Four Pump Heating System?

gaelicyoda

Hi All,

First off, apologies for the essay here.

Had a plumber in today to price up the heating system in our new house and he suggested a configuration I hadn't heard about before, and I'd like to get people's thoughts on it. I should point out first that the house is in the process of being bought as-is, and the heating system has yet to be finished off. The rads are in, and looks like the original plan was for two zones (upstairs and down) with a couple of manifolds already in place in the utility room. The boiler is not yet connected, nor is the hotpress cylinder in place. We want to future proof a full attic conversion at this point, as it will be much more painful to do this type of thing later I'd imagine.

Anyway, the suggestion is to have not one, but four pumps in the system; one for the upstairs rad circuit, one for the downstairs rad circuit, one for the hot water and attic rads (3), and one finally from the boiler into the various manifolds. The rationale was that every circuit would be totally isolated from the rest, and so zoning would be much more effective. He said that while having one pump would work, there were three concerns he would have with that (and I hope I understood him correctly!) - (1) with a single pump, all the heating would either be on or off, up to the temperature set for each of the (existing) planned two zones (2) it would struggle with all of the work required of it (the rads, etc. in the house are reasonable spaced out at 2300 ft.2, excluding attic), and (3) with a single pump, if you cut down it's workload and hav it only partially working (e.g. close off one of the manifolds) it can be as bad for the pump as overworking it.

The control mechanism that has been wired in so far in the utility room is a manual timer clock and a standard room lighting switch with 3 buttons (presumably one for the two zones, and one for hot water), so each zone would have to be manually turned on or off, which he said was pretty antiquated at this stage. He said he would be more in favour of putting a motoroised valve on each manifold and let the system manage itself.

Now, what I suppose I want to know (from any experienced plumbers out there if any are reading) - has anyone else installed such a system, or even heard about it? Does this guy sound like a snake oil salesman looking for extra cash (he said the price difference between the standard config, i.e. a single pump which he said he was happy to do if that's what I wanted, and the system he was proposing was roughly about €1000, but had to price it up formally yet). To me, he seemed to know his stuff and seemed very professional, and he had the opportunity to tag on extra work for himself if he wanted it, but didn't.

Any and all coments welcome.

Cheers,
GY

Red Alert

Multi-pump configurations are common enough on underfloor heating (and combination underfloor/radiator/air systems) and on systems in commercial premises. It sounds like the "manifolds" could be underfloor-heating style ones, which sounds a bit strange. I guess the motorized valves are there already or something?

gaelicyoda

Thanks for that Red Alert - glad to here it's a recognised system at least.

So, let me describe in my finest layman's terms what I've observed of the work completed to date:

Downstairs Utility Room:

- There are two thick copper pipes coming up through the floor screed from the outside (where the boiler will eventually go). There are also two similarly thick plastic-type pipes are going up into the hotpress, but are not yet connected to anything.

- There are two steel/copper manifolds present, not terribly unlike these, with numerous thin, plastic-type pipes connected into them, again coming up through the floor screed. I assume these are for the downstairs rads. There are no pipes connected yet to the "thick" end(s) of either manifold.

Upstairs Hotpress:

- It looks like all the first floor radiators have been brought back to the hotpress individually. There is a large collection of thin plastic-pipes coming up through the floor joists (no hollowcore here) underneath the location for the cylinder.

- There are two sets of the thicker copper pipes coming from the side-wall of the hotpress, beside where the cylinder will go, going up into the attic.

- There is also a smaller bunch of thin plastic-type pipes towards the opposite end of the hotpress, maybe 6 or so. These are probably for the showers (3 upstairs, none downstairs)


Hope this information is useful in trying to figure out what's going on here.

Cheers,
GY

gaelicyoda

Hi All,

I notice lots of viewings of this thread, but not so many responses - I wonder if people are just not familiar with this type of setup, or if more information is required from my end?

