Just bought a wood boiler to heat my shop. I put about 2000 ft of 3/4 pex in the floor (4800 sqft). What size pump will I need to keep good flow?
What size pump?
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NateB
Feeling the Heat
Most any 45 watt ECM pump or 75 watt conventional pump will do the trick.
Here is a printout of a bunch different pumps with four 0.750 PEX pulling in parallel through a Taco 5000 mixing valve. Some pumps are listed at different speeds, like Alpha-I, Alpha-II, ...
Each listing shows
%gpm = percent of maximum flow for the pump. Nearer 50% preferable to either extreme.
watt = watt
gpwh = gallons per watt-hour, a measure of efficiency, bigger number is better.
gpm = total gpm for circuit
L = length in feet
D = actual diameter in inches
head = pressure drop through component
gpm = flow through component
each series circuit list one Taco 5000 valve in series with four PEX loops that are in parallel
Here is a printout of a bunch different pumps with four 0.750 PEX pulling in parallel through a Taco 5000 mixing valve. Some pumps are listed at different speeds, like Alpha-I, Alpha-II, ...
Each listing shows
%gpm = percent of maximum flow for the pump. Nearer 50% preferable to either extreme.
watt = watt
gpwh = gallons per watt-hour, a measure of efficiency, bigger number is better.
gpm = total gpm for circuit
L = length in feet
D = actual diameter in inches
head = pressure drop through component
gpm = flow through component
each series circuit list one Taco 5000 valve in series with four PEX loops that are in parallel
Code:
%gpm watt gpwh head gpm Component
=> 22 8 18.2 2.7 2.44 Grundfos_15-55-Alpha-I
=> series circuit 2.7 2.44 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 1.1 2.44 Taco_5000
=> parallel circuit 1.6 2.44 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 0.55 1.6 0.61 PEX_0.750
=> 500 0.671 0.55 1.6 0.61 PEX_0.750
=> 500 0.671 0.55 1.6 0.61 PEX_0.750
=> 500 0.671 0.55 1.6 0.61 PEX_0.750
%gpm watt gpwh head gpm Component
=> 23 30 8.1 6.9 4.05 Grundfos_15-55-Alpha-II
=> series circuit 6.9 4.05 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 3.1 4.05 Taco_5000
=> parallel circuit 3.8 4.05 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 0.92 3.8 1.01 PEX_0.750
=> 500 0.671 0.92 3.8 1.01 PEX_0.750
=> 500 0.671 0.92 3.8 1.01 PEX_0.750
=> 500 0.671 0.92 3.8 1.01 PEX_0.750
%gpm watt gpwh head gpm Component
=> 20 86 3.3 8.9 4.67 Taco_007
=> series circuit 8.9 4.67 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 4.1 4.67 Taco_5000
=> parallel circuit 4.9 4.67 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.06 4.9 1.17 PEX_0.750
=> 500 0.671 1.06 4.9 1.17 PEX_0.750
=> 500 0.671 1.06 4.9 1.17 PEX_0.750
=> 500 0.671 1.06 4.9 1.17 PEX_0.750
%gpm watt gpwh head gpm Component
=> 39 76 4.1 10.8 5.17 Grundfos_15-58-II
=> series circuit 10.8 5.17 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 5.0 5.17 Taco_5000
=> parallel circuit 5.8 5.17 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.17 5.8 1.29 PEX_0.750
=> 500 0.671 1.17 5.8 1.29 PEX_0.750
=> 500 0.671 1.17 5.8 1.29 PEX_0.750
=> 500 0.671 1.17 5.8 1.29 PEX_0.750
%gpm watt gpwh head gpm Component
=> 39 86 3.9 12.7 5.64 Taco_008
=> series circuit 12.7 5.64 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 5.9 5.64 Taco_5000
=> parallel circuit 6.8 5.64 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.28 6.8 1.41 PEX_0.750
=> 500 0.671 1.28 6.8 1.41 PEX_0.750
=> 500 0.671 1.28 6.8 1.41 PEX_0.750
=> 500 0.671 1.28 6.8 1.41 PEX_0.750
%gpm watt gpwh head gpm Component
=> 24 45 7.6 13.0 5.72 Grundfos_15-55-Alpha-III
=> series circuit 13.0 5.72 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 6.1 5.72 Taco_5000
=> parallel circuit 6.9 5.72 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.30 6.9 1.43 PEX_0.750
=> 500 0.671 1.30 6.9 1.43 PEX_0.750
=> 500 0.671 1.30 6.9 1.43 PEX_0.750
=> 500 0.671 1.30 6.9 1.43 PEX_0.750
%gpm watt gpwh head gpm Component
=> 36 59 5.9 13.4 5.81 Wilo_ECO_16_Stratos-V
