First time sizing boiler options and EDR

ChrisJ

Jamie Hall said:

Chris, while I admire your persistence, one must admit that it borders on stubbornness and an unwillingness to see that things in other places, under other circumstances, might possibly be different.

To be blunt, it's also poor engineering. When one is dealing with systems with relatively poorly defined parameters -- and a heating system in a previously uninstrumented building surely has poorly defined parameters if anything does -- it is only prudent, if one is the engineer or the contractor, to work in a safety factor. If one doesn't care to call it a pickup factor -- which, I will admit, is a rather poor term but one we have to live with -- that's OK. But a safety factor? Yes. Are the parameters well enough defined in a specific situation to get away with 10%? Then do that. 30%? Then do that. 0%? Not on my license. If I come out of the job with 99% of the capacity I need for the system, I wind up picking up the tab to redo it to 100%, and I don't have that kind of money. If I wind up at 110%... everyone's happy -- particularly if I was smart enough to pick a boiler which could be dialed back a bit.

Your mileage may differ.

Again,
I'm going off of information from professionals that tell me it does work in other situations.

I think I'm done for now.
I'm already off of Fred's presents list and next thing will be getting banned from the museum.

Fred

Again,
I'm going off of information from professionals that tell me it does work in other situations.

I think I'm done for now.
I'm already off of Fred's presents list and next thing will be getting banned from the museum.

Lord, Lord, Lord
EDIT: BTW, use "Banished from the museum" It sounds a little more dramatic

vaporvac

I love these conversations and do feel they've helped steam move to a different place. They certainly helped me with my install.
However, I think we can ALL agree that @jackm needs NO bigger than the MST288, and even with that he'll still be slightly oversized by AT LEAST 13edr. He'll be more oversized until he adds in the extra rads. (This is straight edr, not P&PF.)

@jackm, I have a similar edr to Jamie (1466) and my two TR50s are almost an exact match to my edr. I have NO problem heating my house on the coldest night or day and it is plaster on brick with single-pane windows with some storms and insulation in the attic and knee walls. I think it can't be stressed enough that the rads can only condense so much steam at one time, so over-sizing doesn't buy you anything unless you're planning an addition.

MY experience with piping is thus: I have up-sized to a larger header and surely have the tallest risers I've seen on this site. They go into a double drop header from the twinned boilers. I STILL have condensate coming down the equalizer.It's inevitable until the pipes heat up and probably even then. Get as big and as high as you can. The risers are smaller and cost less so go higher; the length of header needed is really small. My local plumbing supply was happy to unload their odd-sized fittings for a deal so I lucked out. I obsessed over this, but today I can't even recall the difference in price. You're only doing this once and that's the least $ of the install. Just my .02, for what it's worth as a HO.

BobC

It looks like more experimentation is in order, it should be done on different systems to see what that turns up.

@ChrisJ are you still venting your risers apart from the radiators?

EDIT at 18:18

You could easily lower the gas pressure to cut the output of steam but you would need to check the combustion results.

Bob

Fred

@Hatterasguy , Looking at Chris' post when he down graded from an EG-45 to an EG-40, he indicated he needed 62K BTU's. The EG-40 is 78K BTU's which suggest to me he has a 25% Pick-up factor in his current boiler. Where does the 0% come from? Maybe I'm not understanding.

Fred

Hatterasguy, Chris is the one who said he needed 62K BTU output, not me. Is it 62K or 94K? Even at 94K he still has a 10% pick-up factor which isn't 0% and according to him he has very short runs so maybe 10% works well in his case. Now, have his runs grown in length too?

KC_Jones

Fred he stated he needs 62K because that is his heatloss, that number has nothing to do with his radiation. He indeed has 392 sq ft of connected load. The only reason he didn't go any lower...he has the boiler already.

ChrisJ

I have 94,000 in radiation not including piping losses.

My house, I thought needed 62,000 but due to infiltration seems closer to 70,000 on the coldest days I've seen.

My current boiler output is 104,000.