Cheers,
GY

reilig

I'm not a plumber, but just finished a self build. Your descriptions of what's in place sound just like my house was after the first fix plumbing. Downstairs utility sounds like it has a flow pipe from the boiler and a return pipe for the boiler. The manifolds sound like they may be there for your radiators.

Sounds to me like you will have 3 zones:

1. Downstairs heating.
2 Upstairs heating
3 Hot water

The manifolds in the utility room probably feed upstairs and downstairs (separately). You also have a main copper pipe that will go to your cylinder to heat the hot water. Plastic pipes in upstairs hotpress are probably for to feed the showers, toilets, handbasins etc upstairs and downstairs.

Above is how my house is set up anyway.

I have 1 circulation pump with 3 zones. Each zone has a motorized valve which is opened by the stat in that zone when the temp goes below the min temp. The stat also turns on the circulation pump. So for example, if the hot water cylinder statgoed below 50 degrees, it opens the motorized valve and turns on the pump to bring hot water to heat the hot water in the cylinder.

At the same time, if the downstairs temp goes below the set temp, the stat opens the motorized valve and allows water to flow around the system to raise the temp downstairs. The same for the upstairs zone.

But as soon as all 3 zones reach their required temp, each motorized valve closes. When the last valve closes, the pump switches off meaning that there is never any pressure on the pump.

I also have a 3 way time clock to control all 3 zones. This also has a boost button facility.

My personal opinion is that you don't need so many pumps and that motorized valves will do instead. They are cheaper to buy, easier to install and cheaper to maintain.

But as I said, I am not a plumber, I'm just telling you how mine was set up.

Hope it makes sense.

gaelicyoda

reilig wrote: »

I'm not a plumber, but just finished a self build. Your descriptions of what's in place sound just like my house was after the first fix plumbing. Downstairs utility sounds like it has a flow pipe from the boiler and a return pipe for the boiler. The manifolds sound like they may be there for your radiators.

Sounds to me like you will have 3 zones:

1. Downstairs heating.
2 Upstairs heating
3 Hot water

The manifolds in the utility room probably feed upstairs and downstairs (separately). You also have a main copper pipe that will go to your cylinder to heat the hot water. Plastic pipes in upstairs hotpress are probably for to feed the showers, toilets, handbasins etc upstairs and downstairs.

Above is how my house is set up anyway.

I have 1 circulation pump with 3 zones. Each zone has a motorized valve which is opened by the stat in that zone when the temp goes below the min temp. The stat also turns on the circulation pump. So for example, if the hot water cylinder statgoed below 50 degrees, it opens the motorized valve and turns on the pump to bring hot water to heat the hot water in the cylinder.

At the same time, if the downstairs temp goes below the set temp, the stat opens the motorized valve and allows water to flow around the system to raise the temp downstairs. The same for the upstairs zone.

But as soon as all 3 zones reach their required temp, each motorized valve closes. When the last valve closes, the pump switches off meaning that there is never any pressure on the pump.

I also have a 3 way time clock to control all 3 zones. This also has a boost button facility.

My personal opinion is that you don't need so many pumps and that motorized valves will do instead. They are cheaper to buy, easier to install and cheaper to maintain.

But as I said, I am not a plumber, I'm just telling you how mine was set up.

Hope it makes sense.

Thanks Reilig, I appreciate your descriptive feedback, and your system makes good sense to me. That was my initial thought on the number of pumps as well, but wanted to hear other people's thoughts on it (I'm clearly not a plumber either).

The only definite benefit I can see really is that multiple pumps builds in some redundancy into the system (i.e. if one pump goes, or even two, it won't knock out the entire heating system), but I'm not sure this is worth an extra €1000 to install, not to mention the extra ESB for running these extra pumps on an ongoing basis (well, probably mostly just in the winter).

