How to tune it better once i replace my steam boiler?

unphased

I have a 35 year old 200k BTU Peerless gas boiler servicing an old house that is only about 2300sqft that is starting to fail. it looks like it leaks (it does so heavily if filled or overfilled) but when operating normally at 90% level or less it does NOT leak. My hope is that i can make it through till spring this year and have some more time to prepare for doing the replacement. I also discovered Hercules Boiler Liquid which might provide me with a miracle to keep it hobbling along like this if it gets slightly worse. I learned a lot more in the past two days and I also now suspect my failure to regularly blowdown the boiler is potentially to blame for its ongoing degradation. Blowdown is probably required every month and it's not been getting … any.

The house is in Boston and at first I thought I wanted to replace the steam (because of all the drawbacks of steam) with mini-splits. But I realize now that the heat pumps will need to be sized hugely just for being able to handle the coldest day, and that will be very far from being economical to run.

So then I am learning more, finally, here, about steam and about the fact that it is actually maybe possible to control, enough to that it can hopefully function efficiently together with minisplits for example. I would like to ask for help regarding:

1. Replacement unit sizing.
   I know that active radiator surface area is to be used to calculate boiler size. I've got about 12 radiators and probably want to actually run 9. The house was built without insulation and i added insulation 9 or so years ago. I clearly need to tune/replace probably all valves. For example I've finally learned that steam valves are meant to vent air and shut the instant steam reaches them, so when valves are blowing out some steam a lot of the time, that indicates that they have failed.
   I also learned that it is probably possible even with my existing boiler to reduce its output level. I guess I am more than ready to learn how to finally do this. My gut tells me a 125k or even a 100k btu/hr boiler would get the job done. If a 200kbtu/hr boiler is costing $6k then don't expect trying to downsize below 100k would net me more than say $1k savings and I may as well have more capacity in the unit just to be prepared for future cold days requiring it. It's looking like I should expect to spend $10-$15k to replace the boiler.
2. I want to supplement the steam with minisplits in order to provide AC during the summer and it also provides efficient heating that should be sufficient on its own during the non extreme winter weeks and can also (hopefully?) help during the extreme cold days. I assume the process for this should be pretty straightforward; I will just want to work with an installer that can do a masssave assessment with me to help me save a chunk on this expenditure. prob looking at $20k. One split unit added to each room.
   When I was researching this yesterday with the intention of replacing steam entirely with minisplits (trying to avoid central ducted air because of so much disruption) what I came to realize is that whether or not a given heat pump setup is going to be able to keep a room warm in a given set of conditions when it comes right down to it is how well the insulation is keeping the heat in the room. Once the heat flux going through the walls exceeds what the unit's capacity is, the temp drops. So, i have insulation in the walls, but, being an old house, i will have to expect the efficiency will be much lower compared to new construction. For any semblance of good efficiency, supplementing heat from steam when it gets cold out will be the ticket.
3. I want to make sure I am actually set up for success with the upcoming boiler replacement. I'll either find someone who really knows steam who can help me tune my pipes and vents (and do the replacement) or in the worst case I can read Dan's book and come in after the replacement and work out the tuning myself, though I don't know where I'm going to find the time to do so now that the house is 30 minutes away from where I sleep, but it's still within the realm of possibility. I do think it's reasonable to expect i will be able to get a replacement that can top itself off automatically so that it can run reliably when it's required even if I am away, but now I am concerned about not having any automated mechanism for boiler blowdowns. I think I can deal with yearly or every other year flushing and cleaning. But if I need to do a blowdown every week or every month I don't know that it will be possible to make that happen. I am convinced that the boiler will not last as long as it could (60+ years as opposed to 30?) if I am not diligent about maintenance… maybe it could still be good enough to do blowdown only once or twice in the season? I guess if the heat pumps are taking care of most of the heating needs and the boiler only fires up for a week or two every year, then I can be hopeful for once a year blowdown. I will want to see what i can do to ensure the pH inside is at a safe level throughout the year when it sits there so it isn't slowly corroding itself.

Thanks for reviewing my wall of text.

unphased

On the other hand I won't even be around if I get the replacement running for 60 years… If I can have it last 30 more that'd be a good enough job by any measure.

Bcos17

I'll defer to the many steam experts on this board, but I have a few thoughts based on what I've learned over the years.

1 - You shouldn't be thinking about BTUs. You need to get your radiators measured properly, find out how many square feet of radiation you have, and then select an appropriately sized boiler. But yes, 200k btu for a house that size is likely to be way too large. My house is 2350 sq feet and my boiler is a 105k and I think it's slightly oversized.

