at HTP's website. Closest I find is the 60-gallon stainless steel version.
If using the same HX (just a "glass-lined" tank instead of stainless), specs don't look good.
7.9 feet of head loss and 10 gpm required.
Vitodens 8-32 MIGHT be able to move 4¼ GPM with that much head. (This with essentially zero head in the associated piping. At 4¼ gpm through 1¼" tube there's not much, but the base flow is way too low to begin with.) I cannot find the water capacity of the HX listed--only an "exchange area" of 20 square feet. From the illustration it looks like a corrugated HX that increases HX area at the expense of greatly increased resistance to flow.
Also looks like it needs a minimum of 174 mbh gross output boiler to achieve published first-hour ratings. From Vitodens spec you have about 112 mbh available.
The closest Viessmann tank I can find is the 52-gallon V100.
When connected to a Vitodens 8-32 you'll have about 18 INCHES of head loss (in the tank) @ nearly 6 gpm. Quite a difference!
With the current setup and assuming about 4¼ gpm to the indirect, you'd need a whopping 53° delta-t to transfer the full boiler output. That might be doable if you could actually get the temp up high enough before the boiler modulates down or cycles but because of a presumably low water volume in the indirect HX that ain't gonna happen as long as the tank is directly connected to the boiler when using the built-in circulator.
You might be able to improve things by installing the indirect on the other side of the LLH to achieve hydraulic decoupling. Problem however is if you move 10gpm through the indirect and the boiler is moving about 6 gpm through the LLH that means 4 gpm (or 40%) of the return from the indirect is blending back into the supply thus reducing its temperature. Even if you use the external call for heat function with max temp of 180° you'll never achieve 180° to the indirect because of the blending from the return! This situation will occur regardless of how you try to pipe or control the problem!
Have you checked with Viessmann to see if they "allow" a 2nd circulator in series to be used for this application? If so, I'll bet they say you can't use a circulator so large that it will increase flow above the max of about 6.2 gpm through the Vitodens HX. Note that's 40% less than recommended by HTP. So...not only will the ratings of the indirect be reduced because the boiler output is smaller than recommended, but it will also be lower because flow is too low!
If a series circulator is not allowed, you could achieve the same thing (again limited both by overall output AND flow) by installing the indirect on the other side of the LLH and using a circulator sized for as close to 6.2 gpm as possible and operating such as a "zone" during an external call for heat AND establishing "priority" for that zone by locking out all others. If you don't lock out the others, flow will increase and supply temp (both to the indirect and the rest of the system) will decrease due to the blending back of the return! At least this [should] allow the indirect to absorb as much of the boiler output as possible because it has access to the highest possible supply temperature from the boiler. But again, because the indirect "wants" a bigger boiler AND higher flow, you will never achieve the published 1st hour ratings.0 -
Amtrol
the Amtrol tanks work fine if there next to the boiler, there dw and commercial need the booster pump with relay though.
Marc0 -
Bingo!
You have done your homework and come up with the same data and conclusions that I have.
The tank is indeed a SSU60 stainless.
I have been able to get the boiler to stop short-cycling and I'm getting barely acceptable heat transfer by adding a 15-58 in series. I'm lucky on this one that I have a solar batch pre-heater on the roof (my tests were done with the preheat off, by the way) which on a day like today can deliver 40 gallons of 120° water ro the the tank inlet instead of the 65° which is standard around here.
My customers will be perfectly happy with their hot water system, but I know I can do better as far as efficiency with a Vitocell tank and that's the big lesson here.
Thanks!
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
Question for you hb:
Am soon connecting a H-300 120 gallon to a Vitodens 6-24. Recommended tube size is 1¼". This to an existing system. Indirect is large to meet high peak flow (100-gallon tub with high-volume filler or "car wash" shower) almost completely from storage. Otherwise demand is "normal" for a good-sized single-family residence.
I can barely fit 1" to the indirect without either nightmarish re-piping problems or creating freaking "air traps" in the piping. (Up-over-down.) Indirect about 8' from the boiler. Should be able to do it with 2-45° (below the boiler) and 1-90° (at the indirect) els (plus a full-port ball valve in each of course) for both supply and return when using 1" tube. About 10' pipe length (not developed) length for each.
