Buderus Return temps

Wayco Wayne_2

a re-pipe on a Buderus G-115. The customer is gutting an old farmhouse and redoing everything. He got a bunch of big cast iron radiators to put in the job, but when he gets done insulating and changing windows they will be greatly oversized. I talked to a Buderus tech on the phone and he said I don't have to worry about low return temps with the Buderus. Why not? In the manual it states that there are no worrys when a Logomatic is installed but to keep the return temps above 150 F when running on an aquastat. Can someone who knows clear my mind about this. I'll also post some pictures, before and after of the job. WW

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Wayco Wayne_2

Pics of job.

An external view of the house. It now has windows and walls. A pic of the boiler piping before, and then a pic of the near finished porduct. WW

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D. Andrews

Hey Waco why use the top of this guys boiler for parts storage?

Wayco Wayne_2

Ha!

Not done at that point. I finished the other day and the top is clean. I promise.

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Ted_9

I always cut and tape card board on top of the boiler.

In this case, WW has no card board since it was an existing unit.

Nice job WW. What brand radiant header are you using?

PATRIOT HEATING & COOLING, INC.

TGO_54

Return Temps

The Logomatic uses pump logic to control the circulator during low temp operation. It will turn off the circulator when the boiler is at condensing temps and allow it to come back on at higher temps. With a large volume cast iron system like yours expect it to happen a lot at startup. Nice job on the piping.

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lchmb

why not?

Why not install the logomatic? I believe you will find that the Buderus is able to withstand low return temp's. The casting is excellent. If the rep told you it was ok, I would keep his name and follow his direction. In reference to the top of the boiler, I keep a bottle of car wax spray in my truck. When I start the job I spray some down. Nothing will stick to it and when you wipe it off it shine's. Be amazed how many homeowner's are shocked to see it shine better than their car!!

J.C.A._3

I believe the question was,

About return Temps. The 115 has a return "difuser" bushing.(That little brass and plastic piece that comes in the box with all the other goodies, and has/HAD(?) a square thread on one side, and tapered thread on the other side for us Americans.)I hear things are changing and on all shipped American units the threads are made for our market now.(tapered)

The 115 doesn't employ the same "return tree" as the 215 and larger, and does NOT use the built in return "header" with the "ports" bringing the return water into the mix. Hence the diffuser on the return bushing.

The Logomatic control does shut down the pump circuts, if the temperature drops below 113°, but if you aren't using it, there will be NO protection.

The instructions and such have always stated that the boiler will accept any return water temps., but personally, if it doesn't come equipped with a Logomatic control, I would opt for a Honeywell 8124 (triple aquastat)OR equivelant.( there are options, and I will suggest we look to Infinity Labs for another one! Personal opinion).

The boiler may be willing to accept any return temp., but will the CUSTOMER be willing to accept a system that is "stealing" temperature from their hot water, to get the boiler up to a "low limit" temperature while trying to cold start an indirect? (Robbing Peter to pay Paul)....I think not.

This is just an observation. If I missed anything, please let me know. I love Buderus boilers, and have used them extensively. I just want to know that I'm thinking on the same plain when NOT using their 210... whatever. Chris

Paul Pollets

Bypass Needed

Wayne, without a 4 way valve and the R2107 control, you'll need to install a full port bypass between the supply and return using a globe valve, not a ball valve. Install a thermometer on the return after the bypass and throttle until the return shows 135 degrees within 5 min after startup. Attached is a picture of a bypass installed on a Viessmann RN. The other rule of thumb is that if the water content of the system exceeds the boiler water content by more than 2x, you need a bypass. If the boiler return temps have not climbed past 130 degrees within 5 min. of startup, you need a bypass. Also, the Bypass piping should be at least 12" between supply and return.

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J.C.A._3

Paul,

I agree with a system bypass. I haven't seen it it the Buderus piping diagrams yet, but as usual I also deal with the systems in the "old parts"of the country and this is used all the time. This is why I suggested the "low limit aquastat". Chris

Wayco Wayne_2

Thanks for the

comments and ideas guys. I don't have a final picture to share, but I am controling the system with a Taco pc705 variable speed injection controller with sr504 relay board. The control has built in boiler min return temp control to protect the return and will shut down the variable speed circulator when temps are below set point. I usually set the min return temp at 140, but when he said the boiler could take more I set it down to 120. Later I got twitchy and feeling maybe that was too low, hench my question to the population at large on The Wall. Thanks for the complimentson the piping. My gradual improvement in that area is due to my friends on the Wall showing me how nice things can be done with the pictures that they share. WW

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Wayco Wayne_2

Hey Ted,

The manifolds are Wirsbo brass manifolds. They now have many tubes of Multicore running from them to all of the cast iron rads. It's nice to look at. WW

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Paul Pollets

Best Insurance

Is to install a thermometer on the return port. If the controls you use allow the return temp to be above 130 within 5 min. of burner start, you won't need a bypass. Sounds like surgery, eh? I like low-cholesterol boilers. I abhor condensation.

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Ted_9

I too install a temp gauge at the return of the boiler on all my gravity install.

PATRIOT HEATING & COOLING, INC.

Steven Grady_2

Return Temps

Dear Wayne,

On the G115 boiler we are not concerned with stress related situations to cold return water only condensation. When we install the R2107 Logamatic control on a large volume system, the pumplogic is set at 104F. As long a the temp in the boiler is above 104F we should not condense in the boiler. You can now pipe the boiler supply to supply and return to return. The G115 and G215 will evaporate condensate on start up situations (you may see a white stain up in the left hand corner of the firing zone). The other advantage of the R2107 is that it will not allow the Hot Water pump to come on until the temp in the boiler is 10F higher than the indirect. No reverse heating.

We also manufacuture a control called a HS2109 that also controls condensate(113F)and replaces the Honeywell aquastat. This control has no outdoor reset, but includes the DHW sensor. This is a price competitive control to help control condensate and speed up you installation.

Steve

Wayco Wayne_2

Thank you Steven

I will look into it. WW

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ScottMP

Wayne

CAn you explain your piping arrangment on the radiant loop ?

Why a flowcheck when you have two circulators with intregal checks ? Why two circ's on the same loop ? Is that a flow setter ?

Thanks

Scott

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Wayco Wayne_2

Hey Scott

Howyadoin. The top circ is for an indirect that is just out of the picture. The one below it is the primary loop circ. The first set of tees and circ is going to a workshop to be heated at a later date. The second is the variable speed injection circ and you're right I probably didn't need a flo check there. Could of saved 25 bucks. Damn! Before I finished I added a flo check on the indirect looop return. I shoulda put an automatic air bleed on the indirect loop supply at the topp because it can trap air there if someone drains system and fills it back up. Easy to purge but I would like to make it idiot proof.

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