High LP use with Bosch 151?
I finally got up the nerve to reach out to the builder. You were right. His reply is below:Gordy said:
For what it’s worth (nothing) to you. Your builder, and hvac specialist will probably tell you all the information you received here is wrong, and the collective of a few dozen soles are all wrong.
>Regarding the boiler I have talked with [Propane Company] and [HVAC Installer] my understanding is that the on demand boiler is sized for the domestic hot water demand because you have two full bathrooms. These boilers have fully modulating gas valves which allow them to fire at different Temperatures depending on the demand. [Propane Company] said you used 165 gallons from 12-30 to 2-13 of this year. That seems pretty normal considering the extreme cold temperatures we have had during that time frame.
I never was able to make sense of the slant fin app. I had no idea what to enter for all the different factors, or cold partition length/factor vs exposed wall factor/length. I felt stupid guessing at so much. So here it is. My builder is saying that my propane use is on-target, the system was designed for hot water demand relate to the two full baths (despite our evidence that it is TOO large for that as well), and that it should modulate the valve down for different demands.
I don't see how I can get my home heated properly without a lawyer, and I don't see why everything has to be so g** D*** difficult. Doesn't anybody take pride in their work and stand behind it anymore? Doesn't anyone say, "The homeowner should be comfortable and happy in this new home. I shouldn't have to say 'we did the bare minimum' to them on more than 10 occasions if I did my job."
I appreciate your help, everyone! I guess it's just my lot in life to only ever get 60% of what I pay for, and always have to fight tooth and nail for what should be guaranteed.0
The program has the factors in it, for example if you have 2x4 wall construction with fiberglass insulation you just select that and it will figure out the factor for you. There are little arrows (>) that you use to go to the next menu that gives you choices of what you may have select and it gives you the number.Gcracker said:
I never was able to make sense of the slant fin app. I had no idea what to enter for all the different factors, or cold partition length/factor vs exposed wall factor/length.
If you need more help you can PM me I'd be happy to make some screenshots and walk you through it if you want.
2014 Weil Mclain EG-40
EcoSteam ES-20 Advanced Boiler Control
Boiler pictures updated 2/21/150
It will be cheaper to hire a heating pro to fix this than to hire a lawyer to go after the builder. Install more baseboard and put this behind you, I doubt you will get anything from the builder.Hydronics inspired homeowner with self-designed high efficiency low temperature baseboard system and professionally installed mod-con boiler with indirect DHW. My system design thread: http://forum.heatinghelp.com/discussion/154385
System Photo: https://us.v-cdn.net/5021738/uploads/FileUpload/79/451e1f19a1e5b345e0951fbe1ff6ca.jpg0
Yes, despite my feeling that this isn't right and should be fixed, it's going to be easiest to fix the problem myself. I expected the builder to see reason when I simply state, "My house gets colder with the heat running if I switch off the kick-space heater." His reply that the kick heater is part of the design and needs to be on was not expected, and effectively shuts me down.
Thank you all for your help. Maybe I can find a HVAC installer in my area that would be willing to take my Bosch 151 in trade for something more appropriate, and I can use the surplus to add some high output baseboard.0
Heating Edge copper baseboard from Smith’s Environmental
Synergy copper baseboard from Sterling
Both copper baseboard that is great for running low water temps.
Lochinvar Noble combi boiler smallest boiler max input 110,000 BTU minimum heating 11,000 BTU
This boiler you can derate the heating BTU and then the boiler will still fire at max 110,000 BTU for domestic hot water needs.
I believe adding a buffer tank 30, 50 gallons or more will help the lower BTU boiler out. When the tank needs to be reheated the condensing boiler will have longer run time and thus the boiler should stay off longer.
I agree that some contractors throw the wrong size boilers in. There is nothing wrong with throwing a larger Combi into a low loss home. However it has to be done properly. When I was an HVAC contractor, if I had any micro zones or boiler was too big, I usually ended up putting a giant cast iron radiator I ripped out of an old house on my return side of my boiler to drop temp down more so boiler wouldn’t short cycle. Perfect example is my friends house, I just installed a IBC DC 20-125 in his 3 bedroom 2 bath split level home. Basement isn’t finished. His heat loss was 30k ish. But needed the gpm for domestic. So, old radiator is in his basement and works great. Sometimes, you have to use your brain and think outside the box.2
^ so you're dumping excess heat into his basement?
Yes, that could prevent short cycling, but not very efficient.
A buffer tank would store the excess and deliver it to the living areas of the house. Better yet, a right sized mod-con with an indirect would negate the need for any band-aid fixes at all.
After some failed attempts to do my heat loss calculations myself, I was able to obtain the official report from my modular home engineering department.
I've attached it to this message (I hope) in PDF format. If I understand this correctly, I see two problems.
1) It appears that the calculations were run at an 80-degree DTD, but in Maine, we should be using a 90-degree DTD, since we can swing down to -20. Doesn't that mean we need more BTUH?
