Boiler return protection. In layman's term please.

[warno]

I'm looking for information on return protection. I understand what it is and that it's to prevent thermo shock and condensation of the flue gases but could someone explain in layman's terms what I need to achieve it. I have been reading a lot of posts on here and online but I'm having a hard really understanding what parts I need to plumb it up correctly. Is it as simple as a mixing valve and balancing valve or is there more to it?

 

[DaveBP]

Is it as simple as a mixing valve and balancing valve or is there more to it?

That's one basic approach. Keep in mind that the boiler circulator needs to PULL the water through the mixing valve, not PUSH it through. This might require mounting the circulator on the other end of the boiler than where it is now.

There are also electronic ways to do it.

 

[warno]

This is going to be my pump for this system.

http://www.zoro.com/bell-gossett-ho...gclid=CP_X1puZq8cCFZKBaQodLr0PiQ&gclsrc=aw.ds

I always thought these pumps were designed to push the water. Would I be ok pulling the water through the whole system with this pump?

Is this very basic drawing how the mixing valve/balancing valve setup is plumbed?

 

[warno]

Or would this drawing be more correct for what I'm trying to achieve?

 

[PassionForFire&Water]

What are you trying to achieve .... ?

 

[warno]

Simply trying to achieve good steady return water temps. In the 140-150 range. This is my first year getting into a boiler system and I'm trying to do the plumbing myself.

 

[PassionForFire&Water]

one valve brand specifically designed to protect against condensation is the Caleffi ThermoMIX.
See attached product sheet with schematics

You can also read more here: http://www.caleffi.com/usa/en-us/technical-magazine
Select Hydronics for Wood-Fired Heat Sources (Issue #10)

An all in one solution is the Caleffi ThermoBloc

 

[maple1]

Good info there.

Also - depending on your boiler & your system (which we don't know anything about), you might not need it.

It is absolutely needed with storage. But if your boiler runs consistently on the hot side and your system doesn't have storage or a really big delta T and large system volume, and you don't have many cold starts, your return temps might stay above 140 anyway. If running just a boiler 'for now', with thoughts of maybe adding storage later, I would put one in anyway.

Out of your two sketches, the second one is more like it - but with a proper mixing valve like the ThermoMix, you won't need a balancing valve, and the 'bypass valves' I don't think serve any purpose. Check out the diagrams there - nice. I would suggest lots of ball valves though to isolate components so you can service them in the future without draining the whole boiler or system - even though big ball valves sure add up $$-wise when doing a system.

 

[warno]

Thanks guys. I'm looking into the thermo mix valve now. I do plan on adding in storage next year it just wasn't in the budget for this winter.

I drew in the bypass valves just because I planned on using them as service valves like you said. I just assumed with their placement in the system they were consider "bypass".

 

[leon]

OK here comes the dumb question,

If you properly install the cooler return water to
the base of the boiler where the pump pulls it through
pushes it into and up and out of the boiler back to the radiation
why are you adding these non essential plumbing items?????????????????????????????

no sense in wasting good money with the winter we have coming.

 

[warno]

I just wanted to be on the safe side because all I ever read about is how boilers that can rust out, will if they have return water temps to low.

 

[maple1]

I just wanted to be on the safe side because all I ever read about is how boilers that can rust out, will if they have return water temps to low.

You read right re. wood boilers. Maybe leon can give some references re. why its not necessary.

 

[leon]

Dont waste your money!

Just plumb the return piping to the return
fitting in the base of the boiler AND use the
hot water out pipe connection back to the heat load

Doing that prevents thermal shock with one port in and
one pipe out.

My home is just set with one zone which is also the
dump zone and a temp balancing pump between
the two boilers.

As long as you have either a closed system or treat the
water in an open system you will have no issue. you can
also purchase a couple of very good books on hydronic heat
from AMAZON books for $50.00.

Spend your time reading before you spend any money to avoid wasting it.

Me, I wish I had a one pipe steam system or a gravity hot water system with
radiators.

 

[Bob Rohr]

You have a few things going on with wood or some pellet boilers. They typically hold more water than fossil fueled boilers. So from a cold start they take longer to warm up above condensing temperatures.

The other concern is the moisture content of the wood and air/fuel ratio. The higher the moisture content of the wood, the higher the dew point. Ideally wood in the 20% or lower would be desirable.

It depends also on how often you cold start the boiler. If you could keep it running hot all season that would be great, but not very realistic.

A 3 way thermostatic valve is a simple way to insure you protect your investment.

 

[Karl_northwind]

No one here has mentioned it on this thread, but here is a huge resource for piping these up, and where return protection is necessary etc.

http://www.caleffi.com/sites/default/files/coll_attach_file/idronics_10_0.pdf
Durn near everything you need to answer your questions.

karl