=> series circuit 13.4 5.81 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 6.3 5.81 Taco_5000
=> parallel circuit 7.1 5.81 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.32 7.1 1.45 PEX_0.750
=> 500 0.671 1.32 7.1 1.45 PEX_0.750
=> 500 0.671 1.32 7.1 1.45 PEX_0.750
=> 500 0.671 1.32 7.1 1.45 PEX_0.750
%gpm watt gpwh head gpm Component
=> 35 86 4.1 13.5 5.82 Grundfos_15-58-III
=> series circuit 13.5 5.82 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 6.3 5.82 Taco_5000
=> parallel circuit 7.2 5.82 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.32 7.2 1.46 PEX_0.750
=> 500 0.671 1.32 7.2 1.46 PEX_0.750
=> 500 0.671 1.32 7.2 1.46 PEX_0.750
=> 500 0.671 1.32 7.2 1.46 PEX_0.750
%gpm watt gpwh head gpm Component
=> 38 44 8.0 13.5 5.84 Taco_VR1816-V
=> series circuit 13.5 5.84 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 6.4 5.84 Taco_5000
=> parallel circuit 7.2 5.84 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.32 7.2 1.46 PEX_0.750
=> 500 0.671 1.32 7.2 1.46 PEX_0.750
=> 500 0.671 1.32 7.2 1.46 PEX_0.750
=> 500 0.671 1.32 7.2 1.46 PEX_0.750
%gpm watt gpwh head gpm Component
=> 34 58 6.3 14.6 6.07 Taco_VT2218-IV
=> series circuit 14.6 6.07 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 6.9 6.07 Taco_5000
=> parallel circuit 7.7 6.07 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.38 7.7 1.52 PEX_0.750
=> 500 0.671 1.38 7.7 1.52 PEX_0.750
=> 500 0.671 1.38 7.7 1.52 PEX_0.750
=> 500 0.671 1.38 7.7 1.52 PEX_0.750
%gpm watt gpwh head gpm Component
=> 45 60 6.3 15.6 6.30 B&G_Vario-VII
=> series circuit 15.6 6.30 Taco_5000 + PEX_0.740 500 x 4
L D fps head gpm Component
=> --- ------ ----- 7.4 6.30 Taco_5000
=> parallel circuit 8.2 6.30 PEX_0.750_500 x 4
L D fps head gpm Component
=> 500 0.671 1.43 8.2 1.57 PEX_0.750
=> 500 0.671 1.43 8.2 1.57 PEX_0.750
=> 500 0.671 1.43 8.2 1.57 PEX_0.750
=> 500 0.671 1.43 8.2 1.57 PEX_0.750Thanks for the info. I'll do some shopping online. Another question, is foam under the concrete truly worth the money?
maple1
Minister of Fire
hondaracer2oo4
Feeling the Heat
Under slab and frost wall insulation is required with radiant slab heating. 2 inches is good, 4 is best. A lot of people will tell you to use reflectix foil bubble wrap. Don't fall for that. Google it and you should find the test someone did which showed heat loss into the ground using foam, reflectix, some other product and nothing at all. Th reflectix was only slightly better then using nothing.
BoilerMan
Minister of Fire
Foam is a no brainer as Maple1 said. 2" EPS (blue board) is standard, double up around the perimeter for 4", I did that when I built my house in 2009 and have been very satisfied. Heating 3,200 square feet and DHW with just over 3 cord of wood with this under my 8" slab. No frost wall and a thickened edge of 12"x12" with 3' of 2" blue board horizontally beyond the edges.
TS
TS
Thanks for the thoughts and techniques. This is a slab for a shop that I park trucks and wrench in occasionally. If this was my house I would surely get carried away. Not sure how much I want to invest in the building is all.
BoilerMan
Minister of Fire
Thanks for the drawing I think I'm going to leave a thicken edge as well. May have other questions when I get close to boiler setup.
maple1
Minister of Fire
Make sure you have boiler return temp protection in place. You'll want to keep the temp of the return water entering the boiler 140° or more - low temp radiant heat makes return temp protection a necessity.
So if my return needs to be 140+ and the supply to concrete is 125, how do I achieve the 140+ return?
maple1
Minister of Fire
A bypass loop on the boiler, a thermostatic return mixing valve, and a pump that would move water around the bypass loop. The mixing valve regulates how much bypasses.
One that comes quickly to mind is a Danfoss ESBE. Another is a Caleffi Thermomix - not sure if I got that name exactly right. Or you could go whole hog and get a loading unit like an LK810 - mixing valve & pump in one unit. Usually that is used with storage though. Are you doing storage?
