Comments on pipe design for pressurised system

[mousebndr]

Hi All,

Just getting ready to start installed out new boiler. Please see attached pipe design. This is based on lot of posts I have read on the forum plus the tarm biomass manuals (PT3).

Curious to know what people think. In particular I am wondering if the pipe sizes are too big. Its a Eko 60kw boiler, heat load could max at 54kw but is expected be be around 40kw most of the time.

The tarm manual reckons 1 1/4" for but my reading of maximum BTUs though copper pipe says you need 1 1/2"....

David

 

[woodsmaster]

I'd go 1 1/2" to reduce mixing in the storage tank. You could probably get by with 1 1/4 with a larger than needed circulator.

 

[maple1]

Should the line go in the bottom of the expansion tank, rather than the top?

 

[DaveBP]

I think the expansion tank would be better connected to the suction side of the circulator (between the circulator and storage tank).

And if you're planning on using a laddomat loading unit (as your symbol looks to be) make sure you use the size appropriate to 60KW. The smallest one may not be big enough. They get expensive but they are important for the harmony of the whole system.

 

[jebatty]

1-1/2" definitely between the boiler and storage. With your load as high as you say, also 1-1/2" between storage and load manifold. 1-1/2" will keep the pump head low at high volume flow. You might consider a bypass circulator with the Laddomat to move more water as delta-T closes on storage loading. There are numerous posts on this topic. Otherwise, make sure the Laddomat is sized to move enough water to handle your boiler output as already mentioned.

 

[Tennman]

G'day MB, Amazing how this site connects folks from around the world.

My BioMass boiler is the same size class as yours EKO. I used 1 1/2" black iron everywhere in my boiler room right up to where I connect to my 1 1/4" pex that goes to the house. My water round trip from black iron in boiler room to pex to HX to pex and back to black iron is nearly 400 ft. Hopefully your round trip is shorter than mine. Sounds like you're going to use copper in your boiler room, which makes a very nice install. When I did my install I was just more familiar/comfortable with tape, dope, and pipe wrench than a torch. I'm pretty sure everyone feeds storage with hot water into the top of the tank. I didn't know it made any difference where the expansion tank is placed when I did my system and later read the preferred location is upstream of the boiler circulator to reduce cavitation (I think it is cavitation). My pump is noisy so Dave's advice is correct, I intend to move my expansion tank. I'm using a Taco 0013, which is a big pump, between boiler and house because the distance and all the fittings added up to quite a bit of head pressure. Now everyone helping you can help me. I'm adding storage this summer and I'd like to get folks opinion on that Laddomat. I currently use a Danfoss at that tee to temper the boiler supply but since I have to add a circulator between the boiler and storage I like the idea of replacing the Danfoss rather than adding another Taco for storage circulation. I know many here with storage use a Danfoss and a storage circulator. I like the idea of combining those like MB is here in his schematic. So for both of us is the Laddomat a better solution and what size Laddomat would you use? I presume the use of a 3-way at the top of the tank to to allow bypass of storage if you want to have hot water going directly to the load? With the 2-way ball valve cut off going into the top of the tank, I'm not sure I understand why the 3-way is there. Seems like the 2-way can provide the isolation, but I do see that the 3-way provides venting of air off the top of the tank.

Ok, I'll stop. My main reason for chiming in is I'm making many of the same decisions as MB at this moment. And to provide MB with some data on what's working on my pipe sizing of our 60 boiler. But input from all using a Laddomat vs Danfoss and pump would be appreciated. BTW MB, my system would be better if I had used 1 1/2" pex between the boiler barn and the house. I was just too cheap back then but smarter now.... oh well.

 

[maple1]

Also wondering about n.o. zone valve & dump zone for power outage overheat protection?

 

[mousebndr]

Thanks all, have attached an update diagram. Dave - is there where you thought the expansion should tee from?

Curious to know more about a bypass circulator to go with the laddomat, where would this fit in? Any posts you can point me too?

Is the dump zone necessary do you think? This boiler has a cooling loop where if the temp gets about 95 degC it pumps cold water though coils in the boiler to cool it down.

 

[maple1]

I might think about tee'ing in the expansion tank just to the right of the accumulator tank outlet - I'm no pro though, would like to see more feedback since I'll be installing over the summer.

On the cooling loop - do you mean cold water from your feed? If so, there would have to be hot water exiting to somewhere for all the cold water that enters. That might be to a drain, which might be Ok if you're good with that. But I'd rather have the heat go to somewhere it could be used. If the conditions are right for good gravity flow in your system, you could run an overheat pipe right out the top of the boiler, through a NO Zone valve, and hook into one or more of your zones right above your other regular zone valves. Then at least the heat would go to the house. Would only require some pipe & fittings to tie into the heat zones, a NO zone valve, and a 24v. power source.

 

[ewdudley]

where the expansion should tee from?

Curious to know more about a bypass circulator to go with the laddomat, where would this fit in? Any posts you can point me too?

Is the dump zone necessary do you think? This boiler has a cooling loop where if the temp gets about 95 degC it pumps cold water though coils in the boiler to cool it down.

The Laddomat bypass just goes from the storage tank side of the Laddomat to the boiler side of the Laddomat. Need a pump with IFC or a check valve as well. An aquastat turns the extra pump on when return from storage is high enough and/or the supply temperature leaving the boiler is too high. In your situation with what appears to be high flow/high temperature loads, it seems likely you'll have fairly high return temperatures to deal with so the extra pump might be necessary.

Expansion tank can tee in most anywhere in the boiler-storage loop. It would be nice to connect to a return line since then you're not pumping heated water to the expansion tank, but no big deal in the scheme of things.

If a significant portion of your storage is a meter or more higher than the top of the boiler then the Laddomat should do a nice job of dumping heat to the storage tank by gravity in the event of power failure, so no dump zone needed on that account. Plus if you have reliable mains water supply, the overtemp cooling loop would be a great failsafe.

As for pipe diameter, 32 mm would require over 1.5 meter per second water velocities with 10 or 12 kelvins of system temperature delta. This is quite doable, but bigger would probably be the better choice.

The circuitry for bypassing the storage tank is unnecessary. Any hot water coming in from storage will rise right up to the top of the tank and will be available quite soon enough.

 

[mousebndr]

So whats the consensus out there on where to put the expansion tank? To me it makes perfect sense to have it tee'd off from the bottom of the accumulator on the right hand side before the drain ball valve.

Colder water in the expansion tank surey would make the rubber last longer?

Someone commented that having it before the pump makes things quieter? Would having it on the cold return like achieve the same result?

 

[DaveBP]

Dave - is there where you thought the expansion should tee from?

I think the ideal location (at least according to Siegenthaler) would be tee'd in at the right of the loading unit , on the blue return line from the bottom of your accumulator tank. Like Eliot says though, with a compactly spaced boiler and accumulator tank arrangement and nice big pipes it could make almost no difference.

The basic idea is that the circulator in the loading unit will be pumping away from the expansion tank, not into it.

It would probably be better near the boiler circulator (rather than the zone circulator as shown in your second schematic) because that one will almost always be running while the boiler is heating (and expanding) water but the zone circulator will be cycling on and off under various conditions. Plus you will be putting cooler water into the expansion tank.

But the whole thing might work differently Down Under...seeing how everything is upside down.

 

[mousebndr]

LOL Dave - I rekon its just the toilets that are backwards

Thanks guys, have attached the latest diagram based on all your advice.

About half of the accumulator will be sitting above the boiler outlet so am hoping there will be some thermosyphon to help the laddomat otherwise might go for the bypass solution since I have an old grundfoss circulator there I am not using anymore.