Need help evaluating a contractor/hydronic heat boiler plan

Katmar

A couple weeks ago I posted a long story about my struggle to find someone competent to address my leaking boiler and partially-unheated home in Albany NY: gas-burning hydronic home with a 15 y o Buderus modcon.

(TLDR: three big hvac companies have gjven me conflicting advice, some of it flat out wrong, and high estimates. Consensus that I just need a good contractor. Update: The contractor @leonz suggested is not answering his phone; I did find a local contractor who specializes in high efficiency hydronic radiant but he’s too busy to return my calls.)

Yesterday I met a guy who was different, and I want to hear what you think:

He’s a plumber and detail oriented around the plumbing. He says he’s not a boiler nerd, but he loves the installation and plumbing issues. His approach couldn’t be more different from the big companies. He wants to install a PurePro Advantage and vent through the chimney. He said the gains on a modcon are minimal but the upkeep is demanding & expensive, and that with the Advantage I should have little maintenance and a long life. My small house is currently two zones; he will put it all on one zone/thermostat. His approach seems minimalistic with the goal of long term functionality without service calls. 

I looked up PurePro on here and posts are largely about oil burning. Any thoughts on this plan? Red flags? A couple things he said:

He dismissed the need for a magnetic filter and said that is just people trying to drive up the price.

He said I don't have a back flow preventer on my boiler input. !!! I find this terrifying and also wonder if it's true. I'll update with a photo shortly.

I'm also worried I will lose much of what makes my current system comfortable if we go from our current modcon to cast iron. Can someone speak to the difference in feel? Specifically, will it make my radiators run really hot? We have been running at about 110 this fall and it's awesome. I have kids who play and sleep near the rads & so I particularly love the low temps of the current system. Also, won't our house get too hot?

My boiler is now leaking close to a bucket a day (I’m afraid to leave it alone for long) and my input valve is not opening so I have to refill manually — so this is a more pressing concern than even two weeks ago. Given my situation, he’d try to install before Thanksgiving and do the work himself — so it’s very tempting. But I don’t want to regret it in 2 months or a year.

Thank you in advance!

Katmar

Photos of the input -- should there be a back flow preventer here that is missing? I thought it was the middle bump (not sure what to call it!).

pecmsg

Code should / may require a back flow protector.

Either way their cheap insurance.
https://www.supplyhouse.com/Resideo-Braukmann-FM911-1-2-FM911-Backflow-Preventer-Boiler-Fill-Valve-Assembly-NPT-or-Sweat

Hot_water_fan

Can someone speak to the difference in feel? Specifically, will it make my radiators run really hot? We have been running at about 110 this fall and it's awesome. I have kids who play and sleep near the rads & so I particularly love the low temps of the current system. Also, won't our house get too hot?

Tell him you want this and he should be able to do it. You can mix down the temperature supplied by the boiler to 110F no problem. 

Katmar

Hot_water_fan said:

Can someone speak to the difference in feel? Specifically, will it make my radiators run really hot? We have been running at about 110 this fall and it's awesome. I have kids who play and sleep near the rads & so I particularly love the low temps of the current system. Also, won't our house get too hot?

Tell him you want this and he should be able to do it. You can mix down the temperature supplied by the boiler to 110F no problem. 

Thanks -- this is really helpful. Can you briefly describe how it is mixed down? Does it need anything additional in install to make this possible?

Hot_water_fan

https://www.tacocomfort.com/documents/FileLibrary/5000HX-Series-LeadFreeMixingValve_Submittal_101-164.pdf

Something like this. You can get them with a fixed temp or have something that changes: the temperature of the radiator would increase as outdoor temp decreases. 

They’re simple: hot water from boiler mixes with cold (relatively) water returning from the system to give medium water by adjusting the proportions. 

Katmar

OK! Thank you so much.

leonz

New York code requires a backflow preventer.
Find another plumber to fix your heating the
right way and bring back the gravity heating system.
Keep trying to contact the plumber I suggested to you.

KC_Jones

How has this person proposed sizing the boiler? Need a heatloss calculation for proper sizing. Anything else is just a guess, and they usually always guess way too big. With cast iron boiler it's critical because it's fixed output. With condensing boilers (like you currently have) it's still important, but because they can turn down the burner, slightly less critical. Either way the Manual J heat loss calcs need run, don't let any contractor convince you otherwise. By your description (small bungalow) you most likely need the smallest boiler you can get and that will still be too big.

