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Replacing A/C, should I keep the furnace and radiators?

Posted by commok (My Page) on
Sat, Mar 24, 12 at 20:44

We are closing on a "new old house" next week, and the a/c and furnace are at the end of their useful life according to the home inspector. The house is a 2300sqft brick ranch with a full basement, now half-finished. The house is in the No Virginia suburbs, and was built in 1960's. The original windows will be replaced, and the attic insulation will be increased. We will likely live in this home for 5-10 years. The house currently has hot water radiators in every main level room, and of course registers for the a/c. I am going to finish the basement, and would like to complete all duct work and, if we go that way, removing the water pipes for the radiators before I start the basement finishing. I have contractors coming by the week after next to give me their thoughts on what to do, but I am leaning towards replacing the a/c unit with a heat pump. The question is should I replace the a/c with a heat pump and then remove the radiators in the rooms, or install a HP and keep the radiators and furnace/boiler, and use for the really cold days... I have read this forum extensively, and it seems to me the smart thing is to replace the a/c with a heat pump since the additional cost is relatively small, but I am stuck on what to do with the furnace/boiler and the radiators. Frankly, I've never lived in a home with radiators, and was initially put off by the space they take up and the impact they have on furniture placement... But, if they are really the way to go, I will gladly learn to live with them. Thanks for your advice!

Follow-Up Postings:

RE: Replacing A/C, should I keep the furnace and radiators?

What type of radiators does the house have, copper tube with metal fins, cast iron baseboard or large cast iron? What temperature does the boiler have to heat the water to?


RE: Replacing A/C, should I keep the furnace and radiators?


It is important to get your terms correct.

When you say furnace, I assume you mean air handler. What is your fuel for the boiler, nat gas or oil. Is nat gas service even available? How old is boiler? This makes a big difference as to my advice whether to keep radiator system or to remove.

I would definitely get a heat pump in lieu of the AC. I will provide specs on that in a separate post.

Please reply to my questions.


RE: Replacing A/C, should I keep the furnace and radiators?

Thank you for your reply Tigedunes and SR. The radiators are large cast iron for the most part, but the bedrooms and family room have horizontal units that span the length of the windows in the room - not baseboard but built into the walls - all have iron pipes feeding them. The boiler is fed by natural gas, and it is an American Standard, whose age I do not know, but appears to be the original unit - house was built in 1964. When I accompanied the home inspector on his tour, we couldn't read the manufacture date, but there was a good deal of rust coming off the cast sections underneath. The flame pattern was OK. I really am just trying to get a sense of what my strategic direction should be for when the HVAC companies show up week after next (we close on Friday). I am thinking replace the a/c with a heat pump, and while the basement is unfinished ensure duct work and registers are correct for independently heating and cooling each room. If heating with the hot water system is better (DC winters are hit or miss for really cold days), I will just keep the radiators in place, and let the old unit run till failure, and then decide to remove or replace. I was thinking it would be easier to remove the radiators and piping while the floor trusses are accessible before finishing, but I guess in the end, I can just leave the piping in place. Thanks!

RE: Replacing A/C, should I keep the furnace and radiators?

Any idea of size of boiler, both input and output in BTUs. Based on the age of this boiler, I would expect it to be oversized with poor efficiency which would be typical of a boiler this vintage.

I would find out the service history of this boiler from the servicing dealer.
It should have a thorough inspection of the boiler and the radiator system itself by a pro.

I like radiator heat. Since you have nat gas service, I would upgrade to a high efficiency boiler of the correct size.


RE: Heat Pump specs


As promised here are the specs you should be looking for in a new HP system with air handler.

there are three equally important components-quality HVAC, the install by dealer, and probably the most overlooked and disregarded is the ductwork system.

these are my minimum specs for a new HP system. both outside and inside units should be replaced to have a properly matched system.

15 SEER, 12.5+ EER, 9 HSPF
best matching VS air handler
full BTUs in both cooling and heating for your rated size
R-410a refrigerant(same as Puron)
scroll compressor preferred
electronic demand defrost preferred
thermostat with "dehumidify on demand" feature
staged backup heat strips
new and correctly sized refrigerant lineset

you want a thorough inspection of your ductwork system. size, overall condition, supply and return lines, insulation qualities, leak test, etc.

any hot/cold spot issues in your home should be addressed.

I would only use authorized dealers for the various brands that provide quotes. see mfg websites.

I would look at Trane/AmStd,Rheem/Rudd,Carrier/Bryant.

Based on your location, I would not purchase a new HP system that did
not have electronic demand defrost.


RE: Replacing A/C, should I keep the furnace and radiators?

I would advise thoroughly investigating a new boiler system and keeping the radiators as a lot can be done with modern hydronic systems. They are very efficient, up to about 96%; they can be wall mounted and are very compact taking up no floor space at all. They can also incorporate an instantaneous domestic hot water capability so you would not require a reservoir tank or separate device. Also they are quiet and induce no drafts. High efficiency condensing gas boilers can be side vented meaning that the present condition of the chimney may not be a factor at all.

Having NG means that you can have a gas stove, dryer, fireplace and outdoor BBQ. A gas stove and fireplace would mean that you would have access to heat and cooking during a power failure.

Keep in mind that a hydronic system, particularly one with cast iron radiators, is fully compatible with a geothermal heat pump that can provide heating, domestic hot water and central cooling without ever having to install duct work. Keeping the hydronic system will also maintain the original look and feel of the home as well as its heritage value as time goes by.

Any renovation or new addition could also include radiant in-floor heating with the hydronic boiler system. This is particularly nice in kitchens and bathrooms. These are highly prized features when it's time to sell.

Even with, or dare I say especially with the 'old' cast iron radiators, a modern hydronic system in the 21st century is NOT your parent's heating system at all!


RE: Replacing A/C, should I keep the furnace and radiators?

You have alot of options. You have the correct idea with getting heatpumps to replace your A/C. That is smart since most of your winters aren't too bad. I really like heatpumps for heating during the milder winter weather (above 30). The radiators provide lovely heat, and don't move around dust. These might not be as benefical since your have ducts and can heat with either a heatpump or a natural gas furnace. And because you don't have the longest coldest winters either.

To be honest, I would consider removing all the radiators and pipe. I would replace your A/C with a new heatpump but instead of a regular air-handler to push the air I would have a 95% natural gas furnace. It shouldn't be a big problem to run the gas pipe to your air-handler.

You would have a very efficient and comfy feeling system with this route I think.You would have more space in your basement and house. You would also have less equipment to worry about.

I could be wrong but I think boilers are expensive and the idea of having 2 gas heat systems for your climate seems like overkill.

RE: Replacing A/C, should I keep the furnace and radiators?

You are going to spend a lot of money ripping out your hot water heating system and boiler and repairing holes in floors and walls where the piping was removed. Before you do this, please realize hot water heating is the most comfortable and reliable heating sytem. Depending on the new gas boiler and your plans for domestic hot water, it could be the most economical. Think twice before you give this up for a heat pump.

My suggestion is to go through a heating and cooling season before you make any decisions. It will give you time to experience your HVAC systems. If you hate the current radiators, you could change them for more stylish models, or change them to baseboard units. Don't rush the decision.

RE: Replacing A/C, should I keep the furnace and radiators?

Thank you for your advice and counsel, folks. I do appreciate the knowledge and professionalism you are willing to share. I will update once I get some quotes from the HVAC companies...

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