Burnham P205 without bypass piping for thermal protection

rob_26

I have a BURNHAM P205 hot water system with about 135 lin of feet of high output copper baseboard & around 2400 sq feet of house. My question is when the plummer installed the boiler he did not tie in the supply with the return for thermal protection. He said it was not needed. I do have an outdoor reset from honeywell (AQ475)set to high 180 low 135 and outside to 10. So i am concerned that if there is a problem it will void the warrenty
Thank you
Robert

J.C.A._3

Did he istall,

Either a boiler or system by-pass with some sort of valve to control the flow? Sounds like he may not have.

If he did, he read the book....If not, maybe you should insist that he does, then show him the book and the "approved piping methods" prescribed in said book.

Glenn? Chris

Robert_15

No help on this subject

Is there anyone going to give him any suggestions ?

Unknown

Rob

Sorry for the delay in responding but I have been in Massachusetts for much of the day. If you are running a low system temperature of only 135F with the AQ control, then your return tempersture can be much lower for prolonged periods of time assuming the control sensor is on the system supply side.A boiler bypass, at the very least, is recommended for this type of operation. Better methods would involve primary-secondary or variable speed injection from the boiler into the system. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Robert_15

Glenn

Thanks for the respone, I just got off the phone with the plummer and he said that on a cold start system there is no chance for thermal shock because the cast iron never gets that hot. He also said that he is goining to call you guys to find out why this is being said. I hope you get him on the phone his name is Dale from Sunray serv.(631)231-5533> this happens to be very frustrating getting conflicting info
Thanks
Rob

Unknown

Robert

I just got off the phone with Dale and he is of full understanding now as to why the bypass is needed. It is not for reasons of thermal shock. It is to keep the boiler hot enough so that the water vapor that is present in the flue gasses does not condense on the surfaces of the heat exchanger when operating with cooler water temperatures for prolonged periods of time. Hope this helps.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

Robert_15

Thanks a lot your a fine gentleman.It may seem he is of the old school method but i may be wrong. he did ask me how many lin. feet of baseboard. he said he would get back to me.
Again thanks
Robert

rob_26

Glenn

What is the difference between boiler bypass & primary-secondary? Also a varible speed injection would that be used with the boiler bypass?I would like to know the best applacation for the boiler. also the honeywell aq475 is that going to be able to control the injection valve.or should i use the 675 model or have him put in the Tekmar unit instead?
Thanks
Robert

hr

Most reset control

will allow a boiler minimun temperature to be set. With this feature, a cast boiler connected to a low mass emitter, like base board, should have enough protection.

Personally I feel only a method with temperature sensing at the boiler return connection should be used. A bypass pipe, even a bypass pump, may not offer 100% protection. again this is more of an issue with radiant slabs or other high mass systems.

Sounds like you have more boiler than baseboard connected to it?? Was a heat loss calc preformed?

hot rod

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rob_26

why would you think the boiler is too big based on what i read it seems that 140 lin feet of baseboard would be perfect?

hr

Just a guess

without knowing you home. 2400 square feet times 25 BTU per square foor (a rough rule of thumb number) that is why I asked about a load calc. So 2400X 25 = a load of 60,000. Isn't the 205 a 130,000 boiler??

Also 135 feet of BB at 550 output per foot (SlantFin #30) (again without knowing your exact board) is 74,000 output at 180. This would indicate more boiler than baseboard connected to it. Perhaps?

hot rod

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rob_26

I thought 700 output for about 30 feet of highout put down stairs & standard 38 year old basboard upstairs? And i was under the impression that the guild for basboards would fall under i=b=r capacity of 94 MBH Maybe i am wrong

rob_26

correct me if im wrong, the plummer said he did the caculations if he is wrong please let me know i will tell him and get this resolved
thanks
Robert

hr

I'm jumping in on the middle

of your project. I don't mean to question your design, just wondering aloud, via the www

Ideally I would like to see a load calc done. the goal would be to get as close as possible to the actual, as built, design load as possible. The free SlantFin load calculator, available at this site, would be a good start.

After a room by room load calc, then you could match the current BB against what the load calc suggests. And of course the exact boiler input would be the number you size to.

A step further would be to use the HDS software Series Baseboard Calculator. This takes baseboard sizing a step further by calculating the temperature drop through each piece of board. As the last boards will see a lower supply temperature, they may need to be a bit longer due to this.

The only reason to go to all this design calculations is to optimize the equipment size, pipe and control methods to get the very best bang for your fuel dollars.

hot rod

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rob_26

I do enjoy the feedback & you jumping in the middle is great i do want the most for my family & what better way is to get that info. So based on my app. having cement slab with the pipes run through my thought was to have high output's on that zone. But like i said he may be wrong and i do need to know. So thanks, but am i correct with the i-b=r or is it based on the input of 130.

rob_26

i did forget to to tell you that my old boiler of 38 years was a input of 110 & it was 15 to 20 % undersized to bring it to 126.5 to 132. Im not sure if his caculation is correct?
What do you think?
Robert

rob_26

also a pickup allowance of 1.15 would be on say 140 lin feet of bb 161 so based on that it is undersized?

rob_26

i would like your view based on the info i just gave you

Unknown

Rob and Others.........

I have already discussed this with Rob's installer and he now understands what needs to be done here. The NET output of this boiler is 94,000 btuh and according to the installer, is adequately size both by heat calculations and is fairly closely matched to the connected load. The 15% pickup losses are already incorporated into the NET IBR ratings of the hot water boilers so there is no need to increase the boiler for that.

My concern about this whole scenario has to do with the AQ Honeywell control maintaining a 130F setting on the numerous warmer days (about 50% of the season). The sensors for these are on the supply meaning that water cooler than 130F can be flowing through the boiler for prolonged periods of time with severe risk of flue gas condensation. As stated, I have already discussed this with Rob's installer so hashing this out here is only going to complicate matters. A simple boiler bypass will provide adequate protection if set properly. Other methods such as Primary-Secondary and Variable Speed Injection with return water sensing are certainly better but we need to let Rob and his installer discuss these because I'm quite sure that they will add to the cost of the installation.

Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.

hr

Had I know

the hashing had beed already done with Glenn and the installer....

I would trust the "fix" Glenn has worked out with the installer.

More than one way to skin a cat, or protect a boiler Typically installers find and embrace a way that fits their comfort range.

Bottom line is, the method Glenn works with protects the boiler he sells and stands behind. Sounds like sizing issues have also been addressed.

Happy heating.

hot rod

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Robert_15

Hi Glenn dale ended up putting a bypass pipe with a ball valve he left it in the open position and the temp. came in around 132 f this seems fine, we also had the zone valves on the supply side and the pipes were banging when one zone shut down so he moved the zone valves to the return side and no banging of the pipes. So is there any adjustments with the ball valve on the bypass as the temp changes outside?
Thanks and Cheers
Robert

Unknown

Bypass Settings

Rob,

As I stated earlier, I'm not overly concerned about a big temperature drop across the system, it's the reset control that I'm concerned about. On warmer days such as we've been having, this control can account for some pretty low supply temperatures depending on your settings. Along with that will come prolonged flow through the boiler of very cool return water. If he has set it for conditions like today, it will only do better on the colder days because the supply water temperature will be much hotter. Hope this helps.



Glenn Stanton

Manager of Training

Burnham Hydronics

U.S. Boiler Co., Inc.