Redoing my boiler setup. Wondering if I should swap the zone side...

rsilvers

I am new to this but have been reading a lot, including the book Pumping Away. I am also studying for my state burner tech license.

My home came with a 1984 oil boiler and I plan to replace it this Spring with a Buderus 115/5. My current one is using a 0.75 nozzle at 140 psi for 22 minutes per hour average when it is 28 degrees out and every zone is set to 68. I think that means that at 0 degrees F (target in my state), I need 63,000 BTU gross or 54,000 BTU DOE to have the production match the loss. Arguably I could do this with a 115/3 that ran almost non-stop. It is a 3800 square foot 1984 house with lots of windows and it seems hard to believe the smallest 115 is appropriate for it. My experienced friend advises to not downsize and to just use an outdoor reset, which virtually downsizes the system. Not sure if I should go down to a 115/3 or 115/4 or do the 115/5. I will use a HydroLevel Primary with outdoor reset. Also I could change to propane, which would allow for a generator later. I believe after one factors in efficiency, oil and propane are the same cost.

Also, since this home has no AC, I plan to add about six minisplits and probably solar electric, so that can heat most of the time and the oil can be cold-day or emergency backup. I am getting heat-pump quotes now. If the minisplit works most of the time, not sure standby losses of an oversized oil boiler matter much.

Thirdly, I currently have the resistance hot water electric not in the loop and will replace it with a heat-pump water heater, and then not use the oil at all for the on-demand hot water.

I am going to put in a Taco 6-zone controller soon which will clean up the wires, and replace the purge valves with new style ball valves or maybe just shutoffs and have a single purge as-per Pumping Away's suggestion. I will replace the corroded shutoff as soon as the freezing weather is past.

But here is my major choice - do I leave the system plumbed as-is, which has the zones and the circulator on the return, or should I get more ambitious and change the zone valves to the supply side by raising them as high as possible, put a circulator just below the zone manifold, and then put the expansion tank, bleeder, and feeder at the point of no pump pressure just before the this new circulator location?

And finally, this system will have anti-freeze, so should I use a microbubble or not? A really good tech told me they clog up with anti-freeze.

Thank you for any advice.

Oilmon

Those old Vaillant boilers give really good numbers, but were kinda a pain to service. I suggest following the "Pumping Away" schematics exactly. I would also suggest moving all of your distribution over to a wall for easier service. Come off of the boiler supply riser to a high tee with a single boiler drain on top. Branch to a full port ball valve for isolation, then Spirovent (only one that works properly, imho) hang Filltrol (combo exp tank and pressure reducing valve) under Spirovent, pipe in a fast fill line as well to a tee between filltrol and Spirovent, then your circulator, then your distribution manifold replacing the wax element Taco zone valves with ball valve type (Taco zone sentry) On return manifold you only need ball valves to isolate each return run and thats it! I would also suggest piping in 1 or 2 additional stubs on your supply and return manifolds for future zones. An indirect water heater is a phenomenal addition to this setup as well. That would pipe in closer to boiler to reduce piping losses in warmer months. Vaughn makes an excellent Poly tank indirect also the Crown Mega-stor. As far as the boiler size, larger heat exchanger area can result in higher efficiencies with downsizing firing rates to match load as long as you dont start condensing. If you want, you can run a bypass loop from supply to return to help boiler tenmperature rise faster.

rsilvers

I was going to use an electric heat pump water heater instead of using oil for heat. I like how in the winter, they suck up the waste heat from the boiler. And in the summer, they cool the room. Also they allow full boiler shutdown in the summer, and we have an $800 rebate I think.

Tell me more about Zone Sentry - I am redoing my main house with a new G215/5 and was wondering if there was some zone valve I should use instead of the old Taco type.

I would like to see some wall setup photos I do have a plywood wall to the right.

HVACNUT

I haven't seen a Valiant in a long time.
All piping gets cut back to the ceiling. All new piping and controls using the pumping away method.

You don't mention if you did a heat loss calculation. You state you need 63K gross, 54K DOE. Based on what?
The net IBR of the G115/3 is 74K. With 3,800 sq ft of heated space, that's almost 19.5 BTU per sq ft. 
The G115/4 will get you 25 BTU per sq ft.
What is needed on a design day?

rsilvers

HVACNUT said:

I haven't seen a Valiant in a long time.
All piping gets cut back to the ceiling. All new piping and controls using the pumping away method.

