heat not reaching one radiator

Pegret

Had a new Weil-McClain steam boiler installed in my 1928 house. It's been a huge struggle. Voilent banging pipes and water gushing all over floor. Plumber tried many things and finally repiped correctly (according to manual) and it's now working fine except...one radiator comes on only if I turn the thermostat up 3 or more degrees at once. Even then it's the last one to come on and sometimes only warms 3 or 4 columns. But sometimes it heats completely. When maintaining the same temp., it never works at all. Of course most of the time I keep it at one temp so this means most of the time it's cold! There's no problem with the radiator itself- plumber confirmed today that the radiator and vent are fine.
The radiator is located in an addition on the first floor, surrounded by windows and is my favorite room. Today plumber turned vents to 1/2 positions on other radiators on first floor thinking the thermostat reads warmth from them before this rad has a chance to come on. Interesting theory but, once again, when I kept temp set and a new cycle came on, the rad didn't come on. I've been on the phone with Weil-Mclain technical services several times and they can't figure this out, either.

JohnNY

It can really only be a venting issue. The radiator needs to be vented more quickly with the largest vent(s) available and the radiator closest to the thermostat should have a restricted air vent, i.e. a smaller, slower vent.
It is usually possible to add a second vent to a slow heating radiator.

Weil-McLain can't help you with this because it's likely not a boiler problem. It's a system problem. A good steam guy will knock this out right away.

JUGHNE

Your problem radiator is in an addition to the house?
The rest of the system works?

The addition may be under piped.
There is a limit to the length of runout pipe without increasing to the next larger pipe size. Easy to exceed that point.

Jamie Hall

And any chance of water trapped in the feed to the radiator? All your slopes are good?

As @JohnNY said, this has nothing to do with the boiler.

JUGHNE

One church I service has mirror image of piping and radiation on the east and west sides.
One difference is the last rad on the east has a 2" runout of about 15'. That rad is last to heat, then only part way and only if call for heat is longer as in coming out of setback. It also has a little water hammer the longer it heats.
By the book it should have a 2 1/2" runout.

The last rad on the west, same size, has a 2" runout of only about 8'. It heats fully without problems.

When you mentioned addition to the house how far is it from the
problem rad to the main in the basement?

Three things helped with the problem rad;
Adding about 12 G2 steam main air vents, (a lot of large pipe) Putting a slow Hoffman air vent on problem rad.
Insulating piping with 1" fiberglass.

Pegret

Wow thanks for all the ideas. Can anyone explain why this radiator works fine when I increase the thermostat by approx 3 or more degrees, but doesn't work when simply maintaining the same heat?

JUGHNE

In my case I believe that happens because the longer run time heats the run out pipe enough to get the steam to that rad.
The pipe has to "become a radiator" first.
It is counterflow, in that the steam has to meet the returning condensate water. It gives up some heat as the two meet inside the pipe. The longer the pipe, the more time needed.

Could you move your thermostat to the cold room?
What do you have for main air vents in the basement?

KC_Jones

Main venting, need to start there and go up. @JohnNY said it right, a good steam guy fixes this easily.

Jamie Hall

Time. Pure time. It just takes that much longer for the steam to get to the radiator.

Pegret

Mystery is when I had the old 1928 "snowman" boiler, which was replaced this summer with this new Weil-Mclain, there was never a problem with heat getting to this radiator. Now I have a brand new boiler but my livingroom is cold because of this one radiator

KC_Jones

How did they size the new boiler?

KC_Jones

Also what is the pressure set to on the pressurtrol?

coelcanth

jughne touched on one problem i experienced, which was that boiler run time was too short to get steam to my furthest radiators, even after my main venting was upgraded.. might be related or at least part of the issues you are seeing..

so i would check the length of the normal heat cycle when you are not getting satisfactory heat and determine what is signalling for boiler to cut out. might be as simple as the thermostat being satisfied because the vents in that room are too quick or might be something like an anticipator or CPH setting keeping the boiler run time too short.
that could be why the steam reaches the trouble radiator when the heating cycle is long (recovering from your 3 degree setback).

other things could cause the boiler to cut out too early, like a LWC triggered by a surging waterline or an actual low water condition.. or a pressuretrol set wrong or triggered by an oversize boiler. these less likely since it sounds like you and your plumber have been investigating

Pegret

pressure is 1/4 cut in and 1 cut out. Its a 98,000btu for an 800 square ft house. Water level has be right. Plumber thought of the other vents in area being too quick for the slower radfiator so we turned thme 1/2 closed. Didn't work. Thankful for all these thougths which I will bring to my plumber. I'm going to time a normal heat cycle.

BobC

It's best to vent the steam mains fast and the radiators slowly. What kind of radiator vents do you have? If they are heatimer's you may be in trouble because they are very fast and hard to adjust at the low end.

pecmsg

Pegret said:

pressure is 1/4 cut in and 1 cut out. Its a 98,000btu for an 800 square ft house.

Thats a lot of BTU's for a little Sq Ft

How long from cold start to shut down?

Pegret

I think 17 min. cycle for cold start to shut down. Haven't timed recently, but last I checked it was 17 min. which seemed long to me but I don't know what it should be.

pecmsg

At design condition 0 cycles.

KC_Jones

I asked earlier how the new boiler was sized, I’m guessing it’s oversized.