It is possible to transition to 1¼" about 5' from the boiler, but the two 45s will be 1".
A much smaller indirect is usually attached to a 6-24. Head loss through the indirect coil at flow rate possible via the circulator does not appear to exceed that of a smaller tank (with shorter HX). Do you think I'll be OK using smaller than recommended tube? If so, should I transition to 1¼" as soon as possible?
0 -
Careful...
Mike, the 120g tank is not really suitable for the 6/24's internal pump. You'd want to talk to Resa at Viessmann Waterloo, before attempting this. He was involved in the export of the Vitodens and is the leading authority on what can be done or not done with the Vitodens.
Resa Mossavi can be reached at the Waterloo headquarters. 800-387-7373
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
Thank you "So Cal Radiant Guy"! I was almost loosing faith in myself due to a certain person down in the "Heating Efficiency Issues" area. Haven't slept well all week due to those "discussions".
I'm not looking up the 15-58 circulator or estimating flow because I know you've done the same. My only suggestion is that you do not want to exceed 6.2 gpm through the Vitodens HX. Don't try to get the 10 gpm "wanted" by the indirect.
What's your flow estimate?
0 -
THANKS Paul! I will check.
If I understand Vitodens operation at all, then the problem will be too little head and I'll want to ADD some slight restriction to the piping to the indirect! ¾" transitioning to 1" would be ideal...
0 -
I
I'm calculating that with the two pumps combined, through the boiler. 1 1/4" pipe, full port iso valves on 15-58 pump, through the hx coil I've got something like 6-7 GPM at about 8ft/hd.
I'm able to raise the tank temp about a 2° minute from about 110° working towards 140°. Boiler temp maxed at 167°.
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
My only added suggestion is a good metering-type valve somewhere in the DHW circuit. If you have access to an accurate (ultrasonic) flowmeter you'll be able to set for optimum flow of around 6.0 - 6.2 gpm. Lacking the flowmeter, you can try it manually.
Adjust the valve such that "boiler target" equals "boiler temperature" as closely as possible but without cycling during a "normal" demand call from the tank, e.g. not peak flow. I suspect that the adjustment will be VERY finicky--thus the suggestion for a metering type valve.0 -
Heads Up!!
Resa has all the tables and charts of any indirect and can also tell you expected recovery rates.
The 120g tank really wants 15-20gpm, usually I use a 26-64 pump and either the 11/44 Vitodens or larger. The 6/24 would have a rather slow recover rate against the 120g.
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
ssu & 8-32
I've learned the hard way. The ssu doesn't have enough surface area to keep the vito from short cycling. This is a bad combo. The solution is; a viessmann tank with a larger coil and low press drop.
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
I'm not concerned with recovery rate as I have LOADS of storage--both in the DHW tank AND the converted gravity system.
My only concern is instantly transferring as many BTUs as possible during near maximum boiler output to the indirect. Thus the question regarding tube sizing. I don't mind "overkill" in tube/pipe sizing at all, but I didn't really plan on ever using the PROPER Viessmann indirect for this system due to cost. Before I specified the boiler I KNEW the indirect size required and figured I could replace a number of 100-gallon or so stand-alone heaters in my lifetime...0 -
Solar w/8-32
Solar pre-heat exacerbates the problem, because the tank is warmer than it normally would be on startup. There are a series of coding address changes that can be made along with putting the 15-58 in series using the relay. When I was working with these boilers we ran into this problem a frequently enough to include the booster pump on all 8-32 pump panel buildups. Any dhw tank with higher head loss than a vitocell will cause problems with the 8-32. The 6-24 does not have these issues. The pump in the 8-32 is just barely big enough.
-Andrew0 -
HB
I understand the Cycling off high fire, but why no transfer of heat ? S.S. has a better coil than an Amtrol and better design.
Why is'nt he getting enough hot water ?
Scott
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"0 -
I have been thinking along what HB says
and this is what I can see (as far as my Monitor MZ and companion heater anyway). It goes to volume in that circuit.
