Replace Monoflow System with Reverse Return system

Ocelaris

Hello, I'm looking to zone out and/or replace our 1950s single zone monoflow system and looking for some advice.

The house is a 1950s ranch, about 2000 square feet first floor and almost the same in an unfinished basement. The old boiler ~250k original boiler was replaced with a Lennox 100k BTU (80% efficiency) a year and a half ago by a local contractor, not terribly pleased with their work (it was ok, but not great) and their service department has been really nasty, so 'm not really tied to them. It's a dual 1.5" pipe around the house to 14 sunrad radiators on the first floor. Eventually we will add 6-7 CI radiators in the basement.

Total EDR for the first floor is 600. At 180* that's 102K BTU, my calculation for the first floor requirements is something like 35K. I'd like to split the first floor into 3 zones (bedroom, living area/kitchen, and room above gararge).

Problems to solve:
Monoflow 1.5" pipe heats unevenly, hangs down into space we're going to build into
no bypass loop on boiler, so for 30 minutes or more it's getting cold return water, water is condensing on outside of jacket.
Radiation is way over sized for our house needs. We insulated to R40 in the attic, all new windows, air sealing etc...
Need new zone in the basement at a minimum
Budget!
Not reasonable to run homeruns to every radiator, new basement walls will hold new pex lines ideally.
lennox gwb-100e boiler not sure as to it's capabilities, seems to be a simple integrated high temp cut off, can not be replaced.

My wife and I bought the house about 2 years ago and basically have replaced almost everything ourselves, plumbing, electric, drywall, tile with permits which just passed final inspection. The boiler, central air, siding/roof was done by contractors.

My thought is to do a reverse return system with 4 zone valves, bypasss diverter, maybe a smart circulator. What I would like, is to hack apart the monoflow main line and run the pex dual lines myself back to the boiler and then have a good professional plumb/wire all that up for me. I'm proficient at sweating joints and pex, but I don't have enough knowledge to plan this out completely. I've gone through 2 boiler replacements (2 different houses) and it's always a let down at the end. Once the guy plumbed the compression tank in a useless place, this time there is no bypass boiler loop or dielectric union so the boiler is corroding after only 2 seasons.

Am I on the right track? I've done all the heat loss calculations for all the rooms, and the EDR calculations for my existing radiators, and need some direction on where to go with the planning. I'd like to find a contractor who'd work with me on doing part as well.

Thanks, Bill

Ironman

You're on the right track.
Be aware that you must use O2 barrier heating pex, not plumbing pex. Personally, I'd use pex-al-pex since it stays bent and has about the same thermal expansion as copper. We use it all the time. You will need the press tool, but it's not that expensive. Non aluminum pex will act like spaghetti when it gets hot.
Where are you located?

icesailor

You've made up your mind.

However, if you have a 1 1/2" supply and return on the boiler and as many Sunrads as you say, the main is split into two 1 1/4" circuits. You'd be better off splitting the two circuits into two zones with zone valves. Whatever else you want to do, do it with your PEX.

If your boiler is getting cold and "condensing on the jacket", the controls are set wrong. No by-pass loop is going to solve your issue. Splitting the two circuits into two zones will mostly solve your problems.

Sounds like your old boiler had a "reverse acting" control that kept the boiler warm by shutting off the circulator when the return became too cold. That 100,000 BTU boiler with the Cold Start configuration slammed in by the Yahoos that don't understand about your high mass system. That the new boiler isn't happy pumping cold water. Neither is your system.

There are other approaches, The last ones were clueless.

But you've made up your mind.

Ocelaris

Thanks, but I definitely haven't made up my mind, it was just a first step to get help. Happy for suggestions otherwise. I am near Paramus, NJ in Bergen County. Basically every time I go through this process I get ideas on here and then can't find anyone to actually implement it, so I end up in the same situation. I'm hoping this time to find a workable solution and/or contractor to make sure the system is set up correctly. I went through 4 bids last time (2 more never would return my call), and this was the best bid believe it or not. i.e. they actually did a heat loss calculation and sized the boiler reasonably, where as the other 3 just quoted the exact same size boiler from 1950. So I'm here asking for advice on how to readjust.

