Will this work?

Tim_39

Thanks for the reply.

Any recommendations for how to provide that protection in my case? A mixing valve/TV in the boiler loop? Or do I use relays to shut off system circulators until the low limit has been reached in the boiler loop?

From reading around, it seems a lot of people recommend constant or near-constant circulation in the system/radiation loop. If I go that direction, do I need the mixing valve?

Thanks.

Tim_39

Will this work?

I have a 1903 gravity hydronic system with a 1989 Dunkirk boiler that was installed to pump toward the boiler. 177mBTU with a simple Honeywell aquastat and a Grundfos UP-15-42F. No complex controls. The boiler currently has no bypass piping or protection whatsoever. I’m in SW Ohio in a 3 storey house with a separate heat pump/ electrical resistance heating system on the 3rd floor. The boiler serves 675 EDR over 2850 square feet on floors 1 and 2.

I want repipe the boiler for protection and to pump away. I also want to add 3 small loops of radiant flooring (2 full bath floors and a kitchen floor). I’m a homeowner who’s been studying this site and Dan’s books long enough to know that what 2 local “experts” tried to sell me on is viewed as fundamentally wrong by everyone here. Could you guys look at the schematic proposal here (see attachment) and tell me if the near boiler piping is right? Is this a recipe for short-cycling and inefficiency or will it do the job? I’d appreciate any comments, criticisms, insults—whatever can make this work.

Obviously, I don’t know much, but I appreciate everything I’ve been able to learn the last 2 years on this site. Thanks in advance.

martin

schematic

I don't see how when the exgravity system kicks in from a cold start how this will protect your boiler, you've drawn up a classic p/s system which by itself does not offer boiler protection.

Abro

Boiler protection on P/S with zones

Can someone point me in the right direction here?

If I’d like to achieve boiler protection on the system sketched here, would I do that with:
1) a bypass loop and a Danfoss TV
2) aquastat control (shut off) of secondary pumps until the boiler loop is at 140 deg
3) variable speed injection pumping btween the primary and secondary loops?
4) some other method?

Any guidance would be greatly appreciated.

Steamhead (in transit)

If you size

your primary circ so its flow exceeds that of all the secondary circs, some warm water will return to the boiler. This may be all you need.

How much radiation is on the old gravity system?

"Steamhead"

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Abro

Thanks for the reply!

I've got 677 EDR on the gravity zone. Using your circulator sizing charts (thank you VERY much for these, by the way!), I calculate I need a maximum of 15.9 GPM on that zone. If stick with Grundfos, as you've recommended in other posts, it seems I’m looking at a UPS15-58FC—which gets me flow check, three speeds and up to 17 GPM for the same price as my existing UP 15-42F. Is that the right choice?

My radiant loops need only .5-2 gpm at design temp (and run 200-250’ of ½” pex each). Could I choose 15-58s for them, too?

That leaves the question of the primary loop? How would I size that to do as you suggest here?

Steamhead (in transit)

Don't see why not

if those Grundfos units look like they'll work, use them.

With those four loops you mention, you're looking at 22 GPM. Your primary circ should be bigger than that. If you want to stay with Grundfos, use the UP-26-99F which delivers 30 GPM at 3-1/2' head. Another good choice would be the Taco 0010, same rating.

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Tim_39

Assuming I set it up with the 30GPM boiler circulator

Do I need any other controls or valves to ensure boiler protection? I.e. will I need to constantly moniter and adjust flow in the boiler loop or can I "set it and forget it?"

Any other suggestions for setting up or controlling this system would be welcome.

Thanks VERY much for you help on this so far. I really appreciate it.

Steamhead (in transit)

Depends on the boiler

and what the manufacturer says. Not sure about Dunkirk, but the Solaia boilers we install don't need anything more with this setup. Here's a pic of one.

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Tim_39

Wow, very nice, neat, clear work. I really appreciate being able to see how this looks in practice.

Did you pipe the system loops on the vertical leg of the boiler loop to create thermal drops (i.e. for flow check) or are you using flow check valves on both supply and return sides of the system zones? I was planning to pipe at least my radiant zones on the last horizontal leg of my boiler loop. Is that a no-no? Do I want flow check on all sides of all zones?

Looks like you piped the boiler loop a size bigger than the supplies to the gravity zone? Am I seeing that right? Is that standard? Currently, I'm piped at 1.5" all the way up to the gravity system. Do I need to recalculate pipe sizes for the boiler loop and gravity zone supplies?

Do you typically use outdoor reset on systems like these?

Hope I'm not wearing down your patience. You've really helped me a lot. I appreciate it.

Steamhead (in transit)

Pipe sizes

were based on the boiler's output and the flow rates into the two zones. The boiler loop is 1-1/2", the indirect loop 1" and the old gravity system loop 1-1/4".

Thermal traps can be iffy, as we found out when we tried one, so we use flow-checks on each zone. The tees off the vertical pipe were a good way to use the available space.

Note that the indirect gets the hot boiler water first, since it requires higher temperatures than the radiators when the shower is running. When both zones are on, the radiators will still get some heat, so we didn't have to prioritize the indirect.

The controls on this one are a simple room thermostat and a multiple relay. We can always add reset later.

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TK03

Just pipe a full size pipe between the supply and return near the boiler with a valve installed between the bypass and the boiler. Reduce the flow through trhe boiler with the valve to a 20f to 40f delta T. All will be good.

Abro

Thanks very much for the help!

Abro

Like this? (see attached image)

Pipe the bypass after the boiler circulator but before the valve? And adjust valves A and B (in the diagram) to throttle just enough water back to the boiler to keep return temp at 140f?

Thanks for the help.