Say my MZ tank gets a call for heat, topping off, not a cold start.
The first slug of water after the valve switches over is warm, having been sitting in the very warm but not hot tank. It moves on back to the boiler. Then the next slug of static heating water enters at room temperature perhaps. Then it gets hot, gradually over time. (It is drawing from the heating system volume that is shared with the heating circuit, the return side.) Generally it runs to high limit. Now, I have 1.25" copper pipe and some minor distance in that area so I have some time.
Once the heating HW is hot, it goes in at X temperature, out at Y temperature and as the DHW reaches temperature, the X-Y Delta-T gradually narrows until the unit shuts off. Tank just happens to be heated by that time.
What I have found in my case is that if I raise my tank setpoint, the MZ shuts off on high limit and has to be manually reset. Different issue but shows that 176 degree water on the supply side is reached too easily because the returning water, while cooler, is still too close to the HWS target temperature. So the unit cycles (in the case of the Vito) or in my case, shuts off on safety/manual reset.
In this Vitodens case being discussed, might that volume between the DHW heater and the Vitodens be so close-coupled and low in volume that the tube exchanger heats up rapidly to its own equilibrium and this is just too close to the Vito setpoint at that time? I really am just guessing here.
But perhaps you can see how, after the "hockey-stick heating curve" from cold start up, there is a leveling off of boiler S-R temperature, less heat transfer because of the convergence of the Delta-T's.
What I am thinking about is the time it takes to heat what might be a small volume. Buffer tank solution perhaps?
Have not had my coffee yet, so my thoughts are a tad scrambled an in no particular order.
My $0.02
Off to Viennese Roast
Brad0 -
Vito
The 8-32 internal pump only has around 2ft residual head left at 35-40 degree rise. Your dT is expanding rapidly with a tank that has any head loss at all. The technical data manual is invaluable when designing these systems. The internal pump in the 8-32 is just a little small for tanks other than the Vitocell or possibly the Phase III.
Set 007 to 000
Set 028 to 000
Set OB8 to 001
Set OA9 to 100
Set OAO to 010
Why they set the DHW pump speed to 98% and not 100% is a mystery. When I was working with these boilers we saw this happen very frequently when using 8-32's with Crown Mega Stor tanks. Adding the 15-58 in series in the DHW loop always cured the problem. Just changing the coding would usually help, but the customer would usually still have intermittent problems. Adding the pump makes the problem go away and it's a pretty inexpensive fix.
-Andrew0 -
Paul: I called Resa. No problem with the 120 gallon H-300 connected to a 6-24. Recovery of a large draw will of course be limited by the boiler output, but no circulator problem. He suggested 1" piping to the indirect, but said I should be fine with one el and about 4' of ¾" before transitioning to 1¼". If I've estimated properly, that piping should result in very similar head loss to the 6-24 with all 1" piping connected to a much smaller H-300 indirect with shorter and smaller diameter HX coil. My problem is that the indirect has to sit on the other side of the old boiler that I'm not removing. (It's isolated but still connected to the system for backup and possible use for snowmelting in the future.) Direct route is behind the old boiler and 1¼" copper won't fit without moving the boiler--not easy with the huge pipes of a gravity conversion... Both boilers against massive brick chimney.0 -
The issue.......
would be with how long it takes to recover hot water when there is a large heat demand. The diverter valve stays engaged as long as there is a DHW demand. Will the house cool off?
To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"There was an error rendering this rich post.
0
This discussion has been closed.
Categories
- All Categories
- 86.7K THE MAIN WALL
- 3.1K A-C, Heat Pumps & Refrigeration
- 56 Biomass
- 423 Carbon Monoxide Awareness
- 104 Chimneys & Flues
- 2K Domestic Hot Water
- 5.6K Gas Heating
- 103 Geothermal
- 158 Indoor-Air Quality
- 3.5K Oil Heating
- 68 Pipe Deterioration
- 938 Plumbing
- 6.2K Radiant Heating
- 385 Solar
- 15.3K Strictly Steam
- 3.4K Thermostats and Controls
- 54 Water Quality
- 43 Industry Classes
- 47 Job Opportunities
- 18 Recall Announcements