Used Boilers and Header questions

mikeg2015

Starting to plan out the eventual replacement of my boiler. It just too big. On the really cold days I have to roast the upstairs and heat all the radiators 100% and then it still cycles on the vaporstat and the air vents get really noisy (probably lots of wet steam). Vaporstat cuts out at 8-10oz and cut in at 1-2oz. That’s the lowest I could seem to set it. Rather than limp it along or add timers, I’m thinking of just replacing it this summer. I’ve added TR-Vs to balance upstairs and downstairs, but it of course makes the short cycling in very cold weather worse. Boiler is 35 years old and has no equalizer, a single tapping (calls for 2 in the manual) and is rated for 940EDR, I have 720 installed, but only need 520EDR after I factor in TRV’s duty cycle at design conditions (Which i know is controversial). So going with a 175. Absolute worst case I could add a 75 or 100k boiler as a summer boiler for DHW and can stage them. I have plenty of room for 2 boilers and a large enough chimney.

Couple questions:

1) On a PEG 50 or 55, it calls for I believe single 2-1/2” , 3” respectively. Can you use two 2” instead then connect them to an existing 3” header. Or do both need to be 2-1/2” or 3”. I only ask because 2” is a lot easier to work on and cheaper.

2) I don’t see a diagram on how to pipe a hot water loop for indirect tank off a EG/PEG and a small hot water coil in the downstairs AHU to zone the downstairs. I’m guessing I’d use the 2nd return tapping as a supply and and the 3/4” boiler drain on the opposite side as a return and use 1-1/4” pipe.

3) A gorgeous Queen Anne caught fire 2 blocks from my house last summer. It had two W-M steam boilers installed by my company. Before I started) that are I think less than 5 years old. They were drained before winter so should be fine.... but I’d want to fill them before moving and check for leaks anyway. I think it’s a PEG 55 and PEG 35, but I need to check. I think it was a 2 pipe system and may have Ben zoned. It was a 3-1/2 story probably 5000+ soft home. Any thought on moving boilers? Worth it? Could probably get them on a good dolly and just roll them the 1/4 mile to my house. I think the doorway to the mechanical room they will fit sideways so no disassembly. existing boiler is the challenge. Will have ot pull the sections apart. Bolts are corroded bad. Probably have to cut all the studs. I think it weighs over 900lbs empty.

EBEBRATT-Ed

Follow the MFG piping directions. That is the minimum. If you increase the # of risers, riser size , header size or drop header that up to . If your staying in the house for a while you want it to run at it's best.....your paying for the fuel and living with the results.

This is the point most jobs go wrong. Many won't bother with pipe larger than 2" because they don't have the tools so they use 2" or resort to 2 1/2 or 3" copper.

If you learn how to measure and plan things and be creative you will find you can pipe most of the boiler with nipples. I am sure there is a supply house in your area or a pipe shop that can cut and thread 2 1/2 or 3"

As for the old boilers check your EDR and the boilers EDR don't try to make something fit if it's not the right size. I would plug and pressure test the boilers before moving if possible and only if they match your EDR.

Your going to live with this so it's your choice

Steamhead

You mean they're ripping the steam system out of the Queen Anne?

Do NOT reduce the size of the steam tappings. Two 2" won't be adequate if the manual calls for 3". They MIGHT be OK if the manual calls for 2-1/2", but why chance it?

If you use a hot-water loop, the tappings should be on opposite sides of the boiler, otherwise you won't pick up any heat.

mikeg2015

Steamhead said:

You mean they're ripping the steam system out of the Queen Anne?

Do NOT reduce the size of the steam tappings. Two 2" won't be adequate if the manual calls for 3". They MIGHT be OK if the manual calls for 2-1/2", but why chance it?

If you use a hot-water loop, the tappings should be on opposite sides of the boiler, otherwise you won't pick up any heat.

It’s not salvageable. Whole roof and 3rd floor are destroyed. Greenish blue flames were shooing 30’ above the 50’ roof peak of the turret as all the copper burned. Water damaged finished off the rest. Didn’t have replacement value coverage, even then, repairs were estimated at $5MM to replicate what was there.


Thanks all for confirming what I thought. They have a Rigid Pipe threader that should do 3”. I’ll have to check. Would be a good learning experience. Supplier should be able ot get what we need. But I might have to eat some 8’ sections of 3” black pipe we will likely never use again.

I’m still torn on sizing. Homes heat loss is around $120k. EDR maximum is 720, but with TRV’s its 520. Header and basement laterals are all insulated. I’m confident that I can balance a “undersized boiler” as it heats evenly and works best from a cold start. It’s the hot starts in cold weather that it has issues.

If I had no insulation on the attic floor and attic roof as original and no insulation on the pipe, then a 275k would be just fine I think.

