Tough one to figure out...

Harman

Hello gentleman and ladies, I need a bit of guidance here, admitting to be a bit out of my league with a job I just inherited.. Heres the situation...

2- small 70K (input) natural draft ci gas (LP) boilers,
a 1" (Im gonna guess 11gpm max flow rate) hydraulic separator,
a good size (no data plate on it) FPHX,
all to run a 50 gallon indirect water heater, 3 radiant floor zones, and 3 radiant panel zones....

The house has 2- 90+ gas furnace each with a heat pump condenser unit ... I originally went to the customer last November because their contractor took off with their money, I finished the duct work, and hooked in the Furnaces so they had heat for the winter, and told them I would return in the spring to figure out the radiant situation... WELL ITS SPRING!!!

Can anyone guess what he was thinking with his design bu that list of materials?

Heres what I am guessing, the boilers go to one side of the hydro separator (a pump on each boilers return, returns tied together into the bottom of HS and supplies tied into the top), then out of the other side of the HS, a primary secondary loop with the FPHX and the indirect coming off of it, then a primary secondary loop off of the FPHX with each low temp radiants manifold installed off of that... FOLLOWING ME? the amount of circulators that are there supports this, as well as 2 expansion tanks and water feeds....

There is a digital aquastat there which I am guessing they were installing in the fphx (judging by the fittings) and they intended on using that to pull the boilers in?

Heres my questions, first Who makes a control that will handle a system like this? It is going to have to be a 2 boiler stage control, then be able to use heat pumps in the shoulder months, and turn the 90+ furnaces on as an aux/backup..... I have never seen anything capable of that?

Second, will this work? The home owners do not want mixing valves, their last system was a mixing valve night mare (not sure why) but it is out of the question, I am going to have to tackle this job soon, and I need some extra brain power to save me the trial and error.... thank you in advance, and thank you for reading through...

Mark Eatherton

Got drawings?

ME

Zman

Probably need a few more bread crumbs on this one. Is there tubing installed? How? Pictures of building plans would be great.

Harman

Ok, so when I first went there the tubing was in the floor but sticking up and wound all over the place, so I tied it into the manifolds, and I ran 3/4" supply/returns down to the boiler room, so they could button up their house...

so all that is in the boiler room is...
6 feeds and 6 returns for the 6 radiant manifolds
They had an electric water heater so that is in there, and that will be replaced by indirect.

I will make a drawing of how I am thinking it can be done with what is there...

Zman

Can you determine whether the tubing is installed with plates or just stapled up? Does the tubing have an O2 barrier?

Harman

OK heres what I am thinking forgive the primitive drawing, it is 1:20am here, lol...

Harman

zman, the tubing is in the floor, not under it. Its in floor panels, I believe they are the wirsbo fast track, or what ever it is called, the smaller peices, not the 4x8 sheets of routed subfloor and not the foam with alloy cover like Roth used to make...

And I think its barrier pex, I will have to check that, thats a good point, since they are using a fphx vs and not mixing valves they could have used non barrier...

Zman

This is not complete. Some quick feedback....

HomerJSmith

The flat plate heat exchanger is piped wrong (maybe your drawing is off). The flow should be counter as to each input.

Instead of a FPHX, it could have been done with injection mixing or a three way mixing valve.

Why does it have a hydro separator on the radiant side? Why not use one ECM pump on the radiant side rather than 7 pumps? How is it all being controlled?

How are you regulating your flow and temperature to your radiant zones? The boiler output to the baseboard, FPHX, and tank is 180 deg.

Why do you have an expansion tank between the hydro separator and indirect tank?

Harman

Yes I see I inverted the fphx in the drawing and I accidentally left the extra expansion tank in between the boilers, I meant to delete that when I seen it fit better near the indirect instead, I just wanted to show it in the system, it was past 1 am here and I start at 6am on weekdays (6:18 right now)...

I am guessing the circulators are going to control flow (they are delta t circs), and I am guessing that digital aquastat is going to control the radiants temperature? I am just going by what parts are there. As far boiler control and staging, and dhw priority I have no idea what control to use for that, this system will obviously benefit from odr, so something that can do them all would be great, and if there was a control that could pull in the furnaces as auxilary that would also be a plus...