My guess, lack of main venting and too big of a boiler.

Old boiler worked “fine”. New boiler does not. New boiler is oversized, producing steam at a faster rate. This is running the pressure up higher faster than the old one. The steam is looking for a place to go so it fills the closer rads quickly, satisfies the thermostat, shuts off boiler and the last rad never gets steam.

Need to find out if they sized the boiler properly, they will say yes so the only way IMHO is for you to run the numbers which isn’t hard. After that need to look at main venting, ignore the rad vents for now they don’t do you any good until the main venting in the basement is correct.

Also please post pics of the new boiler and it’s piping so we can verify it was properly installed.

Dave0176

@Pegret what model Weil-McLain boiler do you have ?

Pegret

my house is 800 sq ft w 3 radiators upstairs and 4 rads downstairs - it's a wiel-mclain peg45 series 5. with150,000 btu. wiel-mclain technical services said all I needed was 98,000btu but the 150 wasn't exorbitantly too big to function properly.
(Can't do pictures til I can use my own laptop which is being fixed.)

Pegret

There is a main vent near the boiler that is new and appears to be working

JUGHNE

Is it on the smaller return piping?
You should maybe hear it passing air for a few minutes after boiler fires until steam gets all the way around the piping.

I ask because sometimes they are wrongly put on the steam main right at the boiler....it has happened.

nicholas bonham-carter

Not only should the main vent work, but it should be the right size. Bicycle tires are round, made of rubber, and filled with air; but won’t work on a car.—NBC

KC_Jones

> @Pegret said:
> my house is 800 sq ft w 3 radiators upstairs and 4 rads downstairs - it's a wiel-mclain peg45 series 5. with150,000 btu. wiel-mclain technical services said all I needed was 98,000btu but the 150 wasn't exorbitantly too big to function properly.
> (Can't do pictures til I can use my own laptop which is being fixed.)

To size the boiler all the rads in the house are to be measured, the total EDR of the radiation is then compared to the boiler rating. This is the proper way, I’m not following what your stating exactly. If you needed 98 and put in 150 I would call that massively over sized.

Again all the rads need measured to do it properly, I’m guessing that wasn’t done?

Pegret

Radiators were not measured. The plumber who gave the first estimate for the job measured every radiator. He dissappeared when he saw aesbestos pipes, didn't return calls. So second plumber came out and did not measure radiators and I asked him why and he said not necessary and I think he said he goes by house sq footage. So frustrating - it would be nice to be able to trust the pros since I know zero about plumbering.
Now I'm worried that no matter how well all problems are resolved it will never run at highest efficiency.

Dave0176

Your radiators need to be measured to come up with an EDR. Then you can compare to the boilers output of 392 EDR, that particular WM boiler is 150,000 input, with 125,000 output and 392 sq ft of steam. When we size a boiler for replacement we never use BTU, it’s always sq ft of steam or (EDR)

KC_Jones

Pegret said:

Radiators were not measured. The plumber who gave the first estimate for the job measured every radiator. He dissappeared when he saw aesbestos pipes, didn't return calls. So second plumber came out and did not measure radiators and I asked him why and he said not necessary and I think he said he goes by house sq footage. So frustrating - it would be nice to be able to trust the pros since I know zero about plumbering.
Now I'm worried that no matter how well all problems are resolved it will never run at highest efficiency.

It doesn't go by square footage for any heating system, so he is 100% wrong every day of the week. Hack's are among us.

If you want to calculate your radiator EDR we can easily help with that exercise so you can get an idea of where you are at. I'm betting it's over sized.

You are correct you will only get it so good if it is over sized.

Honestly, I'd take the measurements, then put the contractor to task and show him with numbers how he did it wrong. Then see what he does, it should be fixed on his dime as it's his mistake. Weil Mclain actually has a boiler sizing sheet available on their website, you could fill that out then show it to him. I'd really love to hear how he would argue with the manufacturer about it.

Have you made final payment?

When you are able to post pictures please do so.

ethicalpaul

This doesn't sound good. Sq feet isn't a good comparator, but I have a two storey wood frame house that is about 1400 sq ft and my boiler is 112k btu and is oversized by 20-30%.

I bet 98K BTU is oversized, but probably OK (as in, it was typical oversized that is in a majority of houses). But 150k BTU in an 800 sq ft house sounds insane, like WAY off the charts.

Edit: I am still slightly confused at the size...I think @Pegret said it was 98k and then later said it was 150k. So to me, 98k = too big but could work and 150k = !!! danger Will Robinson

Dave0176

You can size the radiators yourself here is a chart I use and it includes basically the most popular radiators.

Pegret

Don't know what all this btu information is but this is what catalog says for Model 45

Max Input BTU=150,000 BTU
DOE Heating Capacity=125,000 BTU
Net I=B=R= 94,000 BTU
AFUE 82.9%

so is bottom line that the BTU is 94,000?

Fred

The 94,000 BTU is the amount of BTU's available for the Sq. Ft. of steam, not counting the 33% pipe and Pick-up factor. 94000 divided by 240 BTU's per EDR = 392 Sq. Ft. or 392 EDR

KC_Jones

The only way to know where you are at is to measure the radiators using the chart that Dave posted.

For anecdotal information, I have a 1500 sq ft house and a smaller boiler than you, and honestly I could have used a smaller one and still been ok.