Hydronic oil boiler replacement advice

going_commando

Hey guys, long time lurker first time poster. For reference about me, I am an electrician by trade, but have some experience replacing/fixing oil boilers through the family business. My Dad has done quite a few oil boiler swaps and such, we've worked on industrial boilers (steam Dillon, Cleaver Brooks, and Hurst wood chip) and I've helped over the years and am comfortable with piping and things. Ive been researching hydronics for a few years (with much information from this site and Dan's books) first from curiosity and then from buying a house (West central NH) built in 1908 with the finest of 1964 technology Rheem 6 section oil boiler with a beckett burner retrofitted, and an axeman Anderson coal stoker boiler with a full coal bin sitting off in the wings not running.

Anyway, about my system, I decided it was time to retire the drastically oversized (limit operated, not cold start) Rheem. We downfired it when I moved in to 1 gal/hr (.8 nozzle at 140psi iirc), and it had heated pretty well in that time. As the house is a duplex (up and down), I have 2 zones. We live on the main floor with mostly copper fin tube with a 3 cast iron radiators mixed in, and a mess of piping. I am going to remove the cast iron and replace with copper fin tube so its all the same, and the cast iron radiators will go to my basement to make up for the added thermal efficiency of the new boiler. I did a heat loss via the fuel used and degree day method, and it came out to 60k something btu, based on the mild winter we had last year. My current tenant likes it cold, so I want to add some buffer. Also, for information sake, when it dipped to -20 a couple winters ago the boiler would shut off for about 2 minutes per hour, and made me feel like a 1 gal/hr firing rate was pretty close to accurate for extreme cold.

With that in mind, I am replacing the oil boiler. The old one is gone, I am going to split my unit to 2 zones, I did zone flow calcs based on the fuel use load calc, a CoolCalc load calc (which is dubious on houses this old, but is good enough for mini split sizing), and am going to do primary secondary and have the secondary side figured out (I want to be able to use the coal boiler so P/S seemed like the best way to pipe it). My boiler options that I am considering from supply houses are Purepro Trio, Viessmann Vr1, Peerless, and maybe Buderus. All except the Buderus are about the same money, and all use the Hydrolevel 3250+. I have been looking at 1g/hr firing rate boilers based on the super cold experience. After reading a lot here 3 pass boilers seem like the way to go, but basically I'm struggling choosing between the Trio with its super low water content (4.something gal for the 4 section), and the Viessmann with its 12ish gallon (vr1-140). Won't the super low mass boiler short cycle like crazy on less than design day conditions? I know shorter run times will happen for most of the heating season, but I put in a Fujitsu mini split system to carry the place for the shoulder seasons, so the actual outdoor temp when the boiler needs to run is when it's below freezing.

I apologize for this being so long and rambling. I've been trying to pick a boiler for a few weeks now and decided it was time to ask for help. The amount of info I've gotten from this site is priceless. Also, before someone says call a pro, I have done this work professionally, though not my full time trade and the guys around here just slam in same for same and throw a 007 on every zone and call it a day. I am capable of installing it myself, and have all licensing required by the state. I want a more efficient, better oil hydronic system. Thanks in advance for all advice and recommendations given, I do truly appreciate the knowledge base on here.

Big Ed_4

I like a simple boiler then add quality . I would go with a …push nipple construction cast iron , three pass boiler..Add the out door reset well worth it …

HVACNUT

I'm a fan of the Buderus G115 with the Riello, but a 3 pass for sure. The Peerless is the WBV?

I'm a little confused how you got a 60K BTU heat loss, but looking to fire 140K input.

going_commando

My confusion with the load calc is comparing the firing rate of my old boiler when it was 16 degrees below design temp versus the load calculated from oil usage and heating degree days. I suppose that's silly and an easy way to oversize my boiler.

I will also be adding heat to my uninsulated rubble stone basement to make up for the loss of heat radiating off the old beast of a boiler with maybe 1" of insulation. I havent done a heat loss on that yet, but don't imagine it to be much.

going_commando

Also, yes, the Peerless is a WBV.

going_commando

https://forum.heatinghelp.com/discussion/comment/1810100#Comment_1810100

Do you have any other boiler recommendations I should look at? I have practically every brand available (minus EK) between FW Webb and Plumber Supply Company.

pecmsg

https://forum.heatinghelp.com/discussion/comment/1810114#Comment_1810114

You don't size for the below design days.

Our design here is +5°F. Does it get to zero and below, yes rarely. Not worth being oversized the other 99% of the time.