I’m confident it can run continuously and never hit even 1oz and still heat all the radiators evenly using Ventrites on the lowest settings or #4 vents. I’m going to add 1” tapping with 3 big mouths and a vacuum break (the ~100’ 3” header drops HARD into vacuum). I guess I’ll be the Guinea Pig on downsizing a vapor system. Worst case I can drop 100-140 EDR without much impact or add more TRV’s to accomplish the same thing.

mikeg2015

Look at it this way. Vents are relative to atmosphere. So if the leading edge of the steam is under a slight vacuum, you don’t have to move air as quickly. You only need to vent the risers and radiators at the rate the system heats up.

It would be tempting to plug some orifices on the current boiler at the end of the season before I go to remove it, open the windows on a 50F day as a test to see what happens. Run it at a 200K firing rate plus about 10% for efficiency losses, so block 4 of the 10 burners, dial down the vents to minimum, and see if it still heats evenly. Probably put a fan on a couple radiators to add some more load.

Side note, with a smaller modern boiler, I think I’m going to need a reservoir pipe. because of the steaming time before condensate returns. On my current HB Smith, It’s like 20 gallons, so losing 1-2 gallons is no big deal. Might be able to cheat and also use the reservoir for the hot water loop return.

ratio

If it already wants to run in a vacuum, why not think about going all in? @Pumpguy, @AMservices, @izhadano IIRC do vacuum work.

EBEBRATT-Ed

1 note of caution. We put boilers in a school where the "engineers" sized the replacement boilers. The boilers were borderline small. Each boiler had a 5" supply to a 8" common header.

Here's what happened (and it only happened on a cold start)

Both boilers started to steam and the water lines were fairly steady. As soon as they started to steam water would leave the boiler with the feed pumps struggling to keep up and they would hit low water.

The steam leaving the supply header and heading out to the system would condense so fast and there was so much cold pipe out in the system it would put the supply into a vacuum and suck the water out of the boiler.

They had an electronic transducer on the stem main that showed pressure. As soon as it hit .1 positive everything was ok.

the fix was let it struggle, oarfice the boiler outlet flange, keep the burners on low fire until they made positive pressure. Don't know what they ever did. Engineers don't make mistakes

They headed the building but Pickup factor???

mikeg2015

ratio said:

If it already wants to run in a vacuum, why not think about going all in? @Pumpguy, @AMservices, @izhadano IIRC do vacuum work.

I’d have to repack all 15 of the radiator valves. Then I have to purchase or make my own vacuum vents or run small tubing to 15 radiators. A bigger project that I’m wanting right now. Enough to replace the boiler.

Some minor leak at 1oz pressure is one thing, a leak with 10” of vacuum is another.

mikeg2015

EBEBRATT-Ed said:

1 note of caution. We put boilers in a school where the "engineers" sized the replacement boilers. The boilers were borderline small. Each boiler had a 5" supply to a 8" common header.

Here's what happened (and it only happened on a cold start)

Both boilers started to steam and the water lines were fairly steady. As soon as they started to steam water would leave the boiler with the feed pumps struggling to keep up and they would hit low water.

The steam leaving the supply header and heading out to the system would condense so fast and there was so much cold pipe out in the system it would put the supply into a vacuum and suck the water out of the boiler.

They had an electronic transducer on the stem main that showed pressure. As soon as it hit .1 positive everything was ok.

the fix was let it struggle, oarfice the boiler outlet flange, keep the burners on low fire until they made positive pressure. Don't know what they ever did. Engineers don't make mistakes

They headed the building but Pickup factor???

I don’t think that can happen on a 1 pipe system with equalizer and dry return and non vacuum vents. The vacuum would pull almost equally on both ends. However, on a large system the vacuum would momentarily increase the output of the boiler (but would drop water temp)

Main concern that I have is the steam taking a preferential path up a lateral rather than along the header. So slowing the radiator venting will be critical as will adding excessive main venting to tame the steam.

ratio

Yeah, it's a big job. That's why I haven't given much serious though to converting my church system, even though I'm sure it'd operate a lot nicer than it does now.

mikeg2015

It’s mostly the expense of radiator valves.

I did want to look into seeing if I could install a check valve on a Maid o Mist. Probably just need to precision grind a countersink in the orifice and figure out how to get a little Ptfe ball to sit on top of it some how.

BobC

I think 45 ACP brass is just about the right size to fit over the orifice, now if I could just find the notes I had. . .

mikeg2015

BobC said:

I think 45 ACP brass is just about the right size to fit over the orifice, now if I could just find the notes I had. . .

1/8” NPT hex plug fit perfectly. I plugged the two end burners for now. See how it runs. So far, already runs quieter. Need to run a combustion analysis when I get a chance. Not sure how much efficiency I lost. Might be better to swap out all orifices to debate by 20% and then adjust the shutter to get the mixture dialed in.