Replacing a hot water boiler and radiators

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Old 02-07-18, 09:42 PM
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Replacing a hot water boiler and radiators

Hi

I have a 100 year old house with hot water cast iron radiators. The issue is that the boiler is on its last legs and may be leaking

I can just replace the boiler but there are pros and cons:

Pros

Heat is nice (and from what I’ve read, the most efficient )
The system is in place and all I have to do is retrofit the new boiler to the existing pipes

Cons

The radiators are bulky and take up a lot of space. In addition there are vertical supply pipes that are visible and unsightly

In the basement there are these huge 2” return pipes and 3/4 supply pipes, that run under the joists, for the entire length of the house and are also in the rooms. This is especially bad since the ceiling is only 7’.
There is also this huge expansion tank in the basement

There are no zones to the system so the entire house is heated when the one and only thermostat turns on

I currently have a lot of window a/c’s which obstruct the windows etc. I would like to get a central a/c system but that means putting in ducts etc. And if I am going to do that, why not convert to hot-air etc.

The solution is limited:

1. modernize the boiler/radiator somehow
2. replace the whole system with hot-air, and ducts that can be used with central a/c,
3.Do both

Does anyone have any ideas how to accommodate/resolve all the issues. ( I do not want fin heating, or split systems , or radiant floor heating etc.)

Thanks
 
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  #2  
Old 02-08-18, 04:37 AM
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You did not say if this house is a 1 or 2 story house but since it is about 100 years old I will assume it is a 2 story house. If you really want to add A/C to the house then a forced air system makes sense. You have to make sure that you can run duct work either up or down the walls to be able to supply conditioned air to every room. If the system is in the basement you will have to be able to run duct work up and if the system is in the attic you will have to be able to run the duct work down. Or you could install 2 systems; 1 in the basement and 1 in the attic. Today a lot of A/C contractors want to install a single return duct in a central area to save money, however if it was my house I would do it correctly and have a return in every room, ( if possible) and a high and low return on every duct. ) It is more expensive but well worth the cost. High returns open in the summer and low return open in the winter. With forced air you can choose the type of air filter you want in the return from cheap to drastic depending on your family's health. For my system I choose an electronic air cleaner ( good for asthma people ) plus a charcoal filter ( my wife hates smells )and a good humidifier. That's about it for a forced air system Now for the old system: you can just replace the boiler, keep the radiators and add " Danfoss type" rad valves to control temperature in each room or if you don't like the standing radiators and have a lot of money to spend you can replace them with cast iron baseboard heating with the same zone type valves or electric zone valves ( looks great and heats great ). You would still not have A/C but you could add it if you wanted. what ever you decide to do get numerous bids and have your check list with you when talking to their reps. If they say what you want can't be done they are out. Hope this helps
 
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Old 02-08-18, 07:52 AM
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For bob_bananas, 100 year old heating system rat maze, split air conditioners might be the simplest and best approach.

Split air conditioners are turning the HVAC world upside down. Old thinking had two boxes one for central heating and the other for air conditioning. Splits are a "one box" solution.

Many commercial buildings are using splits instead of separate central heating and AC systems. They also allow individual tenants to control, maintain and pay for costs directly.

One outside unit can serve four more inside zones with individual temperature control. Compared to central systems they can be a big cost savings to install and run.

Would look for contractor with solid experience and tract record on splits. Many established HVAC outfits lack the technical depth to use them effectively.

Chinese made units are often half the price of Japanese. A couple of years ago when buying a split was concerned about Chinese quality. After remembering the zillions of them I have seen on trips to China bought one in NYC for $700. Use it in basement where window AC unit was impossible to install.

For a quick reference see:

https://www.homedepot.com/b/Heating-...vZc4m1Z1z0r0qs
 

Last edited by doughess; 02-08-18 at 09:00 AM.
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Old 02-08-18, 02:01 PM
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Hi guys
I do not want the splits since they stick out of the house and protrude inside the house and are unsightly,

I just found out about smart TRV's - radiator valves that can be controlled from a smart phone etc. so I really don't need a complicated zone system if I stay with the radiators.

The main beef, is with the basement and those huge return pipes. I read somewhere that back in the day they needed to have the pipes huge since the system relied on gravity but that a modern boiler has a better pump. This makes sense since I have never seen such huge pipes in a new hot water system. If I could replace those pipes and the expansion tank (especially with 1/2 pex), it would solve the heating problem somewhat (but not the a/c). I still have the space issues with the rads, but its an old home (2 story) and the radiators are part of the "charm" lol.

I really should go with a forced air system (thanks for the info) that would accommodate the heat and a/c. Its just that I keep hearing that hot air is bad, and that I will regret replacing the rads. I was also thinking about replacing the huge rads with euro rads or the baseboard rad, but the cost is high and I have to research if it get the same heat output as with the current radiator.

Any ideas about this?

Thanks
 
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Old 02-08-18, 02:27 PM
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One thing to keep in mind with cast iron rads is the expansion tank.

You cannot use the typical #30 extrol hanging from a scoop.

You must size your tank according to your system water content and boiler size.

You are going to end up with a minimum #60 and possibly larger so beware.

As far as zoning your rads, it can only be done if each rad is fed individually and not with a loop system.

Just a thought. Hope this helps a little.
 
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Old 02-08-18, 03:13 PM
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Hi Spott

I think the current expansion tank is a #60 ( its about 3' long). It's by the boiler so its not that obtrusive but still it takes up a lot of space, If I keep the cast iron rads, the main thing is if I can replace the maze of huge pipes with smaller pipes without reducing heat output. I already replaced one of the supply lines to an upstairs bathroom rad with 1/2 pex and it seems to be working fine (@ 12 psi) . But that is just 1 rad out of the whole system.

What I do not want, is to have to install the same boiler arrangement, and then regret not having researched if there is a better, more efficient and modern option.
 
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Old 02-08-18, 03:36 PM
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b,
Apparently your rads are fed individually so you either have a monoflo system or a 2 pipe system.

There shouldn't be a problem with feeding the rads with 1/2". Although you may not need the 2"mains that big make sure they are large enough to supply the rads.
 
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Old 02-08-18, 07:17 PM
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Usually, the near boiler piping and the basement horizontal runs were 3 " or larger for a gravity system. They usually worked great unless someone messed around with the piping. Usually we would just add a small B&G circulating pump to increase the flow which would shorten the response time both up and down to even out the comfort level from the system. If you do not mind the oversize piping in the basement you could let that piping alone and concentrate on the vertical runs which would save money. If this were my house I would do as much energy conservation as I could afford, like new energy efficient windows and insulation, do a heat loss calculation room by room and then see just what size radiation I would need. Replacing the radiators will remove the aesthetics of a home from that era,however cast iron baseboards will give you the same type of heating and may allow you to move some of the feed pipes to a place where they can be hidden from view. It's hard to beat the heating from a cast iron radiation system. You have some big decisions to make. Move slowly and plan carefully.
 
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