Have you cleaned the piping system for a converted gravity hot water space heating system?

The Steam Whisperer

I have a very big gravity system where we are probably going to be installing a new heating plant. Current system has 1- 6 inch main, 1- 4 1/2 inch main and 1 -3 1/2 inch main. The two larger mains run along the basement floor and have had welded 2 inch connections added to the top of the pipe when the system was converted to pump, probably in the mid 1960's. Does it make sense to add cleaner to the system and try to clean it out? It's unlikely we'd get heavy stuff out as it would sit in the bottom of those big 6 inch and 4 1/2 inch returns. I haven't cleaned them in the past, but I am working on upping my game.

Replacement boiler is to be a Peerless EC boiler with gas burner. with a Caleffi air separator and dirt separator in the boiler loop., with bypass piping and splitting the system in 4 zones. boiler is sized for providing 100% heat in all typical winter weather, with the units installed primarily for cooling to pick up the extra extreme weather load.

EdTheHeaterMan

Every year. It was my job as a rookie in the 1970s

The Steam Whisperer

HI, Ed… Just finished editing to make the question clearer.

Thanks

EdTheHeaterMan

a wye strainer or a dirt mag placed just before the return inlet to the boiler may be all you need

hot_rod

Any idea how many gallons of water in the system? It may take a lot of cleaner.

I would pipe the new components, boiler etc with some valves and a loop so you could run a cleaner in just the new parts and piping.

This is where solder flux, cutting oil, pipe dope, assembly lube, maybe some storage debris will be. Now you may be looking at a gallon or less of cleaner.

A dirt/ magnetic filter will do the majority of protection.

mattmia2

The magnetic dirt separator is probably going to do far more for you than cleaning though putting in some valves to flush the mains wouldn't be a bad idea if it can be done reasonably. Wey rotor circulators really don't like ferromagnetic particles in the water.

The Steam Whisperer

No idea of the water content, but the current heating load appears to be about 350,000 btu/hr. The current boiler is about 900,000 btu/hr output. The house has 3 gravity air hidden radiators that were disconnected from the outside, but still need to be connected to indoor returns. At around 7000 sq ft of space with very high ceilings, I would imagine the system was designed for around 700,000 btu/hr output. 6 inch main is a minimum of 2400 EDR, 4 1/2 inch 1200EDR and 3 1/2 700 edr, so about probably about 4500 EDR. I haven't found a table for estimated water content for a gravity system this size.

A Dirtmag is going in on the boiler return, to that is covered.

hot_rod

that would be tough to calculate system volume on!
fill it up with a water meter connected to the fill valve might be the only way to get a close number?

But I don’t know of any cleaners that would dissolve rust and scale to flush it out

you would need some very high gpm flow to get 5 fps flow velocity in a 6” pipe. That is what it takes to get solids moving along

This company purges large systems like that, I met them at a IGSHP show years ago.

Their purge pumps start at 5 hp and go up to hundreds of hp!

mattmia2

The return temp protection bypass being thermostatic is almost mandatory. ODR would be a great idea too, just heat all that mass up to what it takes to heat the building otherwise it could overshoot especially with only one zone calling where the boiler can get it up to the high limit fast.

EBEBRATT-Ed

Unless you do a total re-pipe let sleeping dogs lie. You stir up all that stuff and you will never get it out anyhow and it will cause more problems.

use a strainer and a dirt mag a big one and leave it as is

The Steam Whisperer

https://forum.heatinghelp.com/discussion/comment/1855888#Comment_1855888

That's what I was thinking

https://forum.heatinghelp.com/discussion/comment/1855889#Comment_1855889

I plan on using a Hydrolevel Hydrostat 3250…it provides load based reset and holds the boiler loop circ off until the boiler gets up to temperature. I have it on my home system with a Peerless EC boiler ( not nearly so large and piping sized for use also as 2 -pipe steam) , and it works quite well with the system and boiler piped P/S and a bypass loop for the boiler. Sequence of operation is: 1) boiler comes up to temperature, 2) boiler loop circ comes on and a small amount of water crosses over into the system loop while most goes back to the boiler( running right about 20F delta tee) 3 ) Heating call continues with boiler up to temp until thermostat shuts it down or the Hydrostat cycles the boiler off at lower temperature based on load reset (eventually the thermostat shuts it off).

https://forum.heatinghelp.com/discussion/comment/1855890#Comment_1855890

This does seem to be the consensus

hot_rod

https://forum.heatinghelp.com/discussion/comment/1855894#Comment_1855894

So some boilers can fire without any flow? That question comes up when considering TRV controlled systems.

EBEBRATT-Ed

Not a fan of firing any boiler without flow. I am just an old fart but putting a hot flame on one side of the HX and no flow on the other just seems wrong to me especially with the newer boilers that hold less water.

Of course it's done with steam all the time but then steam boiler don't usually last as long as long as a HW boiler. Especially nowadays

mattmia2

https://forum.heatinghelp.com/discussion/comment/1855907#Comment_1855907

or with tankless coils or any warm start boiler.

The Steam Whisperer

This Peerless EC boiler holds about 25 gallons of water and is a power burner, so heat from the flame distributes over a much greater area. The EC can be used for hot water or steam. That's one of the reasons I used it in my own home…I plan on running back to back tests running on steam and then on hot water. A lot of cast iron residential hot water boilers come with these Hydrolevel controls that can hold the pump off until the boiler is up to temperature. They are a lot like the older triple function aquastats….but electronic and with load reset built in to reset operating limit water temperatures. Flow rates in cast iron boilers have always seem to be an area where the manufacturer's are quite sketchy. This is why I like using P/S piping, almost always with a bypass, for any system over a single zone. It goes a long way to prevent thermal shock to a single boiler heating plant. I often makes me wonder how much stress is being caused in mod cons due to thermal shock from zones turning on and off. I haven't ever seen any guidelines on preventing thermal shock to these boilers.

The Steam Whisperer

Also, I'll add that many boilers are designed for gravity circulation within the boiler..so there is no need for pumps to circulate water in the boiler. The Bryan flex tube boilers are a particularly interesting example. Low mass water tube boiler designed for both steam and hot water use.

hot_rod

https://forum.heatinghelp.com/discussion/comment/1855919#Comment_1855919

When you pipe P/S, does that Hydrolevel hold off the boiler or system pump? Or both?

mattmia2

https://forum.heatinghelp.com/discussion/comment/1855919#Comment_1855919

They're pretty sketchy in mod cons too. They giver ranges without adequate explanation. Presumably the lowest flow is at the lowest firing rate and the highest flow is for max firing rate but it doesn't know flow, just temps, which is some of what you were alluding to with the thermal shock.

The Steam Whisperer

I have it only holding off the boiler pump. That way the system can circulate steadily and the boiler loop heat can get injected by pulses into the main loop, if necessary. However, on my own system I have found that once the boiler is up to temperature and the pump comes on, it stays on to the end of the cycle. I have a single 2 inch supply main feeding about 200 EDR of mostly large tube radiation with a 1 inch copper return ( system designed for steam/vapor heating too) Boiler is firing about 85,000 input. Ill be cutting the firing rate down to 55,000 Input hopefully before this winter and adding about 50 EDR to heat about 700 Sq ft of new space. We'll see what happens with these changes. It may still be able to pump continuously after warm up since I will be adjusting the system temperature down. Pretty much the only time the boiler pump is held off is in the spring and fall when heating cycles may be 2 or 3 times a day. Otherwise the boiler holds temperaure between the typical hourly cycles.