Baseboard STILL got me puzzled

Chuck_12

Posted several days ago, I still can't figure why I cant get flow thru the baseboard which replaced an old style rad. Kept the same size supply line and return...only difference is the rad is now 12' and approx. 10' added to the supply run. (see previous posting below)

Simply put... I replaced a 16 fin three col cast iron rad 23" high with a new 12' section of cast iron Baseray. The supply pipes remained the same which were 1" galv off a 1-1/2" main. My problem... the baseboard rad does not heat well. Flow seems restricted due to other rad lines heating up more rapidly than this run. From the main I have approx. 20' of 1"supply to 12' baseboard and then return with approx 12' of return. (8' differential) Also keep in mind the static flow of the new rad compared to old column type. Several things may be happening here... other lines from the "Main" heat up fully at boiler temp and therefore the return (when hot) then restricts the cooler flow return from the baseboard line. Hence...slower (or restricted) flow and cooler baseboard rad. The pitch of my piping is fair but due to the new longer run of 8' supply, the pitch is less. Does that matter? Any suggestoins to help me along to get flow back to this radiator? I prefer NOT to use seperate circ pump for just one rad run. Any suggestions? I am guessing that I need to somehow get the baseboard rad run to heat closely to the temp and time frame of the other rad runs to prevent the cold/hot water bucking each other on the return line. Would a mono flow valve solve this, better pitch of lines? Shorten the length of the supply from main to the Baseray so hot water enters sooner? Help!

Added note: the system has been thoroughly checked for leaks and importantly air in the system. If you take into account the overal capacity of the Baseray per sq.ft. vs the older radiator water capacity per sq.ft.; then naturally the older rads will heat quicker; and hopefully there is a way to compensate by either modulating the flows thru valves of alternate pipe sizes? Also..Can water be naturally forced to flow faster by increasing the pitch of pipe at the horizontal runs off the mains? (and not increasing the water temperature at any time to compensate) I want to maintain 180 degrees IN and approx 150 degrees min OUT (return to boiler)

Mike T., Swampeast MO

Still operating under gravity, e.g. no circulator???

If so, you have too much restriction and too little elevation. Not only have you added in extra piping in the supply, but you've decreased the pitch. Plus you've replaced a cast iron rad (which has essentially zero flow restriction) with a baseboard type that most certainly has much more restriction to flow and likely very little, if any, pitch. (I'm not even certain which way you would want to pitch it or if you'd want to make it dead level! My guess would be to pitch ever so slightly towards the return.) To make matters even worse (particularly if the rad is on the 1st floor above the boiler) you've removed a good chunk of the motive force for gravity by installing a baseboard--the height of the radiator actually counts and likely makes up at least a quarter of the elevation above the boiler! As a final straw, the new baseboard holds very little water and it can't stratify in the rad--again building motive force for circulation.

Some things the dead men did...

1) Supply/Return mains were kept parallel and horizontal runouts to rads as short as possible and as even as possible in length.

2) Horizontal runouts typically had ¼" per foot of slope. If less slope (or fairly long) they would increase the pipe (and radiator tapping) a size above normal. If too flat or too long, they just wouldn't do it 'cause they knew it wouldn't work!

3) Water tends to stratify by temperature in the mains with the low velocities of gravity. The lowest radiators in the system were typically taken off at the top (vertically) of the main. However in your situation with a rather small main (only 2" at that point) they would likely angle the fitting at 45° so that they only needed to use a single 45° el to get horizontal instead of a 90°.

Good luck! I think you'll need it! You can attempt to help by pitching the horizontals more, getting the horizontals closer to the same length, increasing the size of the horizontals and perhaps repositioning the initial takeoffs, but I won't make ANY promises!

Chuck_12

Hopeful modificaitons to Baseray ot be made

Ok...I have HOPE now. I do have a circ pump on the return line. I understand there are no guarantees but I am going to attemp several things I can easily modify on this LINE. FIRST; I can shorten the supply line; SECOND; I can pitch the pipes at least 1/4" per foot and more if needed; THIRD; I can tap the supply off the top of the main and tap the return on the side of the return main; FORTH (but not last) I can increase the line from 1" to 1-1/4" if necesssary. I am in tune with your comments as well as with the help of some of the articles in here about the dead man practices and the methods of the older gravity type hot water systems. If this works, heck ! I may be eligible for a GED in plumbing mechanics. Wish me lots of luck; I'll keep ya posted.

By the way. Burnham advertisies that you can change out older rads with the Baseray with little or no modifications. You can be assured I will be contacting them also for their insight

jim_49

Do you have monoflow tees on system. Or ifyou did are they still there??

Mike T., Swampeast MO

With a circulator in the system, those changes are unlikely to have any effect--something else is going on.