You don't mention if you did a heat loss calculation. You state you need 63K gross, 54K DOE. Based on what?
The net IBR of the G115/3 is 74K. With 3,800 sq ft of heated space, that's almost 19.5 BTU per sq ft. 
The G115/4 will get you 25 BTU per sq ft.
What is needed on a design day?

I made a spreadsheet - see if you think it is valid:

https://docs.google.com/spreadsheets/d/1jeEkgDuzsHiapVdd8wcwvakTbBitY6Qri2MMCHELKJg/edit?usp=sharing

Based on my boiler having a 0.75 nozzle and running 22 minutes per hour when it is 28 degrees out at 80 percent efficiency and with all zones on 68 degrees and stabile (run overnight) and then converting that to 0 degrees out at 86% efficiency.

I later learned that one should multiply the BTU at equilibrium by 1.4 to 1.7. So really I need more like 75-90 DOE. I think that means G115/3 or a G115/4 is best. Does that make sense? It's 3750 square feet in MA with lots of windows and mostly 1984 insulation - though the attic is well insulated.

Also, my radiators and/or pipe diameters are not shedding heat quickly, so having as much boiler capacity as I do is wasted.

rsilvers

I am willing to do new piping and controls, but not sure how to lay this out on a wall.

Also note that I will take the hot water out of the on-demand oil and use a heat-pump hot water heater. I like how they use boiler waste heat in the winter and cool the room in the summer. Also I am probably getting solar. Also, if I get solar, I may use the oil as backup and use the electricity capacity for many miniplits since this place has no existing cooling.

rsilvers

I have a ProPress tool and want to use it. I just need to come up with a wall-based layout plan. I am trying to see if I can design it in Sketchup, Revit, or FloPro - not sure which tool has a nice library of real parts.

rsilvers

Should I use copper or Pex? I believe the first 18 inches of pipe to and from the boiler has to be metal. I was going to do copper if this was just fixing a few things, but if this is a re-do, wouldn't it make sense to use Pex?

rsilvers

Would you recommend I add a sheet of plywood to the back block wall and then build on that (after moving the water heater). Or would you build on the existing plywood on the right? I assume the new boiler would go in the original location as that is where the duct is.

rsilvers

Is it really worth scrapping these zone valves and spending $800 on six new Zone Sentry ones?

NoelAnderson

Her is a picture of a job that I used a Cross Manifold from supplyhouse.com. I piped the expansion tank in after the return manifold in order to use the boiler as a giant air scoop before the Spirovent air and dirt separator.

rsilvers

My head just exploded. 

I have to get something like that. 

rsilvers

Just 6 Taco zone valves costs as much as that entire unit, and with the manifold you also get the manifold and gauges and the zone controller. Wow. It's like $1200 in stuff for $770.

Only a 1 inch connection though. Does it limit BTUs if the 1" portion is short?

rsilvers

I see 1" copper pipe is supposed to be good for 104KBTU. The G115/4 has a 1.25 inch connection. Would I be limiting it by using 1 inch pipe to the manifold? Might be 6 feet or so in and out.

NoelAnderson

Have you done a heat loss on your house? I doubt it needs as big of a boiler as what you think. The Slantfin calculator is free and very easy to use. I find it even oversize's the heat loss a little bit. Also with multi zones you can get away with a smaller boiler, since you very rarely have all zones running at the same time. Every boiler I have replaced I have cut the input by half and never had a call back for insufficient heat.

NoelAnderson

The G115/4 looks to be under 100K BTUs, which would be fine with 1" copper. The little Slantfin boiler above is 60K and comes with 1.5" connections which I bushed down to 1" copper.

NoelAnderson

This is the boiler that was replaced by the Cross manifold.

DJD775

rsilvers said:

Just 6 Taco zone valves costs as much as that entire unit, and with the manifold you also get the manifold and gauges and the zone controller. Wow. It's like $1200 in stuff for $770.

Only a 1 inch connection though. Does it limit BTUs if the 1" portion is short?

