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Cast Iron radiators - Combi Boiler Install Issues
adriantkelly
Member Posts: 7
in Gas Heating
Hi, everyone. Just had our boiler replaced last September for our cast iron radiator system. Was previously a steam system that was converted at some point. We bought the house 3 years ago (100 year old house) and old boiler went last year so we upgraded to a combi boiler system. Initially we were hearing some clanking metal sounds which we believed to be the heat exchanger. Had the manufacturer rep and installation company come out and they said it was a popping noise being caused from cold water inlet being introduced to the system so they turned off the inlet.
Now we’re hearing the system constantly running in high fire mode which defeats the purpose of having a high efficiency system. They said the next step is attempting to replace corroded valves on each of the radiators to see if there is a build up of sediment in the pipes. Their theory is there is poor circulation throughout the system because of the buildup of sediment which is causing the system to constantly run.
Are we getting the run around here? Do we have any other things to look into? Thank you for any feedback
edit: visible pipes in the basement have asbestos wrap so hvac company is worried about replacing valves, breaking pipes and not being licensed to work with asbestos
Now we’re hearing the system constantly running in high fire mode which defeats the purpose of having a high efficiency system. They said the next step is attempting to replace corroded valves on each of the radiators to see if there is a build up of sediment in the pipes. Their theory is there is poor circulation throughout the system because of the buildup of sediment which is causing the system to constantly run.
Are we getting the run around here? Do we have any other things to look into? Thank you for any feedback
edit: visible pipes in the basement have asbestos wrap so hvac company is worried about replacing valves, breaking pipes and not being licensed to work with asbestos
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Now we’re hearing the system constantly running in high fire mode which defeats the purpose of having a high efficiency system. They said the next step is attempting to replace corroded valves on each of the radiators to see if there is a build up of sediment in the pipes. Their theory is there is poor circulation throughout the system because of the buildup of sediment which is causing the system to constantly run.Corroded valves and a build-up of sediment would restrict flow and/or reduce heat transfer which will cause the boiler to short cycle. Your boiler is running all the time; just the opposite. Boiler could be undersized. How big is your house (square feet) and what size boiler (BTU input)?8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab1 -
I would be very curious as to the near boiler and system piping.
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Yes. Pictures please. Never crazy about using old, cruddy steam piping (an open ti the atmosphere-oxygen - system.) For closed loop hydronic, but would be especially wary on a new Mod con with all its intricacies and tight passages. At the very least, you'd benefit from a Caleffi Dirt Mag. As the other guys say, sounds like issues other than that. Pics will help. Mad Dog0
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Hopefully these pics came through. House is about 2000 sqft0
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Sorry, pictures didn't come through.8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
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Yes, those two pictures show up fine.
There should be a boiler plate on the left or right side that will tell you the size of the boiler. Looks like an MFTCW series, either 140K or 199K BTU which should be plenty big for a house your size.8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
Does it adequately heat the house? If it is firing at high fire and the return water temp is still low enough to condense the products of combustion you are getting most of the efficiency of a mod con.
It sounds like the boiler isn't set up as well as it could, it is set to try to make water hotter than necessary to heat the house, outdoor reset isn't set up properly, or some other things might need tweaking. Does it run long heating cycles or is the thermostat satisfied quickly?1 -
You've got two very different flow demands through 1. the boiler, and 2. the piping/radiator system. My opinion is that this setup is begging for a hydraulic separator to decouple the dissimilar demands. I think you've got primary-secondary piping there with closely spaced tees but the reduced pipe size from the secondary side is probably not adequate and neither is that (NRF-22?) pump to create a good temperature differential between supply and return. Anyone who tells you the boiler is running at high fire for too long because there is a problem with reduced distribution doesn't understand hydronic heating systems very well. I've connected boilers to several gravity systems over the years and one of the biggest problems is overcoming the system volume with those large diameter pipes. It sometimes throws the heat loss calculations off.Contact John "JohnNY" Cataneo, NYC Master Plumber, Lic 1784
Consulting & Troubleshooting
Heating in NYC or NJ.
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I didn't see the link to the pictures. Now I see it. That was never steam, it was gravity hot water.
Ideally it would be primary secondary, it should work with a single circulator if it is designed right because the old gravity hot water pipes are so large that the head of the system is almost negligible compared to the boiler. In either case balancing could be an issue, might need to rebuild some valves to do that.
EDIT: I see now, it is primary secondary with a built in pump in the boiler. I think the overall system is ok, it just needs fine tuning by someone that knows what they are doing.(rebuilding/repairing the radiator valves so they can be used for balancing, making sure there aren't orifice plates in the unions of the upper radiators, adjusting the parameters of the boiler to match the system.)
The dirtmag that @Mad Dog_2 suggested would be an excellent idea.
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That asbestos’s should have been abated.