If the new b/b is on a circuit with other radiators (standing iron?) and there is no thermostat in the space with the new b/b, it's possible you just don't have enough of the baseboard relative to the rest of the radiation.

Am also a bit confused when you talk about monoflow tees. Is your system one-pipe or two-pipe? Most, but not all, gravity systems were two-pipe.

What occasioned the removal of the standing radiator in the first place?

Chuck_12

clarifying the system

The gravity system is two-pipe. The circ pump is on the return main at boiler. there are no mono tees. In theory my problem is this. The baseboard is the last rad on the main (on 1st floor) the other two rads that are off the main; both are supplied with 3/4" lines and both are on the 2nd floor. Naturally their flows are good and fast.
What seems to be happening is that by the time the return water from the upstairs rads is reaching the return main hot, the end line with the baseboard is stil returning cooler water. The hotter return water now in the return main from the upstairs rads is preventing the cooler return water of the b/b to flow back to the boiler. Simply put if you could measure the flow of the other rads against the flow to the b/b rad, I need to improve the flow through the baseboard. If you think of the flow like convection currents the hot water is pushin gthe cooler water back up the return line of the b/b. Maybe a mono tee will solve this problem or better yet a way to near equalize the temperatures of the returns from the radiators. Where are all those dead men when you need em? By increasing the line size, pitch, shorten the supply run and increase valve opening, I hope to increase the flow through the baseboard by gravity method. Yeah I know, maybe Im shooting for the stars here?

Chuck_12

no mono tees

No mono tees are on system and none were ever installed. Orig system is intact original lines built with house 1921. The only difference now is the exisitng WAS a 16 fin 26" high cast iron rad with 1" inlet and outlet. The changes I made were replacing with 12' baseray cast iron b/b with 3/4" supply and outlet and 3/4" angle valve. Due to length difference I ended up with approx 10' more of supply line which naturally has a lesser pitch.

Mike T., Swampeast MO

Flow might be a bit of the problem, but there are definitely others: sizing and volume.

Judging by the description you gave for the standing radiator it had an EDR rating of about 64 square feet. A 64 square foot column radiator will hold approximately 12 gallons of water weighing about 100 pounds. (I assumed that it is a column radiator--not thin fin tube.)

The 12' Baseray has a rating of 40.8 square feet EDR. It holds approximately 3.6 gallons of water weighing about 30 pounds.

Beyond the problem that the new baseboard is about 37% smaller than the old there's that "little" matter of the water they hold.

Presuming that your circulator is controlled by the thermostat (e.g. it runs only when the thermostat wants heat) there is another problem:

For S&G let's say that when the circulator stops running that the supply temp in the radiation is 140° and the room temperature is 70°.

The old radiator held 100# of water--each pound of which had 70 BTUs available to give off to the space without the circulator running. There are literally 7,000 BTUs available for heating!

The new baseboard holds 30# of water. Again each pound has 70 available BTUs, but the total available for liberation between heating cycles has been reduced to 2,100. The new baseboard only has 30% of the "reserve" capacity of the old radiator!

IMHO piping changes to reduce restriction of flow to the baseboard aren't going to do much of anything. The easiest solution would be to go back to the old standing iron radiator. The next easiest (maybe) would be to add a LOT more baseboard--I'd honestly try to size it to about 120% of the size of the old standing iron or about 22 feet. (This sizing assumes that the space temp in that room was reasonably balanced with rest of the system and the old rad. If it was relatively cool, add more; if relatively warm, add less.)

Other solutions become ever more difficult, extensive and expensive. You could install TRVs and institute constant circulation and reset--generally not too difficult, but not inexpensive. You could pipe the baseboard as it's own zone--BUT you'll have a problem. Being undersized it's going to be calling for heat much more frequently than the rest--being only a small portion of the system you'll take a BIG efficiency hit running your boiler just to satisfy a small load.

Chuck_12

keep sight of my problem

Mike you are more than helpful but let me say that my problem is not a lack of heat at least not yet. The heat load for the room will be more than satisfied with 40.8 sq.ft. of basebard assuming 150BTUH per foot. So MORE radiator is not what I need. What I need is the radiator to get hot at the same rate that the others get hot.
By the time the room temps satisfy the thermostat the Baseray has hardly gotten warm. Keep in mind with gravity system the first floor is usually sized greater than 2nd floor rads. Capacity is the vaiable needed for proper BTUH followed by flow. The 3/4" line and 12' base is restricting flow; thats where I need to research to see how much water I can get thru this baseboard at the same rate most radiators are getting hot. It may be that I will HAVE TO use a sep circ pump for this line to boost circulation.

Btw, new insualting windows were added to house and insulation which greatly lowered the heating loads. Which by the old standard Dead Man Rule was approximatley 40% over-designed anyway.

