ASHP and microbore CH pipes

LongWalk_2

I'm looking to install an ASHP at my home.  All downstairs radiators run on 8mm microbore pipes fed from upstairs, where all the radiator pipes are on 15mm pipes.  I'm worried I will not have a good enough flow rate downstairs to heat it at a lowish flow temperature.  I don't want to run the CH at 50 degrees as my COP will be poor.  Do I need to install 15mm pipes to the ground floor radiators? Any advice much appreciated. 

Reed_Richards

My ASHP installer mentioned that microbore pipes would have been problematic; fortunately I do not have any.  By the way, if you have a 50 C flow temperature and a lower return temperature you should be able to achieve a rated COP of more than 3.

matelodave

An ASHP needs a fairly high flow rate through it to function properly, so its unlikely that it will even work with microbore pipes unless you fit a buffer tank. Even then you may not get suffient flow through the rads 

You really need your installer to do  detailed  calculations to see what is possible but I suspect that you'll nee to replace the microbore with 15mm

shinytop

I agree; from other forums, mixing pipe bores might be OK but can be problematic. 

Sterlingtimes

I have read in the press that when a heat pump become a necessity that all microbore piping will require replacing and that larger radiators will be required. Is this correct? Would this require the raising of flooring and rechanneling through walls necessitating a complete redecoration into the bargain? 

Rodders53

Sterlingtimes said:

I have read in the press that when a heat pump become a necessity that all microbore piping will require replacing and that larger radiators will be required. Is this correct? Would this require the raising of flooring and rechanneling through walls necessitating a complete redecoration into the bargain? 

All probably true but need to be confirmed by the Installers designing and quoting for your circumstances.

This saving the planet malarky doesn't come cheap you know.

Reed_Richards

Sterlingtimes said:

I have read in the press that when a heat pump become a necessity that all microbore piping will require replacing and that larger radiators will be required. Is this correct? 

I think this is likely to be correct.  However the radiators don't necessarily have to be physically larger, they just need to have a larger surface area so they can achieve the same heat output as your old radiators at a lower water temperature.

Sterlingtimes said:

Would this require the raising of flooring and rechanneling through walls necessitating a complete redecoration into the bargain? 

Typically central heating systems have a core of distribution pipes that are 22 mm bore; individual radiators are fed off this through smaller bore pipes.  The 22 mm distribution pipes, if present, would not need to be replaced.

Sterlingtimes

Reed_Richards said:

Sterlingtimes said:

Would this require the raising of flooring and rechanneling through walls necessitating a complete redecoration into the bargain? 

Typically central heating systems have a core of distribution pipes that are 22 mm bore; individual radiators are fed off this through smaller bore pipes.  The 22 mm distribution pipes, if present, would not need to be replaced.

Thank you. This is helpful. Where would the 22 mm distribution pipes be located in a 1990s property? Would they be embedded under the concrete floor? Would they be enclosed under the upstairs floor (necessitating removal of carpets and chipboard)? Would they be enclosed within the loft area? Would the gouging out and replastering of walls be required? The upheaval with the removal of furniture would be far more concerning to me than the expense of the job.

Reed_Richards

My property, a bungalow built in 1980, had all the distribution pipes embedded in the concrete floor but this had been done without any protection and the pipes were beginning to corrode (as happens with copper in direct contact with concrete).  So we put new distribution pipes in the loft and ran pipes down the walls in a corner then along the skirting board to the radiators.  Some of the pipes are boxed-in and concealed behind the skirting board, some are exposed; we didn't much mind.  There was very little upheaval.

I cannot answer for your house but you must be able to infer where your distribution pipes are, and if there are some in the loft they shouldn't be hard to find.

  

Ectophile

Sterlingtimes said:

Reed_Richards said:

Sterlingtimes said:

Would this require the raising of flooring and rechanneling through walls necessitating a complete redecoration into the bargain? 

Typically central heating systems have a core of distribution pipes that are 22 mm bore; individual radiators are fed off this through smaller bore pipes.  The 22 mm distribution pipes, if present, would not need to be replaced.

Thank you. This is helpful. Where would the 22 mm distribution pipes be located in a 1990s property? Would they be embedded under the concrete floor? Would they be enclosed under the upstairs floor (necessitating removal of carpets and chipboard)? Would they be enclosed within the loft area? Would the gouging out and replastering of walls be required? The upheaval with the removal of furniture would be far more concerning to me than the expense of the job.

You should be able to work that out by seeing where the pipes go.

All my downstairs radiator pipes go up to the ceiling. So the plumbing for upstairs and downstairs must be below the upstairs floors.

Sterlingtimes

Ectophile said:

All my downstairs radiator pipes go up to the ceiling. So the plumbing for upstairs and downstairs must be below the upstairs floors.

Perhaps that is the convention. Thank you. Hopefully, I will never need to replace them. This is a huge barrier to choosing a heat pump. Perhaps, I will have my gas boiler replaced on 31/12/2034 if I am still alive.