And these customers do not want mixing valves controlling the system, they had a bad experience with radiant in their last home, it sounds to me like they never serviced the fluid and the 15 year old glycol made a mess of the mixing valves. either way its not an option, they are willing to pay, I just want to get it right the first time so asking what you guys think would be the best bet...

Harman

Thanks for the drawing zman, yes the circs have built in checks, and yes I am planning on putting purge valves on all the zones including the dhw tank and base board loop, I just didnt have the energy or clarity to do it yesterday, I literally made that drawing on a tablet sitting on the edge of my bed trying not to disturb my sleeping wife, lol.

I am confused as to why they have 2 brand new hydro seps there also, that is the only place I can think of putting it? Unless the other contractor ordered it with the hopes of walking off with a $500 HS for free. I am not sure.

And it is not barrier tubing, I just had my tech check, so the FPHX will help not rot the boilers out, there is also going to be glycol in the radiant and not the rest of the system so the flphx will also help with that, another note is they have / had plans to heat the driveway, either way the FPHX is there and a pair of Hydro seps are there, so I will use them, even if that HS only aids in air and debris removal...

hot_rod

A basic single temperature system, really not that badly piped.

There is no boiler return protection, but in a light, low mass system it may not be an issue.

The HX is a good idea to protect from non barrier tube, is glycol really needed?

The second hydro sep hydraulically separates all the distribution circulators from the HX circ. It will provide air, and dirt separation, but will also give different blended temperatures depending on which zone pumps are running.

The zone circs should be balanced to the exact flow requirement, a PIBV would be a good choice, fixed speed circulator.

Are the boilers on reset control?

Harman

hotrod the boilers only have their included controls, no other controls are there, not even a basic zone controller, so I am not sure what he had in mind, or what to use...

I am not positive if this is how he was piping it, there was literally just a stack of parts sitting on top of the boilers still in their crates when I arrived, I am guessing this is the way he was going to do it..

Zman

I think if you go with my markup and eliminate the HX circ and the separator on the radiant side you will be pretty close.
You can put the circ on the boiler side of the HX on an injection controller like this one https://www.supplyhouse.com/Tekmar-356-Mixing-Control-Variable-Speed-4156000-p?gclid=EAIaIQobChMIi_mai6Ge2gIViZ9-Ch1qPQsqEAQYASABEgKqP_D_BwE I would suggest a flow balancing valve on that loop to keep the controller from seeking/hunting.

We would need more info on the control side. I would be surprised if you wanted forced air and radiant running at the same time.
You could do 2 stage heat (radiant as stage 1) and 1 or 2 stage cool?

hot_rod

If you want to adjust temperature to the zones, some sort of mixing device, temperature responsive is needed. Without knowing the loads and required temperatures on all those various zones and heat emitters, it a bit of a guess.

Was a load calc or system design ever done to indicate what loads are?

If you remove the second sep you would need to add at least another air separator, and ideally a mag sep with ECM circulators, so no harm in leaving it in there.

Ideally the plate HX should be piped counterflow for best performance, it will still transfer as piped. If you do any repiping swap the flow direction to counter flow.

I think you could just use a control like Carl ,mentioned and "inject" into the flat plate, turn that HX cir into your temperature regulating device.

Any number of ways to pipe a system like this, I think it will be fine with a few minor tweaks.

I'd caution against T circs for distribution operation with reset controls. We will talk about constrained ∆ operation more in Idronics 23.

An example below, it hold true for any emitter, radiant loops, panel rads, etc.

Harman

zman since the hs and circ are already there, what would it hurt running it to keep the hx and that loop uniform, may give it a bit of storage too, even if its there just for debris and air removal?
can you explain the flow balancer to me, (link to a model) I am not sure I know what you mean.

what would you use to stage the boilers and run the furnace when the radiant cant keep up or if it is ever down?

Harman

hot rod this isnt piped at all yet, just the manifolds are piped to the radiant emitters, the boiler room is all brand new parts in boxes..

I have used delta t circs before on emitters, I didnt know that was a bad idea, so what should I use instead on the 6 low temp zones?

Harman

What tekmar controls would I need or this system? I was going to call the rep after I nailed down how it was actually going to be piped first...