That looks like a slick product but I would be a little nervous investing that much money in a unit that requires proprietary parts to operate as a whole. if that unit goes down in the middle of heating season will parts be readily available? I personally would prefer the Taco route (or any other competitive brand) as you can mix and match zone valves, relays, etc. in a pinch.

rsilvers

It's a very good point, but I can take the risk as I will have a minisplit heat pump in every room and anti-freeze in the hydronic pipe.

rsilvers

I talked to Cross and the guy suggested I do a primary and secondary loop. This is on page 85 of Pumping Away. He suggested a Grundfos Alpha automated variable speed pump for the secondary loop, and a normal pump on the main loop. Not sure if the Alpha is worth it as it is 3x the cost of a Taco fixed rate pump. Ideas?

DJD775

The alpha pump has the advantage of being able to adjust it's performance based upon how many zones are operating. Are you sure it's 3x more? I was looking at circulators recently and I would say less than 2x based on memory.

rsilvers

NoelAnderson said:

Have you done a heat loss on your house? I doubt it needs as big of a boiler as what you think.

It's a 1984 3750 square foot house in MA with lots of huge glass windows and skylights. I did a test where I ran my existing boiler with a 0.75 nozzle at 140 psi for a 0.89 firing rate. It was 28 degrees out, and it ran for 19.4 minutes per hour. That is 32,000 BTU to maintain. Adjusting for a 0 degree day, that works out to 54,000 DOE BTU (assuming new boiler is 85 percent efficient and old one is 80 percent). An excellent blog post said to multiply that by 1.4 and no more than by 1.7. So, I need between 76000 and 92,000.

That would imply that a G115/3 is perfect at 85,000.
I was planning to get the G115/4, which is 109,000 and then use an outdoor setback primary to reduce the output. The price difference in these two units is tiny, and it's hard to believe my large old house needs the smallest unit they sell. But maybe the G115/3? How much of a big deal are standby losses when the heat goes into the finished basement anyway? And why can't I slightly reduce it with a smaller nozzle if I want to?

Also, the smallest one is slightly more expensive for some reason, and a longer lead time. So what do you think? I am very open to advice even if it sounds like I am pushing back. I still listen and learn.

https://www.bosch-thermotechnology.us/ocsmedia/optimized/full/o416400v272_Bosch_Oil_Boilers_(G115_&_G215)_06-2021.pdf

DJD775

Few quick things to consider. Standby loss means you are also loosing more heat up the chimney. As NoelAnderson already mentioned in a zoned system rarely are all zones active simultaneously.

rsilvers

Ok. The smaller unit is $300 more than the larger one. I asked why, and they said it was more in demand.

Another thing I have to consider is that my state has a $2300 rebate for propane boiler and $0 rebate for oil boiler. That is enough of a difference to get a tank put in and then have the ability to have a propane generator later. Also way less cleaning.

rsilvers

Looking at 30 year, 10 year, and 5 year oil vs propane in my state at average retail prices, and adjusting for cost per million BTUs assuming the oil boiler is 87% efficient and the LP burner is 95% efficient, oil wins at about 70% the cost of LP per heat unit.

NoelAnderson

I would always go with the smaller boiler for efficiency. To let everyone know I am not a HVAC contractor, my profession is a Manufacturing Designer by trait. I have been installing boilers since 1997 when I found out none of the HVAC installers around me knew anything about hydronics and would push people into scrapping their boilers out for forced air. Back then the HVAC contractors would say I was doing it all wrong because I did not put the pump on the return side of the boiler and that my indirect water heaters were illegal because you are not allowed to mix domestic water and boiler water together. They also put down my work because I would used Wirsbo PEX and Tekmar controls which they said they were "Tits on a boar hog" and they would never trust plastic pipe. As for the Cross manifold, coming from a designer point of view I think they are constructed extremely well. I researched Cross out as a company and found their customers felt Cross stood behind their products if there was a problem. Even though in the HVAC industry the stepper/servo motor is new to the market it has been well adopted in my field for decades without problems. If I was to have a problem with the Cross manifold, I would remove the servo motor by unscrewing the two hand knobs and manually turn the valves as you would with zone valves until I got a new motor. I also like the fact that it uses no power except to open or close the valves unlike zone valves and I can power purge the air out of my zones using the shut off and drain valves on the manifold. I agree with Cross about using the Alpha II pump, on Auto adapt mode the system uses less than 25 watts of power. Just make sure you use a magnetic separator in front of the pump. With the Hydrostat and a cast iron boiler running baseboard convector I don't think you need primary/secondary plumbing. I just use condensation protection along with thermal targeting on the Hydrostat, no outdoor reset needed. One thing I also should note, my friend was talked into buying a heat pump to use on his home and to use his steam boiler as auxiliary heat. He found out very quickly that the comfort of the heat was not the same and went back to heating with his steam boiler solely.