Jamie Hall

Here we go again. How big a boiler do I need? It's not rocket science, folks. Some say by fuel usage. Some say by a Manual J using the design day. Some (me) would say, if going from scratch, a Manual J using the known low temperatures reached (which, as I've said before, can be startling different from the Fed's design day — unless you happen to live at the weather station). @going_commando has the ideal situation: he knows what the old boiler did on the colder days. If you have that information, it's easy: did it keep you warm enough, and how much of the time did it run vs. how long was it off to do that?

You can do the arithmetic on the back of an envelope.

If it was running pretty much non-stop, it wasn't oversized. End of story.

In some defence of the "use the design day" theory, it's much the same as the "use natural gas" theory: if you are in an urban or suburban environment, you are probably near enough a weather station reporting location so that the Federal design day figure is reasonably valid. If you are in a rural area, it's not. Use local knowledge, if it's available.

clammy

For oil i have to say buderus ,when i did oil the company i work for switched to buderus for a few years . i will have to say they were the easiest to service and install w piping out of the rear of the boiler makes it easy to pipe everything to a wall 'also front swing door for cleaning and baffles and lets no forget leveling legs no shimming bull . i would say that from a few years in the business that p/s piping using a low limit aquastat to control boiler pump may seem over the top but for oil boiler w low water content that heat quickly its not a bad idea and the costs are not over the top as compared to the results and how clean the section stay from not seeing any low temps on the chamber side and ensuring proper flow through the boiler regardless of system gpm . One finally note about low water content boilers is water quality ,high tds will limeout a low mass boiler so use demineralized water to get your tds down to a proper level and also add a inhibitor like sentinel products . i ve looked at the trio 3 pass and there very similar but in my eyes buderus does the best cast iron . there boiler blocks always look fresh with out a layer of rust gotta respect that gl cast w silicone . A final note is that out of all the boiler i ve ever install my hats go off for buderus and the ease in hand trucking there boiler and the packaging where thought is given to the guys lugging it into a basement ,no de crating no unboxing and no bs over sized crate and a stinking pallet that 99% of the supply houses will not take so your stuck getting rid of it total nonsense . i think ever one was left in the box and hand trucked right down the basement then un boxed and taken off the wood w the exception of the g215 . If only american boiler manufactures did so instead of usually dis assembling the jacket and stripping it down to the block not to damage the jacket to get in the basement what a pia and waste of time .

As for most american oil boilers all i have to say is look at where the come from and look to who has had a higher fuel cost in comparison to the usa historically . That alone should cast some light onto the subject .In closing any thing less then a 3 pass on oil is just wasting oil up your chimney ,the days of pin oil boilers should be outlawed when i comes to oil .

peace and good luck clammy

going_commando

https://forum.heatinghelp.com/discussion/comment/1810121#Comment_1810121

That was my general thought, but then I started questioning myself. I could have used a bit more heat, but the boiler was making 200 degree water (I turned it up a bit for some extra boost) and it ran for all but 2 minutes or so an hour. The radiation could do 64 degrees inside my unit instead of 68, but that wasn't the boilers fault. If I tighten the place up a bit (namely the basement) then I should be able to tighten that up a bit.

Basically, what I didn't phrase well, was comparing the super low mass boilers like the Trio which are less than 5 gallons to a Buderus, Viessmann or the like at about 12. The higher water content would reduce burner short cycling, I think. I've installed a Buderus, but I've never messed with something as small as the Trio other than an EK, but my feeling is they aren't as forgiving to sizing and will have more short cycling of the burner since most of the year is less than design conditions, so it will cycle 3 times as much as a higher water content boiler. Outdoor reset seems like it would exacerbate that condition with the lower high limit, but I don't have personal experience with them. Is this the case? Right now I'm leaning heaviest towards the Viessmann VR1 as a balance of price and water content, while being 20% less than a Buderus, but I am still intrigued by the Trio.

Greening

We live in a similar climate in an old, somewhat insulated house and replaced a WWII era boiler with a low mass boiler (EK). A few observations:

0. No short cycling. Our oil man/neighbor/friend did a great job of properly sizing the system.

1. Biggest savings might be in the summer. Low hot water costs. Basement is colder, so significant reduction in AC demand.

2. Consider a fresh air intake. That made our house a lot more comfortable as cold, drafty air was not being sucked in all the cracks around the house. And conditioned air was not being sucked into the boiler and blown out the chimney. There will be requirements pipe diameter, outside height, inside alternative damper (e.g. for snow blockage), etc. It also boosts efficiency and reduces noise on the EK.

