Hi, I recently purchased a home in Westchester County, NY. Long story short, the heating system is set up as follows: AO Smith Promax Boiler, Model #: FPSH 75l 270 Control board: Taco zvc404-exp Recirculation pump relay: Argo ar822-II Recirculation pump: Taco 008-bf6 Radiant floor heat using PEX tubing I had a plumber stop by recently who looked at the system and said that it is illegal, because apparently the boiler services both domestic AND the radiant heating system. According to him, the water for the heating system "contaminates" the domestic hot water and can get people sick. I have attached a picture. Naturally I was a bit concerned, not really knowing much about this stuff, and feeling like perhaps I had been ripped off. So I've been doing some digging online, trying to under this. I found these forums, and have learned alot thanks to members like BadgerBoilerMN, NRT.Rob and others. So it seems I have a "open loop" system that mixes domestic and heating system water in a single tank. I can see why that would be "sub-optimal", if there is concern about stagnant water, and harmful bacteria, coming back into the domestic water supply. It doesn't appear to be illegal, however. Perhaps someone could correct me. It looks like in MA you have to install a pump to circulate the radiant heat water every 6 hours. The house was built new in 2004. One thought I had- perhaps this is just a "newer" type of installation that the plumber hadn't seen before. From what I can tell, the builder generally did not cheap out on the house. I have seen comments about "just add a heat exchanger and close the loop". I'd like to consider doing that. Could someone provide me with specifics on what that would entail? Is that an entire new boiler, something that would cost me $15k (installation included) which is what the plumber suggested? Is there a simpler solution? The impression I've gotten from comments on this board is that adding a "HX" wouldn't be too complicated or expensive, but I don't really understand what that would entail. Thanks again for everyone on these boards, you have been very helpful. -Zach

Look at a x block, this can be installed between the water heater and your heat system, minimal cost and will isolate your domestic from the heat side.
We do not promote open loop systems here, but there are some who see it as a good option.
The good news is you have a radiant heat system installed, the fix is minimal.
http://www.blueridgecompany.com/radiant/hydronic/496/taco-x-pump-block
As always, to avoid sounding like the on line hawker We sell these as do others.
But this is a good alternate solution to fix an open loop.
X block offers the added function of out door reset as well.
Good luck,
Dan

Hi Dan,
I appreciate your time in answering the question, many thanks.

So, from a layman's perspective, it looks like basically that this device gets heated up by hot water from the boiler on the A side, which in turn heats up water flowing through on the B side. It also sounds like it has an internal pump on the A side to help it maintain temperature.

So, I'm guessing that the drawback is that you lose some efficiency, because heat will simply radiate off of this device, but you achieve a closed system by isolating the domestic from the heating system water. The other drawback, of course, (besides cost), would be that it introduces yet one more component (and not a cheap one) that can fail. Any sense of how much "efficiency" you would lose by introducing this device into the heating loop? I'm not sure how that would be measured...

The specs says it can handle "50,000 BTU's". The label on my boiler says "75,000 BTU". Does that mean I would potentially need two of these, configured in parallel? (assuming that would even work)? Or would one be enough?

Does anyone have any other thoughts on my original question, or on Dan's recommendation for the X block?

One last question: would an AO Smith Promax be considered a "cheap" boiler? Or are they considered mid, or high end?

Thanks again, this is all very interesting stuff.

-Zach

To give you a bit more information on my townhouse: it's 3300 square feet, 4 floors (say roughly 800 sq ft per floor), including the basement. So it's alot of space to heat. That's why I'm wondering if this device could do the job, or if I would need perhaps 2 of these in parallel, and also if that would mean reducing the overall efficiency of my heating system significantly.

Thanks again.

-Zach

Wondering if anybody has any recommendations re. radiant heaters for the garage. I'm just finishing up insulation and drywall, and would like to keep it at a reasonable constant temperature, say 10 Celsius (50 Fahrenheit). I would like it on a thermostat (or remote control perhaps), so I can jack it up as need be. Garage is not huge, standard double garage with 12 foot ceilings, so approx 4800 cubic feet. I don't have a gas line, and my furnace is quite a ways away ... so I'm thinking electric. I don't have a 240v outlet, but I can easily run one if necessary. If anybody has any recommendations or suggestions, would appreciated the input. Seems to be a lot products out there ... but not much in the way of reviews. I don't want to cheap out and buy underpowered unit(s), but I also don't want a commercial system LINE LOCATION

Zoomin,
You bring up a good question on capacity of the x block.
Without an actual heat loss on the Town house and a 3,000 sq ft building you might be close.
Typical town house construction would have units on left side, right side the end units will have greater exposure due to the out side walls.
X block has 2 pumps, constant speed on the heat primary loop, variable on the water heater side heat exchanger isolates the 2 sides. It will maintain set point temp on the primary loop (heat side) and has out door reset so it will also vary delivered heating temp based on weather.
Your water heater is in the 80% range so in actuality you are working with about 60,000 BTU already.
If you are not experiencing any shortage of hot water now when both heating and bathing you most likely have a efficient building envelope and the x block would work well.
Also as noted you could use 2 and divided the system in half, but I tend to think it would be over kill,
First solution if there was some initial problems with one x block would be to increase the water heater temp to the 150 degree range, increasing stored hot water capacity, this will provide a bit of a buffer. You will need a three way mix valve for your potable side if it is not there already.
Primary loop should also be run in about the 1 1/4 pipe size as soon as you leave the 3/4 x block fittings to minimize additional head.
Dan

Hi Dan,
Thanks, that is really useful info. It sounds like the Taco X block might be a good option after all.

I am also being advised to consider replacing my heater with "combi mod/con" boiler, instead of investing $ in isolating the heating system water, only to have my water heater go out in a few years...

