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Question about new Bosch Greenstar 151 combi floor model install
shane_rowles
Member Posts: 10
I am not a plumber so I paid to have my Bosch Greenstar 151 Combi floor model installed. I converted from a single zone coal boiler to a three zone gas boiler. The original plan was to add the Bosch Greenstar FW200 Weather Compensation Boiler Control and outdoor sensor to make my new install as efficient as possible.
Since the FW200 control is not compatible with the CZM100 Zone control, and the CRC thermostats they used a Taco zone control and Honeywell on/off thermostats.
The problem is the outdoor reset never got installed and when I asked about it I was told that the boiler that was installed was a new model and the only thing the outdoor reset did was shut the boiler off when the outdoor temp went above 70F. They claim that there is a sensor on the return water inside of the boiler and that is how it decides on how to modulate for the most efficient water temp. I don't know enough to know if this is true or not and I feel like I now just have a smart boiler using simple on/off controls and I am not getting the most efficiency out of my boiler.
Should I still push to get the FW200 and outdoor sensor or push to convert the Taco zone controller and Honeywell thermostats over to the Bosch CZM100 zone controller and the CRC200 and CRC100 room controllers? Any and all help would be greatly appreciated. Thanks
Boiler name is Bosch Greenstar 151 combi floor model
Boiler model is KWB 42-3 A23 S3123
model number is 7 733 600 084
Since the FW200 control is not compatible with the CZM100 Zone control, and the CRC thermostats they used a Taco zone control and Honeywell on/off thermostats.
The problem is the outdoor reset never got installed and when I asked about it I was told that the boiler that was installed was a new model and the only thing the outdoor reset did was shut the boiler off when the outdoor temp went above 70F. They claim that there is a sensor on the return water inside of the boiler and that is how it decides on how to modulate for the most efficient water temp. I don't know enough to know if this is true or not and I feel like I now just have a smart boiler using simple on/off controls and I am not getting the most efficiency out of my boiler.
Should I still push to get the FW200 and outdoor sensor or push to convert the Taco zone controller and Honeywell thermostats over to the Bosch CZM100 zone controller and the CRC200 and CRC100 room controllers? Any and all help would be greatly appreciated. Thanks
Boiler name is Bosch Greenstar 151 combi floor model
Boiler model is KWB 42-3 A23 S3123
model number is 7 733 600 084
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Comments
A 42kw boiler is pretty large. How big is your house?
You can choose to do what you want, but you cannot choose the consequences.
You can choose to do what you want, but you cannot choose the consequences.
Your installer may lack knowledge. I’m giving him the benefit of the doubt.
You can choose to do what you want, but you cannot choose the consequences.
You can choose to do what you want, but you cannot choose the consequences.
Do you have large iron pipes feeding the radiators? If so, then there's probably enough buffer to reduce or eliminate short cycling - except for any micro zones. If you have any, then you should combine it with another zone.
You can choose to do what you want, but you cannot choose the consequences.
Did your install do a heatloss calculation?
How many bathrooms do you have?
We install buffer tanks to reduce short cycling. The actual modulation on a 151 btu boiler is 4.4.. so your zones need to be close to 34k btus... if not you see alot of short cycles.
I'd recommend you have a heat loss done on your home and then turn down the heating btu output... you can turn down the heat btu and leave the water heating btu at 100%..then you still get 3.6 gpm for hot water capacity.
fenkel, no there was no heatloss calculation done. I have one bathroom but I have a wife and three daughters LOL who unfortunately for me like to take long hot showers. How would I turn down the heating btu output? Would I just turn down the boiler high limit dial?
Also I figured out my square footage of my radiators, I measured the height and the width and used a chart for this:
Zone 1 - 357
Zone 2 - 90.66
Zone 3 - 76.5
Zone 1 is my main house ie. kitchen, livingroom, dinning room, all bedrooms and bath.
Zone 2 is only my enclosed porch/sunroom
Zone 3 is the basement
The reason I had it zoned was the sunroom get colder faster than the main house and it is used as an office, so when people are in there I wanted to be able to warm it up without heating the whole house and the installer suggested that I put the basement on its own zone as well. All the return lines in all zones are tied together and I do get some circulation in zone 2 and 3 when only 1 is calling but nothing is overheating so I don't feel that is a problem.
You have to go into the programming to limit the fire rate, but that won't change the lower end which will always be about 28k btus.
An old converted gravity system has somewhat of a "natural" reset built into it because of its high mass. But getting the indoor reset functional will give you better comfort and efficiency.
Since the boiler came with one CRC100, and Bosch's intention is for it to be used, and since the installer has not been truthful with you (for whatever reason), I'd expect him to put the right controls on. He spent just as much money on the Taco panel and Honeywell thermostats as he would have on the Bosch panel and room controls.
Again, IDK if it was just ignorance, stubbornness, or just plain dishonesty on his part, but you shouldn't have to live with it.
You can choose to do what you want, but you cannot choose the consequences.
Heres how i do a heatloss and set up a boiler..
First do a heat loss calculation,
Then i use the btus from that calculation and divide that number by the net ibr btus for the boiler im installing..
Let say your house have a heatloss calculation of 80 btus.
The net ibr for your boiler is 131
So 80/131 equals 61%.
So i would reduce my heating output to 61%.. i sometimes take another 5% off and start there.. then id use 56%..
Ive read that some installers will cut heat output down to 25%... i wouldnt do that...
Your goal is to reduce your water temp to increase efficiency at the same time reduce the short cycling...reducing the amount of short cycling will increase the longevity of your boiler..
Since you have have the taco controller for your zones, id install the fw200.. this will lower you water temps when the outdoor temp raises, which then will improve the boiler efficiency.
I am not sure which number to use for my boiler net ibr, the max input is 151,600BTU/HR and min is 36,000BTU/HR. Also Max output is 137,500BTU/HR and min is 31,700BTU/HR
If I go off my max input 63902/151,600 = 42.15%
If I go off my max output 63902/137,500 = 46.47%
I checked my max heat output setting and it was set at 100% so for now I adjusted to 55% and kept DHW at 100%.
Because of the following
1. The have to program it.
2. It takes time to setup properly
3. Could cause call backs.
4.takes more time to install it..
If you have to purchase an fw200..check out ebay..the sell cheap..
If you have time..experiment with the settings...just write down what you change and the valves...
So. 64/117 is 55%..so what you set it at is what i would have used...
I already have alot of time in it trying to figure out how it is supposed to work so taking time to program an outdoor reset wont be that big of a deal. I am glad to hear that I have the output setting correct. Thanks for all of the help
There is one more item you might want to try:
Reduce your supply temp for heating the home..
Are you setting the heating supply to max on left controller?
Try and turn it back at little...
Once you install the fw200, you can.set the heating supply temp more accurately.
This can greatly increae your efficiency..
Question ,what do you have for heat omiters? Baseboards, radiators or in floor?
If you have baseboard, the slant fin heatloss calculation will suggest at 180 supply temp how many feet of baseboard are needed to heat the area to design temp.. or 590 btus per foot of baseboard. If you have more baseboard than the required amount the heat loss calculations determined, you can lower your heating supply temp..
I have cast iron radiators, and I have the left controller set to 5 which is around 160F.
Install it in the largest and or warmest zone of your home
Also- I’m not a combi boiler fan- the boiler is always oversized unless your house is yuge (5000 sq ft). To bake cold water and make it hot instantly requires a yuge amount of BTU. Hence an oversized boiler
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