I am considering zoning my current heating system at the same time I upgrade my boiler. Currently I only have one zone. I am considering three. (1st floor, second floor, addition). My questions are:
I will be removing the original metal piping from the crawl space. The existing piping is larger diameter (4″). When I zone it I will replace it with copper am am wondering if I can replace the larger piping with smaller diameter? The current piping is larger because those pipes feed both the first and second floors. There are tees just below the first floor radiators which split off to the second floor.
Will zoning result in considerable savings? Any way to guesstimate how much?
Hope this makes sense. Thanks
Replies
Did one just like that. Replaced all the piping with pex to each rad from headers in the boiler room. Each floor has it's own stat. Kept old cast iron boiler but added outdoor reset. Average savings reported by owner in the range of 15 - 20 % but they love the comfort.
Talk to a good boiler guy, sizing of pumps and near boiler piping can be critical.
If you go with a modulating/condensing boiler, the savings should be even greater.
I think so, but you really need to consult with a heating expert who is conversant with your specific situation.
In my own house, we replaced 3-4" steel pipes that ran blow the basement ceiling with copper (which as I remember was 1 1/4"), which we could run in the joists. The old system was gravity fed, and we installed circulation pumps.
Ours is a big house, so we looked into zoning, but it was impractical. The pipes ran from the basement to the first floor, then branched off (inside the walls) to the second floor, and the same with the pipes to the 3rd floor.
If you're certain you can isolate the pipes to those areas of the house you want to have on separate zones, I don't see any problem. As for dollars saved for heat, I don't know that you should look for much. A lot depends on the size and configuration of your house.
For instance if you want to zone the first and second floors, and you have an open stairway, I don't think I would bother. The heat on the first floor will just migrate to the second floor anyway.
********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
Our place was similar to yours, except the largest piping was 2". There were lots of runs- three separate supply/return headers with separate drops connected to a huge cast flanged manifold at the inlet and outlet of the old coal boiler.
Zoning itself probably won't result in energy savings, unless you had to massively over-heat the 1st floor to keep the 2nd warm etc.. Rather, using a modern boiler will give you the savings. How much you save will depend primarily on whether your old system had a circulator or not- and what type of new boiler you buy.
The rad supply/return piping had to be HUGE on the old systems because they circulated the water by thermosiphon only- hot water rising, cold water sinking. Circulation rates were low, and supply water had to be very hot to get the job done. A pump puts out way more head than you can get from thermosiphon, so you can get higher circulation rates through vastly smaller pipe- or PEX tubing in my case.
Since I was replacing with a modulating condensing boiler which likes low return water temperatures, my plumbing was pretty easy. No worries about keeping the boiler hot to prevent condensation.
The old basement is a low dungeon of a place and the pipe is in absolutely perfect condition despite its age, so I left most of the old supply/return distribution pipe in place. (In your case, you're on a crawlspace so any heat your distribution piping loses probably won't end up heating your house- so you'd be better off ripping the old piping out and insulating the heck out of it).
Since the header drop lines I was going to replace were short, I was able to replace each of the old 1.25 through 2" pipesize lines with a single 1/2" PEX line to the first tee supplying/returning from each group of rads. Each supply has a globe valve on it for balancing. All three of these are connected in parallel and supplied by a single circulator, which happens also to be the main circulator for the boiler in my set-up.
You could just as easily have supplied each group with a separate injection circulator connected to a thermostat, or a separate zone valve off a main manifold etc.
In your case, it's probably best to home-run separate O2-barrier PEX (or better still, PEX-Al-PEX) supply/return tubing to each rad, and zone with manifolds. That will allow you to balance each room much better, as the old rad inlet valves are not worth beans for that purpose once you've got a circulator on there. The old valves aren't designed to throttle the amount of head that a circulator produces.
I would perfer to use pex due to the ease of installation however the temperatures that the system can reach (180 deg) approach the limit for pex. Am I missing something?
180 degrees?Isn't that awfully hot? My system runs at 140 with boiler/radiators.Do you have baseboard units?********************************************************
"It is what we learn after we think we know it all, that counts."
John Wooden 1910-
180 at 12psi is no problem. But most systems are oversized at 180.
Wirsbo He-PEX O2 barrier tubing: 100 psig @ 180 F, 80 psig @ 200 F. That's what I used. And I'm nowhere near 180 F with my rads either.
IPEX Kitec PEX-Al-PEX is good for 125 psig @ 180 F.
yes, but the PAP will hold its shape and have 90% less expansion. PEX is not a preferred high temperature piping, IMHO, PAP is much better.-------------------------------------
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It may be possible to add thermostatic radiator valves (TRVs). If you set up the circuit for constant circulation and these valves can be added, you have a zone for every radiator, at a very reasonable cost.
With a constantly modulated load, use a mod/con boiler (if you're using gas or propane) with an outdoor temperature sensor to control the constant circ water temperature, and watch the savings jump..
