hot-water zone off a steam boiler not working correctly

shredmaster

My neighbor had a contractor installed a hot-water zone off a steam boiler last year to provide heating for new extension added to the house.

Since then the steam air vent on the steam radiators has been spilling dirty water when the hot-water zone start calling for heat. The water level in the sign-glass also raise to full when the hot-water zone come on.

here is the the piping diagram and a picture of actual piping for the hot-water zone. Steam piping remains the same as before and system is working fine when hot-water zone is off




He was told to shutoff valves (#4) and open the drain valve (#5) to fill/bleed the system. After hot-water loop is filled/bleeded, valve #1 is shutoff.

The piping is very different from typical hydronic system.

1) why the supply is off the hot side of domestic hot water and not from fresh water from the city?
2) why the supply line doesn't have backflow preventer, autofeeder?
3) why there is no expansion tank?
4) He was told to shutoff valves (#4) and open the drain valve (#5) to fill/bleed the system. why fill/bleed system is isolated from the steam boiler?
5) what's purpose of two taco flow control valve

lastly, what would cause the water level to raise to full and hot water spill from steam air vent?

Thanks in Advance!

shredmaster

as you can see in this picture, the steam air vent is leaking water and have to be collected with a small bucket.

Jamie Hall

That is a mess.

1. What happened to the steam boiler's normal low water cutoff, water feeder and all? Did the plumber take that out? Shouldn't have.
2. As IU said, that's a mess. A backflow preventer is required. An autofeeder is optional. A boiler low water curoff is mandatory.
3. No expansion tank is needed -- the hot water circulation is open to the boiler.
4. The fill bleed system isn't needed.
5. I have no idea.

Now. All that said, is this new hot water system above the water level in the boiler, or is it on the basement level? If it is on the basement level, one simply pumps out of the boiler, down low, runs the water through the radiation, and back to the boiler. If it's on the floor above, then you need to run the boiler water through a heat exchanger. That, in turn, feeds a conventional hot water system, complete with pump and expansion tank.

You need to find a contractor who actually knows how to do this

EdTheHeaterMan

I agree with Jamie. To clarify the reason you don't need or want "Closed Hot Water System" feeder and expansion tank, you need to consider that those parts are to allow for water pressure of 12 PSI, enough to raise the water in the boiler system to reach the top radiators of the building. Also the hot water system that is CLOSED, needs room for expansion. In a steam system the water never leaves the boiler. It operates at pressure of less than 2 PSI. It is OPEN to the atmosphere by way of the steam vents on the main(s) and radiators.

Since the hot water add on radiator would be connected to the steam boiler water, there is not reason for the expansion tank. The steam boiler water in relationship to the hot water zone is considered OPEN, not CLOSED.

This illustration shows how one might add a hot water loop to a basement off the steam boiler.
As long at the entire hot water loop (zone) is below the water line of the steam boiler, the concept is operational. If however any of the piping or radiators in the hot water loop are above the water line, there is a chance that the boiler waterline may rise above the acceptable operating level for the steam boiler to work properly, or the radiators will become air bound and water will not circulate.

In this case, a heat exchanger would be the better option.

Shane_2

The heat exchanger would be the best way, but I'll let Dan explain better: https://heatinghelp.com/systems-help-center/how-to-run-a-hot-water-zone-off-a-steam-boiler/

Old_Steam

1. Often the boiler water supply comes from the hot water side of the hot water heater. That's so you are not adding cold water to a heated boiler.

Jamie Hall

Old_Steam said:

1. Often the boiler water supply comes from the hot water side of the hot water heater. That's so you are not adding cold water to a heated boiler.

True enough. That, however, does not make it a particularly useful practice. At a gallon a month or so, which a good residential steam system should be taking, it's kind of hard to see what difference it makes. And if it is fed into a cold return, as it should be, the notion that it will damage the boiler in some way by thermal shock is dubious at best

Worse, in many home the hot water may be softened by ion exchange -- and that is truly lethal to a boiler.

henryxu

Hi, then what is the best way to heat two story addition around 500 sq ft total with the hot water zone tapped from steam boiler? I read Dan post and seems to ok to pump heat water to two story without issue. 

The question is if you remove the steam boiler autofeeder , low water level cut off valve, then how to add steam boiler ? If the side glass gage does not show the steam boiler level , then how and when to add water?  Thanks

 

Jamie Hall

First off, you do NOT remove the sight glass or the low water cutoff, whatever else you do. That would void your home insurance -- and quite possibly your house.

Second, the autofeeder should be connected so that it feeds into the wet return of the boiler -- not into the boiler itself. If it isn't, have that fixed.

Now. Having gotten that far. There are two ways to heat a two story addition with hot water off a steam boiler. Both of them are the same with the regard to the boiler. Find a tapping on the boiler low on the block. You will take water from the tapping. Second, when you get the autofeeder connected correctly, pipe a return connection from the hot water system into that location.

That is the sum total of changes to the boiler itself. NOTHING ELSE NEEDS TO BE CHANGED.

Now as I said, there are two ways to go from there. The simplest approach is to just run the lines up to the second floor and the radiation and back down. To make this work, you are going to need a pump, of course. Perhaps more important, you are going to need to be able to fill and purge those pipes --and that will mean either an independent fill port and purge port, which can be valved off from the boiler, or a pump powerful enough to lift the water that far -- which won't be needed the rest of the time. Then the piping must be vacuum tight. Otherwise, it will suck in air and you will lose circulation -- and heat. Further, if something happens and you do lose the vacuum, all that water will come back to the boiler -- and flood it.

I don't like the simple approach.

A far superior approach -- though it costs a bit more up front -- is to circulate the boiler water through a heat exchanger. The other side of the heat exchanger is the closed hot water heat circuit, with its own pump and an expansion tank, just like any other hot water heating system.

henryxu

Thank you, Jim. 

Simple way not working well since the dirty muddy water always enter heat water zone and keep flush the steam boiler.with heat exchanger , this means heat water zone will use separate clean water instead steam condensation water.

Is there any recommendations of heat exchanger and pumper? I checked Dan post and the red heat exchanger right now cost around $1000 more.  

Any master can repair this for me in long island ny area?

ethicalpaul

I'm using the simple approach but my situation is likely different--I just have loops of pex (one on the first floor, one on the second) with no joints so air intrusion is near impossible.

I do have a purge station set up so I use a regular water hose run to my basement utility sink to get the water "up there". After that the smallest circulator they make is plenty big because the water at the top "falls down" and the resulting low pressure helps "suck" the water up. "Suck" is in quotes because that's not really how it works, but that is the way we all think of it.

Finally, why do you have dirty muddy water in your boiler?

Heat exchanger plus a second pump (which will also suffer from your dirty muddy water, right?) equals a lot of complication if you can avoid it.

I used this pump: https://www.supplyhouse.com/Grundfos-59896341-UPS15-58FC-3-Speed-Circulator-Pump-1-25-HP-115-volt-4701000-p

I keep it on the lowest speed which gives me a good flow. Note that this is an inexpensive cast iron pump which we are warned not to use. But I can buy 3 of these for the price of a bronze one so I wanted to try it out. 1.5 years in and no problem yet.

I also have a screen right at the exit from the boiler: It was very clean after the first year https://www.supplyhouse.com/Watts-0379112-3-4-LF777SI-Lead-Free-Brass-Wye-Strainer-Threaded