Is this ridiculous? Pool heat pump for space heating/cooling

BB2024

Hi, I'm looking to get some sense checking if possible please.

I've been looking into implementing ceiling radiant heating/cooling (hydronic) and have come across the capillary tube mats that seem to be widely used in Germany and other such places.

They operate at low temperatures, produce decent heating via radiant (no convection) and quite good cooling through radiant and convection. (Anywhere from 50w/m2 to 140w/m2 / 15BTU/h*ft² to 44BTU/h*ft² across both)

The main issue with the capillary tube mat design is that it's made from polypropylene which doesn't have an oxygen barrier so I believe you need to have 2 circuits. The primary being the heat pump to the heat exchanger and the secondary being the heat exchanger to the mats.

I understand that ASHP's for heating/cooling pools and spa's (which seem to cost less than half of what ASHP's for space heating cost) have built in heat exchangers which are corrosive resistant.

As there would be a lack of need to heat the mats above 30C to 35C (86F to 95F), which I believe is also the max temp rated for most of these mats, nor chill water below 14C (57F) due to dew points, would it be feasible to use a pool and spa based ASHP for this purpose?

Sampling a specific ASHP for pools/spas, the rated max heating range is 40C (104F) and min cooling is 12C (53F). Which would be sufficient for ceiling based radiant heating and cooling using these capillary tube mats.

I don't know very much about pool/spa ASHP's, I just assume they're very similar to space heating ones except built specifically handing corrosive water.

I believe corrosive-resistant plastic, stainless steel and brass components are readily available for the rest of the system (pump, manifold, expansion tank, buffer tank, valves etc).

Is there something I'm missing with such a design?

Spacing heating ASHP's start at around US$6k for 12kW whereas the pool/spa specific ASHP start at around US$2k for 12kW (I'm in Australia). Are pool/spa ASHP's significantly different or does it really just come down to max temperature capabilities?

hot_rod

It may have something to do with the listings on the different type of ASHPs, as far as cost differences.

Years ago there was a radiant contractor around these parts that used pool boilers on radiant systems. They do have return protection built into them as a selling feature, but the sizes he used did not have the ASME "H" stamp and the inspectors caught up with him.

Usually pool heaters, copper tube type, have very high flow rate type HX. I would think pool ASHP heaters would also have high flow capacity.

So it may come down to code approval in your area.

A FPHX is another option, as is ongoing water treatment chemical use to address any O2 ingress.

Open hydronic systems seem to still be commonly installed in the UK. So tanker loads of Fernox and Adey chemicals are sold over there

jumper

My experience is that A/C will overheat pool during Toronto summer.

BB2024

hot_rod said:

It may have something to do with the listings on the different type of ASHPs, as far as cost differences. Years ago there was a radiant contractor around these parts that used pool boilers on radiant systems. They do have return protection built into them as a selling feature, but the sizes he used did not have the ASME "H" stamp and the inspectors caught up with him. Usually pool heaters, copper tube type, have very high flow rate type HX. I would think pool ASHP heaters would also have high flow capacity. So it may come down to code approval in your area. A FPHX is another option, as is ongoing water treatment chemical use to address any O2 ingress. Open hydronic systems seem to still be commonly installed in the UK. So tanker loads of Fernox and Adey chemicals are sold over there

Thanks Bob.

I might just play it safe and run with an FPHX.

Although the lower cost pool ASHP is still very appealing! I'd be keen to hear from anyone who goes done this track and implements one.

pecmsg

Is it designed for space heating..................NO so why even consider it?

EdTheHeaterMan

pecmsg said:

Is it designed for space heating..................NO so why even consider it?

Because new ideas are the Father of invention (we all know the mother is). and when Mom and Dad get together all kinds of new things can happen. Many of those inventions are flops. Just look at the son that your parents put in the NEST. Get it ...NEST... Thermostat. Get it?. However every once in a while some great ideas come from that union of necessity and ideas.

pecmsg

EdTheHeaterMan said:

Is it designed for space heating..................NO so why even consider it?

Because new ideas are the Father of invention (we all know the mother is). and when Mom and Dad get together all kinds of new things can happen. Many of those inventions are flops. Just look at the son that your parents put in the NEST. Get it ...NEST... Thermostat. Get it?. However every once in a while some great ideas come from that union of necessity and ideas.

I see commercial kitchens using domestic refrigerator / freezers. There not designed for that use. But there cheaper. 

dko

This 20" rigid toilet supply is not designed to be a back scratcher, but sure is hitting the spot.

BB2024

pecmsg said:

Is it designed for space heating..................NO so why even consider it?

Yeah I can appreciate that thought, but at the same time, what's the point of using a system that's over engineered for the job required?

Products cost more when they have more features and range, if you don't need 50% of what it can do why pay for it?

I love the idea of hydronic heating and cooling and where I live (Melbourne), we have mild winters and warm/hot summers. I don't believe I need these high end heat pumps that can produce 65c/75c or 7c/8c water when 30c/35c  or 15c/18c is only needed.

At the end of the day, I just need to heat some water to a certain temp and move it through some pipes. A pool ASHP does that doesn't it?   

Not trying to offend, there obviously much more too it than that but you get what I mean.... Hopefully...

GGross

Can you link to an example of a pool heat pump that you are looking at using?

pecmsg

BB2024 said:

pecmsg said:

Is it designed for space heating..................NO so why even consider it?

Yeah I can appreciate that thought, but at the same time, what's the point of using a system that's over engineered for the job required?

Products cost more when they have more features and range, if you don't need 50% of what it can do why pay for it?

I love the idea of hydronic heating and cooling and where I live (Melbourne), we have mild winters and warm/hot summers. I don't believe I need these high end heat pumps that can produce 65c/75c or 7c/8c water when 30c/35c  or 15c/18c is only needed.

At the end of the day, I just need to heat some water to a certain temp and move it through some pipes. A pool ASHP does that doesn't it?   

Not trying to offend, there obviously much more too it than that but you get what I mean.... Hopefully...

Because it was engineered for that purpose. 

Because it was evaluated to be safe for that purpose. 

It’s your house you can do anything you want. You asked a quest and got answers you obviously don’t like!

jumper

>> I see commercial kitchens using domestic refrigerator / freezers. There not designed for that use. But there cheaper.<<

Wise move in my opinion. I've used domestic furnaces for commercial air handlers. Their burners & heat exchangers are a bonus.

hot_rod

BB2024 said:

pecmsg said:

Is it designed for space heating..................NO so why even consider it?

Yeah I can appreciate that thought, but at the same time, what's the point of using a system that's over engineered for the job required?

Products cost more when they have more features and range, if you don't need 50% of what it can do why pay for it?

I love the idea of hydronic heating and cooling and where I live (Melbourne), we have mild winters and warm/hot summers. I don't believe I need these high end heat pumps that can produce 65c/75c or 7c/8c water when 30c/35c  or 15c/18c is only needed.

At the end of the day, I just need to heat some water to a certain temp and move it through some pipes. A pool ASHP does that doesn't it?   

Not trying to offend, there obviously much more too it than that but you get what I mean.... Hopefully...

If the pump is rated for the pressure, temperature and type of fluid, I don't think it matters what it is called.
A pool pump may have a different NEMA motor if it is for outdoor use. And the seal material may be more specific to highly chlorinated water, EPDN or Viton for example.

Some types of pumps have a required suction head, largely ignored in some hydronic application like open systems OWF applications