2) Even if the DTD is correct, my calculations put the actual BTUH provided (under ideal conditions) in my home under the required BTUH by a single BTU. 31' of baseboard (550x31=17,050) and a single toe-kick heater (Beacon-Moris Twin-Flo 3 Model K-42, rated at 4,470 BTUH) adds up to 21,520 BTUH @180-degrees.
To refresh everyone and minimize back-scrolling to get my HVAC system details:
Bosch 151 Combi using LPG, missing Bosch comfort sensor and ODT, supply/return lines spaced out of spec
Basic digital thermostat
Single zone, basic loop, no pri/sec
Taco controller and secondary pump inline on only zone
31 feet of baseboard
One toe-kick heater
Boiler fast-cycles in demand-state, only ever at min modulation
HVAC installer claims system was chosen to satisfy DHW needs for two full baths, not for home heating. Our DHW cycles hot/cold/hot in the shower due to not satisfying min flow rate. HVAC says boiler is made for "rich people with five bathrooms" so we should take two showers at a time. We had to pull the water-restrictors from both shower heads to increase flow, but this contradicts his statement that the boiler was chosen for DHW.
Now that I have the heat loss calc, I need to get my ducks in a row. I have less than 60 days of home warranty left, and the HVAC installer claims that he can do nothing to test the system (that I've been complaining about since
November) until winter.
Do you think this info will make them see they are caught and need to make some changes? What would the best change be, to change the boiler or add baseboard or both?
Any thoughts are welcome and greatly appreciated.0
Bottom line: add some real radiation that can actually take advantage of low temp (less than 120F) and get an indirect water heater or smaller boiler or both!
Way too much of this going on, slap in a boiler pipe it however and put in some tinny cheap baseboard wherever you feel like it.Serving Northern Maine HVAC & Controls. I burn wood, it smells good!-1
@NY_Rob It actually is very efficient. As we all know, heat rises. His basement is pretty consistent 63-65 degrees during heating season. Heat rises, so your not losing efficiency. Do you put heat in rooms that are in the center of a building that don't touch an outside wall? Not all the time. But this same "theory" applies to why I add the radiator to the basement (especially on swap outs of old oil cast with coils). Now by adding the radiator, it reduces the water temp going into the boiler making the condensate rain and in return making the boiler more efficient. My proof of this working, I purchased a house for an investment/rental. It had a peerless cast gas boiler. It was 24 years old. Same people have been renting the house for 4 years. I replaced the boiler with an IBC HC20-125. No cast unit in basement. Used about 20-25 gallons less then the 4 year average. I did a service and ran it, I noticed that the bathroom zones would short cycle the boiler. I added the radiator last fall, and she used 163 gallons less. I know its only one year compared to 4 years average, but there is definitely some savings. I will ask her in the spring of 2020 to compare again, but I believe its absolutely worth doing, again, especially with those giant cast boilers in basements0
Heat does not rise. Warmer fluids (including air) are more buoyant than colder. When it comes to radiant heat, it knows nothing about gravity.HVACguyinME said:
@NY_Rob It actually is very efficient. As we all know, heat rises. His basement is pretty consistent 63-65 degrees during heating season. Heat rises, so your not losing efficiency. Do you put heat in rooms that are in the center of a building that don't touch an outside wall? Not all the time. But this same "theory" applies to why I add the radiator to the basement (especially on swap outs of old oil cast with coils). Now by adding the radiator, it reduces the water temp going into the boiler making the condensate rain and in return making the boiler more efficient. My proof of this working, I purchased a house for an investment/rental. It had a peerless cast gas boiler. It was 24 years old. Same people have been renting the house for 4 years. I replaced the boiler with an IBC HC20-125. No cast unit in basement. Used about 20-25 gallons less then the 4 year average. I did a service and ran it, I noticed that the bathroom zones would short cycle the boiler. I added the radiator last fall, and she used 163 gallons less. I know its only one year compared to 4 years average, but there is definitely some savings. I will ask her in the spring of 2020 to compare again, but I believe its absolutely worth doing, again, especially with those giant cast boilers in basements"If you can't explain it simply, you don't understand it well enough"
On some of @Gcracker 's comments. Although he may have put it rather poorly, your contractor has a point. Combi units have to be sized for the expected maximum domestic hot water load, otherwise they won't be able to deliver hot water. However, they also have a flow sensor to tell them when to run -- and if the fixtures are very recent low flow types, they often won't produce enough flow all by themselves to trip that sensor reliably and the result is very much as you described.
Then on the heating side, in most smaller modern homes -- such as yours -- the heating load is much less than the instantaneous hot water load, and the result is exactly the mismatch you are seeing.
The best solution is an instantaneous hot water heater sized to the load -- and a separate boiler, also sized as close to the load as you can (you may have trouble finding a small enough one...)Br. Jamie, osb
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