Constant circulation problems? Johny2050


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Old 04-06-10, 06:54 AM
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let me give you my 2 cents about my experience with constant circ. In Nov I had my boiler replaced with a Buderus G115WS, Logamatic 2107 with a room sensor w/ constant circulation and an Indirect. During the winter it was great. I always felt comfortable at a temp of 68. Never felt warm cold warm cold. However, with the weather we have right now my logamatic doesn't always go into Warm Weather Shut Down (WWSD). example: My room sensor is set at a temp of 68. The logamtic is reading a room temp of 72 but the circulator is still running because the outdoor temp is lower then what the WWSD is set to. If the boiler doesn't fire it is pushing approx 80 to 90 degree water through the loop because the room temp is satisfied. Now the problem is when the unit fires to make DHW, all that heat to make DHW in the boiler has to go somewhere and where do you think it goes? Through the house. Now I have 140 degree water being pushed through the house that is already overheated.

I really like constant circulation during the colder months but find it to be a nuisance with this type of weather. Right now I have to manually adjust the WWSD to halt the circ.

I hope that made sense Beer 4U2

John
 
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Old 04-06-10, 11:05 AM
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Johny, I'm thinking that something might be amiss with the piping if you are pumping hot water when you shouldn't be ...

This whole thread is getting a bit off the OP's topic, but let me ask you... you had posted some pics of the install a while back, didn't you? If so, why not start a new thread and point to the pics...
 
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Old 04-06-10, 11:13 AM
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Hi Trooper, I have been meaning to post before and after pics but have been to busy to find time. once I get a chance I'll post them.

With a room sensor the logamatic is set to constant circulation. Now from my understanding, the only time the circulator will shut off is during a call for DHW and during Warm Weather Shut Down.
 
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Old 04-06-10, 03:54 PM
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You should have two (or more) pumps, and a primary/secondary piping arrangement for this to work... the SYSTEM pump will run constant, but the BOILER pump will not, and if set up P/S, there should not be any flow through the boiler when that pump is off... so, yeah, let's see how it's set up.

when the unit fires to make DHW, all that heat to make DHW in the boiler has to go somewhere and where do you think it goes?
It should only be going into the indirect tank!
 
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Old 04-06-10, 04:21 PM
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Might be a post purge problem after an IDHW call.
Again, like to see the piping diagram and maybe the boiler settings.
 
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Old 04-07-10, 10:20 PM
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Bit the bullet and got a new system

Ok so here is the pics of my new system that was installed back in Nov. Added to the system which the pics do not show are check valves on all the returns.






Now I have spoke with a buderus service rep and he said its the way it works. the circ only shuts off during Warm Weather Shut Down and when there is a call for DHW. So when there is a call for DHW and the unit is not in WWSD then all that hot water in the boiler gets pushed through the house.

John
 
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Old 04-07-10, 10:30 PM
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Ok I didn't see this new thread until I started a new one "bit the bullet and got a new system." Can you merge them Troop? Beer 4U2
 
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Old 04-08-10, 05:40 AM
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Unless I missed it twice where is the WWSD set? It should never be set higher than the thermostat setting. I also never put constant rum pump on a system which makes domestic hw but I don't think it would be bad with a mod/con.
If it is piped with p/s it should not be a problem as long as the boiler pump was shut off the the indirect piping was off the boiler piping not the system piping and you had a check valve in the secondary piping to the boiler.
What type of radiation do you have? Cast iron or copper tube.
 
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Old 04-08-10, 10:15 AM
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Can't really add anything to the original question but I didn't notice that there are copper fittings screwed directly into an iron fitting in the top left of the third picture. Not really good for the sake of longevity. Can't really see a hanger supporting that expansion tank either. If it ever became water-logged it could be one heck of a problem. Don't really like seeing wires tie rapped to heat pipes either.
 
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Old 04-08-10, 04:52 PM
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Definitely agree about supporting the pipe that the tank is hanging on.

My jury is still out on the copper into iron case...

The main issue though: The way your system is piped, you really don't have a way to properly run with constant circulation. For that you would need a primary/secondary setup, which I don't see in the pictures.

I'm not all too familiar with the Loggy control settings, but you might want to take a look and see if the 'purge' routine is available, as TO mentioned. This would dump most of the excess heat into the indirect after it was satisfied.

Also, as rbeck mentioned, check the WWSD settings.
 
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Old 04-09-10, 07:13 AM
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The WWSD is set at 68 and the room temp is also set to 68. I don't see why this matters because the control monitors the OA sensor and will shut down the circ when the WWSD temp is met or exceeded based on the OA temp reading.

