Panel radiator sizing?

Pulse

#1
The above chart shows the BTU output of several companies' 4" panel rads("model 22s") @ 140 SWT. For some reason Beacon Morris' numbers are a lot lower compared to all the others. Any idea why? I was originally going to use Beacon..

.. and for whatever reason Myson has the best BTU output out of all of them, so I am going to move forward with Myson..

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My second question is how to properly size these Myson panel rads.



The above chart shows the required BTUs of my zones on various days. The indoor temp is 72.



The above chart shows what size Myson panel rads I currently have picked out for each zone and their BTU output at 120/140 SWT.

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#2
As you can see, the plan is to basically never go over 140 SWT, even on a -10 day. Do you feel these rads are sized appropriately? I am not sure how well I have to be zero'd in.

I am planning to use a cross manifold with a thermostat in each zone. A single pump will supply all the rads/home run manifold.

#3
I will have a 30 gallon buffer tank. If my math is correct, I should be fine on even a 55 degree day, with the lowest 491 BTU zone open only? This will be a very unlikely case, but it works. The formula below allows for a 20 min run time to prevent short cycling.

28 GAL BUFFER REQUIRED = (11000 MIN FIRE BOILER BTU - 491LOWEST ZONE * 20 MIN CYCLE MINIMUM) / (15 DELTA T * 500)

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Thanks!

EdTheHeaterMan

Most panel Radiators have an option for a thermostatic non-electric valve that can be adjusted for each radiator and therefore for each room. If a room is too hot, then lower the setting on the thermostatic valve. If a room is too cold, then raise the setting on the thermostatic valve. This will adjust the amount of heat that can travel thru each radiator based on the way the room looses heat at different times of the day and where the sun may change how a room may heat up.

As far as why one panel emits more heat than another, that has to do with the amount of surface area each radiator has. If there are spacers that are made of metal that separate the front from the back of the radiator, and those spacers allow for more air flow across more metal surface, then there will be more heat transferred to the room as the air passes over the radiator surfaces.

Pulse

EdTheHeaterMan said:

Most panel Radiators have an option for a thermostatic non-electric valve that can be adjusted for each radiator and therefore for each room.

I decided against TRVs. I will be using a cross manifold(http://crossmanifold.com/) with thermostats. It makes more sense to have the temp gauge away from the rad.

I did not word my question well enough or maybe it was a stupid question, haha. Lets say the boiler is supplying 100 degree water to all zones. Zone 1's rad is oversized, so it shuts off. Zone 2's rad is perfectly sized so it stays open.

I was trying to get my rad sizing/SWT/BTUs to match, but I guess there is no need. I just couldn't wrap my head around it..lol The zones are meant to be shut off/turned on as needed.

EdTheHeaterMan said:

As far as why one panel emits more heat than another, that has to do with the amount of surface area each radiator has. If there are spacers that are made of metal that separate the front from the back of the radiator, and those spacers allow for more air flow across more metal surface, then there will be more heat transferred to the room as the air passes over the radiator surfaces.

I am looking at pretty much identical panel rads at each of these companies. As you can see all but basically beacon match up. Doesnt make sense.

EdTheHeaterMan

I am looking at pretty much identical panel rads at each of these companies. As you can see all but basically beacon match up. Doesnt make sense.

If you hold a Beacon in one hand and a Myson in the other head, i'm sure you will see a difference. The dimensions in the book do not account for the spacer dimensions. Although I have held the Buderus Radiator in my hand and the Beacon Morris in my hand (never held a Myson) and to look at the outside they are similar, the part you can't see, the spacers and the rear tank are different. here is the rear of a Beacon morris model 11

The rear of a Myson has a full tank identical to the front tank with the addition of hanging brackets


and the support metal between the front and back can have different spacing. All that metal has heat transfer properties

So the numbers in the book don't always tell the full story.

Heat output of a radiator is all about square foot of Equivalent Direct Radiation (EDR). That is to say the square feet of surface area that is hotter than the room temperature in which it is located. More surface = more heat transfer.

hot_rod

There was a time when all heat emitters were tested and rated by IBR in NJ. So the output numbers were based on the exact same test by an independent lab.

Once GAMA took over IBR manufacturers had difference of opinions and most do not certify to IBR anymore. As a result output ratings are all over the map, based on manufacturers own test in different lab settings.

I saw one fin tube manufacturer had two portable fans in their test chamber. There ratings came out high, too high and they had to back pedal a bit.

Maybe there are some Euro listings or standards to reference for panel rads?

72 room at -10 outdoor is a big delta. Any idea how often you are at design?

Pulse

hot_rod said:

Maybe there are some Euro listings or standards to reference for panel rads?

I dont know, I was just using the information provided on each manufacturer website.

hot_rod said:

72 room at -10 outdoor is a big delta. Any idea how often you are at design?

I was just seeing what would happen to BTU load in a worst case scenario. When I looked at prior years, there were just a couple days in the negatives each year. For example, last year: 2 days @ -8, then another two days at -1/-2

My actual 1% design day for my area is 7 degrees. The average temp is probably ~20 degrees.

I dont know what the best practice is for rad sizing. My current picks are not excessively large or anything.

hot_rod

if you fall behind a few days, just crank up the boiler 10 degrees or so. Some mod cons do that for you if they fail to meet load in a time frame 

Pulse

hot_rod said:

if you fall behind a few days, just crank up the boiler 10 degrees or so. Some mod cons do that for you if they fail to meet load in a time frame 

Of course, but what is the best way to initially size your rads? At what temp?

hot_rod

If you size for 140F supply at 25 delta you get the boiler condensing and not get to crazy with radiator sizes

Low temperature purists size for 120SWT. That lends itself to heat pumps and solar thermal. But as you noted, radiator size keeps increasing with lower SWT. Find a happy medium.