2- "don't expect trying to downsize below 100k would net me more than say $1k savings and I may as well have more capacity" - This is absolutely wrong. Picking a boiler is about properly matching your needs to the boiler size. "More capacity" can in fact harm you because the boiler will not run properly and will short cycle if it is oversized for the space. More Boiler is not better!

https://newenglandsteamworks.com/ is a company frequently mentioned on this board who works in your area. Most residential plumbers don't know how to install or fix steam systems properly. I would suggest starting the process by calling them.

unphased

Is it possible to set up a new steam boiler for automated blowdowns? I could probably run a hose to sewer. If it's automated then i hope it could do it early enough to have it not be sludge and then it could work.

Bcos17

I don't know the answer to your question, but I think in general adding new water to your system constantly is the opposite of what you want. New water=more oxygen=more corrosion=increased muddy water. You want your system to be properly skimmed and washed out and then the water treated so that you have clean water consistently and don't need to be removing water very often. It can take some time to get it dialed in after a new install. Some people on this board have suggested adding a small amount of a treatment called 8-way. It raises the PH of your water to a level where it stops most of the corrosion. Do some searches on this board for 8-way, corrosion inhibitors, etc. Watch some of EthicalPaul's videos where he does some tests on his own system. I added a bit of 8-way to my water and I have had great results so far. Again, I'm only a homeowner who has been researching many of these questions over the past few years since I acquired a house with a steam boiler and had a new boiler installed. There are many experienced steam pros here and dozens of existing threads where you can find the answers to most of your questions.

ethicalpaul

That's a lot of text! Here are a few random things jump to mind. To answer all your questions would take a book, which you can buy on this site called "We Got Steam Heat". I don't find it to be the easiest read but there will be a lot of mostly correct information in there that can help you.

Forgot "blowdowns", you don't need them and they hurt your boiler by causing more rust due to the replacement water. Annual partial draining combined with pH boosting additives is all you need.

Your boiler is in fact leaking today by letting a lot of steam out through a hole. Forget about any boiler treatment helping this problem, just limp along at as low a pressure as you can reasonably manage to lose less $$$ out the chimney. You want to contract for replacement in the warm months.

Sizing is a hot button topic, but yeah the MAX size you should consider would be based on your radiators. Of course you can go smaller since your house is tighter and more insulated than when it was built, although for some reason a lot of people here don't think so. Every boiler that is "correctly sized" is actually built at least 1/3 bigger than the rating of how much radiation it supports, there's plenty of slop. Be careful about removing radiators unless you're OK with cold areas.

You can feel free to call me at my information below—these topics are very easy to discuss and difficult to write carefully enough about.

unphased

I am learning from here https://www.reddit.com/r/homeautomation/comments/1cth7gi/comment/l4d2hmb/ that the regular replacement of water into the boiler is not needed. But I am confused here about how, because if I am blowing down the boiler every week like i'm supposed to, at least the volume of water being blowed down will need to be replaced as fresh water.

I get how in theory when all steam vents in the steam system work properly no appreciable amount of steam actually exits the system.

Grallert

If by blow down you man flushing the LWCO until the water runs clear, that should be done rather frequently if you have a float type. Weekly or bi monthly. If it's a probe type that will be done on the annual service. As far as blowing down the whole boiler? that will be unnecessary once you get your water quality/ chemistry correct. Fresh water kills steam boilers.

ethicalpaul

Yes @Grallert is exactly right. If you are talking about LWCO blowdown, that is a weekly thing. The problem is the term, like many, is overloaded so a lot of people talk about blowing down their whole boiler. Sorry about that confusion.

When you get a new boiler it will have a probe-style LWCO and won't require this weekly flushing.

Unless you live in a multi-family building or massive mansion where sometimes code may require multiple LWCO devices and possibly a float-type LWCO among them.

leonz

You have not mentioned whether you have a single pipe system or a two pipe system.

I want to suggest to you that you contact New England Steamworks, to do a heat loss study, measure your radiators and discuss with you the installation of a double drop header if there is adequate ceiling height in your basement to aid in creating dry steam with your new boiler "ONLY if they determine yours is actually leaking".

Your boiler needs to be drained and cleaned/wanded/skimmed and a pair of low water cut offs and perhaps a new pig tail and gauges as well as a skim port installed most likely.

Your boilers system control could be simplified with temperature regulating valves on each radiator to control the steam heat more effectively as well in rooms seeing with little use.

if the home is unoccupied the TRV's will save you a great deal of money if you want more control of the heating system by turning the thermostat down and the TRV's lower.

