You noted that you are well insulated, but aren't you in CA climate zone 16?

And 7/8" pex seems pretty large to stick under floor joists without any other heat transfer medium.

i'm in CA at 5300' feet. attached photo is my back yard on April 12th this year. (and this was exceptionally mild winter). just checked and yes, we are in climate zone 16.

we used aluminium fins on all PEX stapled under joists.

I have a question totally un-related to the heating system. What type of cloths washer are you using and how does it respond to the changes in water pressure, especially the 25psi, when available

The reason I ask is that I just finished a small job where I put a 2000L cistern into the ground and PV pumped the water to a 20GAL pressure tank. The pressure varies from 10-40psi depending on sunlight and pumping time. The water is used only for 1 Toto toilet and one old Maytag washer. The client may get a new front loader but we are not sure how it will react to lower pressure.

FYI, I will put a pressure sensor on to a 3 way ball valve that lets city pressure in if the cistern is empty but I haven't determined the switch over pressure yet.

Hey Mike,

Sorry for the delay. My Frigidaire Front Load washing machine works just fine at 25 psi.

I noticed that knotET's most recent posts have disappeared. As before, I couldn't comprehend most of the information - feel like the discussion is beyond me. But I wanted to clarify if correct that I could leave the expansion tank where it is on the return side of the pumps?

Also, I called Takagi and the discovered that the required temp diff varies according to GPM for example, with outlet temp set at 131F:

at 3 GPM return temp needs to be 121F for takagi to fire (10 dT if I'm understanding correctly)
at 2 GPM 116F (15 dT)
at 1 GPM 101F (20 dT)

In terms of system circulator, I looked that the WILO variable pump and the Grundfos Alpha. The ALPHA 15-55SF is pretty interesting - curious what others think?

i'm putting together a shopping list. anyone have a favorite air separator?

also i spoke to a tech who suggested:
FlatPlate GBE 5x12-10 Plate Heat Exchanger 1"

seem right?

Posted By worthydocs on 18 Jun 2012 04:07 PM
Hey Mike,

Sorry for the delay. My Frigidaire Front Load washing machine works just fine at 25 psi.

I noticed that knotET's most recent posts have disappeared. As before, I couldn't comprehend most of the information - feel like the discussion is beyond me. But I wanted to clarify if correct that I could leave the expansion tank where it is on the return side of the pumps?

Also, I called Takagi and the discovered that the required temp diff varies according to GPM for example, with outlet temp set at 131F:

at 3 GPM return temp needs to be 121F for takagi to fire (10 dT if I'm understanding correctly)
at 2 GPM 116F (15 dT)
at 1 GPM 101F (20 dT)

In terms of system circulator, I looked that the WILO variable pump and the Grundfos Alpha. The ALPHA 15-55SF is pretty interesting - curious what others think?

I have 4 Alphas sitting in the shop waiting for the right project but I am not sure yours it the right one. I would be looking for something that will give a definite flow rate through the tankless. As you can see from their data, it would be best, IMO, to use the the one I mentioned before. Not saying that it won't work but I would feel safer.

I too have wondered where knotETs posts have gone. Not everyone can write the Queens English so maybe the English Police were alerted, LOL

Posted By worthydocs on 18 Jun 2012 05:22 PM
i'm putting together a shopping list. anyone have a favorite air separator?

Leave the expansion tank where it is and put the water feed beside it. Are the floor heat manifolds equipped with air vents? That helps but as the tubing does not have and O2 barrier, look up Spirovent. A bit pricey but it has a wire mesh inside that catches microbubbles.

Posted By worthydocs on 18 Jun 2012 05:42 PM
also i spoke to a tech who suggested:
FlatPlate GBE 5x12-10 Plate Heat Exchanger 1"

seem right?

It may even be a bit big but I wouldn't worry about that.

Hey Mike,

Dare I ask why the UPS15-55 is safer than the Alpha? ie, is it possible to explain in a general way using mostly English words without too many abbreviations or equations? Not that I'm doubting - I just want to understand.

Still confused re expansion tank - it is currently on the return side of the pumps (which will lead into the HX) rather than suction side (out of the HX). Is that OK? I'm planning to install the air eliminator above. Spirovent better than the Taco Vortech or the B&G EASB-JR?

Good to hear re the HX.

Posted By worthydocs on 18 Jun 2012 07:55 PM
Hey Mike,

Dare I ask why the UPS15-55 is safer than the Alpha? ie, is it possible to explain in a general way using mostly English words without too many abbreviations or equations? Not that I'm doubting - I just want to understand.

Still confused re expansion tank - it is currently on the return side of the pumps (which will lead into the HX) rather than suction side (out of the HX). Is that OK? I'm planning to install the air eliminator above. Spirovent better than the Taco Vortech or the B&G EASB-JR?

Good to hear re the HX.

Don't get me wrong...I think the Alpha and the Wilo Stratus are great pumps and use much less power than their brethren. It is just that I like to use them when I am quite sure of the rough range of flow and power needed, not when part of the system has a constantly changing (and not controlled) firing rate. Others might be more confident but unless I have used it in the same circumstances, I would rather recommend one that I have used.

