Pump to boost flow in basement (Thermaskirt)

[fourtears]

Hi,

Question is can we fit another thermostat controlled pump in 'series' with the existing circulation pump to increase flow to one floor.

I have lived in a 4 storey terrace house and the basement (kitchen where we do most of the living) has always taken several hours to get up to temp. There were 4 rads in the basement and it was impossible to get them balanced so they heated quickly without shutting off most of the rads in the rest of the house. We had a big london plumbing firm out several times, power flush (not much sludge), replaced corroded rads, replaced pump and valves, spent hours over 2 days balancing. They could get it so all rads got warm but the basement rads didn't all get get really hot at the same time until TRVs started switching off other rads upstairs. Eventually we solved the problem by installing Honeywell CM Zone wireless TRV zone system and programming it so basement switched on an hour or two before the rest of the house. Not ideal but basement got hot quickly then rest of house came on after.

We have just had some work done in basement and will be fitting Thermaskirt to replace one of the rads in basement so now there will be 3 rads and Thermaskirt. We are hoping that we can add a temperature controlled pump and zone valve in the feed to basement and that can be set to 'suck' enough flow from the rest of the system to heat the basement quickly.. as that is where we want heat fastest. This seems particularly important as Thermaskirt seems to want more flow than a normal rad.

The overall system has a decent potterton boiler that seems to be operating well below capacity (rest of the house gets nice and hot and boiler gets up to temp). Boiler is in basement and 22mm feed and return to airing cupboard on 1st floor (2 floors up from basement.) System is S plan with a circulation pump then two zone valves, one HW and one CH (and an old fashioned stop-cock style bypass.) The CH splits with 22mm going to top floor (2 rads) and 22mm to 1st floor (3 rads) then ground floor (4 rads) branching via a single 15mm to basement 3 rads + Thermaskirt. I presume the problem is no matter how you balance the other 9 rads, the flow for the whole basement has trouble coming over the 15mm. System is pressurised to about 1.3 bar top floor where filler loop is, which is 2.3 bar in basement where boiler and expansion vessel are.

So do people think can it be made to work boosting the basement section like this with a pump? Does it need a separate bypass? How about before pump some kind of reverse bypass in case first pump fails, to stop the pump sucking on a closed pipe? How do we avoid vibration from two pumps at different work rates on the same system?

Unfortunately the 15mm basement pipes are in a concrete floor so we can't change the piping does there.

Thanks.
Tim

 

[SimonG]

What size pump are you using at the moment? Is it a 25/60, i.e. a 6m pump?

 

[Ian10261]

I once got round the same kind of problem using a 6m pump, also using an auto-bypass wouldn't go amiss, stop tap aint the best way of doing things.

 

[stevetheplumber]

obviously your problem is the undersized feed to the basement im assuming this at present is teed in to the 22m after feeding the floor above you could improve it by running the pipework fom baase ment back up to airing cupboard as a seperate pair

 

[fourtears]

Thanks for replies.

Yes the basement feed is 15mm just teed in to the 22 on floor above. Pipes are not easily accessible to run back to airing cupboard but we could get at the feed return of the boiler before it goes up to the airing cupboard i.e. before the main pump and valves. However, all the branching in basement is done in 15mm buried in concrete floor and then with a wooden parquet floor on top so can't get at that. Not sure if it would help to take 22mm to the point of entry to the floor then down to 15mm before it starts branching in the floor. That is why I was thinking of a pump... to push more flow through the 15mm.

The current pump is a Grundfos 15/60 (I think but have to check next time I am at home it might be 15/50.) This was replaced by the plumber last winter and it didn't solve the problem. It is running on the high speed.

Will replacing the bypass make a difference? That would need a whole system drain down.

 

[SimonG]

You could try an 8m pump. Heating World of Spares do one very reasonably. Depending on pipework layout you may be able to fit it without pipework mods. The pump is a little longer than either the 15/50 or 15/60 but you may be able to squeeze it in.

 

[Ian10261]

As you said the bypass you have is nothing more than a stop tap, i would try turning it off completely just to see if it makes a difference, if it dont then you're looking at a bigger pump or pipework alterations. If it does then change it for an automatic one which will open and close as and when needed. This is a requirement for systems on 'S' plan with a pump over-run on the boiler.
I would always try this one first as its the easy option, it costs nothing to turn off a tap and see what happens, just make a note of how many turns it takes to fully close it so you can reset it correctley afetrwards if it dont work.