@Ironman‌
I had planned on regular O2 barrier pex, as we have all the tools from previous DHW work. It looks like the Pex-al-pex requires either compression fittings at 5$ a pop or a 700$ multipress tool? I know regular pex will not handle the heat, but I was assuming the O2 barrier pex would hold up reasonably well if attached well? Is there a cheaper compression tool than the "multi-press" tool?

@icesailor‌
You are correct that the system does split into 2 loops, however the split starts and ends at the ends of the house, and the boiler is in the middle. So it would be impossible to treat those as 2 zones, and they cover the front and back of the house respectively (North and South), however the East/West is the way I want to zone the floors. The bedrooms are the beginning of the loop and obviously at night the doors are closed, so it gets too hot one one end and cold on the other.

The house's envelop has significantly improved with the work we've done, and the system is unbalanced because of those improvements, and in part due to the smaller boiler. So I'm taking a 10,000 foot view of the system before we seal up the basement and lose any opportunity to correct this. Thanks

Steamhead

If you're in Jersey, try Thatcher. One of that company's owners posts here under the name "JStar" and really knows his stuff. Here is their info, from this site's Find a Contractor page:

https://heatinghelp.com/find-a-contractor/detail/thatcher-heating-and-air-conditioning

SWEI

You might want to look into a 3-way or 4-way ODR-controlled mixing valve there.

Ocelaris

@steamhead, Thanks, I dropped him a line.

@SWEI, that looks to be a lot like a great tool. I'll have to see how that would work with my boiler's control.

Really I'm just trying to do my homework, because I just hate "not knowing" what I'm buying, and twice before it's ended up biting me in the end. Also I'm a curious person and hydronics is very interesting to me. Thanks

icesailor

@Ocelaris:

The zone valves go at the split where the size switches to 1 1/4". It doesn't matter which end they go on. As long as there is a valve on each branch/split of the main.

A Taco "I" Series mixer could be a wonderful thing in your application. Especially with zone valves. If the building faces south and the heating mains run East & West, the North side gets cold but the South side gets hot during the day from the sun. Splitting the main branches balances out the heat on sunny days. The North side ends up heating the South side. The South side just adds what is needed.

Snowmelt

Sounds like you need someone to do a heat loss load and give you direction on what way to go. Are you planing to keep the boiler, add outdoor reset, with a bumble bee smart pump, and a few sentry zone valves set up with primery secoundary. You will be set. I left a private mail, I don't know if it went threw. The aluminum Pex is the same as heating pex only difference is obviously the aluminum that's over the pex itself. The pex uses the same fittings, what you have to do is take some of the aluminum off of the pex with a tool.

Ocelaris

@icesailor‌
Thanks, the "split" where it goes into 2 loops are about 30' away from the boiler, and it wouldn't be impossible to put valves there, but I'd rather do zoning east/west and the loops right now split the house north/south.

The main problem is that the east side of the house is at the end of the loops and happens to be the open section of the house, so if I could reverse one loop or both that would help; however I think the diverter Tees only go 1 way.

@Snowmelt‌

Thanks, that was very helpful with the pex-al-pex, and if a professional comes out and agrees with my conclusions, and I can't save the monoflow piping, that's basically what I'm looking at, mixing valve with ODR, and zones. I can't justify tossing the boiler as it's only 2 years old.

I did a heat loss here:
Heat Loss Calculator

Ocelaris

I just attached the heat loss against my radiator's EDR. Not all of the values I entered are in the spreadsheet, but hopefully gives an idea of the thought I've put into this so far.