The only other factor I think I need to consider is whether or not I believe the plumber when he says that having a single pump pumping at full capacity, but only being used at a half or one third load (i.e. if one or two of the three motorized valves were closed) has a detrimental effect on the pump. Logically, I think I would believe that, but the question then is how much that will shorten the lifespan of the pump. How long have you had that pump running for at this stage Reilig?

I think the other point he raised about the pump struggling is fairly irrelevant - surely you could just get a bigger pump?

Anyone see any holes in any of these conclusions?

Cheers,
GY

Snake9

The use of multiple pumps will cause your BER rating to suffer very badly. The optimum heating system for your BER rating will have the least amount of pumps with 3 separate zones to include your domestic hot water supply automatically controlled from zone time and temp/cylinder stats and a boiler with min 98% efficiency.

gaelicyoda

Snake9 wrote: »

The use of multiple pumps will cause your BER rating to suffer very badly. The optimum heating system for your BER rating will have the least amount of pumps with 3 separate zones to include your domestic hot water supply automatically controlled from zone time and temp/cylinder stats and a boiler with min 98% efficiency.

Thanks Snake9, I figured the extra ESB requirement would fairly dog the energy rating alright. One concern is that we would probably need 4 zones (an extra one for the attic). It would be nice to have this zone further controlled by a master on/off switch (as well as the stats) since we wouldn't be spending a lot of time up there. Because it's higher than the cylinder, I suspect this extra zone will need it's own pump.

Any idea of the power used by your average circulation pump?

And what is the most efficient configuration that ensures decent shower pressure? One single (larger) pump that does all the showers, or individually (smaller) pumped showers?

Cheers,
GY

reilig

gaelicyoda wrote: »

The only other factor I think I need to consider is whether or not I believe the plumber when he says that having a single pump pumping at full capacity, but only being used at a half or one third load (i.e. if one or two of the three motorized valves were closed) has a detrimental effect on the pump. Logically, I think I would believe that, but the question then is how much that will shorten the lifespan of the pump. How long have you had that pump running for at this stage Reilig?

Pump has been up and running for about 6 months now. I cannot see where he got the idea of thepump running at full capacity but only on one third or half load. Think about the system in your house???? Its a looped system in all 3 zones. If one or 2 of the zones are closed, it doesn't mean that there is more pressure on the pump - it just means that water is returned faster via the return pipe. Just because one zone is closed, there is not a build up of pressure. The pump's lifespan will not shorten at all!!! Best thing I can advise you to do is put in a Grundfos circulation pump rather than a cheaper alternative. They're the best on the market - just make sure you buy one for the correct head height. My parents have a grundfos pump running in their house for the last 28 years. It never once gave a problem.

gaelicyoda

reilig wrote: »

Pump has been up and running for about 6 months now. I cannot see where he got the idea of thepump running at full capacity but only on one third or half load. Think about the system in your house???? Its a looped system in all 3 zones. If one or 2 of the zones are closed, it doesn't mean that there is more pressure on the pump - it just means that water is returned faster via the return pipe. Just because one zone is closed, there is not a build up of pressure. The pump's lifespan will not shorten at all!!! Best thing I can advise you to do is put in a Grundfos circulation pump rather than a cheaper alternative. They're the best on the market - just make sure you buy one for the correct head height. My parents have a grundfos pump running in their house for the last 28 years. It never once gave a problem.

Thanks for the advice on the Grundfos pump, sounds like the proper job - I'll be sure to request it from whoever does the job.

Good point about the return speed, and yes, that does make sense now that you point it out. The only concern I'd have in that case is in relation to the temperature differential (i.e. flow temp. vs. return temp.) From reading some other posts on these boards, the optimum for a condensing boiler should be about 20 deg. to allow for maximum efficiency. If it were the case that the water was returning faster (if one or two of the zones were closed), wouldn't that mean the temp would not get as long to diffuse through the radiators and so the temp differential would be smaller? Could there be a knock-on effect on the efficiency of the boiler itself?