If I added more length of rad. It will only be MORE RAD that cant get hot anyway. (scratching my head a bit now) I'll keep ya posted. Tahnkx.

Chuck_12

Got it Mike; Right from the horses mouth

Not that my problem got solved today...I talked with tech reps from Burnham. Bottom line is "good luck" when it comes to mixing baseboard with column rads on an existing gravity feed (even if I do have cric pump on the return side). The 3/4" baseboard entry is very restrictive since each section is also fed by each other that way. The only way to match the flow rate to get the proper output in the same TIME frame as the gravity does to the column radiators is....a circ pump on that line. Typical 007 will handle it.
Here is food for thought to all who read this. Gravity systems are very tricky and its best you understand the thermaldynamics of the flow. I have learned alot from this site and some of it's readers. As to my problem..when the water enters a large radiator the chances of the water staying hot is greater due to the volume which keeps adding to the flow factor for gravity will continue to push the cold water back to the boiler. The baseboard has two things different, smaller flow and quicker heat loss of the cast iron compared to column types. Oh yes you can go large to match size but you have to match the flow rate and heat transfer.
Bottom line form Burnham tech..do'nt plan on using baseboard with gravity solely unless you plan on a circ pump. Man!, I am learning real quick. Where have all the Dead Men gone....far far away!

Kal Row

it's not only pitch, but hight difference...

as in acceleration, sometimes you need enough of a height difference between the cooler denser water, and the less dense, warmer water, to get enough gravity acceleration, to overcome the resistance of the pipes, and then, there is the cool down rate of the new radiation, that also affects the acceleration - it’s a “gravity displacement acceleration thing” as long as you keep that in you mind when looking at the stuff, the answer will present itself

– “be the water” as dan always says
“where is it coming from”, “where is it going to”, warm water will not go down through cooler water – sometimes not even if a circulator is pushing it – that’s why hot water entering the top of a panel radiator side wont go straight down to the outlet below it, rather it first travels across it to where the water is cooler and then goes down and back across to the outlet, and this is with a circulator! – also happens in boiler sections – they have to be alternating opening piped otherwise it wont travel through the whole exchanger just across the top

also if the height acceleration IS there – then upside-down u-tube heat traps don’t work – the accelerating water will “fall” right through them – a 30ft drop and a 20f temps difference might even pop a spring check

– this is fun stuff!!!

Mike T., Swampeast MO

I know this may sound confusing, but just because the b/b you installed can meet the heat loss, does not in any way mean that it will.

Am presuming you have an older cast iron boiler.

Gravity systems are generally wildly oversized by today's measure--adding insulation/weatherization only makes them more oversized.

Those systems are typically controlled with the t-stat just telling the boiler AND circulator to come on at the same time. The older, higher water content boilers will though often be set to keep heated to some point at all times.

If the boiler and circulator act in concert, it's unlikely that your supply temperature ever exceeds 140° or so, let alone the return. It's sort of an "indoor reset" system and for some reason there doesn't seem to be much? any? problem with condensation even with the extremely low return temps.

When controlled this way, the supply temperature stays very low in most weather--your baseboard won't get hot because the water isn't hot to begin with...

If your boiler is constantly being heated, behavior is a bit different. In this case, the thermostat turns on the circulator. Even though the water in the boiler might be 180°, there's really not much there in comparison with the rest of the system. Again, the water in the supply lines won't get very hot as the heat from the water in the boiler is VERY rapidly dispersed by the circulating pump and liberated by the radiation.

In that note, you DO NOT HAVE A GRAVITY SYSTEM. Once a circulator is installed, it is a forced system--we just call it a "gravity conversion". The old rules of gravity NO LONGER APPLY.

What does apply however, is the sizing! With either of these common control strategies, you MUST consider the OLD sizing of the radiation before making modifications. To retain either of these forms of control you MUST size replacements similarly to the rest of the radiation in the system. You can still conduct a room-by-room heat loss of course; you just have to size the replacement(s) to have nearly the same proportionate output at the same supply temperature. e.g. the old radiation will be WAY oversized at 180° supply but you still want the new radiation to have the same degree of oversizing at 180°.

You did say though that the space is staying comfortable. If so, don't worry about the temp of the water going into and coming out of the new baseboard. The rest of the radiation in the house is likely taking up the slack as it continues to give off heat when circulation has stopped.

Low-grade

Chuck,
Without seeing a diagram of your system, I don't know if it would work, but - - - hav you tried to increase the flow to your b/b by throttling back the valves on the radiators? I suspect this may be the solution to your troubles. Just a thought

Low-grade

Chuck_12

Hoohray! Problem solved.