Snowmelt

That's a nice spread sheet but your looking up heat of the radiators which is fine but not the heat of the home. Say the home needs only 50,000 btu.
I would go with what you have.
Put out door reset on the boiler.
Smart bumble bee pump.
Put primery secounday on the boiler or a bypass so the boiler doesn't condensate. Can always put a thermostatic valve on the radiators.
You can but a manifold in basement and put the pex to each radiator with a thermostat in each room. Every rad can have a zone. It's ultimitly up to you.

If you want drop me an email
contact@georgeshvac.com
Gwise7000@aol.com

Ocelaris

Sorry, I do have that on the sheet under the column labeled "Estimated BTU", column S. That was more for my info than I meant to share. With that website I plugged in the numbers based on dimensions, windows, and (not in the spread sheet) ceiling, insulation etc... Total for the first floor was like 35K BTU and 15k for the basement. I'm sure that's not as good as a professional would caculate, but it's good for just an estimate.

I like the idea of thermostatic valves on the radiators, but I have flush mounted sun rad style radiators with the connection on the inside , kinda like this. Plus I don't need that much control, I'd be happy with 4 zones.

Harvey Ramer

I support your idea of using PEX-AL-PEX and installing a reverse return piping system. You should be able to run the piping through the joists and really clean everything up. It will also give you the flexibility to zone any radiator you want to. The way I like to zone a radiator is with a TRV.

You need to get a handle on that cold return water at the boiler. I have done it many different ways but here is one of the most effective ways I have found. http://www.caleffi.com/usa/en-us/catalogue/thermomixtm-thermostatic-mixing-valve-high-flow-sweat-280965a You pipe in a bypass and this valve thermostatically controls the return water temp to the boiler by mixing in hot water from the supply. It works really well!

SWEI

Ocelaris said:

that (ODR-controlled mixing valve) looks to be a lot like a great tool. I'll have to see how that would work with my boiler's control.

The valve regulates heat going into your house - properly. The boiler just turns on and off like it's designed to, but much less frequently and crazily.

Ocelaris

I guess my confusion lies with having 2 temperature controls. The boiler has a high temp built into the unit, default of which is 180*. So with a bypass loop on the mixing valve you have maybe a few gallons at 180*, and that gets fed into the radiant loops. Wouldn't the boiler heat up the few gallons in that bypass loop quickly and shut down, just to be cooled off by the water coming in from mixing valve again?

These are a lot of great options, you all are going to keep me busy reading through the literature for hours now!

Snowmelt

That's what I would use also. What that valve will do is take place of the bypass valve and make sure there is nothing under 140 degrees going back to your boiler.
Think of it as just a mixing valve with hot, cold & mix.
The 3 or 4 zones do you want them with zone valves or circulating pumps. Or you can use a nice manifold with powerhead shut offs. how many radiators do you have.

icesailor

Ocelaris said:

Sorry, I do have that on the sheet under the column labeled "Estimated BTU", column S. That was more for my info than I meant to share. With that website I plugged in the numbers based on dimensions, windows, and (not in the spread sheet) ceiling, insulation etc... Total for the first floor was like 35K BTU and 15k for the basement. I'm sure that's not as good as a professional would caculate, but it's good for just an estimate.

I like the idea of thermostatic valves on the radiators, but I have flush mounted sun rad style radiators with the connection on the inside , kinda like this. Plus I don't need that much control, I'd be happy with 4 zones.

If that is a photo of one of your radiators, that is a one pipe steam radiator with a steam vent on the left side. The outlet on the left side of that recessed Sunrad is plugged.

No wonder it splits 30' away and doesn't come back.

Post a photo of the boiler.

Snowmelt

Good eye I didn't catch that, do you have a pump on your existing boiler. I'm sure we will talk more in the morning.

Ocelaris

I've been reading about the importance of balancing a reverse return system, and trying to imagine how I would realistically implement that given my radiators. I have some sort of valve on the radiators already, but I doubt that they work (although they do turn). If I can't use these, how realistic would it be to replace that piping with a TRV or balancing valve under the radiator.

some pictures of the radiators and valves existing.