You may need basic needed repairs and if there is adequate ceiling height a double drop header to make your boiler more efficient to save fuel and have a quicker return on your investment and to bring it up to code.

My thoughts as a homeowner.

AdmiralYoda

A couple thoughts, some already mentioned.

1. A blow-down is supposed to done weekly according to most manufacturers to remove/prevent rust and gunk from building up in the float mechanism. Good news though. Most, if not all new boilers come with probe type LWCO's instead of the old float type. No needs for blowdowns. The boilers do a periodic low-level check and the auto-feeder will add water accordingly.
2. Track down any steam leaks using a mirror. While your system is producing steam and your radiators are starting to get hot use the mirror near the valve parts to see if the mirror fogs up. If it does there is a minor steam leak. Take care of those, even a few little ones create the need for makeup water.
3. A boiler is sized based on the EDR of the radiators, that's it. No need to think about BTU's…just measure the EDR of the radiators and pick a boiler that has the closest "square feet of steam capacity". A 33% correction factor is already built in…so picking a boiler that is 10% less than your EDR is a good thing.
4. EDR measurements should be done with ALL installed radiators, whether you have the valves open or not. You can significantly slow down the heat transfer of some radiators with slower vents or enclosing them.
5. Have a Steam pro like New England Steamworks do the install for you or learn to do it yourself. It has to be done to the manufactures minimum specs or better.
6. Insulate your exposed pipes with 1" fiberglass and install adequate venting for your mains.
7. If you did all of the above your system will be perfectly sized and you will hardly ever build pressure, giving the boiler a low-stress life. Perhaps switch to a vaporstat instead of a pressuretrol.
8. Install a low pressure gauge, in ounces to measure the pressure.
9. After properly skimming the boiler use RectorSeal 8-way. Aside from minor cleaning abilities its pH adjustment is where it shines. Add 0.75-1oz per gallon of water capacity to get to a pH of 10-ish. This will halt corrosion and help your boiler live a long life!

Do all of the above and you will have a system that is perfectly sized and tuned for your situation. You'll only need to add a few gallons of water per year if you don't have any leaks.

KC_Jones

"If a 200kbtu/hr boiler is costing $6k then don't expect trying to downsize below 100k would net me more than say $1k savings and I may as well have more capacity in the unit just to be prepared for future cold days requiring it."

This logic is flawed. The radiation dictates output, not the boiler. If the radiation can give off 100k, you could hook up 1 million btu's and still only get 100k out of the system. Sizing it up for cold days does absolutely nothing since the radiation can't give off the extra btu's the boiler has. What it will do is run pressure up faster, cycle a lot more for no reason and generally make the system operate less comfortably. So it's all downsides. I can not stress this enough, size it correctly, oversizing makes everything worse, much, much worse. I even say the classic sizing is too big. If you go by EDR, and pick the closest boiler less than the EDR in your system, that is your best bet.

winnie

I use hybrid of minisplits and oil fired steam heat at my house, and have commented on my experiences before. In a nutshell, I like it.

I live in a similarly sized similar age house in Massachusetts, so I have experiences that are probably relevant.

My previous comments on the topic:
https://forum.heatinghelp.com/discussion/comment/1855972#Comment_1855972

https://forum.heatinghelp.com/discussion/comment/1827631#Comment_1827631

Happy to answer questions about my experiences.

On boiler size: I know that my boiler and radiators are oversized for my house, because even on the coldest days (-8 ish) the boiler runs less than 6 hours per day. If you are keeping the old radiators, and size the boiler to properly match the radiators, then you should have no problem keeping an old but insulated house warm on the coldest days.

Over a typical heating season the boiler might run 180 hours. I measure this with a hour meter on the burner blower. The usage is low enough that I get the annual maintenance done every 2 years, and only have to fill the oil tank once a year in the summer. This is an old house with cheap modern windows and blown in insulation, so probably relatively tight compared to when it was built, but not tight and insulated by modern standards.

On balancing when you don't live in the house: you need data. You need to know that the venting is adjusted so that all the radiators get filled with steam, and that perhaps rooms that need more heat get filled with steam before the rooms that need less heat.

I am using 'HomeAssistant' (a home automation system) with Broadlink RM4 units in various rooms. The RM4 records temperature and humidity, and can send IR commands to the minisplits. The temperature logging is pretty solid, the IR commands work but are something of a hack. In any case I can see temperature histories for the various rooms and use that to adjust the vent settings on the radiators.

I use Vent Rite #1 adjustable valves on each of the radiators, so that I can tweak the venting as needed.

-Jonathan