Monobloc Heat pump

Paul S_3

Hey guys. We have a customer with an existing atmospheric water boiler with 6 high temperature baseboard zones. Customer is asking for a air to water heat pump. Has anyone have any experience with these in the tristate area? What Manufacturers offer equipment like this. I've read that they do not support high temperature water like the gas fired boiler and we would have to make distribution piping and heat emitter upgrades so the system can properly heat a lower water temps. Any info is greatly appreciated. Thank you

tim smith

They will not work especially where you are located with high temp emitters. If you changed out to low temp emitters, maybe. Would get $$$

fentonc

What is the actual heat loss for the home, and what SWT would be needed by the existing radiation to meet that at the design temp? My house has all 'high-temp' baseboard, but only needs an SWT between 110F-120F at the design temp because it's so oversupplied with radiation.

Robert_25

Are you looking to remove the gas boiler? If it is still in good shape, you could add the Monobloc to the system and have the controls bring the gas boiler online when needed.

Even though many houses have radiation sized for 180F, the number of days that actually require that output is small. e.g. My boiler runs at 160F for 90% of the winter.

DCContrarian

You need two things for this to be successful:

1. In your climate, and with the prices of electricity and gas where you are, it has to make economic sense to switch to a heat pump. This is often not the case and the customer is going to be disappointed if they pay a lot of money for a new system and then they see higher utility bills.

You say you're in "the Tri-State Area." According to Wikipedia there are 18 places in the US that call themselves that, but I'm going to assume you're in the CT/NY/NJ one. About a year ago* we had a discussion here, as part of that discussion I did an analysis of heat pump vs oil in Suffolk County, NY. That analysis is at : https://docs.google.com/spreadsheets/d/1d1Kox9yat2WqYWkqSIk-uqiJD0D-7eK3wQy1305sMCM/edit?gid=788733381#gid=788733381

For the analysis, I assumed electricity at $0.33/kWh and oil at $3.00/gallon, you can adjust for current prices in your region. At those prices, heating our hypothetical house would have cost $2,808.67 using oil and $3,448.31 using all heat pumps. So no matter what switching to a heat pump would increase the annual heating cost by over 20%.

If that's the case where you are, you can stop right there. If not, you can move onto condition two:

2. The house has (or you can install) enough emitting capacity to meet the heating load.

Air to water heat pumps will have trouble producing water above about 120F. The output of a radiator is determined by the difference between the water temperature and the room temperature. At a room temperature of 70F, a water temperature of 120F will produce half as much heat as a water temperature of 170F.

Radiators are often oversized, so half the output may meet more than half of the heating load. But radiators aren't the only emitters in a typical house. There's a good chance the house will have air conditioning. The air conditioning ductwork can also be used to deliver heating. If you're in a place where radiators are commonly installed then it's probably heating-dominant, which means that a ductwork system sized for cooling won't meet the heating load. But there's a good chance that the undersized ductwork and the undersized radiators together do meet the load. So what you're looking at is two heat pumps, one to provide heating and cooling through the ductwork, one to provide even more heating through the radiators. It's an expensive system, but it's a good one.

If you do the math and the existing ductwork and the existing radiators can't meet the heating load, then you need to add either more radiators or more ductwork.

*see

https://forum.heatinghelp.com/discussion/199527/musings-on-the-design-day

DCContrarian

@Robert_25 : "Are you looking to remove the gas boiler? If it is still in good shape, you could add the Monobloc to the system and have the controls bring the gas boiler online when needed."

To my knowledge there is only one monobloc system that has this kind of control. It's one made by US Boiler, and they require it be used with their boiler.

I'm not a fan of dual fuel systems. It adds a lot of complexity with little value. If one fuel is a lot cheaper than the other, there's little to be gained from switching between them. If the fuels are close in cost, there's little to be gained from switching between them.

In the analysis of a hypothetical Suffolk County house that I cited above, using whichever is cheaper, oil or heat pump, based on temperature, saves $18.32 per year on a $2800 fuel bill. That would give a payback period of about 300 years for an air-to-water heat pump.

bjohnhy

I don't have experience with high temp heat pumps in your climate, but I was just reading about Arctics two stage heat pump. I cannot vouch for it or against it. You may want to learn more about that one. It's the only line I am aware of that can produce temp >160, but I'm assuming efficiency is diminished

https://www.arcticheatpumps.com/high-temperature-heat-pump.html

pecmsg

https://forum.heatinghelp.com/discussion/comment/1881684#Comment_1881684

and the complexity is increased!

DCContrarian

https://forum.heatinghelp.com/discussion/comment/1881684#Comment_1881684

That Arctic unit is impressive. They don't have much technical data on their website, but they do have some here:

https://www.arcticheatpumps.com/arctic-hydronic-high-temperature-heat-pump-48000-btu-with-cold-climate-inverter-technology-p-464.html

They have two performance points:

Ambient 7C Water outlet 75C	Heating Capacity	kW	12.4
	Power Input	kW	5.1
	Current Input	A	23.2
Ambient -12C Water outlet 75C	Heating Capacity	kW	9.2
	Power Input	kW	4.7
	Current Input	A	21.1

For those who use US units, at a water temperature of 167F, they claim:

• Outdoor temperature of 44.6, output of 42,309 BTU/hr, COP of 2.4.
• Outdoor temperature of 10.4, output of 31,390 BTU/hr, COP of 1.96

For the sake of comparison, I feel the state of the air when it comes to air-to-air heat pumps is the Mitsubishi M-series. At 44F the M-series has a COP of 3.2 and at 10F, 2.0. It's entirely expected that the Arctic would have a lower COP, because it's warming the water so much hotter. I'm actually surprised it's as high as it is.

The M-series has vapor injection, which allows it to keep more of its capacity at lower temperatures at the expense of COP. So at 10F the M-series has 90% of the capacity that it has at 44F. The Arctic has 74% of its 44F capacity at 10F.

Note that in my analysis above of a hypothetical Suffolk County, NY, house, the break-even COP is 3.64.

hot_rod

this tech journal is a good intro into how heat pumps work in general, and calculations used to determine if your system is or could be a good fit.

There are successful hp systems working in cold climates across the U.S. and Canada. So the technology works.

As for the financial aspect, that depends on you fuel costs and expected ongoing costs.

https://www.caleffi.com/sites/default/files/media/external-file/Idronics_27_NA_Air-to-water%20heat%20pump%20systems.pdf

Kaos

Part of my place is uninsulated double brick construction with original cast rads. I'm in much colder climate and heating the place with an air to water unit without issues.

You need to figure out two things first. One is the actual heat loss of the existing place, the simplest is a fuel use calculation based on past heating use:

https://www.greenbuildingadvisor.com/article/replacing-a-furnace-or-boiler

Next you need to measure all your rads to figure out how much radiation area you have.

From these two, you can now see how hot the rads need to be to supply the heat loss of the home. This will tell you if AWHP conversion is even possible and how big of a unit you need.