SuperJ

You could use a multistage space thermostat with a relay to start the zone pump(s), second stage could start the furnace. A thermostat like the Ecobee3/4 has some staging options to ensure the furnace would only run if really needed. It gets a little more complicated since the furnaces don't have a 1:1 relationship with the radiant zones, you'll need to pick the zone that best represent good feedback for the furnace thermostat or combine radiant zones. Or you could just keep the furnaces completely separate and tell the HO to leave them set a couple degrees lower.

I think it's going to be tough to get the panel rads and infloor zones to both work at normal infloor fluid temperatures. Unless the panel rads were selected for 120F or the radiant floors are staple up.

SuperJ

Putting a single delta P on the secondary side of the HX, TRVs on the panel rads (get rid of the panel rad zone pumps), and maybe some of the programmable Taco 3-way valves in front of the infloor pumps could work but would add a bunch of parts/expense to a job that already has lots of pumps.

If you decided to go with the Taco valve, with a bit of repiping, I think you could use a single temperature scheduling valve for all three zones to keep the costs under control.

(call it a temperature scheduling valve instead of a mixing valve to keep the HO happy ).

Harman

sorry the panel rads do have trv's...

I think the temperature was going to be controlled by the FPHX, so the boiler runs at 180 and then the fphx is set at a temp to satisfy the floors say 105 for example, so when the hx loop drops below 105 it turns on the circulator...

I would rather do that a different way, with a control and an outdoor reset would be great...

HomerJSmith

Look, you have 180 deg water coming out of the boilers to the FPHX. You are going to have 170 deg water moving out of the FPHX, that's way too hot for your radiant tubing circuits.

Are your radiant circuits, zoned and independently controlled with thermostats?

You are way underpowered if you think you are going to add a sno melt sys.

ODR isn't going to work with cast iron boilers, you can only sequence them based upon your load requirements.

As far as mixing valves are concerned, Taco I-series mixing valves are trouble free and great for this application and they come with ODR. Use two, one for the radiant panels if they require a higher temperature, and one for the infloor radiant panels which is at a lower temperature and pump 170 deg water to them. These I-series mixing valves can give you temperature control, then you just have to figure out your flow.

Why do you need anti-freeze unless the house is only partly occupied during winter. I would only use anti-freeze if the situation absolutely called for it. You could simplify the system without it. Anti-freeze, as the owners already know, is troublesome and once in, the owners never check it again. If you do need anti-freeze, you will need the FPHX to separate the two systems.

If the boilers are the primary heat source and the furnaces are a back up heat source, then, you can just use a relay connected to a thermostat to turn the furnaces on. Easy! Or... just use a thermostat set 5 deg below the radiant thermostats and if the radiant fails the furnaces will turn on.

Harman, you have some serious thinking to do to put this all together. You had better figure out your radiant loads, temperature, and flow. That's where I would start.

The reason the other guy took off was probably because he was overwhelmed and short on knowledge. Of course, we're CONtractors with the emphasis on the CON. hmmm!

Know who you are doing business with!

Zman

With the radiant panels installed, you absolutely want to run a 2 temp system. Since the owner will likely fire you and bury you in the yard if you say the word mixing valve, I think injection mixing is the way to go. The common issue with injection mixing is in getting the circulator synced up with the controller. Most circs are too big and just cycle on and off rather than give even performance. If you install a balancing valve https://www.supplyhouse.com/Caleffi-132552A-3-4-NPT-QuickSetter-Balancing-Valve-w-Flow-Meter?gclid=EAIaIQobChMI1vKc07ye2gIVTGp-Ch1D5Q1pEAQYASABEgKNcfD_BwE in the loop, you can easily dial in the flow rates.

Tekmar did a great white paper on this years ago. All I could find was the application instructions http://www.tekmarcontrols.com/images/_literature/356_a_06.pdf?lbisphpreq=1. Picture your HX in place of the closely spaced tees on the system side.

I see no benefit to the extra circ and separator on the system side. I would not install them. The zone circs will certainly provide adequate flow through the HX. The HX is a hydro sep.

Harman

I am not sure why this system needs anti freeze they explained to me that they needed it because they plan on being away for long periods in the winter, where I explained to them then the entire house would need to be winterized and it kind of went no where...

I am trying to make the customer happy, not create a service nightmare for myself, and obviously make a profit for my time.

I think the last contract was over his head and maybe had an idea, but then seen that these people can be difficult, and took off with their money (my math shows even paying him well to drop the floor and mount the panels, plus buying the materials present he walked away with an additional 18k...)