Here's what I did contrary to what Burnham even suggested. Only by shear luck. I took the supply and return and pitched the piping strongly at 1/4" per foot, shortened the risers that verticle up to the radiator and took the rag out of the pipe. Yes guys! When I broke open the piping to shorten the risers and supply I found a piece of rag that lodged in the elbow supply line. Apparently, when the hardware store threaded the pipe for me they pushed a piece of rag in the pipe due to all the oil that went in to cut the threads. I did not notice the rag in the pipe when I assembled. So my word of advise on this job is certainly to understand thermodynamics of the water flow and be sure to eye ball all your pipes for clear passage before installing.
Meanwhile, the 1" line supplying the rad is working very nicely. The pipes heat to the same temps as the other radiators (if not quicker) ...I have one HOTT baseboard radiator on a gravity system....and a good balance by shear luck. Now here is a good campfire story.
I will note this tho. I did compare a rad I had from the second floor. It too was being suppied by a 3/4" line and the size of radiator was the same capacity and the run of supply was within 18" difference. My gut feeling is that the flows would somewhat match. I can't do the flow calculations to prove it but the darn thing works great. Maybe those dead men look over us apprentices.

Chuck_12

A job done by shear luck I'm afraid

see my notes above. I have run the gamut with this radiator and even consulted Burnham about it and they said it wasn't suggested to install on a gravity system (circ pump on return) and wouldnt work without a circ pump on the loop itself. Much to my LUCK tho its now working. Helps to take any blockages out of the pipes first.

Kal Row

goes to show you...

something stupid like a rag or even peice of teflon tape in a system - can reduce seasond people to bungling idiots

Bruce M.

Chuck, the answer is simple

Put the original radiator back in and be done with it. You are making a simple job into a giant project.

Chuck_12

I can only laugh

I can only laugh at such a situation but also be thankful that it happened the way it did. I do believe in Guardian Angels.. I just didn't know that they existed in the Plumbing Department. Makes being an idiot as you say a little bit easier to swallow.

Chuck_12

Thats the way it goes sometimes.

Just like life can be diverse, so can a plumbing job. Putting in a rad like before doesnt solve my problem.. the wife didn't want the radiator near the drapes (Gosh what would you have done in THAT situation) and another column type will not work. Some of the job was frustrating, some was fun and some was rather embarrassing... BUT, I chaulk it up to another experience and a great story I can tell the Dead Men when I finally go to see them in the Everlasting Plumbing Supply House. (not to be confused with Home Depot)

Kal Row

you can laugh..cause you never did it to yourself..

i have, and it aint pretty - and it aint cheap - when you need to swallow a stupid mistake - why does it alwas have to always be an expensive stupid mistake instead of a cheap one - how much time and money did that rag cost ya?

Chuck_12

a good remedy

Your suggestion is a good one since its mostly all about FLOW and CAPACITY when dealing with a gravity system. But in my case as yu can see, I was better to take the rag out of the pipe that was restricting flow. Whoda thunk?

Chuck_12

Life can throw you a curve sometimes

Life can throw you a curve sometimes. That rag...yeah it did cost me a lot of time...not money. Several weeks to be exact. But I'm an optimist. Thank goodness I wasn't doing this job for a living, it was a side project cause the Ms. didn't want the column rad to interfere with the drapes in front of the window. Here's the upside. I learned alot about gravity systems..about 10% probably. I enjoyed it and the help of many people hashing out the problem with me. The best of all was finding the rag as I was able to feel like an idiot, which HARDLY EVER HAPPENS in my life. AND...I got one darn good story to tell at the Annual Plumbers Convention.

Chuck_12

great message for all Plumbers

I really enjoyed and understand this email from you Kal. I do GET IT when it comes to understanding the flow of water with the gravity system and certainly knowing the difference involved once a circ pump (on the return side) has been installed. Your insight was very helpful and also importantly I found it witty. So when in doubt I always remember that it's a "gravity displacement acceleration thing" and everything is so much clearer in my mind. Meanwhile I continue to try and "be the water" by "watching where I'm coming from" in my plumbing endevours and where, in Heavens Name "I'm going to". Seriously, You have been very inspirational - thankx.

Bruce M.

Here is what I would have done about the drapes

If my wife told me to get rid of an old functioning radiator that had been in the house for 80 plus years I would have told my wife that you need to have shorter curtains. Once you start down that road you can never return.

Chuck_12

got more than a radiator to keep me warm.

Unfortunately my wife may not be like most...the dear heart. She makes great drapes and no one better can ad on FRINGE BENEFITS when you move a radiator for her. What can I say...It could be worse....she could have wanted diamonds. Now I have more than a radiator to keep me warm. (Old Plumbers point of view - always keep more than one flame burning - not just the boiler pilot)