How much of a difference would various radiators be? One zone has between 8-15 sections, the other zone has between 20-30 sections. Would it be ok to forgo the balancing valves or TRVs if they sections are reasonably close in size or is that a must?

icesailor

Where did the first radiator come from and then all the rest?

The first one is a steam radiator. The rest look like FHW radiators. Have I seen those photo's before?

Snowmelt

Ice, he called me today. No big deal, he told me the first pic he took from the web. The secound set of pics was his own rads. He sounded like a good guy but he's not ready yet. I think he's better just zoning sections of the house with sentry zone valves.one of his big concern was ballancing the system. He wants to divide the house in four zones which would be nice.

icesailor

The biggest bang for the Buckaroo is to zone it.

Although in the 1960's, I installed a couple of systems with 3-way mixers, and I tried for years to find something reasonable like them, when I found the Taco "I" Series 4-way mixers, I was disappointed that they didn't come in to my life sooner.

ODR and turn down are well established. Whenever someone finally comes up with a reasonably "TURN UP" system, Hydronics will run like the Cruise Control on automobiles.

Today's hydronic boilers are set up like my John Deere tractor was. You set the hand throttle when you are on flat ground and it goes 10 MPH (or what ever you set it at. The ground grade goes down, the Governor on the engine allows it to slow down and maintain the MPH. Start up a hill and the engine stalls unless you downshift.

Ocelaris

Thanks Snowmelt and icesailor, I would be happy if I could get the zones set up with reverse return, a boiler bypass and ODR. If you think it'll work fine without putting a balancing valve (or TRV) on each radiator that would save a few weekends worth of work.

I just don't want to get stuck with radiators getting no flow. But it sounds like cast iron radiators have little to no resistance through them. So I think that means it's ok to do with out the balancing valves?

Thanks again!

icesailor

@Ocelaris:

In my lifetime, I have looked at a lot of old hydronic heating systems. Fascinated at what the old dead guys did. And they all worked fantastically, long before I was born. I learned all I could about them. Then, I started learning more "modern" thoughts about old boilers and why they didn't work.

I finally came to the conclusion. Its a good thing they don't do it liked that anymore.

Those old systems worked by certain rules that seem to have been re-written. When I see some of the new systems that are having problems, I think: Its a good thing those old guys didn't do it like that.

Snark-O-meter set on #10.

SWEI

A properly implemented reverse return system is a beautiful thing to behold. When the rads are properly sized (proportionally based on heat loss) it will require very little balancing to "just work." It's really kind of like magic.

icesailor

SWEI said:

A properly implemented reverse return system is a beautiful thing to behold. When the rads are properly sized (proportionally based on heat loss) it will require very little balancing to "just work." It's really kind of like magic.

I think I said those exact same words.

To keep cost down and use less material and pipe, most every multizone system I ever installed used what I thought was a properly implemented reverse return system. It was always a beautiful thing, and the opening and closing of zone valves never seemed to upset the beauty and simplicity of the systems.

10kREDLINE

@Ocelaris, I've done to my home almost what you're looking to do. I did pex home runs to cast iron radiation,standard boiler. I installed a pressure differential bypass at the end of the supply header, following the pex supply trunks. Three zones with zone valves on the return, pushed by a Grundfos 15-58 on medium. All rads are supplied with 1/2 oxygen barrier pex. Some rads larger than others (some rads being double the size of the smallest). Like @swei said, it balances itself like magic. The pressure differential bypass keeps everything quiet and moving. Also, you need to have the control adjusted correctly. I have a standard high limit aquastat with a 25 degree differential. L8148E? so the circulator keeps moving as long as there is a call for heat, and the boiler cycles on and off with the high limit and the low limit from the differential. If you have any questions let me know, I did the work myself.