The math is in here for all emitters at lower SWTs.

https://www.caleffi.com/sites/default/files/file/idronics_23_na.pdf

hot_rod

More info here for existing system SWT reduction options.

https://www.caleffi.com/sites/default/files/file/idronics_25_na.pdf

Teemok

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Teemok

Cross manifolds look cool and may have benefits for some applications. Low temperature design means getting high emitter water delta T's with low flows. The full port valve is no advantage. I could see it as good as a high flow zoning manifold to feed/control multiple other smaller manifolds on a common zone. Maybe it has a very low operational current draw and that's required. I'd be concerned about inevitable robot repairs? Parts will not likely be local, never mind on a truck at your house. Wiring a zone valve control is not hard. I'd stick with big name compatible stuff. Is it more reliable? Maybe, probably. Easier/faster to diagnose and repair? Yes. As cool as the Cross robot to watch in operation? Not at all.

clammy

Electrical consumption ,added zone wiring ,thermostats and cost of the crossmanifold as compared to trv control at the panel rad and if using a valve w a by pass and constant circ your always assured that each loop to ever rad have flow and lower any issue of possible loop freezing and a lowering cost . Sure you’re going to need a decent manifold but in installing a few of them there flow setters didn’t impress me all that much . Otherwise all in on panel rads using trv have them in my home w a mod con running max 130 at 5 wilo ecm pump
Peace and good luck clammy

Pulse

Teemok said:

Cross manifolds look cool and may have benefits for some applications.

clammy said:

Electrical consumption ,added zone wiring ,thermostats and cost of the crossmanifold as compared to trv control at the panel rad

I was also struggling with all these points. The cross manifold is the best option cost wise, but going with actuators/zone valves does allow you to easily replace one.

I will be using a 12 port manifold. So..

Cross = $1300

Manifold w/actuators = ~$900(manifold) + ~$50x12(actuators) = $1500

Manifold w/TRV = ~$900(manifold) + ~$50-100x12(TRVs) = $1500-2100

Manifold w/zone valves = ~$900(manifold) + ~$130x12(zone valves) = $2460

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I am not a big fan of TRV valves right now, I would much rather have a wall thermostat on an interior wall. ..but, if I were to get TRVs, I would have to get smart ones which will be even more expensive..

TRVs allowing the homerun loop(to rads), to stay warm, was something I never thought of before..

@clammy
How did you size your panel rads for your home?

Teemok

I'm surprised by Cross pricing. You get adapters and a zone control too!? Not clear what adapters. There's also some wiring labor saved- No 4 wire ZV. I can see the attraction. Flip-able vertical outlets with out looking awful. I might try one for my house but I'd make a customer pay for proven parts till Cross proves itself or my hands on quality check and experience with it wins me over. I hate warranty call backs. I like the idea of 3/4 branched runs to 2-4 radiators on a common zone depending on emitter size/ btu load. Could balance flow for delta T of each panel on a common zone with a Flir camera. Might get away with less loops manifold if zoning design permits it. Thanks for bring them to my attention.

clammy

I sized my panel rads by room x room heat lose and used the supply water temp I desired to operate my system at and then figured out the size radiator that was needed . I see you desire alot of control of which in the place where all this stuff comes from is not cost effective this is why they use trv and rid themselves of zone valves and accurators there very smart and fugal they go hand and hand . They know where to spend their money to get the most return not the most assumed control . I have found that w trv and constant circ using low temps that aside from not having warm floors my own home mimics and radiant heated home by having very little temperature differerences from room to room nor floor to floor . Even though my home is small my gas comsumpition is rated as way below the same newer energy eff homes ,my home is 60 to 70 years old and the temp is set at 70 to 72 wife has to be happy and she a native of Brazil so it’s got to be warm . Crossmanifold are very nice great price but I feel that a uponor ep maniafold has a much better flow adjustment if you’re looking price wise . Personally I went w a old Wisbro classic w add on flow setters I found they work better then other build in flow setters and available in high or low flow setters . My whole system has been in about close to 14 to 15 years ,each year I smile when I get my gas bill cause there’s really never a bill over 120 bucks even in month long cold snaps . I yet to have to replace any parts that’s less then I can say for crossmaifolds no disrespect intended it’s a great product but the few little changes they have made to lower over all cost where not like by myself like building the control into the manifold makes it a pia and clutters up the wiring and it’s not for everything being max flow per circuit is what 2.5 gpm and I not to sure that’s achievable . Again great product as for would I use it in your situation on that type of job no I feel it’s really over kill and over complaining the systems I know in Europe it would be dead in the water and most heating guys there would shake there heads and say something in a foreign language and let you do want you plan to .
I ve installed a few of them great product and cheap being the recent increases in zone valve specify taco the hell w Honeywell garbage china junk will never use again last few where garbage and noisy. There big money saver and those who use should closely keep in mind there flow limitation and the learning curve of piping them and making it look beautiful .
This is just me and my preferences being to have the parts to repair them u might as well have a extra one to scab parts off of being no one I ve seen at a supply house even stocks them or the serviceable parts lust some thing to keep in mind .
Peace and good luck clammy

Pulse

@clammy

To confirm, lets say your SWT was 130, inside temp was 72, what did you use as your outside temp to size your rads for each room? Did you use a low design temp that occurs about 1% of the time or an average temp?

clammy

I used 7 odt but our design is about 14 so it only hits its max temp on a few occasion each season .