One that comes quickly to mind is a Danfoss ESBE. Another is a Caleffi Thermomix - not sure if I got that name exactly right. Or you could go whole hog and get a loading unit like an LK810 - mixing valve & pump in one unit. Usually that is used with storage though. Are you doing storage?
Ok I will do some checking on those. The thermostat pump combo sounds like the way to go. Not at this time just the boilers capacity.
BoilerMan
Minister of Fire
As maple1 said there are a few ways to do this. I do a primary/secondary loop. Radiant has a 008 running the loops in the floor, boiler had a 0010 pumping around in a loop, and there is a 006 on an injection control linking the two independent loops with closely spaced T's on either end. Making a big H pattern.
TS
Using this primitive drawing could someone complete the layout? Having 2 manifolds feeding 4 zones on the wall. I will then have a hot supply into building and a return to boiler line. Boiler will be located directly outside.
Times to start plumbing in my boiler. I see some manifolds have individual flow regulators and some don't. Are they neccesary for floor heat ?
maple1
Minister of Fire
'Necessary'? Likely not, but might be handy. If your loops are same length, likely more so not. Do you have a good mixing valve to get your in floor temps right?
All loops are the same length. No I have not I've looks at the options given above. Still a bit confused on the layout for the bypass.
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For hydronic heating what you are referring to is actually purchasing a hydronic circulator not a pump.
The less complicated you keep your the system the better.
Piping in a fossil fuel boiler in series with the wood boiler is always a good idea
to prevent freezing of pipes and circulators. this lets you avid having to plumb them up separately with valves to bypass either of the boilers.
In floor slab heating is finicky and is quickly affected by open garage doors shedding
heat from the floor quickly to the outdoors.
You can purchase non toxic boiler water antifreeze but having a sealed system for this is essential.
It also takes a long while to heat up a slab depending on the outdoor temperatures,
how often the doors are opened and how frozen the ground is and how good the
insulation is under the slab.
I would strongly suggest that you purchase a copy of Dan Holohans book
"Pumping Away" from Amazon or Barnes and Noble before you do anything so you
can learn more about the hydronic heating method before you make a mistake that
will haunt you. Dan writes his plumbing books so the layperson can easily understand
what is required for steam and hot water heating systems and his book "classic hydronics" is a gold mine of heating history with regard to steam and hot water heating.
As my friend and fellow coal burner and neighbor to the north EW Dudley has so kindly
stated you have some options.
A system bypass line diverts some of the hot water made by the boiler back to the boiler sump to keep the water hot and to keep the boiler from cycling too much.
A boiler bypass diverts a portion of the cooler water returning to the boiler in the single return header line back into the heating loop or loops.
SO much is going to depend on what type of wood boiler you have and wether it is a pressurised or unpressurised OWB or a pressurised indoor wood boiler.
We need to know more as you will have issues with air bubbles unless you install power purge lines to fill each of the loops with cold water completely before you open them to the boiler piping. you will learn more about Power Purging in dans book or by visiting www.heatinghelp.com
You do this by hooking up the garden hose to each loop and then open the faucet and let the water run and fill each loop while the boiler drain line on that loop is purged of air, then you can go to the next loop and the next loop and the next loop and all the air is gone from the four loops.
In either case you want to keep the circulator in a warm area to avoid freezing and breaking the casting of the circulators impeller housing and your going to have to decide if you intend to have a fossil fuel boiler as a back up boiler for the heating system as the last thing you need is broken pex loops or a damaged and cracked circulator.
One thing to keep in mind and understand fully is that a low temperature is easier to maintain and supplement with warmer water at all times If you keep your wood boiler
at 160 high and 140 low you will have plenty of hot water to warm your slab simply because the boiler wil have an easier heating load to manage and smoke less if you not have wide temperature swings.
The other thing is you should think about is thermal storage for more hot water as you will have more water to heat with and your boiler will smoke at idle less as you are able to make a hot fire with less wood.
It takes the same amount of energy per gallon to heat a thosand gallons as it does two hundred gallons in BTU per gallon so that is a known energy constant.
The less smoke you have when making heat the better as yoiu are not wasting heat energy.
SO much is going to depend on whether you have dry wood. Putting the wood on the slab to dry out will dry it out faster and the wood will provide more heat per pound the longer you heat the firewood before you use it.
What type and brand of boiler are you investing in?
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I've purchased a used empyre 250 boiler that I found locally. I ordered the box online and plan to do some ready to see what setup will work best for me. Having storage hot water may be an option down the road as I get things setup.
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