Advice on HVAC Upgrade

ThinLandscape620

Hello - I am looking for advice on how to upgrade the aging HVAC system for my ~3,000 square foot house in Massachusetts. The house was built in the early 1900s and has minimal wall insulation but does have attic and basement insulation. We currently have a ~17 year old Buderus GB142-60 gas boiler for heating and hot water, and we have three ~17 year old central AC units with three ~17 year old Space Pak air handlers. Our hot water is stored in an indirect Superstor tank that is also ~17 years old.

Questions

1) We are open to considering a heatpump setup, but it seems like that may not be a straightforward option for our house given the mix of radiant floors and baseboard/radiators and given that we only have high velocity ducts (rather than regular sized heating / cooling ducts). Given our house's HVAC setup and layout, is it even worth exploring heat pumps?

2) What would be the "recommended" HVAC setup for our house given the mix of radiant floors and baseboard/radiators? Should we basically replace the Buderus with a more modern equivalent?

3) Currently, we don't have a way to control the temperature of the radiant floors other than by manually adjusting the Tekmar controllers in the basement utility closet. Our current HVAC service company has said we shouldn't install thermostats because it is better to not adjust the temperature of radiant floors. Are there any thermostat options that work reasonably well with radiant floors?

4) My sense is that both the boiler and AC are getting close to end of life and may not be worth repairing if/when they next break. Is that generally correct?

Thanks in advance for your advice!!

Hot_water_fan

Boiler can last a very long time so you could have decades to go. I’d keep the boiler and replace the ACs with heat pumps, I believe spacepak makes a high velocity version. I think that’s the most painless way to go. Possibly replace the second floor small ducts with large ducts using the attics available space, that’ll open up more options for that part of the home.

JMWHVAC

If your house layout is at all conducive to it, consider multizone minisplits. That way you could ditch the high velocity ducts. You lose some efficiency with the energy required to force the air thru them. I don't consider 17 yrs very old for straight AC units unless they are in a high use office or the occupants keep it set in the 60s.

Jamie Hall

Either of the above will work reasonably well — cost will be different. The minisplit option does offer the advantage of control over each head unit (within reason — they don't like to have one or two heating and one or two cooling at the same time!)

The Tekmar controllers for the radiant floors could perhaps be upgraded to ones controlled by an outdoor sensor. Then you could just leave the floors running — which is the best thing to do — with the boiler adding more heat to the circuits when needed being controlled by an aquastat.

Zones 2 and 4 can and should be controlled by their own thermostats, running hotter water from the boiler.

What WON'T work without really major expense is trying to run the heating side with a heat pump. You'd need an air to water heat pump to power the existing radiation and, while it might be possible to get warm enough water out of it for the floors you'd not likely be able to get enough heat for the rest of the radiation, at least in cooler weather.

ThinLandscape620

Thank you all for the replies, I appreciate it!

@JMWHVAC - The AC units are used pretty sparingly and we definitely don't keep it in the 60s. Is 17 years old also not that old for a Buderus boiler? When we had it serviced last fall, the HVAC person told us that type of boiler generally doesn't last much past 15 years but they may have also just been trying to sell us a new boiler…

@Jamie Hall - I think our Tekmar controllers do have an outdoor sensor as they have a warm weather shutdown setting (and they also have a temperature sensor in the spaces they heat). For reference, the controllers say Tekmar Mixing Control 360 on them. With this sort of radiant floor setup, is it generally not advisable to have an actual controllable thermostat?

SuperTech

A Buderus cast iron boiler can last a very long time. Unfortunately your GB142 is made of aluminum and is probably towards the end of it's lifespan. I've seen several fail around 15 years old. Your HVAC tech was actually being honest with you. You might be able to get a few more years out of it.

psb75

Make sure the Buderus GB142 is serviced regularly. I am working on one that is 17 y. o. also. Clean the heat exchanger, and condensate trap. If you can get beyond 20 years, you are beating the odds. I'm planning to replace this one soon. This one needed a $500 fan last year, and new combustion.air intake parts. Its been a good boiler but it is aluminum.

ThinLandscape620

@psb75 - The company that installed the GB142 says we should have it serviced every other every (at which time they do a "deep" cleaning and full service). At my previous house, we had the HVAC system serviced every year - does servicing a GB142 every other year sound correct to you or should I ask them to visit annually?

hot_rod

It depends on how it looks when they open it. Some can go 2 or 3 years if they are leading a healthy life.

Burner adjustment and clean combustion air is a big plus. If they inhale a lot of dust, pollen, grass clippings, bugs, etc, then they will need more frequent service.

With an aluminum block the water quality is very important also, check the ph as the manual indicates.

ThinLandscape620

Thank you, I appreciate it. The air intake pipe runs to the top of our chimney, so theoretically should be some relatively clean air.