SWEI

Skip the pressure differential bypass and use a pressure-dependent ECM circulator instead.

icesailor

SWEI said:

Skip the pressure differential bypass and use a pressure-dependent ECM circulator instead.

A most wonderful thing, the ECM circulators.

Ocelaris

I was reading about the Taco Bumblebee, but some were complaining about it being loud. The Grundfos Alpha series seem to have a constant pressure mode which would seem to be useful.

However the bumblebee has an ODR which varies the speed based on delta T... I would think a 3 or 4 way mixing valve separate from the circulator would be more reliable though no?

10kREDLINE

in hindsight I should have employed the Alpha or another ECM circ, and i still can. I just have to close the differential bypass. Otherwise, my home warms up in half the time or better than it did in the past, probably due to much less water in the system, and the direct supply/return paths. I used to have a converted gravity setup, with 1.4 or 2 inch mains. I cut them out and plumbed up my home run system. if you need help with the layout or anything let me know. i dont know how to send a private message. but if you do, send me a pm, i live in your area.

SWEI

Ocelaris said:

the bumblebee has an ODR which varies the speed based on delta T... I would think a 3 or 4 way mixing valve separate from the circulator would be more reliable though no?

You seem to be mixing metaphors here. The Bumble Bee ΔT mode knows nothing about the outdoor temp. It will adjust its speed to maintain a constant ΔT between supply and return.

The iSeries-R mixing valves use outdoor air temp to control the supply water temp.

They work together just fine. Whether a ΔT pump or a ΔP pump works better on a distribution loop with multiple zone valves is still being debated. Suffice it to say that either represents a huge improvement over a fixed speed PSC circulator.

icesailor

I personally think that 4-ways, installed correctly in the proper applications, ROCK!!!.

But that's just me.

Snowmelt

Ummm, I would just put an O.D.R. On the boiler with a taco pump & sentry zone valves. I am thinking all the rads are oversized as it is.

SWEI

Chris and I both suggested this from the get go -- leaving the existing valves if they are OK.

Ocelaris

@Snowmelt‌

I think I can't put ODR on the boiler because of the controller which also manages the gas, flame, flue etc... Unless there is a way to put ODR on that controller; but it already has it's own high limit. I think I have to use a separate boiler loop, that the honeywell controller manages, and then a separate 3 or 4 way mixing valve which can send ODR water to the zones.








It explicitly says in the manual "you must pipe in a bypass for high mass systems"... I guess better late than never.

Ocelaris

So it looks like the honeywell control that I have, S9361A is shared among many vendors, Burnham makes an "IQ Option Panel" that you can add on outdoor reset etc... So would it be better to add that Caleffi 280 Anti-Condensation valve, and just a single circulator, then the boiler could control it's own temp via ODR...

usboiler.net/control-system/iq-boiler-control-system.html

Snowmelt

The short answer is your boiler has some kind of aquastat that controls the cut out and cut in of the boiler. The taco outdoor reset will by pass that part of the boiler and take over the comand of turning the boiler on & off. Can you send a pic of boiler itself. Let's see how the old owner did the near boiler piping? See if the boiler has an xx, I'm going to call my taco rep just to make sure. Also need a pic of anything that might look like an aquastat. That honeywell pic that you sent is important and acts as a trouble shooting guide. Not really the aquastat. But like I said I'm going to call my taco rep up to confirm.

Ocelaris

That's the only control on the boiler, so it must be the aquastat. And that is a Honeywell S9361A. I set the high level cutoff to 160 today, and it has a 15 degree differential cut in. The only reason I can think to do a separate odr is if I ever wanted a separate dhw loop, but at the moment the add-on controller seems like a no brainer.

There is no boiler bypass, but that would be easy enough to add, I will try to post pics of the near boiler piping tomorrow.

Snowmelt

The odr has a indirect water heater bypass built into the control meaning if the boiler is calling for domestic water it will ramp up to 180 degrees. Still look for an xx on the boiler?