rsilvers

Forced air is not as good as water. I think I knew that for a long time.

The math is such that oil is beating heat pump, but I am probably adding solar, If I do, it would make sense to use the heat pump as long as I had excess power.

If I do this, I am using barrier Pex-A. I made a spreadsheet and it would be about $400 less than ProPress copper, and that is enough to get me the Milwalkee tool for free. Plus the flexible lines make alignment much easier.

Ok, on the loops.

I just got a quote for $39,000 for 8 tons of minisplits. That is 11 head units and 4 compressors. There is a $10,000 rebate. I want this as there is no AC there now. No rebate if self-installed. Waiting on three more quotes.

DJD775

Make sure you do a load calc for the AC as well. 8 tons seems excessive. I have 3.5 tons for 2500 square feet in RI and I could have gotten away with 3 tons easily on the warmest days. Hardest part is finding competent installers willing to do load calcs.

NoelAnderson

Cross manifold carries fittings for Pex-A for their manifolds. Also do a search for what it takes for maintenance for minisplits, you might be surprised. I also agree 8 ton seems excessive. My house is 105 years old, original single pane double hung windows with counter weights, 6" attic insulation, and 2100 square feet. I have a 2 ton dual stage outdoor unit and keep my house at 64-68 degrees in the summer. It is very rare for me to even come off of the first stage.

NoelAnderson

DJD775, this was my first Cross insulation. As I said I was very impressed with the quality of the manifold and the price for every thing it comes with. The temp gauges are in wells, so no need for draining the system to replace them. All the valves are ball valves and they come with flow meters and fittings. When I went through the reviews, people had positive comments when dealing with Cross's tech support, who would even send relays to them for free when they didn't realize they needed to buy them initially. As I said I have no problems using servo motors, they have been around for decades now. On the Cross manifold the whole servo drive can changed out in less than 5 minutes without tools, and I can manually open the valves if needed. If worst came to worst and I could not get replacement parts, I would just cut the pipes above the manifold and put zone valves in there leaving the manifold valves open and use a zone controller.

DJD775

@NoelAnderson It does look like an attractive system for the price and doing some research it looks like a reputable hydronic manufacturer. For me as a homeowner and not a pro I prefer to have things as simple as possible. As I said recently in another post I rather have a cast iron oil boiler where I have few proprietary parts as compared to a gas mod-con that is pretty much all proprietary and if for some reason I have continuous problems I'm tied to using their system and parts. I do have a small HVAC company do tune ups but I do most of my own repair and emergency service. I have an extra aquastat, circulator, 24v transformer, ZV head, and some burner parts on hand. Most of the parts except for the burner parts are known good used parts. I guess it just comes down to what you are comfortable with.

rsilvers

DJD775 said:

Make sure you do a load calc for the AC as well. 8 tons seems excessive. I have 3.5 tons for 2500 square feet in RI and I could have gotten away with 3 tons easily on the warmest days. Hardest part is finding competent installers willing to do load calcs.

Ok. I actually had three large window units and they worked fine for their respective large rooms, so I will see what those are. This is 3750 square feet. 6-6.5 tons should be enough but partly it's an issue of the sizes that are available. Each of the four condensers may be 1/4 ton larger than needed due to what they make (for example, I may need a 1.75 ton but only a 2.0 is available), but that may mean I end up with 7.5 ton even if I only need 6.5 ton.

rsilvers

NoelAnderson said:

Cross manifold carries fittings for Pex-A for their manifolds. Also do a search for what it takes for maintenance for minisplits, you might be surprised. I also agree 8 ton seems excessive. My house is 105 years old, original single pane double hung windows with counter weights, 6" attic insulation, and 2100 square feet. I have a 2 ton dual stage outdoor unit and keep my house at 64-68 degrees in the summer. It is very rare for me to even come off of the first stage.