-Zach

Exactly right, a good boiler would be a better long-term path than a cheap hot water tank and an expensive, high maintenance heat exchanger. If you elect to use Taco X block, be sure to shop around as there are different models and the prices often vary significantly by vendor too.

Thanks sailawayrb. If you have any suggestions on specific boilers, that would be great.

So,
path of least resistance at this point. Possibly.
There is only to my knowledge one x block model.
http://www.blueridgecompany.com/radiant/hydronic/496/taco-x-pump-block

There are two similar Taco products to the X block see links;
http://www.blueridgecompany.com/radiant/hydronic/484/taco-radiant-mixing-block
The Radiant mixing block is more for mixing down a primary loop on a boiler system, injection pump concept, no heat exchanger.
A good application for this would be multiple temp applications.
http://www.blueridgecompany.com/radiant/hydronic/644/taco-solar-x-pump-block
As it implies this is a solar pump station control.
And yes it is true, these can be found in multiple stores at varying price points.

In this case the cost might support the water heater over a $15,000.00 fix with new boiler.
The current water heater in place is actually a decent unit, upper end of efficiency for its type, power vented unit, not a big expense to replace when the time comes, I am not sure what this appliance product life is.
Not saying a mod con is a bad choice but keep in mind the associated cost, re-vent (cannot use existing B vent), and there will still be that pesky heat exchanger as it would be built in to the boiler and exposed to the same water situation so I am not sure where the benefit is here. Recommended service on most condensing boilers is every 2 years and you will need a fairly savvy tech, water-heaters are a simpler appliance.
If one is worried about the cleaning of the heat-exchanger some simple bypass valves can be installed for a periodic acid or vinegar wash.

Don't get me wrong here though, I do like and spec a lot of mod con boilers, just pointing out a simple low cost solution to an existing system.
15K is a lot of cash for a repair/fix. Can buy a lot of fuel and new water heaters for that. ROI?
Dan

Thanks Dan. Just so I understand, you are saying that the installation of a "combi mod/con" boiler typically would run roughly $15k, give or take? If so, I agree, it might be worth going the heat exchanger route for the time being, and hope I can get another 5 years out of the heater before installing a new boiler that solves this problem "properly".

Also, any chance you might be willing to suggest a few combi od/con boilers, just so i can get a sense of what I would be looking for down the road?

I do like the simplicity of the Taco X Block heat exchanger, my main concern is whether it can handle the load...

Thanks again.

The 15K was the number you put out on your first post.

Prices will vary depending on who installs it.
Typical modcon will run about 3-5k but there are other aspects to the install that will add to the overall cost.
Dan

Thanks Dan. I don't have a good sense of what boiler installations should generally cost. I'll have to do some digging. I realize that you guys aren't supposed to talk numbers. Thanks.

Before you invest in anything, you should verify that the PEX in your future closed system has an oxygen barrier. Hopefully you do, which allows you to use ferrous components. Otherwise you would be well advised to only use non-ferrous components such as brass or stainless steel...which isn't a bad approach even with oxygen barrier PEX. Your current open system contains oxygen and if you currently have any ferrous components in your system, they will likely already be in bad shape...sorry to be the bearer of bad news... You could purchase an electric boiler for about $1,500 and they are relatively easy to DIY install. Our affiliate, PexSupply has several hundred different boilers to choose from. Check their prices and anything more than 30% of the product purchase price is an expensive install.

Borst,
Sound like you have joined the ranks of on line hawker affiliate.

So back to the x block.
X block is non ferrous ( no iron). If your system was set as open loop and was properly done it will be all non ferrous already (bronze or stainless pump).
No problem with numbers, just cant say what a local mechanic might need to do your work, rates and skill vary all across the nation.
A good mechanic can be in and out in a relatively short time with the x block (day). Boiler may take 3 days.
Again skill, job needs, solution all will reflect real time.
Dan

Hi Dan,
Yeah, I screwed up last week. This whole thing got started when we weren't getting enough radiant heat. I did some troubleshooting, and determined that it was a faulty pump- wasn't too hard to figure out. I was having trouble getting a plumber in due to the weather, and to save time (and $) I went out and bought the replacement pump myself, so it would be ready and waiting as soon as I could get the plumber in. The old pump was brass, and when I got to the store they gave me a cast iron one. The plumber filled me in on the issue, and I have a new stainless steel pump being delivered tomorrow, which I'll get installed asap. So, expensive lesson for me. Argh.

(Side note- will having that cast iron pump running for a week cause any long term problems anywhere? I'm assuming the only drawback is that the pump will likely fail quickly)

Thanks again for your feedback, the X block looks like a very good option that might be worth trying. I'm gathering feedback from various sources and will hopefully have this all settled soon enough.

Zach

Iron pump wont hurt anything for a week,
your learning the trades!

OK, good to know- phew.

Ha, yeah, really. Actually, it's all fascinating stuff. I never realized all the different possibilities and variables that go into these systems.

No Dan, there are already too many companies with the hawker distinction and we just try to warn consumers in advance so as to try to minimize the damage they often cause to the hydronic radiant floor heating industry reputation. We are merely an engineering consultation/design and construction company. We don’t sell any hydronic radiant floor heating system products and we don’t any take any sales commission from other companies that sell these products. We do affiliate with companies who refer people to consider us for engineering/construction services and we refer people to consider them for purchasing their products if we deem them to offer competitive/fair pricing and adhering to our company motto. While we can understand the business model and motivation of companies lacking engineering credentials to feign competence by using “catalog engineering” to push the product inventory that they sell, this is not and will never be our business model.  I also see that X-block costs significantly less at PexSupply than the other places I researched.  It never hurts to shop around.