Boiler bypass needed ?

freyheating265342

I am the contractor doing this replacement, and appreciate all the solutions given reguarding this install, but I chose to use Energy Kinetics System 2000 with p/s piping, I am told that this steel boiler will never crack or leak do to thermal temp change. Also the cost would be less than the buderus boiler with added componants. Any feedback, positave or negative please post....Richard

Richard_4

Boiler bypass needed?

We are replacing a very old and large castiron pancake style hot water boiler with again, large castiron radiators. The piping is two inch reverse return with the expansion tank in the attic and vented to outside. The new boiler will be of lower water mass and primary secondary piping will be the method we chose to do this replacement. My question is, do we need to install a bypass loop at the boiler for added protection from thermal shock ?....The atmospheric expansion tank will be removed and replaced with a properly sized bladder type.

Tony_8

No

P/S piping will give you the protection you're looking for.

Use a low mass condensing boiler and let it ride

Boilerpro_3

Thermal Shock

is probably not an issue,if the system is one zone and you don't have heat soak running of the boiler temp after the pump shuts off. The real potential problem is continuous operation at very low return temps at high volume and P/S piping most likely will not protect you from this problem. Most systems like you describe need a supply temp from 140 to 160 F on the coldest day of the year. On the typical day (about 50% load) that supply temp would be only about 120F supply and 110F return. This is not good for a non condensing boiler. If you pipe P/S you will need a higher flow rate through the system loop and a much lower flow rate through the boiler loop. However, if you have a very low water content cast iron boiler, a manufacturer often wants a higher flow rate through the boiler, since the boiler doesn't have enough water volume or is not designed for internal mixing of return water. Then a bypass is needed on the boiler, so the flow rate is high through the boiler and the delta tee across the boileris low, but the flow to the p/s tees is low. For an 80,000 btu/hr load (a typical larger old frame home in most Rust belt cities in the US), you could probably pipe up the system with 1 inch, use 3/4 branches to the boiler and 1 inch for the boiler and boiler bypass loop, with valves to balance the flow, just like in most installation manuals.
I recently spoke to 2 manufacturers about this type of installation. Dunkirk said OK to the very low flow rate of cold return water through their residential boilers (about 1.2 GPM of 90F return water into a 70,000 input higher water content residential boiler) Weil Mclain said no to a 100F return of less than 2 gpm into an older 145,000 input CG series, very low water content residential boiler).

Or you could not worry about the flow rates in the boiler side and just install P/S pipipng with a thermostatic valve on the boiler return such as the Thermix from Danfoss or install an injection pump control by Tekmar.

Boilerpro

Jed_2

Additionally

A Taco iValve with return boiler water sensor is sweet.

Jed

Jamie_6

Richard,

Why not just use a Buderus cast iron boiler with a logimatic and then you do not have to worry about Thermal Shook, Primary Secondary, or low comfort levels?

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Mark Eatherton1

What they ALL said...

What you DON'T want to do is install ANY non condensing boiler without some means of protection. Either a Buderus or Viessmann with inherent boiler protection (pump logic) or a thermix/Danfoss, or tekmar with low temp return protection. I've not used the iValve from Taco yet, but may in the future.

Here's the inside of a Buderus boiler that was done with P/S piping and no low temp return protection. Not pretty eh.. I'll be headed back up to this job to do some sort of protection this summer. This install is about 5 or 6 years old if memory serves me correctly.

Even on low mass CFT boilers, exactly like you describe, I've had DOUBLE boiler bypasses on them and could STILL hear the sizzle of condensate hitting the hot burners on start up.

I'm of the attitude that if you're into using non condensing equipment, you CAN'T have ENOUGH protection.

Why NOT use a condensing boiler? Other than theoretical life expectancy, I can't understand why ANYONE would use an atmpsphericly fired boiler, with all the sealed combustion, ultra high efficiency equipment laying around...

Did I say Dinosaur?

ME

Jed_2

Exactly, but...

Everyone does not have propane or natural gas available, Mark. I totally agree with you about the SC, high efficiency gas boilers(H.B. Smith, take note, your losing). Smith does not have, or care IMHO, to devote resources to enter this market. From my limited knowledge base, I can't understand why they wouldn't. But, Mark, don't most hi-tech boiler manufacturers specify boiler protection piping arrangements in their I/O's? So, is it the installing contractor?

Jed

Jed_2

Jamie?

> Richard,

>

> Why not just use a Buderus cast iron

> boiler with a logimatic and then you do not have

> to worry about Thermal Shook, Primary Secondary,

> or low comfort levels?

>

> _A

> HREF="http://www.heatinghelp.com/getListed.cfm?id=

> 289&Step=30"_To Learn More About This

> Professional, Click Here to Visit Their Ad in

> "Find A Professional"_/A_

Jed_2

Jamie?

Richard probably has not selected a Contractor yet. You obviously are a Buderus agent. But, Buderus does not have the market cornered on this type of application. I say, Richard, pick the Contractor who will understand your system needs, REGARDLESS of the particular boiler affiliation he may have. If he's good, he'll have the right boiler for you're application.

Jed

hr

The ONLY correct

way to provide positive boiler protection is to have a device that senses and reacts to temperature!

Bypas piping, or bypas pumping, may or may not be adequate. It depends on the particular installation. Be leary of rule of thumbs!

Valves like Boilerpro mentioned is one way, although they cost some pump head.

P/S piping only works if the boiler return has a sensor and a control that is attached to it!

VS injection with a tekmar or any other brand of VS mixing control will handle this nicely.

Or a condensor, as ME mentioned.

hot rod

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