Microbore Pipes

NigeWick

We've got 10mm "microbore" pipes and had an Octopus surveyor come round. He stated that they could deal with this challenge and we accepted the quote. Then "computer says NO." 

I complained about this and the explanation is to do with flow. The heat pumps they use need a higher flow rate and therefore larger diameter pipes. 

It appears that a properly set up Vaillant heat pump and accessories can deal with microbore pipes.

Netexporter

Their Cosy heat pumps are high temperature. What capacity heat pump is required? Is it outside what thay can offer with their own brand?

QrizB

NigeWick said:

I complained about this and the explanation is to do with flow. The heat pumps they use need a higher flow rate and therefore larger diameter pipes.

Larger diameter or higher flow velocities.

Higher velocities mean more flow resistance and needs higher pressures.

As an engineering problem it's solvable, but implementation might need some out-of-the-box thinking.

paul991

In the same boat but only the drops are 10 mm the feeds being 15 mm so I dont know effect that will have 

NedS

paul991 said:

In the same boat but only the drops are 10 mm the feeds being 15 mm so I dont know effect that will have 

This is key. You need to know the heat loss of each room and therefore how much heat you need to move to each radiator. Water flowing is just a method of moving heat - the more water you move, the more heat you move. If the pipes cannot handle to flow rates to be able to move the required amount of heat, you'll need bigger pipes (or higher flow)

Generally, most heat pumps need s minimum of 28mm primary pipes from the heat pump into the property. The heating system can then generally branch off into 22mm branches (assuming more than one branch, say upstairs and downstairs, or one end of the house and the other), and then down to 15mm into the radiators.

When we ripped out our old pipework, we discovered we had 22mm copper main branches, but these went down to 10mm plastic microbore to each radiator (note the internal diameter of that 10mm microbore was actually only 6mm unlike a copper pipe with thinner walls.

A system designer will know the amount of heat that needs to be transferred through each part of the system, and can size the pipework accordingly. If your system is plumbed like my original system above, having 10mm microbore into the radiations (sometimes used as it's easier to feed through tight spaces) may not be an issue, but if the whole system is plumbed in smaller pipe sizes, that could be an issue (and not always easy to tell until you start ripping things apart).

It all starts with the calculated room heat losses, and work from there.

thevilla

I suggest a quote from Heat Geek. They're offering 'zero disruption' option which minimises the amount of change to your existing system.

We had a heat geek install in February before the zero disruption option was available but some of our radiators were left on 8mm microbore. We still have a warm house and decent efficiency although as I type, one problematic rad is being re piped due to problems with the old microbore.

Reed_Richards

Gas and oil heating systems traditionally aimed for a temperature drop of 20 C between the flow and return pipes.  Heat pumps target a 5 C drop and to achieve this they have to make the water flow a lot faster.

Alnat1

Octopus fitted ours on 10mm microbore and it all works perfectly. They did re-piped one radiator because it was over 1Kw output. Luckily it was on the opposite side of the wall to where the gas boiler was and they managed to repurpose the boiler in/out pipes through the wall to supply the new bigger radiator.