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https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl DIY Forum >> Plumbing Questions >> Pump relay https://www.askthetrades.co.uk/cgi-bin/yabb/YaBB.pl?num=1163180842 Message started by CWatters on Nov 10^th, 2006, 5:47pm

Title: Pump relay
Post by CWatters on Nov 10^th, 2006, 5:47pm

I've been looking at the drawings for my UFH heating system - trying to make sure I have all the bits ready for our plumber/electrician - and it looks like we may need a relay of some sort.

We have two manifolds and each has it's own pump and mixer. When either of these pumps is running the boiler pump needs to run as well. A simple logic OR function.

In the world of plumbing is there a standard little black box you can buy to do this?

Title: Re: Pump relay
Post by chtechie on Nov 11^th, 2006, 11:06pm

what UFH system are you using ? Most control boxes will include this function. Why do you need 2 manifolds with pumps / mixer, even quite big houses will have no more than 6 - 8 zones.

Title: Re: Pump relay
Post by CWatters on Nov 12^th, 2006, 7:57am

It's an OSMA system fed from a thermal store. We have two seperate manifolds (one per floor) each with it's own built in pump. OSMA say a seperate pump is needed to circulate the water around the store to manifold loop. If we wern't using a store this loop would be the boiler primary loop. Each manifold has a bypass on the front.

There is a wiring center for each manifold and it's pump but I can't see an output for the primary/third pump.

Each wiring center has a signal called "Boiler Enable". There is a drawing showing how to set up two manifolds and this shows them wired together and going off the page... but is this an input or an output? Is this used by the programmer to switch the manifolds on/off ? or is it used by the manifolds to call for heat?

Title: Re: Pump relay
Post by chtechie on Nov 12^th, 2006, 11:14am

I'm assuming you're using a Mk111 manifold / UH1 wiring centre - Boiler enable has 2 connections which can either be used volt free or to switch mains voltage. Because you're using a thermal store your boiler is controlled by heat requirement of the store i.e. when you use heat it is replaced automatically.

I'm not sure you want to control the boiler pump, do you not have a boiler (or primary) pump, a heating circulation pump, and the 2 underfloor heating manifolds / pumps ?

Normally you'd connect 'live' to one of the enable terminals on both the wiring centres then connect the other enable terminals together and connect them to the heating circulation pump live, relays to control this are on board the wiring centres.

David.
______

Title: Re: Pump relay
Post by scotspark on Nov 12^th, 2006, 2:02pm

all UFH i have done has always been a manifold per floor. and on 1 larger house 2 on ground floor.

new house I did this year had 2 manifolds 1 upstairs 7 zones plus the hallway as a bypass zone upstairs 5 zones plus hallway utility room and cloak room on a bypass downstairs. this was a reasonably large house but not massive.

Title: Re: Pump relay
Post by CWatters on Nov 12^th, 2006, 7:16pm

Thanks David..

wrote on Nov 12^th, 2006, 11:14am:

I'm assuming you're using a Mk111 manifold / UH1 wiring centre

Yes on the UH1 wiring center. The manifolds are a pair of these (which might be the Mk111)..

http://www.osmaufh.co.uk/pdfs/manifoldControls.pdf

Quote:

Boiler enable has 2 connections which can either be used volt free or to switch mains voltage. Because you're using a thermal store your boiler is controlled by heat requirement of the store i.e. when you use heat it is replaced automatically.

yes I understand about the store temp controlling the boiler.

Quote:

I'm not sure you want to control the boiler pump, do you not have a boiler (or primary) pump, a heating circulation pump, and the 2 underfloor heating manifolds / pumps ?

It sounds like I'm talking about the "heating circulation pump". Its sits between the store and the manifolds and needs to run when either of the manifold pumps is running.

Quote:

Normally you'd connect 'live' to one of the enable terminals on both the wiring centres then connect the other enable terminals together and connect them to the heating circulation pump live, relays to control this are on board the wiring centres.

So it sounds like one of the boiler enable signals will do the job. I half suspected it might but the drawing doesn't make it clear which direction these go. Ok if it looks like one of these signals will do then I can wait until our electrician is back on the job. Thanks.

Title: Re: Pump relay
Post by CWatters on Nov 12^th, 2006, 7:32pm

scotspark wrote on Nov 12^th, 2006, 2:02pm:

We're using two maifolds with 11 ports on each. I think we are using 10 out of the 11 on each. That's not 20 zones though as a few rooms need more than one loop - partly because of the distance from the manifolds and partly due to room size.

I've not had UFH before and was concerned that we might have a problem with one room too hot and the other too cold and not be able to solve it if they are on the same loop. With a rad system you can easily turn one down a bit. Anyway some loops got added to avoid that risk.

Title: Re: Pump relay
Post by scotspark on Nov 12^th, 2006, 8:23pm

sounds very similar to the setup at this place.

I jujst did the wiring (as an extra that noone informed me of until someone asked where all the cables for the controls where at the manifolds??????????????????)

this place has ground source heat pump for the UFH and a solar panel for hot water.

Title: Re: Pump relay
Post by chtechie on Nov 13^th, 2006, 12:34am

I normally work on NuHeat which has a main distribution manifold (with pump and mixer valve) which then feeds zone manifolds, the wiring centre I think has a max of 12 zones as you say zones & loops aren't the same thing. If you've had the system designed by the manufacturers then it should work well. ANyway if you've anymore questions just post again.

Scotspark were all these zones controlled by their own stats I think the biggest house I've done was a 6 bed 2 bath (+ensuites) place which had 6 zone stats covering 14 rooms + hall, utility & downstairs cloak.

Title: Re: Pump relay
Post by scotspark on Nov 13^th, 2006, 5:39pm

upstairs:

4 beds each on own stat 1 ensuite on seperate stat 1 ensuite with bedroom stat. family bathroom on seperate stat outside with probe in the screed and upstairs lounge on its own stat (also has real fireplace) upstairs hall/ corridor left as a bypass/open loop

Downstairs:

Downstairs lounge(wich also has real fireplace), living room, office, Kitchen/dining(wich also has log burning stove). all on own stats hallway,cloakroom and utility left as open/bypass and a loop and stat are in the garage in advance of it being converted into a bedroom with ensuite next yer.

as ypou said some stats control more than 1 loop due to size of room etc

Title: Re: Pump relay
Post by CWatters on Nov 13^th, 2006, 7:55pm

One last question from me...

Does it matter what pressure the UFH loops are run at? I ask because the store I'm using (DPS heatbank) is vented so the loops will be at low pressure - just a few meters head.