I am going to try to convince them to scrap the glycol idea, I can install a wall mounted compressor with the valving to make winterizing the entire system simple, I have done this for many customers in that area).

If I do use the thermostats to control primary and aux/emergency heat, I still need to stage the boilers, and work out the heat pumps...

5 contractors walked away from this, and I will be paid well for my work, I just want to make sure I do it the best way and it would be nice to use the parts supplied, I use that same HS regularly so I have no problem taking it off their hands, and HX is kind of large, but also I can throw it on a shelf...

As far as their snow melt system, they were going to add another boiler to the pair when they decided to pull the trigger on that...

HomerJSmith

Look! You need to show them the Taco I-series mixing valve brochure and explain to them the technology behind it. It is perfect for this application. They may have had proportionally thermostatic mixing valves before and they do have functional problems especially with hard water.

You should plan to use a good quality water, DI, with the system especially mixing in anti-freeze. Yes, you are right, the whole sys needs protection. Anti-freeze at a lower temperature is going to last a lot longer than anti-freeze at 180 deg. You need to explain that anti-freeze has a life cycle and needs to be replenished or replaced.

Zman

If in fact you have non barrier tubing, everything on that side of the exchanger should be non ferrous. Pumps, air sep, exp tank et al. What have they provided? I have seen jobs where cast circs last pretty long at low temps with non O2 tubing. I have seen them eaten in a year.

I think you are at the point where you need to firm up your piping, write a control narrative, and talk to controls people. Tekmar can handle this well. They even have a nice home/away setup that activates all zones with the push of a button(even remotely).

Harman

I agree zman, I just want to do this job once...

So what if I add a 3 way i series odr mixing valve to the fphx on the boiler side, set that for the higher temperature radiant device and add another one to the lower temp on the opposite side of the fphx, that would work? correct?

Harman

but I guess at that point running 1 for each radiant system would be much easier and cost the same in materials...

hot_rod

Lots of options, as you can see.
The HX needs to be included if you have non barrier tube.

Glycol brings too much baggage if you don't need freeze protection. With furnace back up, why is it needed?

I'd use a single ∆P for the zones and zone valves or TRVs, or a mix of both. The ∆P circs are intended for exactly this type of application.

So your choice of mixing devices. With a tekmar control you get a lot of other functions, like a simple boiler protection.

With injection mixing you would need to run the boilers hotter, but with cast iron you'll want to run 150° or so for return protection. that tekmar Carl mentioned may have that function onboard.

I have nearly an identical system at my shop, multiple boilers, wood and LP, AH with HW coil, low temperature radiant.

A Caleffi mixing station, motorized with tekmar 360 driving it for the radiant.

I'd tie indirect in on the boiler side of the separator, no need to blend temperature down for that load.

I have an early version Ecobee running my AC and two stage heat, radiant and coil in the air handler. The newer versions are supposedly easier to wire up, I had to add a RIB to get my right. Ecobee tech support is good and will send wiring guide. Or a local rep if you have one may be able to help.

Tekmar reps are generally up to speed on wiring more complex systems. You could go entirely tekmar, mixing and boiler control t-stats, etc, but it may get $$.

Ideally you want outdoor and indoor feedback for reset controls. Just because it is getting colder outside does not necessarily mean you need higher SWT. Outdoor temperature influences, not dictates heat energy required to maintain comfort conditions.

Harman

Im going to check that tubing myself, its a brand I am not familiar with, if it is non barrier, the fphx is staying if it isnt I will not install it..

HomerJSmith

I would use Taco I-series (temperature control valve) with outdoor reset with a ECM pump on the panel rads with the TRV's and a Taco I-series (temperature control valve) on the infloor with a ECM pump if they are zones separately with balancing valves to control flow and Caleffi zone valves or thermo-actuators connected to the thermostats for each zone to shut each circuit down when the thermostat is satisfied.

If the 3 infloor radiant panels are on a single thermostat and operate as a unit, I would use balancing valve on each circuit and a fixed speed pump that is controlled by the single thermostat with a Taco I-series (temperature control valve).

It is ok to use what's already there, but system functionality is what is important.

SuperJ, I like the way you think! (call it a temperature scheduling valve instead of a mixing valve to keep the HO happy ).