If you look at page 2 and 3 in the link below it states under what conditions the circ shuts down. So I don't understand how P/S will resolve this issue? Once one or all those conditons are cleared the circ will push water through the loop. So if there is heat in the boiler that heat will go through the house. Correct? If I'm completely wrong please enlighten me.

I really don't think it is a piping issue because if you look at page 10, it is my setup. The pic is not the greatest so I hope you can see it.

http://www.buderus.us/files/20100223...2109AppMan.pdf



John
 
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Old 04-09-10, 07:25 AM
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I would set the WWSD temperature lower. Try 64* (down from 68) and see if that is OK. If not then keep dropping it 2* at a time until the house maintains the proper temperature.

What is happening is that the heat gain in the house is making up for some of the heating requirement. PC's, ovens, lights, people are all adding heat to the house. So to maintain an indoor temperature of 68* on a 68* day, no heat from the blue box is required.

Now just need to find out via the WWSD setting how low it can go outside and still maintain 68* inside.

Al.
 
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Old 04-09-10, 04:29 PM
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You saw this in the manual, right?

"Careful consideration must be given to placement of room sensors. Keep in mind that not all applications are
suitable for using a constant circulation zone
. Avoid using a room sensor in a small baseboard zone as overheating
may occur during DHW production. A standard room thermostat can be used in conjunction with the room
sensor to give high limit protection
."

You might wanna query B about how to wire up that extra thermostat. This would sorta solve your problem by cutting off the system circ when the high limit setting of the added thermostat was met. I'm sure it's a simple relay setup.

So, it seems that the big Blue B is aware of the limitations of it's control strategy... and after reading through as much of the manual as I did, I can say that I'm not a fan of their way of thinking.

Forget what you have for a minute, and picture a primary loop consisting of your system pump and your three parallel heating loops.

Picture a pair of closely spaced tees, and the boiler piped as secondary, with it's own pump.

Next, picture the indirect pipe in parallel with the boiler loop, also with it's own pump.

With this arrangement, you can pump the system primary loop continuously, and only add heat when needed, by firing the boiler and running it's pump.

Anything that happens in the indirect, stays in the indirect.

Something like this (ignore the zone valves you don't have):


photo courtesy www.comfort-calc.net

But I don't think your control can support this strategy.
 
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Old 04-09-10, 07:09 PM
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Originally Posted by NJ Trooper View Post
You saw this in the manual, right?

"Careful consideration must be given to placement of room sensors. Keep in mind that not all applications are
suitable for using a constant circulation zone
. Avoid using a room sensor in a small baseboard zone as overheating
may occur during DHW production. A standard room thermostat can be used in conjunction with the room
sensor to give high limit protection
."
Trooper, I did not see that statement in the manual. Was that in the application manual? I really haven't had the chance to throughly read the manuals. I have a 2yr old and a 6 month old so it seems like the only thing I do is change diapers, clean bottles, make formula and go to work

That P/S pic really put it in perspective of how that would work. Thanks for that info Beer 4U2. Unfortunately, I don't think I want to go that route. Thats going to add more money on top of this already expensive install. That money is going toward Central A/C before the summer starts. So I think I will try what OldBoiler mentioned and see how well that works. If it doesn't cut it I'll go with the added thermostat. That sounds like an easy solution.

Its funny that when I spoke to a Buderus tech support person about this issue that he never mentioned adding a thermostat. He did say that they get a lot of complaints about overheating during this type of weather. He also mentioned that continuous circulation may not work in my situation. You would think that if they do get complaints about this that they would try and fix it. Probably an easy firmware fix to just cut the circ when the room overheats.

Thanks for all the recommendations. You guys go above and beyond to help us homeowners out. I really appreciate it!! Thanks Beer 4U2

John
 
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Old 04-10-10, 12:07 AM
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Yeah, that was near the front somewhere... before the application diagrams I think.

I don't know that messing with the WWSD is going to do anything for you, setting it higher than the tstat will mean that the pumps will run needlessly at times... in some cases for long times... and that will simply waste power. I think setting it lower you will end up with times that you want heat but don't get it...

Thinking about it some more... with the added thermostat, set a degree or two above the room sensor, it would cut the pump off when no heat was needed. It would seem the most effective solution to me... cost would be a cheap thermostat (wouldn't need a programmable job), a $50 relay (and R8845 would work), and a few bits of wire and time to hook it up. (Time seems to be your most costly item!)
 
 

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