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Hi Rob,A couple of questions, while we've got your ear.
Do you have a favorite brand for TRV's? I've been looking at the Honeywell which seems like what I need, though they are hard to find around here. Particularly for 1" pipes.
Is it possible to bury the control capillary tube in a wall? I'm not so keen on the idea of having that tube hanging out...
Finally, are there other names for the radiator spud wrench used to put the tail piece into the rad? Whenever I ask for it the guys at the counter look at me like I've got three eyes.Thanks!
Todd
We use Oventrops that we get through Runtal Radiators (the brand of radiator we use). You can put capillary tubes in walls but I'm told you should put them in conduit and be very, very sure not to kink it. And these valves just need an allen wrench of the appropriate size... being a 1/2" valve, that's not too hard.For a 1" pipe.. sheesh.. you just need a valve body of the right size and a correct actuator head. At least, the Oventrops are modular like that.. not sure about the honeywells.Best of luck!-------------------------------------
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Thanks for the input Rob. The oventrop stuff looks good. I just found a supplier that can get the valves in pretty soon. Pricing for the actuators is interesting - the on-valve actuator is $37, the wall mount is $82. Do you have a feeling for how effective the valve mounted actuator is? Due to space constraints, we need to use the vertically mounted actuator, with puts it close to the rad. Will it feel too much of the rad's heat to work properly?jrenick: sorry for the hi-jack. I did exactly what you are thinking of - replaced the giant iron pipe with Kitec PAP (IPEX). Nice stuff to work with.
well, you don't dial in a room temp, you set the "comfort dial".. since it's constant circulation, whatever it feels next to the radiator should be vaguely proportional to the room temp unless the radiator is in a strange location relative to the room as a whole.We've only done a few of these constant circ systems though.. only with radiator mounted valves... and they seem to work well. But I'm far from a well-seasoned expert in their usage at this time. General feedback from others though is that they work great.-------------------------------------
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If you are using circulator pumps, with one per zone, why not have one per room/zone at point of use? Then you could put a programmable thermostat in each zone, whether the zone is a room or a floor and feed it on demand, instead of a constant reticulating system.
Admittedly it might be more expensive to install that way, but it would also be more efficient.
I'm not sure what you mean. A constant circulation system is as efficient as it gets.-------------------------------------
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Rob, from what I have read here, I have a mental image of a system which is constantly pumped through a loop, regardless of demand in any of the zones, and then allowed to short circuit the loop dependant on a thermally actuated valve in each zone which lets the water flow through the radiators in that zone.
My idea of a better system would be an individual pump for each zone, installed where the thermal valves would be. The pumps would be hooked to a thermostat in that zone, and only pump water through it when the temperature drops to the low set point, and would stop when it gets back up to the high set point. Four or five pumps instead of one, but the mechanical thermal valves are gone, and if no zone is below it's low set point the pump isn't on.
I have attached a sketch of what I'm visualizing.
For constant circulation you need to reset the water temp based on the outdoor air temp and ideally the indoor temp.
when combined with trv's, the amount of heat put into the rads is equall to the heat loss of the room.
Now combine that with a modulating burner, the boiler output will match the heatloss.
And coming soon, pumps that will vary their output based on the position of the valves.
Can't get much better than that.
There is no practical difference between on/off valves and pumps. They both do the same thing.
I did my design and shopping together to try to get the cost down- this stuff is VERY expensive, even if you do all the work yourself and you get decent discounting from your supplier. I found that using Grundfos circulators as injection pumps was considerably cheaper than using zone valves to supply each manifold. I was paying $100 for a Grundfos cast iron 3-speed circulator pump. Individual manifold-mounted thermal actuators were ~$40 each, and zone valves were at least $150-$250 depending on what you were buying. So if you had more than three users on a manifold in a particular zone, a pump was the best choice for zoning.
My system is pretty simple: the old rads are all on one zone- the main circulation through the boiler- and the boiler is controlled by the main room thermostat. This is how the old heating system worked, and it kept the existing house comfortable so there was no real need to go more complex than that. Since my addition has a significantly lower heat loss than the existing house, each of the new zones in the addition consists of a manifold and dedicated injection circulator. The relays are wired such that the main circulator runs whenever any of the zones is calling for heat. The main rad loop has such a stored volume of hot water in it that the other zones can usually be satisfied without the need for the boiler to fire again.
$150 to $200 for a zone valve????I've never even heard of a price that high. Generally, zone valves are equivalent to the "standard" circulator pumps. You incur the cost of a system pump, but you save electrical usage for the life of the home.-------------------------------------
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Rob: we agree that continuous circulation with modulated zoning and modulated heat input, controlled with outdoor setback, is the most thermally efficient way to go. But that method runs the circulators all the time too.
