Seeking advice, new to boilers, boiler broke over winter

Welcome to NJ! (just guessing)

Show us some pictures. We like pictures!

Based on what you said, and your description of yourself, I would spend the spring learning about cast iron hot water boilers and their controls and get it going.

You will be able to use this knowledge for the next X years living with this boiler (or its eventual replacement), and you can always spend the big money later if you don't like the results of fixing up this old one. Or you can do like I (and several others) did and install your own replacement boiler.

PS: free hint: your expansion tank in your drawing looks like the old kind that they strapped up to the floor joists that is just a tank with no bladder. Which is fine, but it's probably flooded so drain it. You can't tell by tapping if it's full of water.

The air inside it has nowhere to go (that's why they put it in the ceiling), so it compresses to equal the pressure of the water in the system.

But after some years, all the air either leaks out or it gets absorbed into the water and so these old tanks are often waterlogged and then they don't provide any compression (because you can't squeeze water very easily)

But anyway, you will learn all kinds of other helpful nuggets of knowledge as you get your boiler operating again and you will not be subject to the whims of market pricing of scarce knowledgeable contractors anymore.

(the expansion tank example is an interesting one—I helped a friend drain hers which solved her leaking pressure relief valve issues after 3 different contractors were there and couldn't figure it out. Then 6 months later she had another plumber there and he was even old like me and told her "there are no expansion tanks that don't have bladders". You can't make this stuff up!!! She now knows more about her boiler than at least 4 different HVAC Plumber guys in her town! This is not a statement on her or my level of awesomeness, but rather a statement on how hard it can be to find knowledgeable contractors especially when it comes to older systems. But if you use the Find A Contractor feature on this site you will increase your odds significantly)

Did any of the contractors perform a heat load calc? How many sq ft of home? A 200,000 boiler is quite large.

It is always a tough question when to start new or keep dumping $$ into old boilers and components.

You could do a heat load to at least get a starting point for the project.

How do you generate DHW?

There is no substitute for a load cals. Room by room is ideal to confirm all the emitters match the actual room loads.

Just a WAG with a fairly big load number of 30 btu/sq ft.

30 btu/ft. X 2200= 66,000 btu/hr required.

Your current boiler/ bid, 200,000 boiler at 85%=170,000 output.

How do you feel about these guesstimates?

As you plan on updating the building envelop , the load should continue to go down. As well as fuel use :)

A modulating type boiler is ideal for several reasons;

Efficiency, with outdoor reset, temperature always modulates

Comfort afforded by continuous circ via ODR

Boiler can derate as you continue to upgrade building, if you need 66K now maybe that load drops to 40K after upgrades.

A % of the year you will run in 90% + condensing mode

Combustion air grills can be eliminated

Rebates available in many areas for efficiency upgrades www.dsireusa.org for info on that

please edit to remove prices, we can't talk about prices of services. i will say if you're replacing the boiler you replace all of the trim and all of that and the fittings and wiring to connect it all up adds up pretty fast, even the big pipe fittings to connect it to the mains are pricey although if you do the load calculations you might find that you can adapt that down and use much smaller piping around the boiler.

are you sure this started out as steam and not gravity hot water?

if it is indeed a gravity hot water system a conventional boiler needs protection from the low water return temps, a modulating condensing boiler gets more efficient with the low water temps.

i would not change it to pumping away until you replace the boiler.

replacing the gas train with a modern combination valve would not be a difficult job for a competent tech however you do need combustion analysis equipment and know how to use it.

What year was the house built? Sounds like the boiler was when they sold the same block for either steam or hot water.

109A_5 also said: "Your boiler (the block) could fail in 6 months or 20 years" 

That probably is true of everything in a house

Indeed it is. Do you replace everything that’s true for? Just asking 😅

@triode Which ever boiler you choose you should also be choosing the company that recommends that boiler and will maintain that boiler.

The company you choose should do a complete heat loss calculation to determine the properly sized replacement boiler to properly heat your home. If they come in and say that they will just replace the boiler and do not do a heat loss calculation than they are not the right folks to do business with. That said, you can broach the subject yourself and judge there reaction. Either way the company that installs your new boiler should also be your maintenance provider. Hope you will keep us posted on how things go.

The controls look rough, but the cast looks good. I would check with the municipality to make sure the tjernlund is venting in an acceptable location out the window. When replacing the gas valve, @mattmia2 is right, the second pilot should be connected. The tridicator looks like its in an awful location and the wrong angle, and the relay looks like its not long for this world. You can do this though. Straighten out the wiring mess, im sure @EdTheHeaterMan can draw you a diagram.

one of the pilots was connected here:

although i'm not 100% sure how, if there was a safety with a switch or what since it would need to interlock the burner and turn off the pilot gas if the pilot went out.

there may be a schematic inside the front cover that shows what was there.

