Preventing boiler thermal shock

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Old 12-08-08, 09:08 AM
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Preventing boiler thermal shock

I am in the process of designing a baseboard heating system with an indirect WH. I am using a burnham 2B (cast iron)boiler and a superstor ultra indirect. I am planning a primary/secondary piping system. My problem is that the boiler room does not have space for the indirect so it is separated by 30 ft of 1" copper. I intend to thoroughly insulate these lines. However my concern is that after many hours of sitting idle the water in these lines will cool enough to really shock the boiler when it calls for heat. I initially thought I could just use a thermostatic mixing valve to boost the return temps. However I am unable to figure a way to use this system that will then allow full high temp flow to the indirect after the cold water is purged. Has anyone run into this issue before?

My only ideas so far(which I don't know how to implement) are to somehow slowly ramp up the DHW circulator, or install a second small bypass circulator and would operate at a very slow flow for a set period of time before the main DHW circulator started up.
I would sure appreciate any advice
 
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Old 12-08-08, 09:36 AM
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Primary/secondary piping, alone tends to solve much of this problem by itself, with proper primary circ selection, pipe sizes and tee location/spacing.

Many people will install a system or boiler bypass, choosing the type which works best depending again on piping and circ size. This is done with a simple cross connect with a balancing valve.

Danfoss makes a thermostatic valve, usually mounted at near boiler piping that recirculates water at boiler till temp reaches about 130 degrees F and then opens allowing water to system, with the purpose of controlling thermal shock and condensing of cast iron boilers.

Just a quick ?. Is this a new system? Why then select the lowest efficient boiler for this app, especially with a indirect involved????
 
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Old 12-08-08, 01:33 PM
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ZL700,
Thank you for the advise. I looked into the danfoss valve you mentioned and it looks promising. My only concern is how fast it would react to a large temperature swing. Any idea? The more time I spend on this problem, the more I lean towards building an addition onto my boiler room for the indirect

The reason for my boiler selection is based wholly on cost. I picked up the boiler from a local contact who pulled it out of a house being torn down. It is about 10 yrs old and he seems to think it has a lot of life left. If I decide to stay here long term I will probably switch it out with a condensing boiler.

Thanks again
 
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Old 12-08-08, 06:58 PM
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On this system save some money and install a manifold system with a simple boiler bypass. This will heat the boiler faster and protect the boiler. The piping to the indirect does not go through the bypass.
See this link
Bypass_Piping_Explaination
 
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