Keep in mind, my boiler is 10% above my radiation, but I am also using Gorton 6s and Cs on a few radiators. I'm by no means venting my radiation slow as per Dave Brunnell's rules. This is why my pressure stays so low. If I had balancing issues, I would just switch to slower vents.

@BobC
I was only venting one riser, and I stopped as I found it uncessary with the EcoSteam doing 2 CPH. I put a bigger vent on the TRV to get heat in the room faster, and no longer needed to vent the pipe.

ChrisJ

Hatterasguy said:

ChrisJ said:

My house, I thought needed 62,000 but due to infiltration seems closer to 70,000 on the coldest days I've seen.

I'm sorry but you're now going to be forced to replace the EG-40 with the EG-35 to prove the theory of matching heat loss rather than EDR.

You say this as if the thought had not actually crossed my mind.
I've got a pipe threader. I could have that bad boy in within 5 hours.

KC_Jones

@ChrisJ I wonder what your current boiler is worth to sell and use that to finance the purchase of the EG-35?

Fred

KC_Jones said:

Fred he stated he needs 62K because that is his heatloss, that number has nothing to do with his radiation. He indeed has 392 sq ft of connected load. The only reason he didn't go any lower...he has the boiler already.

I just reread his post. I stand corrected. I saw that.

Fred

Hatterasguy said:

ChrisJ said:

You say this as if the thought had not actually crossed my mind.
I've got a pipe threader. I could have that bad boy in within 5 hours.

The mad scientist will prove that you can heat with a negative pickup factor!! All the naysayers will pound sand!!

lol

Mark N

Chris should have got a hi lo gas valve when he replaced his gas valve. He could then run his boiler at high fire with a pick up factor or low fire with zero pick up factor. Could have been interesting.

SWEI

I did suggest a two stage gas valve when he was shopping for a replacement.

Before changing the boiler, I would experiment with downfiring the EG-40 a few percent (with an analyzer hooked up of course.)

ChrisJ

My issue with a two stage valve is the burner without a doubt will be less efficient on low fire than high fire.

Why would I want to run it lower, less efficiently when on high I'm only making 1" W.C. pressure at the absolute most? I typically see .50 - .75".

This is why I switched burners. I still get my 82.9% AFUE and I get less output.

Steamhead

Fred said:

Jack M said:

I think this point of discussion from Burnham is worth discussing. I found it digging around the forum. It's really throwing me for a loop:

"The MST288 and MST396 are for the most part the same boiler. The burner of the MST288 is down-fired using a 0.60 gph nozzle versus the 0.80 gph nozzle in the MST396. In order to do that a Low-Fire baffle is installed in the oil burner housing to choke down and redirect the air through the burner housing. The boiler can't be down-fired any more than it already is for risk of excessively low stack temperatures. You may have noticed that the MST288 operates without the flue baffles installed while the other sizes can use them. This is already as low as it can go. Hope this helps and thank you for your interest in the MegaSteam boiler.
Glenn Stanton
Manager of Technical Development
Burnham Hydronics
U.S. Boiler Co., Inc."

Really? these two are the same boilers? After all the effort to decide which is the best, it just comes down to a nozzle?

@Steamhead has a lot of experience with the Megasteam boilers. Let's see if we can get his take on this and his opinion/input.

EDIT: Nozzle and baffles.

Sorry I'm late to the party here.......

In general, on the MST-288, 396 and 513, we'll take Burnham's minimum header specs and go up one pipe size. So in the case of these boilers we'll use 2-1/2" drop headers. The MegaSteam boilers have larger steam chests than others do, so we think making headers any larger than that is overkill- besides, it increases the piping heat loss. The 629, on the other hand, runs beautifully with a 3" drop header so we have not seen the need to oversize here.

If, on the other hand, you're dealing with a boiler known for wet steam like the Dunkirk Plymouth series (under whatever name they stick on them), oversizing the header is one way to dry out the steam. Obviously in a case like this, the header has more work to do.