Cheers,
GY

Red Alert

The use of multiple pumps will also need relays to be provided to run the boiler, and you'll also need to have anti-gravity check valves on the zones to stop reverse circulation occurring when zones are switched off. The automatic valves in most cases have end switches which can do this bit for you. So basically I think the single pump + motorized valve setup is the way to go. (If you were looking for redundancy I'd plumb the two pumps in parallel with check valves and have a changeover switch, but I'd say hardly anybody needs that kind of reliability.)

Your system needs an automatic bypass in most cases, so the pump loading should be relatively constant. Our system at home runs all summer with no radiators on to heat the hot water and our pump isn't the worse for it.

gaelicyoda

Thanks Red Alert!

Red Alert wrote: »

The use of multiple pumps will also need relays to be provided to run the boiler, and you'll also need to have anti-gravity check valves on the zones to stop reverse circulation occurring when zones are switched off. The automatic valves in most cases have end switches which can do this bit for you.

Yes, I would hope that I could get a motorized valve with this built in to stop back flow. Shouldn't this be standard?

Red Alert wrote: »

So basically I think the single pump + motorized valve setup is the way to go. (If you were looking for redundancy I'd plumb the two pumps in parallel with check valves and have a changeover switch, but I'd say hardly anybody needs that kind of reliability.)

In terms of redundancy, I think you're right here - having said that I've been staying with my parents the over the Easter weekend and the pump in their boiler was gone (ironically enough, given what we're talking about here) and it is a serious pain/chill in the ass (and it's not even that cold at the moment). For the sake of €100 or whatever it is, it might be a lifesaver someday.

One thing I hadn't thought about actually until now - is there any kind of redundancy for the motorized valves? Presumably if one of those goes it's either fully off or on full blast - can these be opened/closed manually (the name of the valve notwithstanding)? And are thermostatic radiator valves a viable redundancy here (for the full blast condition)?

Red Alert wrote: »

Your system needs an automatic bypass in most cases, so the pump loading should be relatively constant. Our system at home runs all summer with no radiators on to heat the hot water and our pump isn't the worse for it.

Excuse my ignorance here, but what is it the automatic bypass is actually bypassing? Is there a pump out there that could step up/down throughput in response to the opening/closing of the motorized valves, just to keep it all on a level keel so to speak?

Cheers,
GY

Red Alert

The motorized valve won't need backflow prevention - I meant if you were using a pump per-zone setup then you'd need it. That kind of setup is more common in radiator systems in the US rather than over here. The end switch is just an electrical contact that can be wired up so it turns on the boiler and pump when the valve opens.

The automatic bypass just lets some water bypass from the pipe flowing in the direction of the radiators to the pipe returning the water to the boiler. It stops the pump having to pump against total resistance and prevents the boiler overheating. Standard bit of kit these days.

Motorized valves tend to have a lever on them that you can move manually if they fail.

gaelicyoda

Update for folks on this -

In the end, we decided to go for a single circulation pump for the central heating, and a single 2 bar pump to pressurise the two showers and electric shower. Plumber reckons it should be fine for two showers simultaneously, and I said that will be grand because what's the likelyhood of all 3 going at the same time? (In that unlikely event, someone can just wait! )

I will post again when the work is done (if I remember!) and see how it all comes together in the end.

Cheers,
GY

heinbloed

In the end, we decided to go for a single circulation pump for the central heating

Plain logic. I've seen several pumps pumping one singel home's central heating system only in Ireland.....
What you have decided now for - the single pump system - can be made even more efficient if you go for an electronically controlled circulation pump.These modern pumps available 'only' since 10 or 20 years use no more electric energy than necessary. Maintaining the pressure at the right level, no matter how many radiators are open or closed.
Modern boilers have them already build-in.
And the A-rated pumps are even more effizient, see here

http://www.energypluspumps.eu/en/data_editor/File/Finalreport.pdf

Insist on the boiler manufacturer to have such a pump installed, otherwise don't buy the boiler.