Heat pumps and pipework

[naylorpd]

So with all the news about heat pumps I just started idly thinking about investigating in more detail. So I came here and browsed a bit and from what I understand heat pumps are just not going to work for me. I have two houses:

• Early 1980s, 4 bed detached, copper microbore pipework, downstairs is buried in the concrete floor, upstairs is under the floorboards (chipboard)
• Newbuild 2016, 5 bed detached, well insulated but plastic microbore pipework behind dot & dab plasterboard

Am I understanding right that neither will be viable unless doing major renovations?

Thanks

 

[SJB060685]

A modern condensing boiler has a ΔT across the primary flow and return of roughly 20°c. Heat pumps typically have a ΔT of 5-7°c. This means by their very nature they pump 3 to 4 times the flow rate. Pipes for heat pumps have to be sized to accommodate this increased flow and usually a fluid with around 25% glycol mix ( don’t quote me on the 25%, it’s around that). If one run the maths you’ll find even microbore can carry up to certain outputs while maintaining the typical velocity of 0.9m/s. Velocity is important in hydronic systems but I won’t go into great detail here. The problem is do those microbore pipes come from a manifold feeding one dedicated radiator or branching of main flow and return and feeding more?
Another thing to consider is mass of the system. Heat pumps need volume else you will likely find high pressure faults etc but there’s ways to combat this with a buffer or volumiser. The design and execution of these systems is very important if you want a working system at the end and I’m only an oil burner technician by trade but I’ve given you some idea.
Of course all the above comes after deciding whether a heat pump is a good choice. They are typically low output low temperature systems. If your house/houses have poor insulation and a high heat loss then the insulation has to be improved and as you can imagine that can cost thousands. Then there’s recalculating the size of the radiators needed and so on.
The short answer is heat pumps are not suitable for all properties, unless lots of work is done improving the buildings heat loss.

 

[ShaunCorbs]

New build with spiders not a chance even as heat loss is better than normal supposedly depending on how good the builder is

If it was me 28mm main runs and 15mm to each rad would get a good cop and size for 35 flow / 32.5 mwt

 

[SJB060685]

New build with spiders not a chance

Haha. Never heard microbore referred to as spiders

 

[naylorpd]

Increasing the flow rate must mean increasing the pressure - so in push-fit plastic microbore that seems to be asking for trouble even if it's technically possible.

I've no idea whether the new house has manifolds, if it has then they are hidden behind plasterboard or under floorboards. I can see pipes in the wall using a FLIR IR camera. I think the older house has manifolds, but only because there's a warm spot in the floor of the master bedroom.

Bottom line seems to be that heat pumps have to be designed into the house, and are unlikely to be suitable for retro-fitting into existing houses old or new. I'll quietly forget this idea, thanks

 

[king of pipes]

Heat pumps wouldn't work for you in this case, there are improvements you could make to your properties but we would need to know what type of system you have and your reasons for wanting to upgrade ? Do you have a Combi boiler ? , Heat only boiler with a cylinder ? , Open vent or sealed system ? Hot water vented or unvented ?
. Kop