air problem in 2 story open system

Leo

I didn't say you can't change it to a closed system, I said it should have a heat exchanger to keep it seperate from the boiler (house side). As far as being an open system it is my understanding it isn't ASME (?) certified as a pressure vessel. I'm not exactly sure about that but it doesn't matter to me personally, I hate the things. There are a few towns around here banning them.

Leo

Royboy

OK, here's the deal

for several years I have periodically gotten calls from a client asking me to purge air from the baseboard convector loops delivering heat from his outdoor wood boiler fired system.

(no comments needed about outdoor wood boilers - I don't like them and had nothing to do with this one being installed)

the air appears especially in the second floor zone, which is about 8'(?) above the water level in the open boiler. the client is getting tired of this recurring problem and asked me what can be done to alleviate it. turning it into a closed system seems impractical/unlikely - the boiler isn't designed for that.

the system is set up with a constant circulating pump running a loop from the wood boiler through the basement of the house. on demand in one of the 2 zones, water is diverted into it by a zone valve closing in the main line and one opening in the zone loop.

my only thought to date is that the 2nd floor loop must be operating at minimal pressure - due entirely to that imparted by the pump - a Grundfos 3 speed unit. and that the air would likely be coming out of solution due to the minimal pressure in that zone loop. I noticed that the pump was set on the lowest speed and so I bumped it up to the high speed, thinking that would increase the pressure in the loop and decrease the tendency for disolved air to come out of solution due to low pressure.

any other ideas for how to deal with this?

LarryC

closed loop

Make the house a closed pressurized system and isolate it from the outdoor furnace with a heat exchanger.

kevin coppinger_4

is there a...

heat exchanger? That would be a start...If it is a totally open system air will always be a problem since the air will always come out of soltion at normal atmospheric pressure.....if you build pressure it will be less of a problem ie. the HX. Also being open the you are sujecting the ferrous parts to a lot of corrosion...again the HX will help....kpc

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Leo

I'm Glad

I'm glad I'm not the only one that get's these calls. We are an oil company, the boiler guy sells them, the plumbers (nonheating guys) put them in and WE get blamed when the oil boiler goes air bound. Plus a couple boiler companies say the warranty is void if it is no longer a closed system. The boiler guy gets quite a bit for these yet tells people they don't need a heat exchanger.

Leo

Royboy

there is not a ...

heat exchanger. and I can see that this would possibly be the best way to get the pressure up in the second floor loop.

any suggestions as to the best sort of heat exchanger to use for this sort of application? I have used quite a few brazed plate heat exchangers for other applications. would they be good or is some other variety better suited to this sort of application. space is not a big problem - so it wouldn't need to be as compact as a brzed plate unit ...

Steve L.

I have never run into a system like this. Does anyone have anymore info on how they work? Also why does it "have" to be an open system. Just interested for my own knowledge.

kevin coppinger_4

the BP hx....

will work...other options could be a superstor ultra that would give you some more volume in the system...always good w/ a wood boiler. kpc

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

LarryC_2

TACO wiz-bang HX

Home owner here:
Didn't TACO just come out with a little wiz-bang (highly technical term) heat exchanger pump combination do-hicky?

If I remember right, that might be able to supply the house circulation, plus isolation, and all you would need is an expansion tank, BFP, water fill line, etc.

Or you could use an indirect HW storage tank and run the outdoor boiler at full bore, to maximize efficiencies, and store the BTUs for later use. Plus all that other stuff necessary for a safe closed loop system.

Leo

It's an open system

It's an open system as opposed to a pressure vessel. If the wood fire runs away the water just expands and flows out.

Leo

Steve L.

I know what an open system is. But you had stated that you couldn't change it to a closed system and I was wondering why that was.

Joe Mattiello

May I suggest using the Taco X-pump to isolate the Medias? For your reference I attached the catalog data.

Royboy

thanks to all

for the thoughts. seems like setting the house up separately as a pressurized system might be a real good idea on a variety of fronts (including protecting the propane backup boiler from the O2 in the open system). the X-pump block may be a good option but I will need to look into it further (including prices). my sense is that it could be a little small at a max of 50K BTU. and, I do have one good grundfos pump already present in the system ...