3. Basement became significantly cooler year round. Now pretty tight in 55-65F range, with a few weeks a year outside. Our concrete basement is quite deep in the ground so there is some natural insulation which you might not enjoy. We don't have any heating installed in the basement but it is used as a workshop / exercise room so those temps are fine for us. The exposed heating pipes in the ceiling provide some heat.

4. Some "inefficiencies" of the old boiler were "free" basement heating rising to the first floor.

5. We added some zones. People at home loved the ability to tweak temperature to their liking. In our case, we also keep upstairs zones around 60F. Generally, second floor is kept warm by rising heat from the first floor.

6. Figure what you will do with hot water. Put on a mixer for safety and get "more" hot water time. We have a 40 gallon stainless tank connected to the oil burner; I don't think that would be enough for 2 units but others will have a view.

7. If you consider a modern electric hot water system based on NH subsidies but you might need some electric upgrades too. That will cool and somewhat dehumidify the basement. It also might change your oil burner strategy.

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1810254#Comment_1810254

I believe the OP said he doesn't have access to EK. It's a DIY job.

going_commando

Yup, no EK, I am doing it myself and I don't particularly like them and don't get along with the local "qualified" installer. I also didn't mention I already have a 65 gal Ruud hybrid water heater that has been working great, but I am going to add a ball valve for a future zone for an indirect if I feel like it, but the Ruud works pretty well. Previously there was a tankless coil that only fed 1 bathroom, but I discontinued it when I put in the Ruud.

I got a quote on a Viessmann today, and going to get quotes on a Trio and a Buderus from Webb tomorrow.

SuperTech

Thats a shame. With oil EK would be your best option by far in my opinion. The Trio is a nice boiler,all the three pass ones are good, provided they are sized and installed properly.

Greening

I know OP doesn't have access to EK. But I think he might find some of the comments useful with any "low mass" boiler.

HVACNUT

https://forum.heatinghelp.com/discussion/comment/1810317#Comment_1810317

Apples and Oranges. A typical low mass oil boiler moves water through the boiler AND the heat loop(s) on a demand, where with the EK Frontier, the heat loops stay off until boiler temperature reaches 140°. The boiler circulator is running, but there's a bypass on the EK, where a typical oil boiler there is no bypass, unless piped and wired for P/S.

going_commando

The Hydrolevel hydro stat has a setting if I remember right so the boiler pump ( I am doing primary/secondary) won't turn on until the boiler is at 125 or 140, can't remember the exact #. I believe it also has a post purge option, so with a couple relays I could make it so it post purges into my basement for extra heat by opening a zone valve or circ (haven't done flow calcs on my basement loop yet) when no other zone is calling but the boiler pump is running. That way the heat gets dumped into my basement instead of going up the chimney. Either that or let it circulate through the 1-1/4 boiler pumping through the p/s and just using the piping as an emitter. That's something I can play around with.

Insulating my basement is on the list of things to do, but I have to finish rewiring the house, fix some rot in sill beams, add a capillary break between the brick above grade foundation and sill beams, repoint and parge the exterior brick and then have a couple inches of closed cell sprayed over a dimple mat inside.

I will also look into piping in makeup air. That is a good suggestion for sure.

HVACNUT

If you're doing P/S piping with a Low Mass boiler, the boiler circulator must be energized any time B1 is energized in the 3250 Plus. (There should actually be an interlock flow switch, so the burner CAN'T run if the boiler circulator isn't running.) You would then utilize the Circulator Hold Off feature at C1 in the 3250 Plus, and wire it to ZC (remove jumper) in the zone panel to hold the system circulators off until the boiler makes temperature.

With a High Mass boiler and P/S, you would (could) do the opposite. Keep the boiler circulator off until the boiler make temperature, and just let the system circulators run on a demand.

going_commando

Interesting, makes sense.

I actually found a really good deal on a New Yorker 3 pass cast iron that holds 12 gallons ish of water, which should be perfect for what I need. Since I have heat pumps for the shoulder seasons and a heat pump water heater, the low standby losses of a low mass boiler are kind of lost on me since I want heat in my basement anyway, but a 3 pass gives me the easy cleaning and efficiency gains and the price is right.

When I eventually insulate my basement I've been toying with the idea of adding a plate heat exchanger on my water heater and dumping the residual heat in the boiler after a call to heat is satisfied with some relays and such, but thats down the road.

Thanks again for all the help, guys.

Steamhead

If that New Yorker is what I think it is, it's the same basic boiler as the Burnham MPO. Very nice unit.

going_commando

Its the ci-hgs, so that is what I was hoping. From what I could dig up about it, it sure sounds like a solid unit, that should last many years, properly cared for.