Go all-in with heat pumps?

woobagooba

What started as the desire to add AC to a 1910 Zone 5 MA build with gas fired hydronics + local rebates has resulted in Mitsubishi Hyper Heat pumps / air handlers installed on both floors. Now we are questioning the need and cost to restore the hydronics (boiler, indirect HW tank, and piping are end of life). Being a hydronics user my entire life, I have no intuition re: comfort levels with the ducted Mistubishi install, particularly on cold January nights.

Appreciate some feedback.

Should we install hydro coils instead of restoring the existing cast baseboards, radiators, and piping?

I am also partial to boiler w/ HW indirect tank versus on-demand HW.

What does hydro coil inclusion mean to the controls/thermostat kit? Dual fuel etc.

Just FYI the house air barrier and insulation have been considerably improved.

Thanks

icy78

The new heat pumps have remarkable capacity at even +5  and heat at -14 still. Full rated capacity I think.
They've been used in Europe for years and are just starting to be a big thing on this side.
     Breakdowns are almost nil. So they say.
A real key is  building upgrades and envelope tightning.
 The Mitsubishi hyperheat does really well in low temps. Sizing is important as the unit is sized for heat load, but one has to be sure that cooling turndown is acceptable if using multiple heads on one condenser.
 Also no fossil fuels in , or to, the home, if stove and dryer and water heater (could also be heatpump) are used.
 As always, installation is key.
I learned something interesting about minisplits today. That is that you get full capacity going 1 to 1, indoor to outdoor. But, you lose a bit, say 10% if you go 2-3 heads on one outdoor unit. I think it was due to the lineset losses, and probably slightly  to loss at each head.
Electric strip heat has been added to ducted minisplits.
 I think you can get 130°f degrees out of many minisplit heatpumps now.
   I think the hyperheat injects refrigerant into the compressor to allow the compressor speed to climb and produce higher discharge temps.
   Oh, crud, I didnt answer your question, but thought you might like to know that about your hyperheats. 🙂

Steamhead

Keep your hydronics. You'll have much greater winter comfort than minisplits can offer.

woobagooba

Steamhead said:

Keep your hydronics. You'll have much greater winter comfort than minisplits can offer.

How so?

Do note this is a ducted system and not mini split heads.

EBEBRATT-Ed

IMHO nothing will provide better comfort than hot water or steam in a cold climate.

The other consideration to me (well used to be when I did service) is who wants to go outside in the snow and ice to change a unit or a compressor when it's 0 deg outside?

SuperTech

I would never, ever consider getting rid of hydronic heat and just running mini splits. Hydronic heat is more comfortable and much more service friendly.  I have just about everything needed to repair a boiler on my van. If you need something for your Mitsubishi....we'll order it and see you when the part gets in. They do breakdown,  they are a pain in the butt to service and repair.  Besides,  you need hot water for showers, laundry, etc. Why not keep the boiler that you can always count on to keep you warm? Especially if you have cast iron emitters, they are the best.  Use the Mitsu for A/C and heating during the milder months keep the boiler for hot water and extreme cold. You will not regret it. If you ditch the boiler, I can be pretty sure you will regret it.  It never hurts to have two ways to heat a house.

Robert_25

You will want another form of heat to supplement the heat pumps when it is below zero.  That can be your existing system, or something different.  Electric baseboard may be something to consider.

woobagooba

I will likely ask for a design plan for both later addition of hydro coils and restoration of radiant baseboard, then pipe second floor for both before the walls are closed up (first floor is fully accessible from basement). Try the heat pumps for a season, then make the call re: install hydro coils or radiant baseboard on both floors. I wonder how much the boiler sizing will vary between hydro coils versus baseboard?

Steamhead

woobagooba said:

Steamhead said:

Keep your hydronics. You'll have much greater winter comfort than minisplits can offer.

How so?

Do note this is a ducted system and not mini split heads.

Makes no difference. Stay with hydronics.

Jamie Hall

On the boiler sizing -- it won't make a difference. Either one needs to be sized according the heat loss of the building, in the usual way. Do NOT count on the heat pumps for anything useful in doing the sizing, and whatever -- do NOT use the electric resistance heat in them. You'll break the bank on that.