slab heat issues (temps,pressures,short cyling of boiler)
Last Post 06 Feb 2018 03:49 PM by john201. 6 Replies.
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john201User is Offline
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04 Feb 2018 01:10 AM
Ok...I was helping a friend replace a flue exaust motor on his radiant floor boiler..(that part went fine) so,he started the system up and that was that. I stopped back a couple days later and a heating guy was there looking at the boiler. He said the boiler was short cycling (off 6-7 and on 2 min.) also the supply manifold temp was 110 and the return temp was 63. The boiler pressure was 16lbs. Only a 53 temp was able to get to in the garage. It was 27 today. The heating guy said he doesn't mess with these systems too much and he is without a comuter.. So my job was to see what I could find out. thnx for any info
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04 Feb 2018 03:36 PM
Interesting saga. I wonder if this HR system was working okay (including NOT short-cycling) prior to the recent repair? If the slab was allowed to significantly lose temperature, it could take days to bring it back up to temperature to sufficiently heat the space. I wonder why the boiler would short-cycle if it generating a 110F supply temperature and only seeing a 63F return temperature. The boiler should turn off when it reaches some high temperature setting and it should turn on when it reaches some low temperature setting. Was the circuit balance valve positions or any other valve positions altered during the recent repair?
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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04 Feb 2018 04:31 PM
I guess it was running fine.. THe boiler shuts off at 155 and turns on at 125.. From what I know no valves were adjusted(on or off)
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04 Feb 2018 04:45 PM
If you also know the volume of fluid in the HR system (boiler + distribution plumbing + circuits), the minimum modulated heat output in Btu/h and the HR slab emitter load in Btu/h we could calculate what the boiler cycle time should be to see if it agrees with what you are actually experiencing now. Perhaps the boiler is not modulating properly because of some other issue?
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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04 Feb 2018 05:49 PM
good lord...lol It might be easier to move
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04 Feb 2018 08:10 PM
Well, I am sure you will soon figure it out. These systems are not that complicated to setup properly if the person doing it is knowledgeable about them. If not, it can be an exercise in futility. The best place to gain this knowledge is John Siegenthaler's "Modern Hydronic Heating". Good luck!
Borst Engineering & Construction LLC - Competence, Integrity and Professionalism are integral to all that we do!
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06 Feb 2018 03:49 PM
I managed to get some info. there r 4 circuits/ 1/2" id tubing the length of runs are 290-280-230-200......the flow rate is a little over 1/4 gpm. thanx for the help
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