The pick-up factor does confuse people. Bottom line is this: Unless there is a definite reason to do otherwise (see Dan's discussion of this in Lost Art), go by the Net BTUH or Square Feet rating which has the factor built in. This will give enough capacity to also run an indirect or a hot-water loop, and if the boiler seems to short-cycle one can always tweak the firing rate slightly- while running a digital combustion test of course!

On larger boilers where such equipment is available, we'll use lo-hi-lo firing to "shed" the pickup factor when the system has warmed up and pressure starts to build. If done right, this will reduce or eliminate the boiler completely shutting down on pressure.

The above methods have worked well for us.

ChrisJ

Hatterasguy said:

ChrisJ said:

My issue with a two stage valve is the burner without a doubt will be less efficient on low fire than high fire.

Why would I want to run it lower, less efficiently when on high I'm only making 1" W.C. pressure at the absolute most? I typically see .50 - .75".

This is why I switched burners. I still get my 82.9% AFUE and I get less output.

What I am struggling with is as follows:

Say the two stage gas valve allows you to downfire the EG-45 from 150MBTU to 125MBTU input.

And we already know that reducing the number of burners on the EG-45 will allow the unit to fire just like an EG-40 at 125MBTU input.

So, if the efficiency of the EG-40 remains at 82.9% with the burner reduction, why would the efficiency of the EG-45 be lower with the two stage gas valve that provides the same input?

The EG45 has six burners.
The EG40 has five burners.

They all fire at 25,000 btus.

My guess is trying to fire 6 of them at a lower input will result in a reduced efficiency. I'm not an expert, but that's my assumption.

ChrisJ

Steamhead said:

Fred said:

Jack M said:

I think this point of discussion from Burnham is worth discussing. I found it digging around the forum. It's really throwing me for a loop:

"The MST288 and MST396 are for the most part the same boiler. The burner of the MST288 is down-fired using a 0.60 gph nozzle versus the 0.80 gph nozzle in the MST396. In order to do that a Low-Fire baffle is installed in the oil burner housing to choke down and redirect the air through the burner housing. The boiler can't be down-fired any more than it already is for risk of excessively low stack temperatures. You may have noticed that the MST288 operates without the flue baffles installed while the other sizes can use them. This is already as low as it can go. Hope this helps and thank you for your interest in the MegaSteam boiler.
Glenn Stanton
Manager of Technical Development
Burnham Hydronics
U.S. Boiler Co., Inc."

Really? these two are the same boilers? After all the effort to decide which is the best, it just comes down to a nozzle?

@Steamhead has a lot of experience with the Megasteam boilers. Let's see if we can get his take on this and his opinion/input.

EDIT: Nozzle and baffles.

Sorry I'm late to the party here.......

In general, on the MST-288, 396 and 513, we'll take Burnham's minimum header specs and go up one pipe size. So in the case of these boilers we'll use 2-1/2" drop headers. The MegaSteam boilers have larger steam chests than others do, so we think making headers any larger than that is overkill- besides, it increases the piping heat loss. The 629, on the other hand, runs beautifully with a 3" drop header so we have not seen the need to oversize here.

If, on the other hand, you're dealing with a boiler known for wet steam like the Dunkirk Plymouth series (under whatever name they stick on them), oversizing the header is one way to dry out the steam. Obviously in a case like this, the header has more work to do.

The pick-up factor does confuse people. Bottom line is this: Unless there is a definite reason to do otherwise (see Dan's discussion of this in Lost Art), go by the Net BTUH or Square Feet rating which has the factor built in. This will give enough capacity to also run an indirect or a hot-water loop, and if the boiler seems to short-cycle one can always tweak the firing rate slightly- while running a digital combustion test of course!

On larger boilers where such equipment is available, we'll use lo-hi-lo firing to "shed" the pickup factor when the system has warmed up and pressure starts to build. If done right, this will reduce or eliminate the boiler completely shutting down on pressure.

The above methods have worked well for us.

@Steamhead
If the Dunkirks are known for wet steam, why do people still use them?

Steamhead

'Cause they're cheap.