My state has zero rebates for central air, and $10,000 rebate for heat-pumps. I am planning to put in solar, and if I do, I want a way to use electric for heat. If not mini split, I would need a central heat-pump. Those need ducts - which would mean having to add ducts and new drywall covers to my finished basement. I don't have a real attic and only a crawl space up there with a small access hatch. Putting air handlers up there would be very hard to get them in, let alone service.

So, even if 4 ton is enough for cooling, which is possible if not likely, I may need 7.5 ton just to cover the heating load.

DJD775

I you have another source for heat I would not size your heat pump for the heating load. Oversized AC does not effectively remove moisture due to the short cycles. When I first moved into my house I had a 5 ton central unit. Cooled great but it would never dehumidify properly. I personally would rather have it slightly undersized and get fantastic dehumidification and slightly higher temperature.

rsilvers

DJD775 said:

I you have another source for heat I would not size your heat pump for the heating load. Oversized AC does not effectively remove moisture due to the short cycles. When I first moved into my house I had a 5 ton central unit. Cooled great but it would never dehumidify properly. I personally would rather have it slightly undersized and get fantastic dehumidification and slightly higher temperature.

Fair enough but let me run two complications past you... If it was 0 degrees out, the heat pumps may not be working well and I would be using only oil I think. Also, they raised the price (due to inflation) for the smallest one, but didn't get to the mid-size one yet.

rsilvers

Ok, I placed an order for the Cross kit and for the smaller G115/3.

They very recently raised the price at SupplyHouse for this model, and so it was actually about $300 more than the larger one!

But I noticed that they didn't yet change the price in their computer for the boiler without the burner. So I added the boiler without the burner to my cart, and then added the burner assembly - and that came to $517 cheaper than getting them as a package.

DJD775

rsilvers said:

DJD775 said:

I you have another source for heat I would not size your heat pump for the heating load. Oversized AC does not effectively remove moisture due to the short cycles. When I first moved into my house I had a 5 ton central unit. Cooled great but it would never dehumidify properly. I personally would rather have it slightly undersized and get fantastic dehumidification and slightly higher temperature.

Fair enough but let me run two complications past you... If it was 0 degrees out, the heat pumps may not be working well and I would be using only oil I think. Also, they raised the price (due to inflation) for the smallest one, but didn't get to the mid-size one yet.

I'm by no means an expert on the new high efficiency heat pumps and their lower threshold for efficient heat but I would assume set the system up almost as a hybrid system where the heat pump can work down to temp X and any lower the oil boiler would take over. I rather a have 1 proper sized heating and 1 proper sized cooling system than 2 proper sized heating systems and 1 way oversized cooling system. From your previous post it sounds like you are choosing going the heat pump route solely because of the rebate. if that's the case and you would have gotten AC only without the rebate, size to the AC load. At the end of the day it's personal preference.

rsilvers

I would say I am going heat pump because I plan to get solar and need something to consume electricity that will also save burning oil. 

With my electric rates of 0.27, oil is 30 percent cheaper than heat pump. Heat pump is equal to propane and no longer makes sense unless you have excess solar capacity. 

Ductless is often 21 or higher SEER plus more control with more zones and no ducts in the attic to absorb heat. 

I do not need to do as I said and get lots of BTUs just for heat because I won’t use it if it is very cold anyway. So I can go down in size. 

Maybe my bedroom and kitchen can be 9,000 and 9,000 instead of 12,000 and 12,000 like the quote has. I have a window unit DOE 9500 in the bedroom and think it cooled the room ok last summer. 

rsilvers

This is what I have so far. I know there must be a better way to lay it out, so I am open to suggestions.

Zman

Does your boiler have a minimum flow rate? I am not sure you need two loops, you might be able to just do a mixed loop with a 3 way mixing valve.
I would like to try to talk you out of PEX for the near boiler piping. The factual reason is that it has a much smaller inside diameter than copper pipe. My personal opinion is that it looks really unprofessional.

SuperTech

Please don't use pex on the near boiler piping.  Make the connections from copper to pex out of sight, up in the joists.