As far as combining the zones, that's fine, but have they suggested how to ensure the system is balanced for comfort? Are the zones separated by the fin tube and cast iron? If so, combining those could be a very bad idea. They work in very different ways and your comfort could suffer as a result. Again balance is important and needs to be addressed.

I would agree with you about the temperature of the radiation. The lower and longer you can run the greater the comfort so ask how that will be addressed and make sure they understand not getting that is a deal breaker, well it would be for me. As mentioned above there are ways to make this happen with mid efficiency boilers, the modern condensing boilers do this out of the box, with outdoor reset, for the most part. The outdoor reset you now have, is something that would need to be added externally to a cast iron boiler, and the associated controls added as well. My gut tells me this plumber has no plans for that, but I would definitely ask, and again, for me not getting it would be a deal breaker.

It's sad what these clueless contractors have been putting you through, even telling you things that aren't true. "can't connect copper to cast iron" that's laughable. And it seems it goes on from there.

EdTheHeaterMan

This sounds like your detail oriented guy is going minimal. Is he using the existing feed valve, expansion tank, thermostat, and probably many other parts?
I never do a job that way... It avoids this conversation:
I can install the "boiler only" for less.
A year later
Customer: "I have no heat"
Contractor: "I be right over... You need a new thermostat for $1XX,00
Customer: "I just spent over $1X,YYY.00 on a new heater and you want to charge me to fix it"?
Contractor: "the thermostat was not included"
Customer: "what a rip off"

hot_rod

A cast boiler will need to run at least 150f to allow for the return to be warm enough to no condense. 85% efficiency is a reasonable expectation, unless it short cycles a lot, like on milder days. The could drive efficiency into the 70,s%

Mod cons work better for low temperate on operation, and often the bigger win is the fact they modulate to the load and reset control can run them down to low, condensing temperatures.

If you are heating comfortably with 110 SWT, the mod con will be very happy and efficient at those operating conditions

I find the best comfort comes from running the systems as continuously as possible. A modulating boiler likes that condition also.

Teemok

Domestic 3 way mixers are very limited in flow with a 2.3 Cv. They are ok for small loads but I'd never put a house on just one. I expect the suggestion was just an example of a mixing device. True mixing costs money and the value of it is case by case. As said above all boiler trim should be included. A new back-flow preventer and fill valve and all the other trim should be a non-issue given. The quality mod-con vs cast iron for low temperature applications question is a hard one. If you can heat the structure well with condensing temperatures, I'd be inclined that way. But I fix boilers. The durability of cast iron is a fact but they have weaknesses. If set up well with good mixing, not much difference comfort wise. A small cast iron will still cycle with light loads and that is loss. My new tech 25 year old son here in CA just came to the understanding that a single outdoor reset related service call blows most, if not all, saving out the window but if comfort is the real product it's still worth it. Go simple and get durable but less flexible and efficient. Making cast iron low temperature flexible costs more and makes it less simple and not really more efficient. A quality mod-con set up well and running in full condensing is the ideal. A mag. filter and ECM pumps is going full measure state of the art. When a sale depends on efficiency, say 16%. 16% of what is the right question? Knowing your structures heat loss helps answer that. If comfort is you primary concern, mixing cast iron might be the move. If durability and low service costs are primary, stay simple and except any slight comfort difference.

hot_rod

The common 3 way thermostatic valves 3/4 & 1" are 3 Cv some a bit more. So 5 gpm, 6.4' head, is doable with a common wet rotor 1/12 hp circ.

The 2.3 Cv are mostly the ASSE 1070 or dual listed valves, valves intended for point of use, limited to 120F max.

8, 10, 12 gpm is a deal breaker in 3 Cv mixers. Another good example why you should not use pipe size when selecting a control valve. While 1" could handle 8 gpm or so, a restrictive vales Cv needs to be accounted for.

They are an accurate, inexpensive way to get a mixed down temperature, both plumbing and hydronics.

Teemok

There was a time when a boss of mine had me installing multiple pump with 3 way mixer pairs. A hill side house had a long mechanical hall parallel to the hill and had 10 zones with 3 different temperatures needed in different spots. We ran the boiler loop down and back and perched mixers and pumps along the way. Some zones had twin setups because of flow needs. It worked but was not that efficient or elegant. Year 8-12 saw many mixer change outs. Just because you can doesn't make it a good choice. There are obviously times when it's the right thing to do. Designer call.

hot_rod

It is not uncommon to see a system with too much technology applied. Many hydronic nerds love the gizmos. $10,000 worth of various tekmar controls is another example.

I get the same impression when I see 8, 10 or more zone circulators on a 100K boiler.