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After a lot of squinting and cross referencing, it's an NRF-25
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The delta t on the mass of that gravity system is probably huge. It wouldn't surprise me if the return water is still cold when the thermostat is satisfied in mild and moderate weather.1
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ACM...Unless $$$ is super tight, I ALWAYS suggest proper abatement. What are you waiting for? Its only going to come back to haunt you at the most inopportune time. For example, you get a bad leak on a section packed in it and you're going to have no heat until its fixed. So, now your under duress to A) Ignore proper procedure and repair it.
Hire someone at a premium. Unfortunately, the average Josie is going to prefer to spend any extra $$ on granite tops or a new couch and Average Joe on a New Fender 🎸 Guitar and White wall tires.....Mad Dog
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Add to that the cost of installing new pipe insulation after the asbestos has been removed. One inch fiberglass or polyolefin (black foam) are the best.Mad Dog_2 said:ACM...Unless $$$ is super tight, I ALWAYS suggest proper abatement. What are you waiting for? Its only going to come back to haunt you at the most inopportune time. For example, you get a bad leak on a section packed in it and you're going to have no heat until its fixed. So, now your under duress to A) Ignore proper procedure and repair it.
Hire someone at a premium. Unfortunately, the average Josie is going to prefer to spend any extra $$ on granite tops or a new couch and Average Joe on a New Fender 🎸 Guitar and White wall tires.....Mad Dog8.33 lbs./gal. x 60 min./hr. x 20°ΔT = 10,000 BTU's/hour
Two btu per sq ft for degree difference for a slab0 -
It definitely can heat the house adequately. My biggest concern right now is the metal clanging sound - which I'm told is cold water from poor efficiency on the return hitting the heat exchanger. I wouldn't say the heating cycles run abnormally long but we can hear them more often on this system than the previous system. With a high efficiency system, we expected to see some level of savings this year with heating and the bill has only continued to go up, unfortunatelymattmia2 said:Does it adequately heat the house? If it is firing at high fire and the return water temp is still low enough to condense the products of combustion you are getting most of the efficiency of a mod con.
It sounds like the boiler isn't set up as well as it could, it is set to try to make water hotter than necessary to heat the house, outdoor reset isn't set up properly, or some other things might need tweaking. Does it run long heating cycles or is the thermostat satisfied quickly?0 -
It's still in good shape right now. That's the plan at some point but just not enough money to go around at the moment lolpecmsg said:That asbestos’s should have been abated.
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The only reason that a MODCON boiler goes to high fire is because it believes that it needs to. Firing rate is a function of load/differential, and possibly control settings. Does it have an outdoor sensor? You mentioned that it runs constantly. Does it run constantly, or does it constantly run in high fire when it runs? These are two very different problems. Running constantly is a boiler sizing problem and constantly running in high fire is a setup, system tuning issue. Assuming that it does not run nonstop. How long are the on and off cycles? How big are the temperature swings in the living spaces? I am guessing pretty large. When a very high mass system cools significantly between calls for heat the boiler will likely ramp up to high fire on the next call. I doubt that your system is a converted steam system and is a converted gravity hot water system. It was designed for very long, very slow and gentle cycles.
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Best to abate and insulate, or go with new piping entirely? Thank you all for all of the feedback
Add to that the cost of installing new pipe insulation after the asbestos has been removed. One inch fiberglass or polyolefin (black foam) are the best.Mad Dog_2 said:ACM...Unless $$$ is super tight, I ALWAYS suggest proper abatement. What are you waiting for? Its only going to come back to haunt you at the most inopportune time. For example, you get a bad leak on a section packed in it and you're going to have no heat until its fixed. So, now your under duress to A) Ignore proper procedure and repair it.
Hire someone at a premium. Unfortunately, the average Josie is going to prefer to spend any extra $$ on granite tops or a new couch and Average Joe on a New Fender 🎸 Guitar and White wall tires.....Mad Dog
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There's a lot of water in that 2" pipe that you're paying to heat. Add to that if or when there's an issue it now becomes major and that equals expensive. Get the abatement done, inspect the pipes and decide!adriantkelly said:
Best to abate and insulate, or go with new piping entirely? Thank you all for all of the feedback
Add to that the cost of installing new pipe insulation after the asbestos has been removed. One inch fiberglass or polyolefin (black foam) are the best.Mad Dog_2 said:ACM...Unless $$$ is super tight, I ALWAYS suggest proper abatement. What are you waiting for? Its only going to come back to haunt you at the most inopportune time. For example, you get a bad leak on a section packed in it and you're going to have no heat until its fixed. So, now your under duress to A) Ignore proper procedure and repair it.
Hire someone at a premium. Unfortunately, the average Josie is going to prefer to spend any extra $$ on granite tops or a new couch and Average Joe on a New Fender 🎸 Guitar and White wall tires.....Mad Dog0
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