That was a Mouat system. If you enlarge the pic of the valve, you can see the name. @triode , if we can get a pic of the return fitting on one of those radiators, that would confirm it.

Tom Mouat is spinning in his grave…………………

Since your existing Burnham boiler is probably grossly oversized, and you will be using this as your main source of heat, the total system efficiency may be as low as 50% after taking into consideration the 180°F water temperature you will be using and the fact that it will short cycle after reaching that limit temperature. This happens because your home cannot use all the heat the boiler can produce as quickly as it makes it.

When it was manufactured, the combustion efficiency was about 75%, and there are likely many uninsulated pipes in the basement or crawl space where you don’t necessarily need that heat. Your actual flame-to-room efficiency may end up costing you the price of a new boiler over the next 10 to 15 years.

At the end of those 10 years, you will still own an inefficient boiler and continue paying higher fuel bills. If you install a new high-efficiency modulating-condensing (mod-con) boiler, you will lower your fuel usage, and those savings will help offset the cost of the new boiler installation. At the end of that same 10-year period, you will continue to benefit from the lower operating costs.

Either way you look at it, you will be paying for a new boiler over the next 10 years—the difference is whether you actually own the new boiler or not.

Check with your natural gas supplier; they often offer low-interest or even no-interest financing for energy-efficient equipment, which can make a new boiler more affordable. However, you need a load calculation so you don’t buy a boiler that is too large. This form is a simple and easy way to find the boiler size you need—Form 1504WH. It is not a room-by-room calculation, but your whole-house load will still give you a proper boiler size.

Thought so. The Mouat was an excellent system. If that were my house I'd go back to the original Vapor configuration.

@gerry gill is our resident Mouat expert, maybe he'll chime in.

If you’re considering going back to steam, you need to think hard about what’s happened to the piping over the years. Those hangers have been carrying water weight, not steam conditions. Any sagging or loss of pitch is going to show up fast as water hammer once you put it back into steam service. The question isn’t just “will it run,” it’s “will it run quietly?” Pooled condensate in the mains or runouts will make it noisy in a hurry. @Steamhead and @gerry gill would have good insight there, but based on what you’ve described, I’d lean toward staying with water since that’s what the system has been operating as.

On the hydronic side, the load calculation is the key starting point. That will define the proper boiler size, and in many of these conversions you’ll find there is more radiation than you actually need at 180°F. That opens the door to lower water temperatures and better seasonal efficiency. If you introduce outdoor reset on a cast iron boiler, you must protect the boiler from sustained low return temperatures. You want to see 135°F+ return within the first 6–10 minutes to stay out of the condensing range. Given that you may only need 110°F supply on mild days and ~140°F at design, some form of boiler protection/mixing (bypass, 3-way, or variable-speed injection) becomes necessary.

Whether you go with something like a Weil-McLain GV90+ boiler or keep the existing unit, the load calc is really about right-sizing the replacement. The existing boiler is already past its prime, so it’s a candidate for downsizing. One option—if you want to experiment before replacing—is to stage the input. A two-stage gas valve can effectively “resize” the boiler by operating primarily on low fire. That said, this is not DIY territory. It requires someone who knows what they’re doing, with a combustion analyzer, to verify safe operation at low fire and high fire if needed.

If you undershoot slightly, high fire is still there as a safety net—but in most cases like this, the original boiler is so oversized that even low fire will cover the load.

Bottom line: You are going to pay for a properly sized boiler one way or another—either through higher fuel costs over the next 10 years or upfront with a replacement that actually matches the load. The difference is whether you end up owning an efficient boiler at the end of that period.

A load calculation is not required if you return to a Mouat steam system. Steam systems are sized based on the connected radiation, not the building heat loss. This is because you must produce enough steam to heat all of the radiation in the system in order to achieve proper balance.

With a hot water system, however, you can reduce the output of the radiators by lowering the water temperature. This allows you to select a smaller boiler that more closely matches the actual building load.

Hope this helps to make this as clear as MUD!

Ed Y.

Dont forget he has an induced fan on this. It probably does everything @mattmia2 said, except actually rolling out. More likely you are just blowing raw fuel out the side of your house without the proper pilot assemblies.

The two pilot arrangement may be possible with intermittent pilot operation. I'll have to look at some larger commercial boiler manuals to see how they do it.

With your claimed loose building construction I would not worry about a standing pilot. Also there may some draft through the active venting even when it is not active.

I would not use "lots of custom duct tape and bailing wire" to get it running, do a nice job if that is the route you choose.