So, the manifolds are already there? and they are six circuit manifolds? Then, there's a problem with different temperatures for the infloor radiant panels and the radiant panels with the TRV's. What's on top of the infloor radiant panels, tile, carpet, or wood flooring.

Harman, you have to decide your heat load requirements.

ratio

If they still balk at the mixing valve, maybe you could offer them an extended warranty on it, something like "10 years parts and labor on the valve itself, IF you have us do the maintenance on the system."

Harman

I am leaving the office now, going there and going to talk to the home owner, they are both home, so I will see what I can accomplish, and I am going to personally check the tubing, because my tech that was there this morning and checked it, may not have understood what I was asking him...

hot_rod

yes, lose the HX if possible, that clears up a lot of the piping.

Boilers as you show, hydro sep, one hi temp, one mixed temp, ∆P and valves.

SuperJ

To simplify and reduce mixing valves.
You could inject on the primary side of the fphx to get down to the panel rad temperature and then use a single mixing valve for the infloor (off of the medium temp panel water) . The less desirable alternative is another injection pump for the infloor.

hot_rod

Without a load calc and design it would be hard to know, but IF you could run the panel rads and radiant at one SWT, it simplifies it as SuperJ mentioned.

SuperJ

I was actually suggesting 3 cascading temps (possible with some sort of ODR where applicable):

1. BoilerPrimaryLoop(180F-160F)
   
2. InjectionPumpFPHXPanelRad(170F-120F)
   
3. InfloorMixValve(120F-90F) (the source of this would be the Panel Rad Loop)
   

But agree this is all constrained to the design/load calc.

Mark Eatherton

Does the DHW storage tank have heat exchangers in it? Because if it doesn't, you shouldn't pipe it directly as drawn. Cast iron doesn't like oxygenated water... And I agree with the others in that you "inherited" someone else's problems, and if you don't want them to become yours, do a full blown load calc so you will know where you stand. If it's wrong, you own it for life. Otherwise, have your attorney write up their contract....

ME

Harman

OK, so I had a meeting with the HO's, 2- things 1 I checked the tubing and it is barrier tubing. And I explained to them that they are spending real money to get this job finished. We went over the anti freeze situation and they agreed and OK'd me to install an integrated compressor with winterizing valves.

I explained to them I will do the system to work and it doesn't make sense to build it on a crippled design.

I am doing a manual J and going to figure out the loads for each zone.

I think the original contractor figured he was putting every room on its own thermostat, and was going to run all the radiant even the panels at 1 temp, since the panels are all on the top floor in the bedrooms and are going to be pretty easy to heat, the radiant is on the first floor and the baseboard is in the basement, the basement and first floor have duct work off of furnace 1 and the second floor has dw off of furnace 2.

Now I am kind of left starting over in a way, if I was doing this job from the start I would do reverse return system with a mixing valve on each zone of radiant, and for the wiring I would install a simple adjustable make on delay relay on boiler #2, set that at 8 minutes (example) so that if boiler 1 didn't satisfy the call for heat in 8 minutes it would call in boiler 2. and thinking about it I could probably do the same thing with the furnace, if boiler 2 doesnt satisfy the call in 10 minutes the furnace kicks on, but doing all of that through the thermostat is just as easy... I know this wont exercise or alternate the boilers, but it seems the staging controls out there are so expensive and over built for a situation like this.

I am interested in installing just 2 mixing valves and using the ODR series I 3 ways from taco, I am going to look into that some more, do you guys have good luck with them?

I would love to take this opportunity to learn how others would tackle this piping configuration...

Now with this new situation what do you think my best course of action is? thanks guys

heres a quick drawing of how I would do it if I was starting from scratch, dont worry about hurting my feelings, lol, tell me where I can improve it... (normally I would do a separate mixing valve on each radiant loop, but them i series are $$$ I think the system will work this way...)

hot_rod

Really 10 circulators?! For maybe a 120K design load?

Why not zone all the floors with ZVs and the panel rads with TRV and use a single ∆P circulator on each? Drop 4 circs and get better control.

With TRVs and ODR you will get near continous circulation, very even and efficient way to move energy.

TRVs are non electric, proportional valves, ideal for ∆P circulation. Giver the owner individual radiator temperature control, even a freeze protection mode on most TRVs.

Harman

Problem is theres 3 cases of delta t circs there, what do I do with them, lol...