My original design had zone valves and only two circulators, but I was deterred by the cost. The prices I was getting were for valves and actuators- all sorts- at sizes big enough to zone a whole manifold. That's both for stuff from the Wirsbo catalog and from IPEX's catalog, plus whatever I could find from the local plumbing wholesaler's catalog. What are you using for whole-manifold zone valves that are $100 or less for both valve and actuator?
Though I agree that zone valves would waste less power, I don't feel so bad about the electrical consumption of the circulators. They're three speed units and only operated at the power needed to obtain the required flow- and only operate when the zone is calling for heat. My loop lengths are balanced, so there's little energy wasted in throttling valves. And the old rads respond quickly enough that we can still do a night-time setback without throwing everything else out of whack.
We use Erie Zone valves and bodies, and they are pricing very similarly to the Super Brute 3-speed pumps we're using. In a constant circ system, only one pump is running continuously. the primary circuit pump only runs on a demand for more heat in the CC circuit.If you can do a night time setback, your water temps are too high ;) that's an overstatement, of course.. but in general I don't see setback-ability as a selling point. anyway, I've done plenty of zoned circ systems. I just abandoned them on larger systems because if your water temps are sane for your system, they will run a lot, and I'd rather run just one or two. If you only have a few zones, then the differential is smaller and it's just a matter of what the overpumping is doing for you (or not doing for you). The smaller the system the more the addition of the system pump and bypass will shift the comparison of cost, though, for sure.-------------------------------------
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I think we are getting hosed up here. Pumps are at least twice as much.
Well, let me know where you're buying erie zone valves then ;)-------------------------------------
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Yep- I want to know too: where are you getting a zone valve body at 3/4" or greater, plus an actuator, for less than $100 total? That's what I'm paying for a cast iron 3-speed Grundfos circ. We're not talking about manifold-mounted individual actuators here- those are $40 each.
NRTrob: keep posting- I learn something useful every time I read one.
Our list for an eire zone valve and poptop is about 100. Grundfos superbrute is at least double.
But then again, we are in Canada.
wow. I don't know what pricing is like in canada, but that's a pretty high price for a pump!-------------------------------------
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Wow- I'm in Canada too, and paying $101 plus $10 for the flange kit for a SuperBrute.
Just for curiosity, who are you buying the Erie valves from?
The Erie zone valves were news to me- never heard of them before NRTrob mentioned them. I priced just about every valve option from Ipex and Wirsbo's catalogs, along with Howell Plumbing (an industrial plumbing distributor local to me), and couldn't find an automated valve option with a decent Cv suitable for whole-manifold zoning for less than $150+ ea.
I,m talking list. Any of the plumbing wholesalers carry Erie. Don't use grundfos flanges. Go with watts or b&g isoflanges. Flange, ball valve, check valve all in one.
That doesn't help at all. Then instead of bypassing a small amount of flow, you are pushing WAY more flow than you need to, for one. so your electrical usage is higher.Secondly, on/off action can never be as efficient as constant circulation w/modulating valves, especially with a modulating heat source. Constant circ is magic stuff. Dont' get me wrong; most of our current systems are (admittedly sophisticated) on/off right now.. it's the standard.. but that doesn't make it the best.As rich1 points out, soon they will even have pressure sensitive pumps, so it can run a little if the TRVs are open a little, and a lot if they are open a lot. That could be pretty cool, though personally I'm not convinced yet that delta-p pumping is really necessary.-------------------------------------
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But think of using a delta p pump along with a buffer tank. In the spring and fall your boiler is hardly ever going to run.
the delta P pump doesn't make your emitter emit less heat... at least, not a lot less.A BTU lost is a BTU lost, and if it's not lost, it stays in the system for the most part.Buffer tanks are great, but I don't see much of an effect by varying flow rates out of it. Either it comes back hotter and faster or it comes back cooler and slower... a BTU is still a BTU. You have X stored before firing the boiler and you'll lose those X BTUs at pretty much the same rate either way... you didn't change the heat loss!-------------------------------------
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No arguement, but how about constant flow with trv's and a heat loss of 2100 btu.
At a delta t of 20 that is 2 gpm.
Still get constant flow without short cycling the boiler.
I guess the real question is where is the "sweet spot" for operating a system without the occupants knowing that it is working.
And at what cost.
Edited 12/22/2006 3:15 pm ET by rich1
Edited 12/22/2006 3:16 pm ET by rich1
The buffer tank is doing that though, not the pump; the pump on the heating side doesn't influence the cycling of the boiler in any significant way, IMHO. I really don't see any real benefit to this variable pressure pumping other than somewhat reduced electrical usage. Of course, I've been wrong before, I just don't see it yet anyway!But yes, buffer tanks certainly have their place. As I'm finding out right now on a project where we are running the boiler so cool the burner itself is condensing and locking out.. groan..-------------------------------------
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If you have not been to Heating help.com try clicking this to get to the wall (their forum)
http://forums.invision.net/index.cfm?CFApp=2l.