Sorry, but yes, I would like to see the EXP tank moved but didn't know if you wanted to go that far with the piping.

The Taco is a good air eliminator but the Spirovent is the first one out there and probably more well known. I don't typically use B&G products, partly because most of them, in the past, lacked innovation compared to companies like Grundfos and Wilo (Taco and B&G also make pumps) and also that some brands are very regional and wholesalers tend to carry one or two brands. I don't buy my parts off the internet unless it is really innovative and one of my wholesalers doesn't carry it.

It is interesting that nearly all new developments in heating (forced air excepted) have come from Europe and in this way, America plays catch-up.

mike - don't get me started re the sorry state of american innovation. (and it's off topic anyway)

one more question re the alpha - as i understand it can be operated in fixed speed mode and still use less power than the UPS15-55. which seems like a big advantage so i feel like i'm missing something in terms of the drawback of using it vs the UPS15-55. any further insight you can offer?

not a big deal to move the EXP tank.
will check pricing at local wholesaler for air eliminator. there is an advantage to using whatever is used locally so that's worthy knowing

thanks again. your insight and advice has been super helpful!

me again! we've switched over to a heat exchanger system. it has solved the problem of zone 1 stealing from other other two zones.

however, we seem to have a bigger problem because on the radiant side of our heat exchanger the supply temp is only 80 Deg F and the return temp is 78 Deg F. on the other side of the HX, water coming out of the Takagi is at 122 Deg F and returning at 85 Deg F. We would have expected that a) the water flowing into our floors would be higher (it used to be 131 Deg F in our Open system) and b) that the return temp would have a bigger drop on temperature. we are concerned that our HX is not sized properly - or something else not right.

ideas? suggestions?

Without knowing more info or actually seeing what your installation looks like, it would appear that either air is in the radiant system or the flow rate of the pump is too high and no heat transfer is occuring across the heat exchanger.

increasing flow rate ALWAYS increases heat transfer. it NEVER decreases heat transfer. it can result in a lower temperature rise, but you will pull more energy.

not sure why you'd have such a high temp drop on the takagi side. You'd have to have quite a flow mismatch to see a 40 degree drop on one side and a 2 degree on the other, as in 20x as much flow. is it possible that you took your reading after the takagi side pump stopped running or something?

Possibilities are:

1. Takagi side pump isnt working, or is VERY BARELY working, and what heat transfer you are getting is via "thermal convection". but the takagi would be cycling like crazy if that were the case.... the flow would be so low it wouldn't extract heat from the takagi very well. it would also be so little energy that it wouldn't maintain radiant side temp very well. this would be very unlikely to maintain room temperature in your house so you'd be cool/cold.

this could be bad pump, bad pump wiring, mostly closed valving, air restriction on the takagi side...

2. both pumps are working properly but you caught the system when at least the takagi side pump wasn't running. if you are maintain your room temps, this is possible.

3. you are running an outdoor reset controller, which is running the takagi side pump veeerrryyy slowly because you don't need much heat. if you ar maintaining your room temps, this is possible too. and you'd probably have the same short cycling problems I mention in #1.

Rob , I stand to be corrected regarding heat transfer and flowrates. My brain was turned off at the time I replied.The temperature measured on each side of the flatplate heat exchanger surely reperesents a problem Is it the primary side or secondary side or both.I had not read the previous post until now.The Tagaki being used as a radiant boiler is not a very good idea from the get go.The scale buildup in the heat exchanger of the Tagaki will shorten the life of the heater in a very short period of time.This system needs to be reengineered correctly before it will ever work correctly.

Hello all,
converting open loop to closed loop, look at the X Block,
all the bell, whistles and brackets in one , fits this size application, out door reset, modulation injectors, bronze pumps, it is a good value when you consider all the building and time messin aboot in the shop,
http://www.blueridgecompany.com/radiant/hydronic/496/taco-x-pump-block---xpb-1

Dan

other than it destroying his on demand through rampant short cycling, that's not a bad idea dan

Well I think not, The idea of building out the flat plated proposed earlier in the thread are the same thing just labor and cost intensive, where is the difference from running Takagi all the time now? But.... I know there are fans out there of buffer tanks,,,
perhaps a cheep 20 gallon electric tank would calm you er ah the takagi down, ; )
These x blocks do work well in this application, we have shipped many to correct evil open loop systems. Clearly it is not a condensing boiler, but it hits the budget, offers forward looking solutions as well.
Best
Dan

The problem here is that the heat load for the 3 zones are 10Mbtu, 2.5Mbtu and 2.5Mbtu and with a pump for each one, they cannot be working anywhere within the good part of their curves. The OP needs to use one zone and one pump. Each pump will be pulling way too much and it is not controllable.

I think the buffer tank idea is a worthwhile idea. I have used it many times on a tankless and the tankless will only respond to the t-stat on the tank and not the room stats and the takagi may have to run at a higher temp than it is now.